Aviation Electronics Technician (Organizational) (ATO)

Aviation Electronics Technician (Organizational) (ATO)
NONRESIDENT
TRAINING
COURSE
June 2015
Aviation Electronics
Technician (Organizational)
(ATO)
NAVEDTRA 14030A
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PREFACE
By obtaining this rate training manual, you have demonstrated a desire to improve yourself and the
Navy. Remember, however, this manual is only one part of the total Navy training program. Practical
experience, schools, selected reading, and your desire to succeed are also necessary to successfully
round out a fully meaningful training program.
THE MANUAL: This manual is organized into subject matter areas, each containing learning
objectives to help you determine what you should learn, along with text and illustrations to help you
understand the information. The subject matter reflects day-to-day requirements and experiences of
personnel in the rating or skill area. It also reflects guidance provided by Enlisted Community
Managers (ECMs) and other senior personnel, technical references, instructions, etc., and either the
occupational or naval standards that are listed in the Manual of Navy Enlisted Manpower and
Personnel Classifications and Occupational Standards, NAVPERS 18068(series).
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the material in the text. The answers for the end of chapter questions are located in the appendixes.
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June 2015 Edition Prepared by
AVCM (AW/SW) Thomas Rousseau
AT1 (AW/SW) Christopher Latiolais
AT1 (AW) Joseph Comer
NAVSUP Logistics Tracking Number
0504-LP-115-0006
i
NAVEDTRA 14030A COPYRIGHT MATERIAL
Copyright material within this document has been identified and approved and is listed below.
Copyright Owner
Date
Chapter
Pages
ii
Remarks
iii
TABLE OF CONTENTS
CHAPTER
PAGE
1.
Communications ............................................................................................... 1-1
2.
Navigation ......................................................................................................... 2-1
3.
Radar ................................................................................................................ 3-1
4.
Antisubmarine Warfare...................................................................................... 4-1
5.
Indicators........................................................................................................... 5-1
6.
Infrared .............................................................................................................. 6-1
7.
Weapons Systems ............................................................................................ 7-1
8.
Computers......................................................................................................... 8-1
9.
Automatic Carrier Landing System/Instrument Landing System ....................... 9-1
10. Electrostatic Discharge.................................................................................... 10-1
APPENDIXES
I.
Glossary ........................................................................................................... AI-1
II.
Symbols, Formulas, and Tables ...................................................................... AII-1
III.
References ..................................................................................................... AIII-1
IV.
Answers to End of Chapter Questions ........................................................... AIV-1
Index ................................................................................................................... Index 1
iv
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CHAPTER 1
COMMUNICATIONS
As an aviation electronics technician (AT), you will be tasked to operate and maintain many different
types of airborne communications equipment. These systems may differ in some respects, but they
are similar in many ways. For example, there are various models of amplitude modulation (AM)
radios, yet they all serve the same function and operate on the same basic principles. This chapter
will focus on the basic principles involved in radio communications and provide examples of the
common systems used in Navy aircraft.
LEARNING OBJECTIVES
When you have completed this chapter, you will be able to do the following:
1. Recognize the various types of electrical communications.
2. Describe the uses of various frequency bands.
3. Describe the basic terms associated with radio transmitters and receivers.
4. Describe the basic operating functions of radio transmitters.
5. Describe the basic operating functions of radio receivers.
6. Identify the components of aircraft communication systems.
7. Describe the operating principles of aircraft communications systems.
RADIO COMMUNICATIONS
In basic terms, communication is defined as the meaningful transfer of intelligence (information) from
one location (the sender or source) to another location (the destination or receiver). Electrical
communication occurs when intelligence is converted from its original form (speech) into electrical
energy. The electrical energy can then be transmitted via wires or radiated through space to a
receiver. The receiver converts the electrical energy back into its original form. The electrical
communication process occurs in a fraction of a second because electrical energy travels at the
speed of light (approximately 186,000 statute miles per second).
Types of Electrical Communications
Communications have become a highly sophisticated field of electronics. All Navy aircraft have the
capability to access the ship-to-ship, ship-to-air, air-to-air, air-to-ground, and ship-to-shore circuits by
using compatible and flexible communication systems. The following paragraphs will describe four
types of electrical communication systems: radiotelegraph, radiotelephone, teletypewriter, and
facsimile.
Radiotelegraph
Radiotelegraph is commonly called continuous wave telegraphy. Telegraphy is accomplished by
opening and closing a switch to separate a continuously transmitted wave into dots and dashes
based on Morse code. The major disadvantage of this type of communication is the relatively slow
transmission speed and the need for experienced operators at both ends.
1-1
Radiotelephone
Radiotelephone (radio) is one of the most
useful military communication methods. It is
used by aircraft, ships, and shore stations
because of its directness, convenience, and
ease of operation. An example of a
radiotelephone in operation is shown in Figure
1-1. The equipment used for tactical purposes
usually operates on frequencies that are high
enough to have line-of-sight characteristics.
This characteristic reduces the risk of an
enemy being able to intercept the messages
being transmitted. One of the disadvantages to
using this type of system is that the effective
transmission and receiving range is limited. In
addition, the transmissions are susceptible to
wave propagation characteristics that may
make communications unpredictable.
Teletypewriter
Teletypewriter (TTY) signals may be
transmitted by landlines, cable, or radio. The
Figure 1-1 — Typical radiotelephone in
Navy uses radio teletypewriter (RTTY) for highoperation.
speed automatic communications across
ocean areas. The keyboard used with a standard TTY system is similar to that of a typewriter. When
the operator strikes a key, a sequence of signals is transmitted. At the receiving station, the signals
are translated back into letters, figures, and symbols and the system replicates the message
automatically.
Facsimile
Facsimile (fax) is the process used to transmit photographs, charts, and other graphic information
electronically. The image that is going to be transmitted is scanned by a photoelectric cell. Electrical
changes in the scanning cell output corresponding to the light and dark areas being scanned are
transmitted to the receiver. At the receiver, the signal operates a recorder that reproduces the picture.
The fax signals may be transmitted either by landline or radio.
NAVY FREQUENCY BAND USE
The radiofrequency (RF) spectrum is any frequency of electromagnetic energy capable of
transmission into space. The frequency bands used by that military are shown in Table 1-1. Each
band of frequencies has its own characteristics. For further information on the RF spectrum refer to
Navy Electricity and Electronics Training Series, Module 17, Radio-Frequency Communications
Principles.
1-2
Table 1-1 — RF Spectrum
FREQUENCY
DESCRIPTION
30 gigahertz (GHz) – 300 GHz
Extremely high frequency (EHF)
3 GHz – 30 GHz
Super high frequency (SHF)
300 megahertz (MHz) – 3 GHz
Ultrahigh frequency (UHF)
30 MHz – 300 MHz
Very high frequency (VHF)
3 MHz – 30 MHz
300 kilohertz (kHz) – 3 MHz
30 kHz – 300 kHz
3 kHz – 30 kHz
300 hertz (Hz) – 3 kHz
Up to 300 Hz
High frequency (HF)
Medium frequency (MF)
Low frequency (LF)
Very low frequency (VLF)
Voice frequency
Extremely low frequency (ELF)
VLF and LF Band Communications
The VLF and LF bands were originally used for radio telegraphy. Today, the VLF band is used to
communicate with satellites and is a backup to shortwave communication systems. The LF bands are
used to provide eight channels of frequency division multiplex RTTY traffic for the fleet multichannel
broadcast system. Because the wavelengths were in the kHz range and higher (30 kHz has a
wavelength of 10 kilometers, or about 6.2 miles), enormous antennas had to be used. This is no
longer a factor with current technology.
MF and HF Band Communications
The MF and HF bands are not only used by the
Navy, but portions are also used by commercial
AM broadcasting stations. These spectrums
also include the international distress
frequencies (500 kHz, 2182 kHz, 8364 kHz,
3023.5 kHz, and 5680 kHz).
Interaction Available
Signal radiation in these frequency ranges have
the important characteristic of being reflected by
the ionosphere. The ionosphere is a layer of
electrically charged particles at the top of the
Earth’s atmosphere. It starts at approximately
37 miles above the Earth’s surface and is
caused by strong solar radiation entering the
upper atmosphere. When a radio wave in the
MF or HF range hits this layer, it is reflected
back to Earth. An example of the reflection of
radio waves off the ionosphere is shown in
Figure 1-2. Multiple radio wave reflections
between the ionosphere and Earth are possible.
MF and HF transmissions can travel long
distances because of the reflective
characteristics of the ionosphere. This is
particularly true in the HF band.
Figure 1-2 — RF reflection off the ionosphere.
1-3
The disadvantage of this type of propagation is that it is dependent on the characteristics of the
ionosphere, which varies widely, especially during daylight hours. Variations in the ionosphere can
cause RF waves to reflect differently and take different paths over a period of time. This will cause the
signal at the receiver to vary in strength and the transmission to fade in and out.
VHF and UHF Band Communications
Signal radiation in the VHF and UHF frequency ranges does not normally reflect off the ionosphere.
As a result, communications in these ranges tend to be line-of-sight and normally cover short
distances. The term line-of-sight describes a straight, unobstructed path between the transmitter and
receiver. Although the VHF and UHF bands have disadvantages, they are the most commonly used
media for tactical communications.
TRANSMITTER AND RECEIVER
FUNDAMENTALS
A radio transmitter and receiver both serve very important
functions in a communication system. Transmitters are
responsible for generating the proper amount of RF energy to
transmit intelligence from one to point to another. Receivers
must have the capability to filter unwanted transmissions and to
decode the intelligence into a usable form. Before the types
and characteristics of transmitters and receivers are explained,
an overview of terms is provided to describe the basic
functions.
Basic Terms
The following is a list of the basic terms used to describe the
functions and components of radio transmitters and receivers:
•
Antenna
•
Harmonics
•
Subharmonics
•
Suppression
•
Fading
•
Attenuation
•
Tuned circuits
•
Oscillators
•
Varactors
•
Microphone
•
Speaker
Antenna
Antennas (Figure 1-3) are conductors or sets of conductors
used to collect or radiate RF energy.
1-4
Figure 1-3 — Typical radio
tower antennas.
Harmonics
The term harmonics is used to describe multiples of the basic frequency. The basic frequency is also
known as the fundamental frequency. There are two types of harmonics, even and odd. Even
harmonics are described as the fundamental frequency times an even number (2, 4, 6, etc.) Odd
harmonics are the fundamental frequency times odd numbers (1, 3, 5, etc.)
Subharmonics
The term subharmonics is used to describe the submultiple of the fundamental frequency.
Subharmonics are expressed in a similar manner as harmonics (even and odd). However,
subharmonics are not whole numbers. Instead they are expressed as a fraction of a whole number.
For example, even subharmonics would be 1/2, 1/4, etc. of the fundamental frequency. Odd
subharmonics would be 1/3, 1/5, etc. of the fundamental frequency.
Suppression
The term suppression describes the electrical elimination of an undesired portion of a radio signal.
Fading
The term fading describes the variation of signal strength at the receiver due to the difference in the
phase relationships.
Attenuation
The term attenuation describes the reduction of a radio signal strength due to atmospheric or system
loss conditions.
Tuned Circuits
A tuned circuit is used as a filter in a radio communication system. A tuned circuit allows or rejects
specific frequency ranges.
Oscillator
An oscillator is a component that is used to provide a constant frequency for radio transmitters and
receivers. A basic oscillator consists of the following basic components: frequency determining
network, amplifier, and feedback network.
•
A frequency determining network is an inductive or capacitive circuit that contains a crystal. A
crystal is a natural or man-made element that is manufactured to vibrate at specific resonant
frequency.
•
An amplifier increases the output of the signal to the desired level.
•
A feedback network is used to route parts of the signal back to the frequency determining
network to maintain oscillation.
Varactors
A varactor is a semiconductor diode whose capacitance is varied with the amount of voltage applied.
This component is used to vary the frequency output of the oscillator.
Microphone
Microphones are devices that are used to convert sound energy into electrical energy.
1-5
Speaker
Speakers are devices that are used to convert electrical energy into sound energy.
Types of Transmitters
There are three basic types of transmitters used in aircraft radio communications. They are AM,
frequency modulated (FM), and single sideband (SSB) types.
Amplitude Modulation Transmitter
The AM transmitter varies the amplitude of the RF output in proportion to the modulating signal. The
modulating signal may consist of many frequencies of various amplitudes and phases. An example of
a modulating signal is a speech pattern. The basic operation of an AM transmitter is described below.
In addition, a simplified AM transmitter block diagram is shown in Figure 1-4. A basic AM transmitter
consists of the following components:
•
Microphone
•
Audio power amplifier
•
Oscillator
•
Buffer amplifier
•
Modulator
•
RF power amplifier
•
Antenna
•
Power supply
Figure 1-4 — AM transmitter simplified block diagram.
1-6
An audiofrequency (AF) is provided to the transmitter through the use of a microphone. The electrical
energy is amplified and modulated to the appropriate level. The modulated signal is routed to the
power amplifier to produce the AM signal, which is transmitted via the antenna.
Frequency Modulation Transmitter
The FM transmitter combines the carrier frequency with the modulating signal to cause the frequency
of the resultant wave to vary with the instantaneous amplitude of the modulating signal. The basic
operation of a FM transmitter is described below. In addition, a simplified FM transmitter block
diagram is shown in Figure 1-5. A basic FM transmitter consists of the following components:
•
Microphone
•
Oscillator
•
Varactor
•
Frequency multiplier
•
RF power amplifier
•
Antenna
•
Power supply
Figure 1-5 — FM transmitter simplified block diagram.
First, a sound signal (modulating) is applied to a varactor to vary the capacitance. The varactor
causes the oscillator frequency to vary around the fundamental frequency in accordance with the
modulating signal. The output of the oscillator is routed to the frequency multiplier which increases
the frequency. Finally, the signal is routed to the power amplifier and increased to the desired output
level for transmission via the antenna.
Single Sideband Transmitter
Any carrier signal that has been modulated is accompanied by two identical sidebands (upper and
lower). Each sideband carries the identical intelligence. An SSB transmitter is used to transmit either
the upper or lower sideband, with the other sideband being suppressed. An SSB transmission is less
susceptible to atmospheric interference than an AM transmission. The basic operation of an SSB
1-7
transmitter is described below. In addition, a simplified SSB transmitter block diagram is shown in
Figure 1-6. An SSB transmitter consists of the following components:
•
Microphone
•
Audio power amplifier
•
SSB generator
•
Oscillator
•
Frequency multiplier
•
Filter
•
Mixer/band-pass filter
•
Antenna
•
Power supply
Figure 1-6 — SSB transmitter simplified block diagram.
The audio amplifier increases a signal to a level that is sufficient to operate the SSB generator. The
signal is then routed to the frequency generator, which produces a carrier frequency that is applied to
both the SSB generator and the frequency multiplier. The SSB generator combines both the audio
input and the carrier input to create the upper and lower sidebands. The upper and lower sidebands
are then routed through the filter, which selects the desired sideband for transmission and
suppresses the other. The signal is then routed to the mixer for conversion to the desired radio
frequency. The signal then passes through the band-pass filter where it is filtered before
transmission. Finally, the signal is routed to the amplifier where it is increased to the desired output
level for transmission via the antenna.
1-8
Receivers
Receivers are components that are built to process the signals received via the antenna assembly.
The output of the receiver is the intelligence that was modulated and amplified by a transmitter.
Receivers have four basic functions: reception, selection, detection, and reproduction.
Reception
Receiver reception occurs when an RF wave passes through the receiver antenna and induces a
voltage level into the antenna.
Selection
The selection function in a receiver selects the particular frequency of a station that is different from
the rest of frequencies that appear at the antenna.
Detection
Detection occurs when the receiver separates the AF signal from the RF carrier signal through the
use of a detector circuit.
Reproduction
Reproduction describes the process of converting the electrical signal into audio.
Receiver Characteristics and Components
Receiver Characteristics
The four characteristics important to receivers are sensitivity, noise, selectivity, and fidelity.
•
Sensitivity is one of the important factors in converting RF signals. Sensitivity describes the
ability of a receiver to reproduce a weak signal into a useable output. Sensitivity in a receiver is
expressed in terms of voltage, usually in the microvolt range. The level change in the signal or
sound level is expressed as a decibel (dB).
•
All receivers generate some amount of noise, which in turn affects the sensitivity of a receiver.
Receivers should have the ability to produce at least 10 times as much output signal power
compared to noise. Noise can be generated from atmospheric conditions, like lighting, or by
components that are internal to a receiver.
•
Selectivity describes the degree of distinction that a receiver can make between the desired
and unwanted signals. The degree of selectivity is based on how well the frequency
determining circuits have been built and tuned.
•
Fidelity describes the ability of a receiver to accurately replicate the signal output as input. One
of the characteristics of effective fidelity is the ability to pass all the modulated frequencies that
were transmitted. In general terms, a receiver should be designed to have an acceptable
compromise between good selectivity and high fidelity.
Receiver Components
A typical receiver consists of the following sections: antenna, selector, detector, and reproducer.
•
The antenna section consists of components that are designed to intercept and route incoming
radio waves (RF energy).
1-9
•
The selector section of a receiver is used to select the desired frequency, which in turn is
coupled to the detector section.
•
The detector section of the receiver is used to recover and extract the intelligence that was
passed through the antenna and selector sections. In addition, the detector section filters out
unwanted frequencies.
•
The reproducer section of a receiver takes the filtered intelligence and converts it to an audio
output.
Types of Receivers
The superheterodyne receiver is one of the most familiar types of receivers in use today.
Heterodyning is a term that describes the process of combining the incoming signal with the signal
generated in the local oscillator. The result of this process is an intermediate frequency (IF) signal.
Superheterodyne receivers come in two forms, AM and FM.
Amplitude Modulation Receiver
An overview of the basic operation of a typical AM receiver is described below. A simplified AM
receiver block diagram is shown in Figure 1-7. An AM receiver consists of the following components:
•
Antenna
•
RF amplifier
•
Local oscillator
•
Mixer
•
IF amplifier
•
Detector
•
AF amplifier
•
Speaker
Figure 1-7 — AM receiver simplified block diagram.
1-10
A signal received by the antenna section is first routed to the RF amplifier for signal amplification. The
amplified signal is then sent to the mixer where the original signal and local oscillator signals are
combined by heterodyning (mixing). The IF signal is then amplified and routed to the detector section.
Finally, the detector section filters the IF signal and routes it to the AF amplifier before the output
(audio) is sent to the speaker.
Frequency Modulation Receiver
An overview of the basic operation of a typical FM receiver is described below. A simplified FM
receiver block diagram is shown in Figure 1-8. An FM receiver consists of the following components:
•
Antenna
•
RF amplifier
•
Local oscillator
•
Mixer
•
Wide-band IF amplifier
•
Limiter
•
Discriminator
•
AF amplifier
•
Speaker
Figure 1-8 — FM receiver simplified block diagram.
The incoming signal is amplified by the RF amplifier and routed to the mixer. The mixer combines the
amplified RF signal with the local oscillator signal using the process of heterodyning. The resultant IF
signal is amplified by the wide-band IF amplifier section. The amplified signal is routed to the limiter
circuit in the receiver. The limiter circuit removes all of the signals that do match the same amplitude
1-11
levels, which in turn reduces the amount of noise interference. The signal is then routed to the
discriminator circuit, which is built to respond to the shifts in frequency variation. The AF component
is then extracted and routed to the speaker for output.
AIRCRAFT COMMUNICATIONS SYSTEMS
Aircraft communication systems are critical components for the aircrew. Without an effective
communication system the aircrew would be unable to safely and effectively complete the assigned
mission. The next paragraphs will provide an overview of the following: ARC-210 communication
system, digital communication system (DCS), multifunctional information distribution system (MIDS),
intercommunication system, and the data link.
ARC-210 Communication System
The ARC-210 communications system is used for RF transmission and reception of plain voice and
encrypted AM and FM signals and is used in a variety of Navy aircraft. The following paragraphs will
provide an overview of the ARC-210 communication system components and modes of operation
used in the F/A-18 series of aircraft. The ARC-210 system is made up of the following components:
•
VHF/UHF receiver-transmitter no. 1 and no. 2 (Figure 1-9)
•
Communications antennas (3)
•
Antenna selector
•
ANT SEL COMM 1 switch
VHF/UHF Receiver/Transmitter No. 1 and No. 2
The F/A-18 series aircraft can be configured with
two ARC-210 radios, which will act as receivertransmitter number 1 (COMM 1) and receivertransmitter number 2 (COMM 2). The ARC-210
radio operates in the 30 Hz to 399.975 MHz AM
and FM frequency ranges. The frequency bands
and modes of operation are shown in Table 1-2.
Each radio provides the operator with the ability
to receive and transmit voice communications to
other aircraft or ground stations in plain voice or
anti-jam mode. The ARC-210 radios also have
the capability of monitoring the guard frequency
(121.50 MHz) while still using other
communication frequencies through the use of a
separate guard receiver. The guard channel is
segregated from the other channels and is only
used in case of emergency.
Figure 1-9 — VHF/UHF receiver-transmitter.
COMM 1 and COMM 2 operate in both the frequency modulation (FM) and amplitude modulation
(AM) frequency bands. COMM 1 and COMM2 can operate in relay mode, which will retransmit
intelligence received to other aircraft or ground stations.
1-12
Table 1-2 — ARC-210 Frequency Bands and Operating Modes
FREQUENCY (MHz)
MODE OF OPERATION
30.00 – 87.975
FM
108.000 – 117.975
(receive only)
AM
118.000 – 155.975
AM
156.000 – 173.975
FM
225.000 – 399.975
AM or FM
The ARC-210 radios have three modes of operation: fixed frequency, maritime, and anti-jam.
•
Fixed frequency mode allows the operator to transmit and receive voice communications by
selecting one of the 20 preset channels using the upfront control display (UFCD).
•
Maritime mode allows the operator to select one of the 57 preset channels to communicate
with ships or stations. Selection of this mode is made on the UFCD.
•
Anti-jam mode uses two sub modes of operation to provide jam resistant communications,
single channel ground and airborne radio system (SINGCARS), and havequick.
o The SINCGARS mode of operation provides line-of-sight, jam resistant VHF FM band
voice communications.
o The havequick mode of operation provides line-of-sight, jam resistant UHF AM band
voice communications.
Communications Antennas
The ARC-210 radio system uses three dual blade antennas for receiving and transmitting. The upper
and lower forward antenna is used by COMM 1 and the data link system. The lower aft antenna is
used by COMM 2.
Antenna Selector
The antenna selector is an RF switching
unit that connects the receiver-transmitter
to an antenna. COMM 1 is either
manually or automatically connected to
the upper or lower forward antenna.
ANT-SEL COMM 1 Switch
The COMM 1 switch of the ANT-SEL
control panel assembly (Figure 1-10) is
used to select the upper or lower antenna
for use by COMM 1. AUTO position
allows the COMM 1 and the data link to
switch automatically between upper and
lower antenna as required.
Figure 1-10 — ANT-SEL control panel.
1-13
Digital Communications System
The F/A-18 series aircraft can be configured with
the RT-1824(C) DCS compatible radio (Figure 111). When DCS is installed in the F/A-18 series
aircraft it will take the place of COMM 2 but still
provides all of the standard voice
communications. DCS was designed to lower
the workload for the operator during close air
support (CAS) missions by visually displaying
mission information in a text format. In addition,
DCS provides secure voice communications
between the operator and a forward air
controller (FAC).
The system provides the operator with 9-line text
briefs provided by the FAC on the appropriate
display. The 9-line brief consists of target,
mission, and navigation data. The purpose of
this information is to decrease the possibility of
miscommunication during a CAS mission.
Figure 1-11 — DCS radio set.
Multifunctional Information Distribution System
The MIDS is designed to improve the situational awareness of aircrew and improve the effectiveness
of the command and control centers. The MIDS network accomplishes this by using secure digital
communications to display the location and status of participating friendly air and surface forces. The
MIDS consists of the following components: radio terminal unit, remote power supply, switchable
notch filter, and fixed notch filter.
Radio Terminal Unit
The radio terminal unit is the main component of the MIDS. The radio terminal unit is used to
exchange real time information among the secure network participants. An example of a typical MIDS
secure network is shown in Figure1-12. In addition, the radio terminal unit houses the components
and provides the functions of the Tactical Air Navigation (TACAN) system. The radio terminal unit
provides the operator with four functions: secure data link, secure voice communications, relative
navigation, and TACAN.
•
The secure data link enables the MIDS to exchange and display real time tactical information
among the participating units active in an established secure network.
•
The secure voice function allows active network participants to use jam resistant
communications.
•
Relative navigation improves the navigational accuracy of a host aircraft using the secured
MIDS network. The host aircraft compares the location of other network participants to its
location by measuring the time it takes for a participant to receive a message. The resultant
data is then used by the host aircraft navigational systems to make corrections if relative
navigation is the only active position keeping source.
•
The TACAN system is used to provide the operator with the distance and bearing to a
compatible aircraft, ship, or shore station.
1-14
Figure 1-12 — Typical MIDS secure network.
Remote Power Supply
The remote power supply provides the operating power for the MIDS radio terminal unit and
associated equipment.
Switchable Notch Filter
The switchable notch filter is used to prevent the interference between the MIDS and the Identification
Friend or Foe (IFF) RF transmissions. The switchable notch filter also switches out when the operator
is using the TACAN function of the radio terminal unit.
Fixed Notch Filter
The fixed notch filter is used to limit the number of TACAN channels transmitted by the upper
antenna.
Intercommunication System
The F/A-18 series aircraft intercommunication system is used to provide the aircrew with amplification
and distribution of inter-cockpit communications, aircrew-to-ground communications, voice alerts,
warning tones, and advisory tones. The intercommunication system consists of the following
components: intercommunication amplifier-control (IAC) and the communications control (COMM
CONT) panel.
1-15
Intercommunication Amplifier-Control
The IAC is used to amplify audio outputs and to provide the aircrew with communication-, navigation-,
and identification-related warnings and advisories. In addition, the IAC provides a means to adjust the
volume for avionics systems warnings, advisories, and ground crew communications. The IAC
interacts with the following systems:
•
Tactical Air Navigation – audio tones associated with TACAN station identification are
amplified and routed by the IAC.
•
Identification Friend or Foe – the IAC provides the aircrew with audio tones associated with the
IFF system operation.
•
Multifunctional information distribution – secure voice audio associated with the MIDS is
amplified and routed by the IAC.
•
Landing gear –the IAC provides the aircrew an unsafe landing gear tone when the landing
gear operating outside of normal parameters.
•
Stores management – the armament computer routes weapons audio to the IAC for
amplification and output.
•
Tactical electronic warfare – the IAC provides warning and advisory tones initiated by the ALR67 electronic warfare computer system.
•
Mission computer – the mission computer system routes voice alerting commands to the IAC
for amplification and output to aircrew headsets.
•
Fire detection – a voice alert message is amplified and routed to aircrew headsets when a fire
is detected in the engine or auxiliary power unit bays.
•
Bleed air detection – a voice alert message is amplified and routed to aircrew headsets when a
bleed air system overheat condition is detected.
An IAC systems interaction block diagram is shown in Figure 1-13.
COMM CONT Panel
The COMM CONT panel is used to provide ground crews with the ability to communicate with the
aircrew in the cockpit. The COMM CONT panel is part of the ground services panel as shown in
Figure 1-14.
Data Link
A data link system is used for the electronic exchange of secure data between two capable and
participating units (aircraft, ship, shore station, etc.) The following paragraphs provide a basic
overview of the data link system used in the P-3C Orion aircraft. The ACQ-5 data link system consists
of the following components:
•
C-7790A data terminal set control-monitor
•
CV-2528 data terminal set convertor-control
•
PP-6140 data terminal set power supply
•
A507 data terminal set communications interface 2
1-16
C-7790A Data
Terminal Set
Control-Monitor
The control-monitor
enables the
operator to select
the modes of
operation and
monitors the system
for operational
failures.
CV-2528 Data
Terminal Set
Converter-Control
The convertorcontrol modulates
and demodulates
digital data and
converts the data to
audio tones. The
audio tones are then
routed to the aircrew
headsets.
Figure 1-13 — IAC systems interaction block diagram.
PP-6140 Data Terminal Set Power Supply
The power supply provides the data terminal set
with the required regulated voltages for operation.
A507 Data Terminal Set Communications
Interface 2
The communications interface 2 is used to provide
a digital connection between the aircraft central
computer and the data link system.
Figure 1-14 — COMM CONT panel.
1-17
End of Chapter 1
Communications
Review Questions
1-1.
What type of energy transmission is used in radio communications?
A.
B.
C.
D.
1-2.
The speed of light travels at approximately how many miles per second?
A.
B.
C.
D.
1-3.
Teletypewriter
Radiotelegraph
Facsimile
Radiotelephone
What type of code uses a series of dots and dashes to relay intelligence?
A.
B.
C.
D.
1-6.
Teletypewriter
Radiotelegraph
Facsimile
Radiotelephone
What radio equipment signal may be transmitted by landlines, cable, or radio?
A.
B.
C.
D.
1-5.
146,000
166,000
186,000
206,000
What communication method is the most useful to the military?
A.
B.
C.
D.
1-4.
Thermal
Electrical
Mechanical
Chemical
Binary
Morse
Python
Semaphore
What frequency band is used to communicate with satellites?
A.
B.
C.
D.
Very low
Low
Medium
Very high
1-18
1-7.
Other than the high frequency band, what frequency band is also used by commercial
broadcasting stations?
A.
B.
C.
D.
1-8.
What atmospheric layer is caused by strong solar radiation?
A.
B.
C.
D.
1-9.
Very low
Low
Medium
Very high
Troposphere
Stratosphere
Mesosphere
Ionosphere
What frequency band is used to provide eight channels for fleet multichannel broadcast?
A.
B.
C.
D.
Low
Medium
Very high
Ultra high
1-10. Other than the ultrahigh frequency band, what frequency band is commonly used for tactical
communications?
A.
B.
C.
D.
Extremely low
Low
High
Very high
1-11. What term describes multiples of the fundamental frequency?
A.
B.
C.
D.
Fading
Harmonics
Suppression
Varactors
1-12. What type of circuit allows or rejects specific frequency ranges?
A.
B.
C.
D.
Varactor
Oscillator
Tuned
Parallel
1-13. What term describes the reduction of the signal strength due to the atmospheric conditions?
A.
B.
C.
D.
Subharmonics
Suppression
Fading
Attenuation
1-19
1-14. What component is used to maintain a constant frequency for transmitters and receivers?
A.
B.
C.
D.
Oscillator
Capacitor
Diode
Varactor
1-15. Which of the following fractions can be used to express an odd subharmonic?
A.
B.
C.
D.
One-half
One-third
One-sixth
One-eighth
1-16. What component of a frequency modulating transmitter varies sound signal capacitance?
A.
B.
C.
D.
Varactor
Oscillator
Frequency multiplier
Radiofrequency amplifier
1-17. What component of an amplitude modulated transmitter provides audiofrequency?
A.
B.
C.
D.
Audio power amplifier
Oscillator
Buffer amplifier
Microphone
1-18. What component of an amplitude modulated transmitter combines the audio and
radiofrequency signals?
A.
B.
C.
D.
Buffer amplifier
Modulator
Oscillator
Power supply
1-19. What frequency modulated transmitter component increases the routed signal?
A.
B.
C.
D.
Oscillator
Varactor
Frequency multiplier
Radiofrequency power amplifier
1-20. What component of the single sideband transmitter creates the upper and lower sidebands?
A.
B.
C.
D.
Power amplifier
Generator
Oscillator
Frequency multiplier
1-20
1-21. What measurement is used to express changes in sound levels?
A.
B.
C.
D.
Microfarad
Milliamp
Decibel
Foot pound
1-22. What receiver characteristic is expressed in volts?
A.
B.
C.
D.
Noise
Fidelity
Selectivity
Sensitivity
1-23. How many more times should a receiver signal output be compared to potential noise?
A.
B.
C.
D.
10
20
30
40
1-24. What receiver characteristic is the degree of distinction between desired and unwanted
signals?
A.
B.
C.
D.
Noise
Fidelity
Selectivity
Sensitivity
1-25. A receiver is designed to have a compromise between selectivity and what characteristic?
A.
B.
C.
D.
Noise
Fidelity
Selectivity
Sensitivity
1-26. What frequency signal results from heterodyning?
A.
B.
C.
D.
Midway
Equidistant
Transitional
Intermediate
1-27. What section of an amplitude modulated receiver filters the intermediate frequency?
A.
B.
C.
D.
Detector
Mixer
Speaker
Local oscillator
1-21
1-28. What section of a frequency modulated receiver reduces the amount of noise interference?
A.
B.
C.
D.
Speaker
Mixer
Discriminator
Limiter
1-29. What section of a frequency modulated receiver extracts the audiofrequency component of the
signal?
A.
B.
C.
D.
Speaker
Mixer
Discriminator
Limiter
1-30. How many antennas are used in the F/A-18 ARC-210 communication system?
A.
B.
C.
D.
2
3
4
5
1-31. How many ARC-210 receiver transmitters are used in the F/A-18?
A.
B.
C.
D.
2
3
4
5
1-32. What frequency in megahertz is the ARC-210 radio’s highest operating range?
A.
B.
C.
D.
117.975
155.975
173.975
399.945
1-33. How many preset channels are available in the ARC-210 fixed frequency mode?
A.
B.
C.
D.
10
15
20
25
1-34. Other than plain voice, what mode of communication is provided by the ARC-210 radio?
A.
B.
C.
D.
Anti-jam
Clear
Target
Jettison
1-22
1-35. What system provides a method of secure communication between the operator and a forward
air controller?
A.
B.
C.
D.
Analog
Manual
Digital
Automatic
1-36. What system provides the intercommunication amplifier-control with weapons audio?
A.
B.
C.
D.
Identification friend or foe
Landing gear
Stores management
Tactical Air Navigation
1-23
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1-24
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CHAPTER 2
NAVIGATION
The term navigation is defined as the process of directing
the movement of a craft from one point to another. Some
type of navigation has been in use since humans started to
venture away from their homes. Exactly how they managed
to find their way will remain a matter of conjecture, but some
of their methods are known. The Greeks used primitive
charts and a crude form of dead reckoning by using the sun
and the North Star to determine direction. Early explorers
created the astrolabe shown in Figure 2-1 to guide their
way. However, many of the early methods were extremely
inaccurate. Accurate navigation became a reality in the
early 1700s when the chronometer and sextant were
invented. These tools allowed explorers to travel even
greater distances from their homes.
LEARNING OBJECTIVES
When you have completed this chapter, you will be able to
do the following:
1. Describe some common navigational terms.
2. Recognize the various methods of navigation.
3. Describe the operating principles of airborne
navigation systems.
Figure 2-1 — Ancient astrolabe.
NAVIGATIONAL TERMS
Air navigation, unlike naval navigation, involves movements above the surface of the Earth. This
creates a set of conditions that make air navigation unique. For example, a ship can stop and resolve
any uncertainty of motion or wait for more favorable conditions if necessary; most types of aircraft, on
the other hand, must keep going. Therefore, air navigation methods and procedures must be done
quickly and accurately. Another obstacle that aircraft face is weather changes that affect visibility of
landmarks. However, advances in technology and improvements in aircraft avionics have made it less
complicated for aircrew to navigate during inclement weather.
There are certain terms that you must learn to understand navigation. Aircrew use these terms to
express and accomplish the practical aspects of air navigation. The following paragraphs define the
terms position, direction, distance, and time in relation to navigation.
Position
Position is a location defined by stated or implied coordinates. It always refers to some place that can
be identified. Aircrew must know the aircraft’s immediate position before they can direct it to another
position.
2-1
Direction
Direction is the position of one point in space relative to another without reference to the distance
between them. Direction is not in itself an angle, but it is measured in terms of its angular distance
from a reference direction.
Distance
Distance is the spatial separation between two points and is measured by the length of a line joining
them. This is a simple problem on a plane surface. However, consider distance on a sphere, where
the separation between points may be expressed as a variety of curves.
Time
Time is defined in many ways, but for air navigation purposes, it is either the hour of the day or an
elapsed interval.
The terms above represent definite quantities or
conditions that can be measured in several
different ways. For example, the position of an
aircraft may be expressed in coordinates such
as latitude and longitude, or as being 10 miles
south of a certain landmark.
EARTH’S SIZE AND SHAPE
For navigational purposes, the Earth (Figure 2-2)
is assumed to be a perfect sphere, although it is
not. There is an approximate 12-mile difference
between the highest point and the lowest point
of the Earth’s crust. The variations in the surface
(valleys, mountains, oceans, etc.) give the Earth
an irregular appearance.
Measured at the equator, the Earth is
approximately 6,887.91 nautical miles in
diameter. The polar diameter is approximately
6,864.57 nautical miles. This difference between
the two measurements is 23.34 nautical miles.
This measurement may be used to express the
ellipticity of the Earth.
Figure 2-2 — View of the Earth.
Great Circles and Small Circles
The intersection of a sphere and a plane is a circle. If the intersection of the plane passes through the
center of the sphere, it is a great circle. If it does not, then it is defined as a small circle. The arc of a
great circle is the shortest distance between two points on a sphere, just as a straight line is the
shortest distance between two points on a plane. On any sphere, an infinite number of great circles
may be drawn through any point, though only one great circle may be drawn through any two points
that are not diametrically opposite. An example of great and small circles is shown in Figure 2-3.
Circles on the surface of the sphere other than great circles are small circles. On the surface of the
Earth, as on any sphere, a small circle is a circle whose center and/or radius are not that of the
2-2
sphere. Special sets of small circles, called latitude and longitude,
are discussed in the next paragraph.
Latitude and Longitude
The nature of a sphere is such that any point on it is exactly like any
other point. There is neither a beginning nor an ending as far as
differentiation of points is concerned. Points and lines of reference
are necessary so that locations may be identified on the Earth. The
location of New York City with reference to Washington, DC, is
stated as a number of miles in a certain direction (north, south, east,
and west) from Washington, DC. Any point on the Earth can be
located the same way based on this system.
This system does not work easily for navigation purposes. For
example, a point could not be precisely located in the mid-Pacific
Ocean without any nearby geographic features to use as a
reference. That is why a system of imaginary reference lines is used
to locate any point on Earth. These reference lines are the parallels
of latitude and the meridians of longitude.
Latitude
Each day the Earth rotates once on its north-south axis. This axis
terminates at the two poles. The equator is constructed at the
midpoint of this axis at right angles to it. A great circle drawn through
the poles is called a meridian, and an infinite number of great circles
maybe constructed in this manner. Each meridian is divided into four
quadrants by the equator and the poles. Because a circle is divided
into 360 degrees, each of the four quadrants encompasses 90
degrees.
Take a point on one of these meridians 30 degrees north of the
equator. Through this point passes a plane perpendicular to the
north-south axis. This plane will be parallel to the plane of the
equator, as shown in Figure 2-4, and will intersect the Earth in a
small circle called a parallel or parallel of latitude. This particular
parallel of latitude is called 30 degrees north and every point on this
parallel will be at 30 degrees north. Parallels can be constructed at
any desired latitude.
Figure 2-3 — Great circle is
the largest circle in a
sphere.
The equator is the great circle midway between the poles. The parallels of latitude are small circles
constructed with reference to the equator. The angular distance measured on a meridian north or
south of the equator is known as latitude and forms one component of the coordinate system.
Longitude
The latitude of a point can be shown as 20 degrees north or 20 degrees south of the equator, but
there is no way of determining whether one point is east or west of another. This is resolved by the
use of the other component of the coordinate system, longitude. Longitude is the measurement of the
east-west distance.
Unlike latitude, longitude has no natural starting point. The only way that this problem could be solved
was by selecting an arbitrary starting point. Many places had been used in the past, but when the
2-3
English speaking people
started to make charts,
they chose the meridian
through their principal
observatory in Greenwich,
England. This meridian
has now been adopted by
most of the world as the
official starting point to
calculate longitude.
Greenwich meridian,
sometimes called the
prime meridian or first
meridian, is the 0 meridian.
Longitude is counted east
or west from this meridian
through 180 degrees
beginning at the prime
meridian.
Figure 2-4 — Planes of the Earth.
Therefore, the Greenwich meridian is the 0-degree
meridian on one side of the Earth and, after
crossing the poles, the 180th meridian on the
opposite side (180 degrees east or west of the 0degree meridian).
If a globe has the circles of latitude and longitude
drawn on it according to the principles described,
and the latitude and longitude of a certain place
has been determined, this point can be located on
the globe in its proper position (Figure 2-5). In this
way, a globe can be formed that resembles a
small-scale copy of the Earth.
Latitude is measured in degrees up to 90, and
longitude is measured in degrees up to 180. The
total number of degrees in any one circle cannot
exceed 360. A degree of arc may be subdivided
into smaller units by dividing each degree into 60
minutes (′) of arc. Each minute can be further
divided into 60 seconds (″) of arc. Measurements
may also be made in units as small as thousandths
of minutes if it is required.
Figure 2-5 — Latitude is measured from the
equator; longitude from the prime meridian.
Distance
Distance as previously defined is measured by the length of a line joining two points. In navigation,
the most common unit for measuring distance is the nautical mile. All of the following units can be
used interchangeably as the equivalent of 1 nautical mile:
•
6,076.10 feet (nautical mile)
•
1′ of arc of a great circle on a sphere having an area equal to that of the Earth
2-4
•
6,087.08 feet (geographic mile)
•
1′ of arc on a meridian (1′ of latitude)
•
2,000 yards (for short distances)
It is sometimes necessary to convert nautical miles into statute miles or statute miles into nautical
miles. This conversion is made with the following ratio:
𝐍𝐍𝐍𝐍𝐍𝐍𝐍𝐍𝐍𝐍𝐍𝐍𝐍𝐍𝐍𝐍 𝐦𝐦𝐦𝐦𝐦𝐦𝐦𝐦
𝟔𝟔, 𝟎𝟎𝟎𝟎𝟎𝟎 𝐟𝐟𝐟𝐟
=
= 𝟏𝟏. 𝟏𝟏𝟏𝟏
𝐒𝐒𝐒𝐒𝐒𝐒𝐒𝐒𝐒𝐒𝐒𝐒𝐒𝐒 𝐦𝐦𝐦𝐦𝐦𝐦𝐦𝐦
𝟓𝟓, 𝟐𝟐𝟐𝟐𝟐𝟐 𝐟𝐟𝐟𝐟
The rate of change of position is determined by speed. Speed is expressed in miles per hour either
statute miles or nautical miles. A knot is 1 nautical mile per hour (1 knot is equal to 1.15 statute miles
per hour). Therefore, a speed of 200 nautical miles per hour and a speed of 200 knots are the same.
Note that the phrase “200 knots per hour” is incorrect unless referring to acceleration.
Direction
Direction is the position of one point in space
relative to another without reference to the
distance between them. The time-honored
system for specifying direction (north, south,
east, and west) does not meet the needs of
modern navigation. Therefore, a numerical
system is used to meet navigational needs. The
numerical system (Figure 2-6) divides the
horizon into 360 degrees, starting with north as
000 degrees. Going clockwise, east is 090
degrees, south 180 degrees, west 270 degrees,
and back to north.
The circle, called a compass rose, represents the
horizon divided into 360 degrees. The nearly
vertical lines represent the meridians, with the
meridian of position “A” passing through 000
degrees and 180 degrees. Position “B” lies at a
true direction of 062 degrees from “A,” and
position “C” is at a true direction of 295 degrees
from “A.”
Figure 2-6 — Numerical system used in air
navigation.
Determination of direction is one of the most important parts of air navigation. Therefore, the terms
involved must be clearly understood. Generally in navigation, unless otherwise stated, all directions
are called true directions.
•
Course is the intended horizontal direction of travel.
•
Heading is the horizontal direction in which an aircraft is pointed.
•
Track is the actual horizontal direction made by the aircraft over the Earth.
•
Bearing is the horizontal direction of one point to another. The direction from the aircraft to
some point on the Earth’s surface is marked by the line of sight (visual bearing). Bearings are
usually expressed in terms of one of two reference directions: (1) true north, or (2) the direction
in which the aircraft is pointed. If true north is being used as the reference, the bearing is called
2-5
a true bearing. If the heading of the aircraft is the reference, the bearing is called a relative
bearing (Figure 2-7).
Figure 2-7 — Measuring relative bearing.
Altitude and Atmosphere
A basic understanding of altitude is required to understand how the various types of altimeters
(instruments used to measure altitude). Altitude is defined as the vertical distance of a level, a point,
or an object measured from a given surface. Knowing the aircraft’s altitude is imperative for terrain
clearance, aircraft separation, and a multitude of operational reasons.
Standard Datum Plane
The standard datum plane is a theoretical plane where the atmospheric pressure is 29.92 inches of
mercury (Hg) and the temperature is 15 degrees Celsius (°C) or 59 degrees Fahrenheit (°F). The
standard datum plane is the zero-elevation level of an imaginary atmosphere known as the standard
atmosphere. In the standard atmosphere, pressure is at 29.92 Hg at 0 feet, and decreases upward at
the standard pressure lapse rate. The temperature is 15 °C at 0 feet, and also decreases upward but
at the standard temperature lapse rate. Standard lapse rates are shown in Table 2-1.
2-6
Table 2-1 — Standard Lapse Rates
Temperature
Standard
Altitude (ft)
Pressure (Hg) (°C)
(°F)
0
29.92
15.0
59.0
1,000
28.86
13.0
55.4
2,000
27.82
11.0
51.9
3,000
26.82
9.1
48.3
4,000
25.84
7.1
44.7
5,000
24.89
5.1
41.2
6,000
23.98
3.1
37.6
7,000
23.09
1.1
34.0
8,000
22.22
-0.9
30.5
9,000
21.38
-2.8
26.9
10,000
20.57
-4.8
23.3
11,000
19.79
-6.8
19.8
12,000
19.02
-8.8
16.2
13,000
18.29
-10.8
12.6
14,000
17.57
-12.7
9.1
15,000
16.88
-14.7
5.5
16,000
16.21
-16.7
1.9
17,000
15.56
-18.7
-1.6
18,000
14.94
-20.7
-5.2
19,000
14.33
-22.6
-8.8
20,000
13.74
-24.6
-12.3
21,000
13.18
-26.6
-15.9
22,000
12.64
-28.6
-19.5
23,000
12.11
-30.6
-23.0
24,000
11.60
-32.5
-26.6
25,000
11.10
-34.5
-30.2
26,000
10.63
-36.5
-33.7
27,000
10.17
-38.5
-37.3
28,000
9.72
-40.5
-40.9
29,000
9.30
-42.5
-44.4
30,000
8.89
-44.4
-48.0
The standard atmosphere is theoretical. It was derived by averaging the readings taken over a period
of years. The list of altitudes and their corresponding values of temperature and pressure given in
Table 2-1 were determined by these averages.
2-7
Planes of Altitude
There are as many kinds of altitudes as there are reference planes from which to measure them. Only
six of these planes concern the navigator. They are indicated altitude, calibrated altitude, pressure
altitude, density altitude, true altitude, and absolute altitude. Examples of the types of altitude are
shown in Figure 2-8.
•
Indicated altitude is the value of altitude that is displayed on the pressure altimeter.
•
Calibrated altitude is indicated altitude corrected for installation/positional error.
•
Pressure altitude is the height of the aircraft above the standard datum plane.
•
Density altitude is the pressure altitude corrected for temperature. Density altitude is used in
performance data and true airspeed calculations.
•
True altitude is the actual vertical distance above mean sea level, measured in feet. It can be
determined by two methods:
1. Set the local altimeter setting on the barometric scale of the pressure altimeter to obtain
the indicated true altitude.
2. Measure altitude over water with an absolute altimeter.
•
Absolute altitude is the height above the terrain. It is computed by subtracting terrain elevation
from true altitude, or it can be read directly from an absolute altimeter.
Figure 2-8 — Types of altitude.
Altimeters
There are two main altimeters used in aircraft. They are the pressure altimeter and the absolute
(radar) altimeter.
2-8
Pressure Altimeter
The pressure altimeter is an aneroid barometer calibrated to indicate feet of altitude instead of
pressure. The pointers are connected by a mechanical linkage to a set of aneroid cells. Aneroid cells
expand or contract with changes in barometric pressure. The cells assume a particular thickness at a
given pressure level, and thereby position the altitude pointers accordingly. On the face of the
indicator is a barometric scale that indicates the barometric pressure of the point or plane from which
the instrument is measuring altitude. If you turn the barometric pressure set knob on the altimeter, it
manually changes the setting on the scale. In addition, adjusting the knob results in the simultaneous
movement of the pointers to the corresponding altitude reading.
Like all measurements, an altitude reading is meaningless if the reference point is unknown. The
pressure altimeter face supplies both values. The pointer position indicates the altitude in feet, and
the barometric scale indicates the pressure of the reference plane.
There are two different types of pressure
altimeters used in naval aircraft. They are the
counter-pointer and the counter-drum-pointer
altimeters.
•
•
A counter-pointer altimeter (Figure 2-9)
has a two-digit counter display, which
indicates altitude in 1,000-foot increments
from 0 to 80,000 feet. A single
conventional pointer indicates hundreds of
feet on the fixed circular scale. The pointer
makes one revolution per 1,000 feet of
altitude, and as it passes through the 900to 1,000-foot area of the dial, the 1,000foot counter is actuated. The shaft of the
1,000-foot counter actuates the 10,000foot counter at each 10,000 feet of altitude
change. To determine the indicated
altitude, you read the 1,000-foot counter
and then add the 100-foot pointer
indication.
Figure 2-9 — Counter-pointer altimeter.
A counter-drum-pointer altimeter is different from the counter-pointer altimeter because of the
addition of a 100-foot drum. The drum follows the 100-foot pointer and actuates the 1,000-foot
counter. In this way it prevents the reading error when the 1,000-foot counter switches.
There are five categories of errors relating to pressure altimeters. They are the mechanical error,
scale error, installation/position error, reversal error, and hysteresis error.
•
Mechanical error is caused by misalignments in gears and levers that transmit the aneroid cell
expansion and contraction to the pointers of the altimeter. This error is not constant, and it
must be checked before each flight by the setting procedure.
•
Scale error is caused by irregular expansion of the aneroid cells. It is recorded on a scale
correction card maintained for each altimeter in the instrument maintenance shop.
•
Installation/Position error is caused by the airflow around the static ports. This error varies with
the type of aircraft, airspeed, and altitude. The magnitude and direction of this error can be
determined by referring to the performance data section in the aircraft Naval Air Training and
Operating Procedures Standardization (NATOPS) manual.
2-9
NOTE
An altimeter correction card is installed in some aircraft that
combines the installation/position and scale errors. The
card shows the amount of correction needed at different
altitudes and airspeeds.
•
Reversal error is caused by inducing false static pressure into the system. This normally
occurs during abrupt or huge pitch changes. This error appears on the altimeter as a
momentary indication in the opposite direction.
•
Hysteresis error is a lag in altitude indication due to the elastic properties of the material within
the altimeter. This occurs after an aircraft has maintained a constant altitude for an extended
period of time and then makes a large, rapid altitude change. After a rapid descent, altimeter
readings are higher than actual. This error is negligible during slow climbs and descents or
after maintaining a new altitude for a short period of time.
Absolute (Radar) Altimeter
Accurate absolute altitude is important for
navigation, bombing, and close air support
missions. Absolute altitude can be computed
from the pressure altimeter readings, but the
results are often inaccurate. Under changing
atmospheric conditions, corrections applied to
pressure altimeter readings to obtain true
altitudes are only approximate. In addition, any
errors made in determining the terrain elevation
will result in a corresponding error in the
absolute altitude.
An aircraft radar altimeter uses pulsed rangetracking radiofrequency (RF) energy that
measures the surface of terrain clearance
below the aircraft. Typical radar altimeter
systems consist of a receiver-transmitter,
transmit/receive antennas, cockpit height
indicator (Figure 2-10), and interference blanker
system. The interference blanker system sends
blanking RF pulses that allow the radar
altimeter to operate without interfering with
other avionics systems.
Figure 2-10 — Typical cockpit height indicator.
Radar altimeters are reliable in the altitude range of 0 to 5,000 feet. Radar altimeters develop
information by radiating a short duration RF pulse from a transmit antenna and measuring the time
interval it takes to receive the reflected signal. The altitude information is then continuously sent to the
height indicator in feet of altitude. The height indicator is disabled when the aircraft is above 5,000
feet. When the aircraft is on the ground, the system is disabled by the aircraft weight-on-wheels
switch. An example of a radar altimeter transmit and receive cycle is shown in Figure 2-11.
2-10
Interaction Available
Figure 2-11 — Typical radar altimeter system in operation.
AIRBORNE NAVIGATION SYSTEMS
Airborne navigation systems can be self-contained units or ground-referenced units. A self-contained
unit is complete and does not depend on transmissions from a ground station. A ground-referenced
unit requires a transmission from an outside source, such as a ground station. Both types aid aircrew
in completing their mission safely and efficiently. The following navigation systems will be discussed:
automatic direction finder (ADF), Tactical Air Navigation (TACAN), global positioning system (GPS),
and inertial navigation system (INS).
Automatic Direction Finder
The ADF system is used to provide a bearing to a selected station. This system is primarily used
when other navigation methods have failed. A typical ADF system uses a specific frequency band to
transmit and receive bearing signals from a station. The data received from the ADF is processed by
computer systems and displayed on aircraft navigational equipment. In some cases, the ADF system
is an operational mode of aircraft radio communication systems.
Tactical Air Navigation
The TACAN system is a polar coordinate type radio air-navigation system that provides an aircrew
with distance information, obtained from distance measuring equipment (DME), and bearing
(azimuth) information. Aircrew can obtain navigational data from other TACAN-capable aircraft, ships,
or shore stations.
2-11
TACAN Principles
A TACAN system uses proven radar-ranging techniques to determine distance by measuring the
round-trip travel of pulsed-RF energy. The strength of a radar return signal normally depends on the
natural reflection of the radio waves. However, TACAN beacon-transponders can generate artificial
replies instead of depending on the natural reflection of radio waves. A typical TACAN system uses
126 two-way operating channels in 962 to 1213 megahertz (MHz) frequency range. Each of the
operating channels uses separate frequencies when transmitting or receiving.
TACAN Pulse-Pairs
A TACAN system uses twin pulse-pairs to communicate between receivers and transponders. The
twin pulse-pairs increase the average radiation power and reduce the possibility of transmitting false
signals.
Bearing and Distance Information
The timing of the transmitted pulses supplies the actual distance information to the aircraft. The
TACAN beacon-transponder modulates the strength of the pulse to convey bearing information by
producing a specific directional-radiating pattern around a vertical axis. This signal, when properly
referenced, indicates the aircraft’s direction from the TACAN facility. The signal and distance data
give the aircraft a two-piece fix (distance and direction) for determining specific aircraft location.
Radiation Pattern
Ground stations (Figure 2-12) or
ships feed RF energy to a central
antenna element, which does not
have any directivity in the
horizontal plane. The parasitic
(conductive) elements positioned
around the central element are
switched on and off (electronically)
at a rate of 15 revolutions per
second (900 revolutions per
minute). This process creates a
15-hertz (HZ) amplitudemodulated signal.
The aircraft TACAN equipment
obtains bearing information by
comparing the 15 Hz modulated
signal with a 15 Hz reference burst
signal it receives from the ground
facility. The phase relationship
Figure 2-12 — Typical TACAN ground station antenna.
between the 15 Hz modulated
signal and the 15 Hz reference
burst signal depends on the location of the aircraft. In addition, 32 outer parasitic antennas are added
to the electronically scanned antenna to reduce site error. When the 32 antennas are switched on
and off (electronically), a 135 Hz signal, known as the auxiliary reference burst, is created.
A composite TACAN signal is composed of 2,700 interrogation replies and noise pulse-pairs-persecond. The composite signal also includes 180 north burst pulse-pairs and 720 auxiliary-burst-pulsepairs for a total of 3,600 pulse-pairs-per-second.
2-12
Global Positioning System
An unlimited number of users can use GPS because it is a space-based radio navigation system that
provides continuous, all-weather, passive operation anywhere in the world. The Department of
Defense uses a GPS that was designed for and operated by the U.S. military. Three major
segments—space, control, and user—make up GPS.
Space Segment
The GPS satellite constellation consists of 21 operational and 3 spare satellites, positioned
approximately 12,550 miles high in a semi-synchronous orbit around the Earth. The satellites are in
six orbital planes with three or four operational satellites in each plane. There are a minimum of four
satellites observable from anywhere in the world. A basic GPS network is shown in Figure 2-13.
Figure 2-13 — Basic GPS network.
Satellites transmit two GPS carrier frequencies that are commonly referred to as L1 and L2. Both
signals contain codes that provide positioning, timing, and navigation data. The L1 carrier signal
operates in 1575.42 MHz frequency range and the L2 carrier signal operates in the 1227.6 MHz
range. L1 and L2 carrier signals are used to transmit position, velocity, and time (PVT) signals for use
by compatible equipment.
The L1 and L2 carrier frequencies are transmitted from the satellites using the spread spectrum
technique. The spread spectrum technique increases the availability of the signals and improves the
resistance against jamming and natural interference. There L1 and L2 carrier frequencies transmit
two codes: course acquisition (C/A) and precise (P). C/A codes are available to both civilian and
military users. P code use is currently restricted to military and other users determined by the
Department of Defense.
2-13
Control Segment
This segment is made up of a master control station and a number of separate monitor stations
located around the world. The master control station is responsible for tracking, monitoring, and
managing the satellite constellation. The master control station is also responsible for updating
navigation data messages.
User Segment
The user segment of GPS is the equipment used to receive, decode, and process PVT information.
Aircraft GPS
Satellites in the GPS constellation transmit a one-way (listen only) signal. Aircraft must have specific
components installed to use this signal and the associated navigation data. Typical GPS installed in
an aircraft consists of the following components:
•
A GPS receiver determines distance to a satellite by measuring the time difference between
the time the satellite transmits the signal and the time GPS receives the signal. The time that is
received is determined by the GPS clock. If the GPS clock is not perfectly synchronized with
the satellite clock, the time measurement is inaccurate. A GPS receiver can be initialized with
crypto keys enabling it to receive highly accurate anti-spoofing and precise navigation signals.
•
A GPS antenna (Figure 2-14) is normally
mounted on the aircraft’s upper fuselage
surface. Mounting the antenna in this
area improves RF signal reception. The
purpose of the GPS antenna is to
provide RF navigation signals to the
GPS receiver.
The RF cable assemblies connect the
GPS antenna to the receiver.
Assemblies consist of coaxial cables that
normally have a frequency range of 1 to
1.6 gigahertz (GHz).
The keyfill panels are used to input
cryptological keys into the GPS receiver
that allow access to highly accurate,
precise navigation signals.
•
•
Figure 2-14 — Typical GPS antenna mounting.
Inertial Navigation System
An INS is a self-contained, electronic, all-altitude navigation system with host aircraft interface. It
transmits navigational outputs when requested to the aircraft. The INS detects aircraft motion and
provides acceleration, velocity, present position, pitch, roll, and true heading data. In addition, INS
uses dead reckoning to provide accurate position navigation. Dead reckoning is the process of
estimating present position from known information. A typical inertial navigation unit (INU) is shown in
Figure 2-15.
Basic Components
The INS continuously measures aircraft accelerations to compute aircraft velocity and change in
present position. These measurements are made by precision inertial devices mounted on a three2-14
axis stable element, which is
part of a four-gimbal structure.
The four-gimbal structure allows
the stable element to move with
360 degrees of freedom about
the three axes.
Two gyros provide gimbal
stabilization signals to maintain
the stable element level with the
Earth’s surface and aligned to
true north. The system uses
these signals to measure aircraft
pitch-and-roll attitudes. The
inertial characteristics of the
gyroscopes used in the system
define and maintain the
reference axes for relatively long
periods with great accuracy.
Gyroscopes are mechanical
devices that contain a spinning
mass (gyro) that is universally
mounted (by gimbals) allowing it
to assume any position in space.
With a gyrostabilized platform as
a reference, it is possible to
accurately detect components of
motion in any direction. To do
this, precision accelerometers
and analog or digital computers
are used in an INS.
Figure 2-15 — Typical inertial navigation unit.
Accelerometers
The primary data source for the INS is the accelerometer. An accelerometer is a device used to
produce a voltage proportional to the acceleration input. Three accelerometers are mounted on the
stable element between the gyros. They provide output signals proportional to total accelerations
experienced along the three axes of the stable element. The system uses these accelerations to
produce aircraft velocities and changes in position.
By mounting three accelerometers on a stable element, the platform “X” (east and west), “Y” (north
and south), and “Z” (up and down) velocities are continually measured. The “X” and “Y” velocities are
also resolved into the north and east velocities by using aircraft heading. The combination of these
velocities gives the change in latitude and longitude from the last known position.
Inertial Corrections
In a space-stabilized system, the platform appears to rotate as the Earth turns on its axis. In addition,
the platform would not remain level to the vertical as the aircraft moves over the surface of the Earth.
To overpower these appearing gyro precessions as the aircraft travels and the Earth rotates, the
platform must be torqued so that it remains normal (perpendicular) to the Earth surface. Earth rate
converts space-stable INS to a geographical-stable (Earth-oriented) system. Gyro-torquing
2-15
computations are made as a function of time and distance traveled. The gyro-torquing computations
(corrections) are described below:
•
The alpha angle is the angular difference between the platform heading and true north. Alpha
angle is used as a gyro-torquing correction factor during alignment and navigation.
•
Earth rate correction is used to maintain the platform heading alignment and level in order to
allow accelerometers to sense aircraft acceleration only.
•
Schuler loop mechanization is used to prevent the aircraft acceleration from causing an
oscillation in the INU platform. Schuler loop correction is used as a gyro-torquing correction
factor during navigation.
•
Centripetal force is a true acceleration sensed by accelerometers because the Earth and its
atmosphere are moving with respect to inertial space. Centripetal force correction is made by
correcting the difference between centripetal force, aircraft velocity, and position.
•
The Coriolis force is a false acceleration caused by the Earth rotating around its polar axis as
related to inertial space. Coriolis force acceleration correction is required to keep the platform
level to the Earth.
Alignment
The process of INS alignment uses a statistical estimation known as Kalman filtering. The platform
outputs and reference data are compared to external reference data inputs. Kalman filtering
estimates the errors in the compared data to correct platform heading, velocity, and attitude.
•
A ground alignment (Figure 2-16) analyzes position data (latitude and longitude) manually
entered into the aircraft.
o A carrier alignment uses the ship’s inertial navigation system (SINS) to provide the
aircraft with reference data (ship’s velocity, position, and attitude). Carrier aircraft
receive updated position information from either a SINS cable or an aircraft data link. A
Figure 2-16 — Typical ground alignment cockpit display.
2-16
SINS cable can be connected from a deck edge receptacle on the ship to a receptacle
on the aircraft to receive updated reference data.
•
o The aircraft data link uses electronic methods to receive updated reference information
from the SINS.
An inflight alignment (Figure 2-17) uses inputs and reference data from avionics systems to
either preserve an existing alignment or to start a new alignment. During the alignment, air
data dead reckoning is used for navigation and for maintaining the current existing position.
Figure 2-17 — Typical inflight alignment cockpit display.
2-17
End of Chapter 2
Navigation
Review Questions
2-1.
What navigational term is defined as one point in space relative to another, without reference
to distance?
A.
B.
C.
D.
2-2.
What navigational term is defined as the spatial separation between two points measured by a
line?
A.
B.
C.
D.
2-3.
20.25
21.75
22.36
23.34
What geographic location is the official starting point to calculate longitude?
A.
B.
C.
D.
2-6.
12
14
16
18
The ellipticity of Earth can be expressed in how many nautical miles?
A.
B.
C.
D.
2-5.
Position
Direction
Distance
Time
How many miles is the approximate distance between the highest and lowest point of the
Earth?
A.
B.
C.
D.
2-4.
Position
Direction
Distance
Time
London, England
Leeds, England
Greenwich, England
Wisbech, England
One knot is equal to how many statute miles per hour?
A.
B.
C.
D.
0.75
1.15
1.25
1.75
2-18
2-7.
What true direction is defined as the intended horizontal direction of travel?
A.
B.
C.
D.
2-8.
What altitude reference plane is the height of the aircraft above the standard datum plane?
A.
B.
C.
D.
2-9.
Bearing
Track
Heading
Course
Pressure
Indicated
Density
Calibrated
What type of cell is connected to mechanical linkage inside pressure altimeters?
A.
B.
C.
D.
Anode
Aerate
Aneroid
Android
2-10. What pressure altimeter error is caused by misalignments in gears and levers?
A.
B.
C.
D.
Reversal
Scale
Hysteresis
Mechanical
2-11. What pressure altimeter error is caused by inducing false static pressure into the system?
A.
B.
C.
D.
Reversal
Scale
Hysteresis
Mechanical
2-12. What type of altimeter uses radio frequency pulses to measure aircraft height?
A.
B.
C.
D.
Static
Pressure
Absolute
Pitot
2-13. What airborne navigation system uses polar coordinate type radio signals?
A.
B.
C.
D.
Automatic direction finder
Tactical Air Navigation
Global positioning
Inertial navigation
2-19
2-14. What signal, in hertz, does the Tactical Air Navigation system use to obtain bearing
information?
A.
B.
C.
D.
5
11
15
19
2-15. What segment of the global positioning system consists of satellite monitoring stations?
A.
B.
C.
D.
Space
User
Carrier
Control
2-16. The global positioning system L1 carrier signal operates in what megahertz frequency?
A.
B.
C.
D.
1227.61
1424.82
1575.42
1610.71
2-17. What global positioning system carrier signal operates in the 1227.6 megahertz range?
A.
B.
C.
D.
L1
L2
L3
L4
2-18. What aircraft characteristic is continually measured by the inertial navigation system?
A.
B.
C.
D.
Altitude
Speed
Acceleration
Attitude
2-19. What components are the inertial navigation system’s main sources of data?
A.
B.
C.
D.
Accelerometers
Gyros
Gimbals
Servos
2-20. What mode of inertial alignment is initiated by manually entering positon data?
A.
B.
C.
D.
Carrier
Inflight
Ground
Composite
2-20
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2-21
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CHAPTER 3
RADAR
Radio detection and ranging (radar) systems are one of the most important offensive and defensive
tools used in tactical aircraft. Modern radar systems provide the operator with the enhanced ability to
detect, track, and intercept hostile air and surface targets. Organizational aviation electronics
technicians (AT) will operate, troubleshoot, and repair complex radar systems. Therefore, a basic
understanding of the principles and components of radar systems is important to complete the tasks.
This chapter will provide an overview of the basic concepts, principles, and components of a typical
radar set. The radar used in the Fighter/Attack (F/A)-18 series, Multi-Mission Helicopter (MH)-60R,
and the Patrol (P)-3 Orion platforms will be provided as examples of the systems being used in the
fleet. In addition, because they are normally integrated with radar systems, the basic principles and
the components used in Identification Friend or Foe (IFF) systems will be described.
LEARNING OBJECTIVES
When you have completed this chapter, you will be able to do the following:
1.
Describe the basic operating principles of a radar system.
2.
Recognize the basic components used in typical radar systems.
3.
Describe the types of typical radar systems.
4.
Identify the components of the APG-73 radar system.
5.
Describe the operating principles of the APG-73 radar system.
6.
Identify the components of the multi-mode radar (MMR) system.
7.
Describe the operating principles of the MMR system.
8.
Identify the components of the APN-234 color weather radar system.
9.
Describe the operating principles of the APN-234 color weather radar system.
10.
Identify the components of a typical IFF system.
11.
Describe the operating principles of a typical IFF system.
12.
Identify the components of the APX-123(V) IFF system.
13.
Describe the operating principles of the APX-123(V) IFF system.
BASIC RADAR PRINCIPLES AND OPERATION
Radar systems operate using a concept that is very similar to hearing an echo reflecting off of a
surface (cave, canyon, etc.). The distance and the general direction of the object can be determined
because the speed of sound in the air is a known quantity. Radar systems use a similar theory to
determine the direction and distance to a target. However, radar systems use radiofrequency (RF)
energy instead of sound waves. A typical radar system in operation is shown in Figure 3-1. The
following basic radar operating principles will be discussed in this section:
•
Range
•
Bearing
•
Resolution
3-1
•
Accuracy
Interaction Available
Figure 3-1 — Typical radar system in operation.
Range
A radar system can measure the range (distance) to a target because RF energy travels through
space in a straight line at a constant speed (186,000 statute miles or 162,000 nautical miles per
second). There are some standard measurements to consider before the range to a target can be
determined. The Navy uses nautical miles to measure standard distances. The distance of 1 nautical
mile is about 6,080 feet in comparison to 1 statute mile, which is about 5,280 feet. Standard timing in
radar systems is expressed in microseconds (µs). Therefore, transmitted RF energy travels at a
constant speed of approximately 984 feet per µs. The time that it takes for RF energy to travel 1
nautical mile, using the information above, can be calculated by using the following formula:
𝟔𝟔, 𝟎𝟎𝟎𝟎𝟎𝟎 𝐟𝐟𝐟𝐟𝐟𝐟𝐟𝐟
= 𝟔𝟔. 𝟏𝟏𝟏𝟏 µ𝐬𝐬
𝟗𝟗𝟗𝟗𝟒𝟒 𝐟𝐟𝐟𝐟𝐟𝐟𝐟𝐟 𝐩𝐩𝐩𝐩𝐩𝐩 µ𝐬𝐬
Further calculations are required because a radar system determines the range to a target by
measuring the elapsed time it takes for the RF energy to travel to a target and return to the
transmission medium. This is easily accomplished by using the following formula:
𝟔𝟔. 𝟏𝟏𝟏𝟏 µ𝐬𝐬 × 𝟐𝟐 (𝐑𝐑𝐑𝐑 𝐩𝐩𝐩𝐩𝐩𝐩𝐩𝐩𝐩𝐩 𝐨𝐨𝐨𝐨𝐨𝐨 𝐚𝐚𝐚𝐚𝐚𝐚 𝐑𝐑𝐑𝐑 𝐩𝐩𝐩𝐩𝐩𝐩𝐩𝐩𝐩𝐩 𝐛𝐛𝐛𝐛𝐛𝐛𝐛𝐛) = 𝟏𝟏𝟏𝟏. 𝟑𝟑𝟑𝟑 µ𝐬𝐬
3-2
The resulting 12.36 µs time interval is known as a radar mile or nautical radar mile. The range to a
target can now be calculated by measuring the elapsed time it takes for a radar pulse to travel round
trip then dividing it by 12.36 µs. The formula is as follows:
𝐑𝐑𝐑𝐑𝐑𝐑𝐑𝐑𝐑𝐑 =
𝐄𝐄𝐄𝐄𝐄𝐄𝐄𝐄𝐄𝐄𝐄𝐄𝐄𝐄 𝐭𝐭𝐭𝐭𝐭𝐭𝐭𝐭
𝟏𝟏𝟏𝟏. 𝟑𝟑𝟑𝟑 µ𝐬𝐬 𝐩𝐩𝐩𝐩𝐩𝐩 𝐧𝐧𝐧𝐧𝐧𝐧𝐧𝐧𝐧𝐧𝐧𝐧𝐧𝐧𝐧𝐧 𝐦𝐦𝐦𝐦𝐦𝐦𝐦𝐦
To further clarify this concept, an example of determining the range to a target is given below:
𝐑𝐑𝐑𝐑𝐑𝐑𝐑𝐑𝐑𝐑 =
𝟔𝟔𝟔𝟔 µ𝐬𝐬
= 𝟓𝟓 𝐧𝐧𝐧𝐧𝐧𝐧𝐧𝐧𝐧𝐧𝐧𝐧𝐧𝐧𝐧𝐧 𝐦𝐦𝐦𝐦𝐦𝐦𝐦𝐦𝐦𝐦
𝟏𝟏𝟏𝟏. 𝟑𝟑𝟑𝟑 µ𝐬𝐬 𝐩𝐩𝐩𝐩𝐩𝐩 𝐧𝐧𝐧𝐧𝐧𝐧𝐧𝐧𝐧𝐧𝐧𝐧𝐧𝐧𝐧𝐧 𝐦𝐦𝐦𝐦𝐦𝐦𝐦𝐦
Based on the above calculation, the target is approximately 5 nautical miles away from the radar
system.
Minimum Range
The minimum range of a radar system is dependent on timing, pulse width, and recovery time.
Minimum range can be calculated using the following formula:
𝐌𝐌𝐌𝐌𝐌𝐌𝐌𝐌𝐌𝐌𝐌𝐌𝐌𝐌 𝐫𝐫𝐫𝐫𝐫𝐫𝐫𝐫𝐫𝐫 = (𝐩𝐩𝐩𝐩𝐩𝐩𝐩𝐩𝐩𝐩 𝐰𝐰𝐰𝐰𝐰𝐰𝐰𝐰𝐰𝐰 + 𝐫𝐫𝐫𝐫𝐫𝐫𝐫𝐫𝐫𝐫𝐫𝐫𝐫𝐫𝐫𝐫 𝐭𝐭𝐢𝐢𝐦𝐦𝐦𝐦) × 𝟏𝟏𝟏𝟏𝟏𝟏 𝐲𝐲𝐲𝐲𝐲𝐲𝐲𝐲𝐲𝐲
Below is an example of using this formula to calculate a radar system’s minimum range:
𝐌𝐌𝐌𝐌𝐌𝐌𝐌𝐌𝐌𝐌𝐌𝐌𝐌𝐌 𝐫𝐫𝐫𝐫𝐫𝐫𝐫𝐫𝐫𝐫 = (𝟐𝟐𝟐𝟐 + 𝟎𝟎. 𝟏𝟏) × 𝟏𝟏𝟏𝟏𝟏𝟏 𝐲𝐲𝐲𝐲𝐲𝐲𝐲𝐲𝐲𝐲
= 𝟐𝟐𝟐𝟐. 𝟏𝟏 × 𝟏𝟏𝟏𝟏𝟏𝟏 𝐲𝐲𝐲𝐲𝐲𝐲𝐲𝐲𝐲𝐲
= 𝟒𝟒, 𝟏𝟏𝟏𝟏𝟏𝟏 𝐲𝐲𝐲𝐲𝐲𝐲𝐲𝐲𝐲𝐲 (𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚𝐚)
Maximum Range
The maximum range of a radar system is dependent on the signal carrier frequency, peak power of
the transmitted pulse, pulse repetition frequency (PRF), and the sensitivity of the receiver. The carried
frequency is the actual frequency of the transmitted RF energy. The PRF is the primary limiting factor
in determining the maximum range of a radar system. The timing between one pulse and the other is
called pulse repetition time (PRT). The PRT is equal to the reciprocal of the PRF:
𝟏𝟏
𝐏𝐏𝐏𝐏𝐏𝐏
There are outside limiting factors that can affect the maximum range of a radar system such as
atmospheric conditions. These factors can make it difficult to determine the maximum range of a
radar system. However, it is possible to determine the maximum theoretical range of a radar system
operating in optimal conditions by using the following formula:
𝐏𝐏𝐏𝐏𝐏𝐏 =
Bearing
𝐌𝐌𝐌𝐌𝐌𝐌𝐌𝐌𝐌𝐌𝐌𝐌𝐌𝐌 𝐫𝐫𝐫𝐫𝐫𝐫𝐫𝐫𝐫𝐫 =
𝟏𝟏𝟏𝟏𝟏𝟏, 𝟎𝟎𝟎𝟎𝟎𝟎 𝐦𝐦𝐦𝐦𝐦𝐦𝐦𝐦𝐦𝐦/𝐬𝐬𝐬𝐬𝐬𝐬𝐬𝐬𝐬𝐬𝐬𝐬
× 𝐏𝐏𝐏𝐏𝐏𝐏
𝟐𝟐
The term bearing is used to describe the position of a target in relation to the radar system. The
bearing to a target can be expressed in two ways: true and relative.
True Bearing
True bearing (Figure 3-2) is the angle between true north and the line directly pointed at the target.
Notice that the angle is measured in the horizontal plane in a clockwise direction from true north.
3-3
Relative Bearing
Relative bearing (Figure 3-2) is measured in a
clockwise direction using the centerline of the
radar antenna as the reference point.
Resolution
The term resolution refers to the ability of a radar
system to distinguish between targets. Resolution
in radar systems can be expressed in three ways:
target, range, and bearing.
Target Resolution
Target resolution is defined as the radar system’s
ability to distinguish between two targets that are
close together in either range or bearing. This
characteristic is very important for weapons
control radar systems.
Figure 3-2 — True and relative bearing.
Range Resolution
Range resolution is defined as the radar system’s ability to distinguish between two targets that are
on the same bearing but at different ranges. Range resolution is dependent on the width of the pulse
and the type and size of the target.
Bearing Resolution
Bearing resolution is the radar system’s ability to distinguish between two targets that are at the same
range but at different bearings. Bearing resolution is dependent on the radar system’s beam width
and the range of the target.
Accuracy
Radar accuracy is the ability of the system to determine the correct range, bearing, and, in some
cases, altitude of a target. The overall accuracy of radar is dependent on the overall resolution of the
system. There are two factors that can directly affect the accuracy of a radar system: pulse shape
and atmospheric conditions.
Pulse Shape
The perfect shape of a radar pulse can be defined as a square wave that has vertical leading and
trailing edges. The perfect radar pulse enables the radar to accurately define a target. However, due
to limiting factors, most radar systems are unable to consistently produce a perfect pulse shape.
Radar systems vary the shape of the pulses to identify targets at short or long ranges For example,
radar systems use narrow pulse shapes to identify targets at short ranges. The narrow pulse shape
allows the radar to rapidly transmit and receive the RF energy. In comparison, in order to identify
targets at longer ranges, the radar system must widen the width of a pulse and modulate the PRF.
Atmospheric Conditions
The speed of RF energy traveling through space is affected by temperature, pressure, and the
amount of water vapor (humidity) in the atmosphere. This effect on RF energy traveling through the
atmosphere is called refraction. Refraction is the deflection or change in direction of RF waves as
3-4
they travel through space at different speeds. RF refraction through the atmosphere will affect a radar
system’s ability to accurately identify a target at various ranges.
Radar System Components
A typical radar system requires the following components to operate:
•
Synchronizer
•
Transmitter
•
Duplexer
•
Antenna
•
Receiver
•
Indicator
•
Power supply
The components in many cases are combined in single units. A functional block diagram of a basic
radar system is shown in Figure 3-3.
Figure 3-3 — Functional block diagram of a basic radar system.
Synchronizer
A synchronizer (timer) supplies the signals that time the transmitted pulses, the indicator, and other
associated circuits. A synchronizer also sets the interval between transmitted pulses to ensure the
pulsed RF energy is the proper length. The timing of the RF pulses is directly related to the PRF.
3-5
Transmitter
A radar transmitter is a component that generates RF energy in the form of short and powerful
pulses. Transmitters use oscillators to turn a low-power RF energy signal into a high-power output
signal. Extremely high voltage is used to switch the oscillator on and off, which in turn generates the
high-power RF energy pulse.
WARNING
Radar transmitters are capable of producing high voltages
that can be extremely hazardous to personnel. Safety
procedures and precautions must always be observed by
personnel working on or around radar transmitters.
Duplexer
The duplexer is an electronic switch that allows a radar system to use the same antenna to alternate
between transmitting and receiving RF energy. The switching time is called receiver recovery time. A
duplexer must be capable of switching between the two cycles rapidly to improve the detection of
short range targets. In addition, duplexers should absorb very little power during transmit and receive
cycles. This characteristic is very important because received echoes can be very low amplitude.
Antenna
Radiated energy has the tendency to spread out equally in all directions. The antenna routes the RF
energy from the transmitter and radiates the energy in a highly directional beam. An echo received by
the antenna is routed to the receiver for processing. Antenna systems normally include transmission
lines, waveguides, and duplexers. Additionally, most airborne radar systems use some form of an
array antenna. Array antennas are groups of individual radiating elements arranged horizontally and
vertically to form a plane.
Receiver
A radar receiver amplifies the weak echoes returned by the reflecting object (target) and reproduces
the echoes into a video pulse that is routed to an indicator. One of the primary functions of a radar
receiver is to convert the frequency of the echo into a lower frequency that is easier to amplify. This
function is important because radar frequencies are in very high ranges, which make them difficult to
amplify.
Indicator
A radar system indicator is used to provide the operator with a visual display of the returned echo
signals that indicate the bearing, range, and altitude of a target. Most modern aircraft use
multipurpose displays to show radar data and to control system functions.
Power Supply
The power supply provides the regulated voltages and signal routing required for operation of a
typical radar system.
Methods of Radiofrequency Transmission
There are four methods a radar system uses to transmit RF energy to detect and track targets: pulse
modulation, frequency modulation, continuous wave, and pulse-doppler.
3-6
Pulse Modulation
The pulse modulation method of transmission uses very short and powerful bursts of RF energy
(pulses). Additionally, pulse transmissions normally occur in a very short period of time (between 0.1
to about 50 µs). The time duration of the pulse travel time is measured and used to calculate range.
What makes pulse modulation unique is that it does not depend on the relative frequency of the
returning signal or the motion of a target. Pulse modulated radar systems use one antenna and a
duplexer to transmit and receive RF energy.
Frequency Modulation
The frequency modulation of transmission radiates RF energy whose frequency increases and
decreases from a fixed reference frequency. The frequency of the returned signal differs from the
radiated signal by the amount of time it takes for that signal to travel to the target and return. This
type of modulation is normally used in radar altimeter systems.
Continuous Wave
The continuous wave (Doppler) method of transmission directs continuously transmitted RF energy at
a target. A shift in frequency occurs when the target moves towards and away from the transmitted
RF energy. The apparent shift in frequency is known as the Doppler effect.
A good example of the Doppler effect in action (Figure 3-4) is the changing pitch of a train whistle as
a train moves towards a stationary listener. As the train moves closer to the listener, the whistle tone
is higher (increase in frequency). The tone of the whistle decreases (decrease in frequency) as the
train moves away from the listener. Therefore, the amount of shift is proportional to the speed of the
reflecting target. This characteristic makes the continuous wave transmission method the best way to
detect a fast moving target in situations where range resolution is not important. Fire control radar
systems use this method to illuminate a target for missile systems.
Interaction Available
Figure 3-4 — Doppler effect.
Pulse-Doppler
Pulse radar systems can be used to track targets using the Doppler effect. When a transmitted pulse
is received, it is compared to the transmission frequency. If there is a difference in the transmitted and
received frequencies (Doppler shift) the target is moving. If the frequencies remain the same, then the
target is stationary.
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Methods of Scanning
Interaction Available
Scanning in a radar system is defined as
the systematic movement of a radar beam
in a pattern while searching for or tracking
a target. The method of scanning is
dependent on the purpose of the radar
system and the antenna size and design.
Some radar systems can use different
scanning patterns that depend on the
selected mode of operation. There are two
methods of scanning: stationary lobe and
beam.
Stationary-Lobe Scanning
Stationary-lobe scanning radar is the
simplest type of scanning system (Figure 35). This method of scanning uses a single
beam that is stationary in reference to the
antenna. The antenna must be
mechanically rotated to obtain 360-degree
coverage.
Figure 3-5 — Typical lobe scanning pattern.
Beam Scanning
There are two methods that can be used in a beam scanning radar system: mechanical and
electronic.
•
In a mechanically scanning radar system, either the entire antenna can move in the desired
scanning pattern, or the energy source can be moved relative to a fixed reflector or vice versa.
The most common type of mechanical scanning is used to rotate an antenna to obtain 360degree coverage.
•
An electronically scanning radar system changes the scanning pattern by electronically
switching a multi-element array or by switching between a set of energy sources. Electronic
scanning systems are more efficient at changing scan patterns compared to mechanical
scanning systems.
It is important to note that most modern radar systems use a combination of both mechanical and
electronic scanning methods.
Types of Radar Systems
The following paragraphs will provide a brief overview of the search, tracking, missile guidance,
approach, and airborne radar systems.
Search Radar
A search radar system is designed to scan a volume of space in order to detect any target within that
space. A typical search radar system installed onboard a ship is shown in Figure 3-6. Search radar
systems are further divided into the following types: surface, air, and height finding.
3-8
•
A surface search radar system has
two primary purposes. First, surface
search radar is used to determine the
range and bearing of surface targets
or low-flying aircraft. Second, surface
search radar systems generate a
pattern for all of the objects within
line-of-sight distance from the
antenna.
•
An air search radar system is used to
detect and determine the position,
course, and speed of air targets.
There are two types of air search
radar systems: two-dimensional (2D)
and three-dimensional (3D).
o A 2D air search radar system
provides the range and
bearing of a target.
•
o A 3D air search radar system
provides the range, bearing,
and altitude of a target.
Figure 3-6 — Typical search radar system.
A height finding search radar system
is used to provide accurate range,
bearing, and altitude of air targets detected by air search radar systems.
Tracking Radar
A tracking radar system (also called fire control radar) is used to provide continuous positional data
on a target. These systems normally use a narrow, circular beam to track a target.
Missile Guidance Radar
There are three basic types of radar guidance used to
guide a missile to a target: beam-rider, homing, and
passive.
•
A beam-rider missile follows a beam of directed
continuous wave RF energy to intercept a target.
•
A homing missile detects the reflected radar
energy and uses it to intercept a target.
•
A passive missile intercepts a target by using the
energy radiated by the target.
Approach Radar
An approach radar system (Figure 3-7) is used to guide
aircraft to a safe landing in all weather conditions. There
are two types of approach radar systems: carriercontrolled approach (CCA) and ground-controlled
approach (GCA).
3-9
Figure 3-7 — Typical approach radar
system.
•
The CCA radar is a highly sophisticated system designed to provide guidance information to
an aircraft landing on the flight deck of an aircraft carrier. The CCA radar is more complicated
than a GCA because the system must compensate for the movement of the ship.
•
The GCA radar system is a land-based version of the CCA radar system.
Airborne Radar
Airborne radar systems are designed to meet the strict weight and space limitations necessary to be
installed into aircraft. An airborne radar system uses the same characteristics and performs the same
functions as ship and land-based systems.
AIRCRAFT RADAR SYSTEMS
The following section will provide a basic overview of the APG-73 radar system used in the F/A-18
series aircraft, the MMR system used in the MH-60R Seahawk helicopter, and the APN-234 color
weather radar system used in the P-3 Orion.
APG-73 Radar System
The APG-73 radar system provides the operator with the ability to detect, acquire, and track airborne
and surface targets. The APG-73 radar system uses target range, range rate, antenna angles, and
antenna rates to formulate weapons delivery solutions.
Components
The APG-73 radar system consists of the following components:
•
The radar antenna (Figure 3-8) is an electrically driven, high-gain, low-side lobe, two-axis
gimbal assembly that provides RF radiation and reception abilities for radar operation. The
antenna is made up of the following components:
o The planar array is used to
radiate a high power and high
gain RF pencil beam or
mapping beam depending on
the operator-selected mode.
o The guard horn assembly is
used to suppress received
signals by the array.
o The null horn assembly is used
in the air intercept missile
(AIM)-7 Sparrow illumination
mode of operation.
o The waveguide assembly
routes microwave energy
between the antenna,
transmitter, and radar receiver.
o The servo assembly provides
the signals to the antenna and
commands the positon of the
antenna.
Figure 3-8 — APG-73 radar antenna.
3-10
•
The flood antenna is used as a backup illumination source for the AIM-7 Sparrow illumination
mode of operation.
•
The radar power supply converts aircraft or ground equipment 115-volt alternating current,
400-hertz (Hz) power into direct power for use by the radar system. In addition, the radar
power supply provides power rectification, output power control, fault sensing, and fault
protection.
•
The radar receiver is used to process RF energy into a useable signal that is routed to the
radar data processor (RDP). The radar receiver converts the received RF energy into an
intermediate frequency (IF) signal.
•
The RDP is a general purpose dual processor digital computer that performs the following
functions: radar management control, data processing, and performance monitoring. The RDP
is an input and output device that interfaces with the mission computer system. The RDP
provides target information, display conditions, and built-in-test commands. The RDP also
commands the radar system into the air-to-air and air-to-ground modes of operation.
•
The radar transmitter is a high-power
RF amplifier that houses a three-port
waveguide switch to route RF to a
dummy load, main antenna, or flood
antenna.
•
The electrical equipment rack (Figure
3-9) provides for the physical support
and mounting for the APG-73 radar
system. In addition, the electrical
equipment rack provides the
framework for routing electrical
connections, coolant lines, and
waveguides. It allows the radar
package to be easily extended for
maintenance and protects the system
from the high temperatures when the
gun system is fired. The electrical
equipment rack is physically and
electrically connected to the aircraft by
the pantograph assembly.
Controls and Indicators
Figure 3-9 — APG-73 electrical equipment rack.
The APG-73 radar system uses the following controls and indicators:
•
The master arm control panel is used to select the air-to-air and air-to-ground modes of
operation.
•
The map gain control panel controls the gain (clarity) of the radar map display.
•
The left hand vertical control panel contains the brake assembly. The parking brake function of
the brake assembly is required to keep the aircraft stable during the radar built-in-test.
•
The lock/shoot light assembly supplies a head-up display of a radar lock-on condition when the
radar is in the air-to-air master mode of operation. The lock light indicates that the radar is
3-11
tracking a target. The shoot light indicates that the launch criterion has been met for air-to-air
weapons launch.
•
The sensor pod control panel
assembly (Figure 3-10) houses
the following radar system
controls:
o OFF – removes power
from the radar system.
o Standby (STBY) –
activates all of the radar
system components
except the transmitter.
This selection allows the
radar system to warm-up
before the application of
high voltage or can be
used to remove the high
voltage being applied to
the radar system.
Figure 3-10 — Sensor control pod control assembly.
o Operate (OPR) – is used to turn all components of the radar system in to an operating
condition.
o Emergency (EMERG) – allows for the full emergency operation of the radar system
when the aircraft is in a weight-off-wheels (airborne) condition.
•
The right throttle grip provides the operator
with the ability to select the radar modes of
operation, designate and lock targets, and
control antenna elevations.
•
The left throttle grip contains a switch that is
used to cycle targets for the High Speed AntiRadiation Missile (HARM).
•
The aircraft controller grip assembly can be
used to select modes of radar operation.
•
The two (left and right) digital display
indicators (DDIs) provide the operator with
interface capabilities and visual radar
displays. The left and right DDIs are
functionally interchangeable.
Modes of Operation
The APG-73 radar system uses three main modes
of operation: air-to-air (A/A), air-to-ground (A/G), and
navigation.
•
The A/A mode (Figure 3-11) of operation
detects, tracks, assesses, and designates
airborne targets. A/A mode enables the
3-12
Figure 3-11 — Typical A/A radar display.
operator to focus on engaging hostile airborne targets by minimizing the number of switch
selections to enable and release A/A weapons. The A/A mode uses the following submodes:
o Velocity search – detects A/A targets at long range.
o Range while search – provides the operator with all aspect detection of A/A targets.
o Track while scan – provides the operator with the ability to detect targets in medium to
long ranges and to continue to search for other A/A targets.
o Single target track – designates and tracks an individual target until the radar lock is
broken.
o Automatic acquisition – automatically designates a target within the radar field-of-view.
o Manual acquisition – initiates when the operator manually selects a target using the
throttle designation switch or cage/uncage switch.
o Air combat maneuvering – is an operator-selected mode that uses the following
submodes:
•

Wide acquisition – automatically acquires targets to the left and right of the nose
of the aircraft.

Vertical acquisition – automatically acquires targets in the vertical plane of the
aircraft.

Boresight – is used to align the radar antenna to the horizontal plane.

Gun acquisition – is activated when the operator selects the aircraft gun system.
The A/G mode of operation provides the
operator with the ability to map, navigate,
detect targets, and track targets. The A/G
mode automates many of the weapons
delivery tasks normally conducted by the
aircrew. The A/G mode of operation is
divided into the following submodes:
o A/G ranging – automatically initiates
when the operator selects A/G
weapons or when A/G target data is
required.
o Real beam ground map – assists in
sensor-aided A/G weapons delivery.
o Sea surface search – detects surface
targets over large bodies of water. An
example of the APG-73 sea surface
display is shown in Figure 3-12.
o Doppler beam sharpened – uses three
selected resolution modes to increase
the A/G field-of-view.
o Ground moving target – provides the
operator with the ability to detect
moving targets on the surface.
3-13
Figure 3-12 — APG-73 sea surface search
display.
o Real beam ground map-ground
moving target indication – provides
the operator with better resolution and
detail while detecting surface targets.
o Precision velocity update – computes
velocity error signals that are used by
the inertial navigation system during
an in-flight alignment.
o Terrain avoidance – commands the
radar to search and display detected
terrain directly in front of the aircraft.
o Fixed target and ground moving target
track – both submodes track surface
target movements. An example of a
ground moving target display is shown
in Figure 3-13.
•
The navigation mode of operation is the
default mode of operation when the A/A and
A/G modes are not selected by the operator.
The operator can easily select the other two
main modes of operation while in the
navigation mode of operation.
Multi-Mode Radar System
Figure 3-13 — APG-73 ground moving target
display.
The MH-60R Seahawk uses a radar system that provides the operator with the ability to track and
identify targets, scan surface targets, and use the functions of the IFF system.
Components
The MMR processing subsystem uses the following components:
•
The radar receiver-transmitter generates the high-power RF energy required to transmit the
required operating mode waveforms. The receiver section collects and interprets RF signals
and routes the signal to the RDP for processing.
•
The RDP performs signal and data processing on all target data received from the radar
receiver-transmitter. The RDP provides command signals and interfaces with the helicopter
mission computer system. In addition, the RDP processes and generates video signals that
are displayed on the appropriate mission displays.
•
The antenna assembly is located on the underside of the MH-60R helicopter. The antenna
radiates X-band RF energy via a waveguide assembly. In addition, the antenna assembly
houses the L-band IFF antenna and interrogator receiver-transmitter used to transmit and
receive coded RF IFF challenges and replies.
•
The pedestal assembly rotates the antenna assembly in response to operator inputs. In
addition, the pedestal assembly provides the signal interface between the IFF interrogator
receiver-transmitter, RDP, antenna assembly, and radar receiver-transmitter.
3-14
Controls and Indicators
All aspects of MMR operation are performed via the mission display systems and the functional
keypad (Figure 3-14). The interface and signal routing between the MMR and the mission computer
system is facilitated by the aircraft data handling unit.
Figure 3-14 — MMR control and indicator.
Modes of Operation
The MMR operates in four general modes: long-and short-range search, surface target imaging,
target designate, and navigation.
•
Long-and short-range search – identifies and tracks targets at both short and long ranges by
using radiated RF energy. Long-range search is useful for surveillance operations at distances
greater than 100 nautical miles. Short-range search is useful for low-visibility navigation and
search and rescue operations. In addition, the MMR, in conjunction with the IFF interrogator,
can be used to identify a participating unit or a hostile target.
•
Surface target imaging – provides the operator with a 2D digitally scanned image of a surface
target (ship) in all weather conditions by using synthetic aperture radar.
•
Target designate – radiates a target to provide data for weapons targeting or to designate a
target for another aircraft or ship.
•
Navigation (mapping) – maps coastlines and other terrain features for operator display to
increase positional awareness.
3-15
APN-234 Color Weather Radar System
The APN-234 color weather radar system is installed in the P-3 Orion. The system provides the
operator with continuous weather information on cloud formation, rainfall rates, thunderstorms, and
icing conditions. The purpose of the system is to detect hazardous weather and to identify clear flight
corridors.
Components
The APN-234 color weather radar system consists of the following components:
•
The receiver-transmitter produces a constant-level microwave pulse (between 200 to 800 Hz)
that is routed to the antenna assembly via a waveguide system. The receiver-transmitter
converts reflected pulses into range and bearing data. The digital range and bearing is
transmitted to the indicator-control for display.
•
The antenna assembly transmits microwave pulses routed from the receiver-transmitter via a
waveguide assembly. The antenna assembly also receives the reflected microwave pulse and
routes them to the receiver-transmitter for processing. The antenna assembly is physically
made up of a 10-inch flat planar array and drive assembly.
•
The waveguide assembly is a pressurized component used to conduct microwave energy
between the receiver-transmitter and antenna assembly.
Controls and Indicators
The APN-234 color weather radar uses an indicator-control (Figure 3-15) to provide the interface for
control of the system. The indicator-control uses a three-color display (red, yellow, and green) to
provide visual display of the area scanned by the antenna assembly.
Modes of Operation
The APN-234 color weather
radar uses four modes of
operation: weather, weather
alert, map, and search.
•
Weather – displays areas
of high moisture density
by measuring the return of
reflected microwave
energy off of cloud
formations. Displayed
colors reflect the intensity
of the returned microwave
energy and are based on
the strength of the
returned signal. High
levels of moisture will
return high levels of
microwave energy.
Figure 3-15 — APN-234 indicator-control.
3-16
•
Weather alert – operates the same as the weather mode except special circuits cause red
areas to flash, notifying the operator of areas of intense rainfall.
•
Map – allows the weather radar system to display ground features. Rough terrain and urban
areas are displayed in red, open ground is yellow, and rough waters appear as green on the
indicator-display. Calm water will not return a signal because it reflects very little energy.
•
Search – tracks surface objects overwater. Special circuits reduce the amount of noise, which
in turn enhances the ability to discern small targets.
BASIC IFF SYSTEMS PRINCIPLES
A typical IFF system provides a means for identifying friendly aircraft from enemy aircraft. An IFF
system permits a friendly aircraft to identify itself automatically by transmitting a reply when
challenged by a valid interrogator. In addition, an IFF system can be used to report aircraft and
altitude information to air traffic control radar systems, ships, and other aircraft.
Typical IFF System Components
A typical IFF system is made up of the following components:
•
The interrogator unit responds to coded pulse signals from a challenger. The challenger can
be another aircraft, ship, or ground station. The reply signals are routed to the codersynchronizer unit.
•
The coder-synchronizer unit in a
typical IFF system is
synchronized to the radar
system so that reception of an
IFF response and radar RF
signals cannot occur at the
same time.
•
The transponder unit in a typical
IFF system receives the
challenge signals from an
interrogator unit and transmits
the properly coded response.
•
The search radar unit in a typical
IFF system initiates the trigger
pulse and radar video signals
when an unidentified aircraft has
been detected by the radar. An
example of typical IFF display
indications is shown in Figure 316.
Figure 3-16 — Example of a typical IFF display.
IFF Modes of Operation
A typical IFF system uses the following modes of operation: modes 1, 2, 3/A, C, and 4.
•
Mode 1 – provides the general identification of military aircraft only; has 32 different codes.
•
Mode 2 – identifies specific military aircraft; has 4,096 different codes.
3-17
•
Mode 3/A – is used by both the military and civilian air traffic control to identify aircraft; has
4,096 different codes.
•
Mode C – provides aircraft altitude information based on the aircraft’s current pressure
altimeter reading; has 2,048 different codes.
•
Mode 4 – is a classified secure mode of operation used only by military aircraft.
AIRCRAFT IFF SYSTEMS
The following paragraphs will describe the IFF system found in the P-3 Orion aircraft. The P-3 Orion
uses the AN/APX-123(V) IFF transponder system.
APX-123(V) IFF Transponder System
The APX-123(V) IFF transponder system used in the P-3 Orion aircraft receives IFF coded signals
and decodes the signal to determine its validity. In addition, the IFF transponder system responds to
valid IFF interrogations by using the correct code for the mode and set.
Components
The APX-123(V) IFF transponder system consists of the following components:
•
The APX-123(V) IFF and very high frequency (VHF)/ultrahigh frequency (UHF) antennas
receive and transmit IFF coded interrogation signals and responses.
•
The aircraft control display units (CDUs) are used by the pilot, copilot, and the
navigation/communication officer to access and operate the functions of the APX-123(V) IFF
transponder system.
•
The APX-123(V) IFF transponder receives the interrogation signals and detects and amplifies
the signal. The transponder then analyzes the spacing between the pulse-pairs to determine
the proper reply. The pulse-pair can contain one or more of the following codes:
o Emergency signal
o Identification (IDENT)
o Special position indicator (SPI) pulse (mode 3/A)
•
o Altitude information (mode C)
The APX-123(V) IFF transponder incorporates embedded cryptological functions used to
interface and control modes 4 and 5.
Modes of Operation
The APX-123(V) IFF transponder has seven different modes of operation. Modes 1, 2, 3/A, C, and 4
provide the same information as described in the typical IFF system section. Modes S and 5 are
described below:
•
Mode selective interrogation (S) – is a civilian air traffic control capability that reduces the
number of unwanted IFF replies. Each aircraft is assigned a unique and permanent mode S
address that allows air traffic control to direct interrogations and to send data messages to the
desired aircraft.
•
Mode 5 – is a secured cryptological mode that uses two methods of data transmission, level 1
and level 2.
3-18
The APX-123(V) IFF transponder also has two special and three functional testing modes of
operation: identification of position, emergency, power up built-in-test, initiated built-in-test, and
periodic built-in-test.
•
Identification of position (I/P) – is transmitted in modes 1, 2, 3/A, and S to provide the ability for
air traffic control to determine the identification between two aircraft.
•
Emergency mode – is used for emergency replies in all modes of operation except mode C.
•
The power up built-in-test (PUBIT) – provides the operator with the operational performance
status of the IFF transponder system when power is applied via the CDU.
•
The initiated built-in-test (IBIT) – provides the operator with the operational performance status
of the IFF transponder system when the test function is manually selected via the CDU.
•
The periodic built-in-test (PBIT) – runs automatically during IFF transponder operations and
provides the operator with up-to-date operational status indications.
A typical APX-123(V) IFF bit status display page is shown in Figure 3-17.
Figure 3-17 — Typical APX-123(V) IFF bit status display.
3-19
End of Chapter 3
Radar
Review Questions
3-1.
At what speed, in statute miles per second, does radiofrequency energy travel?
A.
B.
C.
D.
3-2.
What term is used to describe the position of a target in relation to a radar system?
A.
B.
C.
D.
3-3.
Target
Range
Bearing
Relative
What term defines a radar system’s ability to determine range, bearing, and altitude?
A.
B.
C.
D.
3-6.
3,080
4,080
5,080
6,080
What type of resolution is defined as the radar system’s ability to distinguish between two
close objects regardless of distance or bearing?
A.
B.
C.
D.
3-5.
Accuracy
Bearing
Range
Resolution
One nautical mile equals how many total feet?
A.
B.
C.
D.
3-4.
166,000
176,000
186,000
196,000
Altitude
Accuracy
Bearing
Resolution
What radar system component generates short and powerful radiofrequency pulses?
A.
B.
C.
D.
Duplexer
Antenna
Indicator
Transmitter
3-20
3-7.
What radar system component provides the operator with a visual display of returned
radiofrequency echoes?
A.
B.
C.
D.
3-8.
What method of radiofrequency transmission occurs between 0.1 to about 50 microseconds?
A.
B.
C.
D.
3-9.
Duplexer
Antenna
Indicator
Transmitter
Pulse-doppler
Continuous wave
Pulse modulation
Frequency modulation
What is the name of the apparent shift in frequency?
A.
B.
C.
D.
Doppler
Pulse
Amplitude
Modulate
3-10. What type of search radar system provides range, bearing, and altitude?
A.
B.
C.
D.
Two-dimensional
Three-dimensional
Four-dimensional
Five-dimensional
3-11. What type of radar system is also known as fire control?
A.
B.
C.
D.
Search
Missile
Approach
Tracking
3-12. What type of radar system is used to guide aircraft to a safe landing?
A.
B.
C.
D.
Approach
Missile
Search
Tracking
3-13. What type of missile guidance system detects and uses reflected radar energy?
A.
B.
C.
D.
Beam
Passive
Homing
Unguided
3-21
3-14. What type of approach control radar is the most complicated?
A.
B.
C.
D.
Beam
Ground
Homing
Carrier
3-15. What APG-73 antenna assembly is used to route microwave energy to the transmitter and
receiver?
A.
B.
C.
D.
Servo
Null horn
Waveguide
Guard horn
3-16. What APG-73 radar component converts radiofrequency energy into an intermediate
frequency signal?
A.
B.
C.
D.
Receiver
Transmitter
Power supply
Data processor
3-17. What APG-73 radar component is a general purpose computer?
A.
B.
C.
D.
Receiver
Transmitter
Power supply
Data processor
3-18. What APG-73 radar component is a high-power amplifier with a three-port waveguide switch?
A.
B.
C.
D.
Receiver
Transmitter
Power supply
Data processor
3-19. What APG-73 antenna is used as a backup Sparrow missile illumination source?
A.
B.
C.
D.
Null
Guard
Flood
Sentry
3-22
3-20. What APG-73 radar system control panel can be used to select the air-to-air mode of
operation?
A.
B.
C.
D.
Map gain
Master arm
Left vertical
Aircraft controller
3-21. What APG-73 air-to-air search mode of operation can be used to detect targets at long range?
A.
B.
C.
D.
Wide
Range
Manual
Velocity
3-22. Other than air-to-air and air-to-ground, what is a main APG-73 radar mode of operation?
A.
B.
C.
D.
Velocity
Acquisition
Combat
Navigation
3-23. What APG-73 radar acquisition mode can be selected using the cage/uncage switch?
A.
B.
C.
D.
Manual
Wide
Vertical
Automatic
3-24. Other than ground moving target track, what APG-73 radar submode can be used to track
surface target movements?
A.
B.
C.
D.
Floating
Ground
Fixed
Precision
3-25. What frequency band of radiofrequency energy is radiated by the multi-mode radar antenna?
A.
B.
C.
D.
L
K
C
X
3-26. What section of the multi-mode radar collects and interprets radiofrequency signals?
A.
B.
C.
D.
Receiver
Processor
Interrogator
Transmitter
3-23
3-27. What multi-mode radar assembly provides all signal interfaces for the system?
A.
B.
C.
D.
Antenna
Pedestal
Receiver
Processor
3-28. What multi-mode radar component interfaces with the mission computer system?
A.
B.
C.
D.
Antenna
Pedestal
Data processor
Receiver-transmitter
3-29. The multi-mode radar antenna is located on what side of the MH-60R Seahawk?
A.
B.
C.
D.
Top
Under
Port
Starboard
3-30. What multi-mode radar mode can be used to map coastlines and other terrain features?
A.
B.
C.
D.
Navigation
Target designate
Short-range search
Long-range search
3-31. What multi-mode radar mode provides the operator with a two-dimensional scanned image?
A.
B.
C.
D.
Target designate
Long-range search
Short-range search
Surface target imaging
3-32. What multi-mode radar mode provides weapons data?
A.
B.
C.
D.
Target designate
Long-range search
Short-range search
Surface target imaging
3-33. What system works in conjunction with multi-mode radar to classify hostile targets?
A.
B.
C.
D.
Weapon
Navigation
Communication
Identification Friend or Foe
3-24
3-34. How many general modes of operation are used by the multi-mode radar?
A.
B.
C.
D.
Two
Three
Four
Five
3-35. Which of the following aircraft use the APN-234 radar system?
A.
B.
C.
D.
P-3 Orion
F/A-18 Hornet
E-2C Hawkeye
MH-60R Seahawk
3-36. What APN-234 component converts reflected pulses into range data?
A.
B.
C.
D.
Indicator-control
Antenna assembly
Receiver-transmitter
Waveguide assembly
3-37. What component of the APN-234 radar is pressurized?
A.
B.
C.
D.
Indicator-control
Antenna assembly
Receiver-transmitter
Waveguide assembly
3-38. What is the diameter, in inches, of the APN-234 planar array?
A.
B.
C.
D.
5
10
15
20
3-39. What component of the APN-234 radar displays digital range and bearing information?
A.
B.
C.
D.
Indicator-control
Antenna assembly
Receiver-transmitter
Waveguide assembly
3-40. The APN-234 uses how many colors to display information?
A.
B.
C.
D.
Two
Three
Four
Five
3-25
3-41. The APN-234 provides the operator with how many modes of operation?
A.
B.
C.
D.
Two
Three
Four
Five
3-42. Colors displayed by the APN-234 are dependent on what characteristic of the returned
energy?
A.
B.
C.
D.
Intensity
Amplitude
Frequency
Wavelength
3-43. What APN-234 mode uses special circuits to display flashing red areas on the display?
A.
B.
C.
D.
Map
Search
Weather
Weather alert
3-44. What color are rough terrain and urban areas displayed in the APN-234 search mode?
A.
B.
C.
D.
Red
Green
Yellow
Orange
3-45. What typical Identification Friend or Foe component is matched to the radar system?
A.
B.
C.
D.
Interrogator
Transponder
Search radar unit
Coder-synchronizer
3-46. What typical Identification Friend or Foe component initiates the trigger pulse and radar video
signals?
A.
B.
C.
D.
Interrogator
Transponder
Search radar unit
Coder-synchronizer
3-26
3-47. What typical Identification Friend or Foe component responds to the coded signals from the
challenger?
A.
B.
C.
D.
Interrogator
Transponder
Search radar unit
Coder-synchronizer
3-48. What typical Identification Friend or Foe component transmits the proper coded response to a
valid interrogation?
A.
B.
C.
D.
Interrogator
Transponder
Search radar unit
Coder-synchronizer
3-49. Other than aircraft data, what other type of information can be transmitted by typical
identification friend or foe systems?
A.
B.
C.
D.
Range
Bearing
Altitude
Velocity
3-50. What typical Identification Friend or Foe mode uses 32 different codes?
A.
B.
C.
D.
1
2
3/A
4
3-51. What typical Identification Friend or Foe mode is used by both military and civilian aircraft?
A.
B.
C.
D.
1
2
3/A
4
3-52. Identification Friend of Foe mode C contains what total number of codes?
A.
B.
C.
D.
1,048
2,048
3,048
4,048
3-27
3-53. What typical Identification Friend or Foe mode is used for general identification of military
aircraft?
A.
B.
C.
D.
1
2
3/A
4
3-54. What typical Identification Friend or Foe mode is a secure mode used only by military aircraft?
A.
B.
C.
D.
1
2
3/A
4
3-55. Other than very high frequency what other frequency antenna is used by the APX-123(V)
system?
A.
B.
C.
D.
Low
High
Super high
Ultrahigh
3-56. What APX-123(V) component incorporates embedded cryptological functions?
A.
B.
C.
D.
Antenna
Interrogator
Transponder
Control display
3-57. Identification friend or foe pulse pairs can contain how many codes?
A.
B.
C.
D.
Three
Four
Five
Six
3-58. How many modes of operation are used by the APX-123(V) system?
A.
B.
C.
D.
Four
Five
Six
Seven
3-59. What APX-123(V) mode reduces the number of unwanted Identification Friend or Foe replies?
A.
B.
C.
D.
Q
R
S
T
3-28
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3-29
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CHAPTER 4
ANTISUBMARINE WARFARE
The detection of enemy submarines is important mission for the Navy. One of the most important
tools in detecting enemy submarines is sound navigation ranging (sonar) equipment. As an aviation
electronics technician (AT), you will need to understand the principles used in the operation of
antisubmarine warfare (ASW) equipment. This chapter will provide an overview of the basic principles
of sonar, sonobuoys, and the principles of magnetic anomaly detection (MAD) equipment. Every
effort has been made to provide relevant examples of the equipment being used in the fleet.
LEARNING OBJECTIVES
When you have completed this chapter, you will be able to do the following:
1. Identify the factors that affect the behavior of a sound beam in the water.
2. Identify the components of typical sonobuoys.
3. Identify the different types of typical sonobuoys.
4. Recognize the components of a typical sonobuoy receiver.
5. Describe the operating principles of a typical sonobuoy receiver.
6. Describe the operating principles of a typical acoustic processing system.
7. Recognize the components of an airborne sonar system.
8. Describe the operating principles of an airborne sonar system.
9. Describe the operating principles of MAD systems.
SONAR PRINCIPLES
The term sonar is used to describe equipment that transmits and receives sound energy propagated
through water. The operating principles of sonar are similar to that of radio detection and ranging
(radar), except the transmission medium is sound waves instead of radiofrequency (RF) waves.
Similar to radar, range can be determined in sonar because the speed of a sound wave (echo) and
the time it takes to travel out and back are known quantities. Additionally, the bearing (direction) of
the sound can be determined by identifying the point the sound echo was reflected.
Active and Passive Sonar
Sonar equipment is generally categorized as being either active or passive. Active sonar equipment
depends on a transmitted sound wave and the return of the echo. In contrast, passive sonar
equipment uses the sound generated by the target as the source of the echo. An example of active
and passive acoustic sensors is shown in Figure 4-1.
Transducers
Active sonar equipment requires the use of a component called a transducer. A transducer converts
an electrical signal into acoustical energy and vice versa. Transducers are watertight and act in the
same manner as a loudspeaker when used to transmit a sound wave and as a microphone when
receiving the transmitted echo. A typical transducer uses a diaphragm to create areas of low and high
4-1
pressure underwater. The
mechanical action of the
diaphragm creates two types of
sound waves: rarefaction and
compression.
•
Rarefaction occurs when
the transducer
diaphragm moves
inward which in turn
creates a low-pressure
wave.
•
Compression occurs
when the transducer
diaphragm moves in an
outward motion. The
outward movement
creates a wave of high
pressure underwater.
The vibration of the diaphragm
creates the sound wave pattern
Figure 4-1 — Active and passive acoustic sensors.
shown in Figure 4-2. The
distance between two
successive rarefactions or compressions is the
wavelength of the sound wave. The frequency
of the sound wave can then be determined by
counting the number of wavelengths that occur
per second.
Factors Affecting the Sound Wave
The term transmission loss can be used to
describe the loss of signal strength as a sound
wave travels through the water. There are
seven factors that can cause transmission loss:
•
Absorption and scattering
•
Reflection
•
Reverberation
•
Divergence
•
Temperature
•
Refraction
•
Salinity
Figure 4-2 — Transducer sound wave pattern.
Absorption and Scattering
Sound energy emitted by a source will be absorbed while passing through the water. The amount of
energy that will be absorbed can depend on the sea state. When the winds are high enough to
produce whitecaps and a concentration of bubbles at the surface level, the absorption level of sound
4-2
energy will be higher. Further, the loss of sound energy is greater in areas of wakes and strong ocean
currents, such as riptides. These characteristics can create false echoes and high reverberations that
make accurate echo-ranging nearly impossible. It is also important to note that the absorption of
sound waves is greater at higher frequencies.
Sound waves are weakened when they reach a region of seawater that contains foreign matter, such
as seaweed, silt, animal life, or air bubbles. Foreign matter in the water scatters the sound beam and
causes the loss of sound energy. The practical result of scattering is the reduction of the echo
strength especially at long ranges.
Reflection
When a sound wave hits an object or a boundary region between transmission mediums it echoes
(reflects) back to its origin. The echo will occur in cases where the two mediums are of sufficiently
different densities and the sound wave strikes at a large angle. The echo will occur because the
sound wave travels at different speeds through the two different densities. The reflection of a sound
wave off of a submarine is shown in Figure 4-3.
Interaction Available
Figure 4-3 — Sound wave reflecting off of a submarine.
Sound waves travel about 4 times faster in water than they do in the air. Additionally, the density of
water is more than 800 times greater than the density of the air. Therefore, nearly all sound waves
will be reflected in a downward direction from the sea surface.
When a sound wave strikes the bottom of the ocean it naturally reflects in an upward direction. There
will be very little signal loss if the bottom happens to be a smooth, hard surface. Other factors being
equal, the transmission loss of a sound wave will be less over a smooth, sandy bottom and greater
over soft mud. Over rough and rocky bottoms, the sound is scattered, resulting in strong bottom
reverberations. However, it is important to note that a sound wave may never strike the bottom due to
extremely deep waters (600 feet or more). The water pressure at extreme depths is so great that a
sound wave will actually speed up and bend back towards the surface.
In calm seas, most of the sound energy that strikes the water surface from below will be reflected
back down into the sea. A scattering effect occurs as the sea gets progressively rougher. In these
circumstances, part of any sound striking the surface is lost in the air, and part is reflected in
scattering directions in the sea. In water less than 600 feet deep, the sound may also be reflected off
the bottom.
4-3
Reverberation
Reverberations are multiple reflections of a sound wave. A good example of natural reverberation is
the sound of thunder. The discharge of lightning causes a quick, sharp sound but by the time the
sound of thunder is heard, it is usually drawn out to a prolonged roar due to the characteristics of
reverberation.
Reverberations often occur when using sonar systems. Sound waves strike small objects in the
water, like fish or air bubbles, which cause the sound waves to scatter. Each of the scattered sound
waves produces a small echo that may be returned to a transducer. Echoes are also created by the
reflections of sound from the surface and bottom of the sea. The combinations of the echoes from the
cumulative disturbances are reverberations. Because the waves are reflected back from different
ranges, the combination can become a continuous sound that can become so loud that it interferes
with the returning target echo.
There are three main types of reverberations of a sound wave. They are as follows:
•
There is reverberation from the mass of water. The cause of this type of reverberation is not
completely known, although fish and other objects contribute to it.
•
There is reverberation from the surface. The reverberation is most intense immediately after
the sonar transmission; it then decreases rapidly. The intensity of the reverberation increases
with the change of sea state.
•
There is reverberation from the bottom. In shallow water, this type of reverberation is the most
intense of the three, especially over rocky and rough bottoms.
Divergence
Sound waves, like light waves, weaken with distance. The farther a target is from a sonar transducer,
the weaker the sound waves will be when they reach it. This characteristic is known as spreading or
divergence.
Temperature
Temperature is the most important factor that can affect the speed of a sound wave traveling in sea
water. Near sea level, a sound wave will travel at approximately 1,080 feet per second. In seawater,
sound waves can travel at approximately 4,700 to 5,300 feet per second. One degree of temperature
change can increase the speed of a sound wave by 4 to 8 feet per second. The temperature of the
sea can vary greatly from freezing in the polar regions to over 85 degrees Fahrenheit (°F) in the
tropical regions. The temperature can vary by more than 30 °F from the surface to a depth of greater
than 450 feet. Thermal gradient is a term used to describe the direction and the rate of temperature
changes around a particular location. There are two types of temperature gradients: positive and
negative.
•
A positive thermal gradient occurs when the surface temperature is cooler than the layers
beneath it. This condition rarely occurs, but when it does it will cause a sound wave to travel in
sharp upward angle.
•
A negative thermal gradient describes the colder temperatures that occur with the increase of
depth. A negative thermal gradient will cause a sound wave to be refracted in a downward
angle.
If the temperature gradient remains the same throughout, then the layer is called isothermal (constant
temperature). If the temperature of water is a region of rapidly decreasing temperature then the layer
is called a thermocline.
4-4
Under normal conditions the temperature of the sea
consists of the following layers:
•
The surface layer is an isothermal or mixed layer
in which the temperature changes slightly with
depth.
•
The layer below the surface consists of a
thermocline.
•
The layer below the thermocline consists of a
region of water that slowly decreases in
temperature.
The temperature layers of the ocean are shown in
Figure 4-4.
Any change in the above combination will change the
path of the sound wave. The change in the path of
sound waves due to temperature can be advantageous
to a submarine trying to avoid detection. This
advantage is especially true if the submarine dives
below a thermocline.
Refraction
A sound beam would travel in a straight line if there
were no temperature differences in the water. The
straight line of travel will occur because the speed of
sound would stay roughly the same at all depths and
would become weaker at the same rate.
Figure 4-4 — Temperature layers of the
ocean.
The reality is that the speed of sound is not
uniform at all depths. Refraction is a term used
to describe the bending of a sound wave
caused by the variations of temperature. The
path of the sound beam will bend away from
areas of higher temperature and towards lower
temperatures (Figure 4-5). The characteristics
of refraction can significantly lower the
detection range of an undersea target.
Figure 4-5 — The effect of a positive thermal
gradient.
4-5
Salinity
The term salinity is used to describe the amount of salt content in seawater. Fresh water has a
density of about 62.4 pounds per cubic foot but saltwater weighs approximately 64 pounds per cubic
foot. The reason for the difference in the overall weight is the salt in the seawater. Salinity does affect
the speed of a sound wave but in a lesser manner than temperature. The higher the salt content of
the seawater, the faster the sound wave will travel through it. A good example of an area with high
salinity is the mouth of a river that empties into a sea. In most other areas, salinity has such little
effect that this characteristic can be ignored.
When the surface of the sea is cooler than the layers beneath it, the temperature increases with
depth, and the water has a positive thermal gradient. This condition is unusual, but when it does
happen, it causes the sound beam to be refracted sharply upwards.
If the temperature remains the same throughout the water, the temperature gradient is isothermal (of
a constant temperature). The surface layer of water is isothermal, but beneath this layer the
temperature decreases with depth. The temperature decrease causes the sound beam to split and
bend upward in the isothermal layer and downward below it.
Sound wave behavior in isothermal
conditions is shown in Figure 4-6.
Doppler Effect
The Doppler effect plays as big a role in
sonar systems as it does in fire control radar
systems. The received frequency differs from
the transmitted frequency when there is
relative motion between a target and a
receiver. The number of waves will increase if
the target is moving towards the receiver. The
effect at the receiver is an apparent decrease
in wavelength or an increase in frequency. In
contrast, if the target is moving away from the
receiver the wavelength will become longer
and the frequency will be lower. The amount
of change in the wavelength and the
frequency is dependent on relative velocity
between the target and the receiver.
Doppler Effect and Sonar
Figure 4-6 — Sound wave behavior in
isothermal conditions.
There are three basic sounds used by typical
sonar equipment.
•
The actual sound wave or ping generated by the equipment
•
The reverberations that return from the generated sound wave
•
The returned echo from the target
The ping is not normally heard by the operator because most sonar equipment is designed to block it
out, which leaves the operator with the challenge of identifying a returned echo from a target against
the received reverberations. This challenge is where the Doppler effect becomes very important.
4-6
A helicopter using a sonar transducer to
transmit a 10 kilohertz (kHz) ping is
illustrated in Figure 4-7. The object near the
target is causing reverberations that are
being received at the same transmitted
frequency (10 kHz), which is indicative of a
stationary object. The transducer is also
receiving a sound wave that is being
received at a frequency of 10.1 kHz (high
Doppler) from the submarine. The increase
in the received frequency indicates that the
submarine is moving towards the
helicopter’s position.
The difference in the received frequency
when the submarine is moving away from
the position of the helicopter is shown in
Figure 4-8. The transducer is transmitting a
signal at a frequency of 10 kHz. The
returning echo being received by the
transducer is a frequency of 9.9 kHz (low
Doppler). The lower frequency indicates the
submarine is moving away from the
transmitted sound wave.
Figure 4-7 — Submarine moving towards a
transducer.
In Figure 4-9, the results when a target is
either stopped or crossing the sound beam
at a right angle are illustrated. Notice that
the transmitted and received frequency
remains the same at 10 kHz (no Doppler).
The operator might believe that they are
receiving a reverberation or that the target
is not moving.
SONOBUOYS
The primary mission of the Navy’s ASW
forces is the detection, localization, and
identification of submarines. One of the
most useful tools supporting this mission
has been the sonobuoy. Since its
development during World War II, the
sonobuoy has gone through many
changes. The improvements in the design
over the years have created large numbers
of specialized and reliable sonobuoys.
Figure 4-8 — Submarine moving away from a
transducer.
4-7
Figure 4-9 — Submarine stationary or at a right
angle to a transducer.
Description and Components
A sonobuoy (Figure 4-10) is a cylindrical metal tube that is about 3 feet long
and 5 inches in diameter. A typical sonobuoy can weigh anywhere from 20 to
39 pounds depending on its purpose. They are encased in a plastic
cylindrical housing called a sonobuoy launch container.
It is important to note that sonobuoys are expendable devices that are never
recovered after they are launched from an aircraft. Not recovering the
sonobuoys may seem like a waste of assets, but it has proven to be the
cheapest and most reliable method to search the ocean.
A typical sonobuoy consists of the following components:
•
Inflation bottles
•
Float bags
•
Batteries
•
RF cabling
•
Hydrophone
•
Electronic processors
•
Antennas
Figure 4-10 —
Typical sonobuoy.
Each type of sonobuoy is designed to meet a very specific set of specifications that are unique to the
particular type of sonobuoy. The operational specifications are the same for all the manufacturers.
However, there are some differences in the prelaunch selection of life and depth settings of the same
4-8
type of sonobuoy. The storing, handling, and setting of a particular type of sonobuoy can be found in
the following publication, Sonobuoy Instruction Manual, NAVAIR-28-SSQ-500-1.
External Markings
Each sonobuoy has the following information marked on the sonobuoy case:
•
Nomenclature or type
•
Serial number
•
Manufacturer’s code number
•
RF channel number
•
Contract lot number
•
Weight
•
Prelaunch setting
Principles of Operation
Many of the tactical sonobuoys are designed to detect underwater sounds, such as
submarine noise. The sound waves detected by the sonobuoy are modulated by an
oscillator in the RF transmitter portion of the sonobuoy. The output of the
transmitter is a frequency modulated (FM) very high frequency (VHF) signal that is
transmitted from the antenna. The signal is received by the aircraft, then detected
and processed by a sonobuoy receiver. By analyzing the detected sounds, the
operator can determine various characteristics of the detected submarine. The use
of several sonobuoys operating on different VHF frequencies deployed in a tactical
pattern enables the operator to localize, track, and classify a submerged submarine.
Frequency Channels
Certain sonobuoy designs are equipped with an electronic function select (EFS)
system. The EFS system provides each sonobuoy with 99 selectable channels. The
EFS also provides each sonobuoy with 50 life and 50 depth setting selections. The
operator must reset all three settings any time any one of the three are changed.
Sonobuoy type and RF channel number are also stamped on each end of the buoy.
Sonobuoys with EFS will not be stamped with the RF channel number marking
because the channel will be selected by the operator.
Deployment
Sonobuoys are dropped by aircraft in area that is thought to contain a submarine.
The pattern normally involves dropping three or more buoys in a tactical pattern. A
typical sonobuoy launch container is shown in Figure 4-11.The operator will
select the best pattern to that will provide the best coverage and increase the
chances of identifying or tracking the target.
Sonobuoys in a launch container can be deployed from an aircraft using any of
the following methods:
•
Spring
•
Pneumatic
4-9
Figure 4-11 —
Typical sonobuoy
launch container.
•
Free-fall
•
Cartridge
Deployment of a sonobuoy from an aircraft can occur at altitudes approaching 30,000 feet and at
speeds of up to 370 knots. A descent-retarding device is required because descent velocities can
exceed 120 feet per second. The descent-retarding devices are used to increase the aerodynamic
stability and to reduce water-entry shock. The devices used to control the descent of the sonobuoy
consist of one of the following:
•
Parachute
•
Rotating-blade assembly (rotochute)
NOTE
Do not mix parachute and rotochute sonobuoys during a
tactical deployment because of the different descent
characteristics. If the two are intermixed, the spacing of the
tactical pattern will be incorrect and submarines might be
missed.
Water Entry and Activation
There are two methods that can activate a sonobuoy, water impact or
battery activation. Jettisoning of the bottom plate allows the hydrophone
and other internal components to descend to the preselected depth. Upon
the release of the parachute or rotochute, the antenna is erected. In some
sonobuoys, a seawater-activated battery fires a squib, which deploys a
float containing the antenna. A termination mass (drogue) is used to
stabilize the hydrophone at the selected depth, while the buoyant
sonobuoy section (float) follows the motion of the waves. A section of
elastic suspension cable isolates the hydrophone from the wave action on
the buoyant section. Most of the sonobuoys in the fleet today are
equipped with seawater-activated batteries, which provide the power
required for the sonobuoy electronics. Data transmission from the buoys
usually begins within 3 minutes after the buoy enters the water. In cold
water or water with low salinity, the activation time might be increased.
There are some models of sonobuoys that use lithium batteries that are
not water activated.
Operating Life
Sonobuoy transmitters are designed to deactivate at the end of a
preselected time. The sonobuoy either uses an electronic RF OFF timer,
or the transmitter is deactivated when the buoy is scuttled. Some types of
sonobuoys use an RF command to activate a mechanism designed to
flood the flotation section with seawater. Other types of sonobuoys deflate
the flotation balloon to scuttle the unit. In either case, the unit fills with
seawater and sinks. A typical deployed sonobuoy is shown in Figure 4-12.
4-10
Figure 4-12 —
Typical deployed
sonobuoy.
Sonobuoy Classification
Sonobuoys are grouped into three categories: passive, active, and special purpose. Examples of the
sonobuoys in each category are discussed below.
Passive Sonobuoys
The passive sonobuoy is a listen-only buoy. An overview of the directional frequency analysis and
recording (DIFAR) and the vertical line array directional frequency and recording (VLAD) sonobuoys
is provided below.
•
The DIFAR sonobuoy is an improved passive acoustic sensing system that is programmed
prior to deployment using EFS circuitry. The newest versions of DIFAR sonobuoys use a
directional or an omnidirectional antenna to detect sound waves. They also incorporate the
command function selection (CFS) capability. The CFS allows an operator to turn the system
on or off, change modes of operation, adjust depths, and change RF channels. The DIFAR
sonobuoy provides a magnetic bearing to a target and can be used for search, detection, and
classification operations. When the buoy receives an acoustic signal, the unit will convert the
pressure wave into an amplified electronic signal. Additionally, a magnetic reference for each
received signal is provided by flux gate compass. This capability lowers the number of DIFAR
sonobuoys needed to fix the location of a target. A block diagram of a DIFAR sonobuoy is
shown in Figure 4-13.
•
The VLAD sonobuoy is a passive
directional sensor that is used to
detect and localize a submerged
target. The VLAD deploys a vertical
line array that consists of directional
or omnidirectional hydrophones.
The VLAD sonobuoy can be
programmed prior to deployment
through the use of EFS circuitry.
The VLAD sonobuoy also
incorporates CFS capability. What
makes the VLAD sonobuoy unique
is the ability of the system to detect
a target in an area of high ambient
noise. Detection is accomplished by
using beamforming technology. The
beamforming technology gives the
unit the ability to search, detect, and
classify a target at extended ranges Figure 4-13 — Block diagram of a DIFAR sonobuoy.
with minimal expenditure.
Active Sonobuoys
The active sonobuoy uses a transducer to radiate a sonar pulse that is reflected back from the target.
The time interval between the ping (sound pulse) and the echo return to the sonobuoy is measured
using the Doppler effect. The time-measurement data is used to calculate both range and speed of a
target in relation to sonobuoy. An overview of the directional command activated sonobuoy system
(DICASS) is provided below.
•
The DICASS sonobuoy and the monitoring unit signal processor equipment provides active
sonar ranging, bearing, and Doppler information on submerged target. The unit incorporates
4-11
CFS capability and is designed to develop and maintain attack criteria. These sonobuoys are
normally deployed in multiple patterns but they were designed to permit a single buoy attack
criteria. When an ultrahigh frequency (UHF) command signal is received, the DICASS
sonobuoy will emit a continuous wave of frequency modulated ping. The transducer array
emits omnidirectional pulses on the horizontal plane and beam formed on the vertical plane.
When a signal is received it is amplified and filtered prior to assigning a magnetic bearing
reference. The signal is then transmitted to the monitoring platform. This flexibility of the
sonobuoy and the signal processor equipment allows for the control of a wide range of
environments and target conditions.
Special-Purpose Sonobuoys
Special purpose sonobuoys are not designed for use in target detection, identification, or localization.
An overview of the bathythermograph (BT) sonobuoy is provided below.
•
The BT sonobuoy is an expendable thermal gradient measurement unit that provides a
continuous reading of temperature versus depth. Once the BT buoy enters the water, a
thermistor probe descends automatically at a constant 5 feet per second. The BT sonobuoy
will provide the operator with updated data exceeding depths of 2,000 feet. The temperature
gradient is converted to an electrical signal and is applied to the preset carrier frequency.
SONOBUOY RECEIVERS
A typical sonobuoy receiver set uses radios to receive, demodulate, and amplify sonobuoy
transmissions in the VHF spectrum bands. A typical receiver system relays acoustic data to other
units (ships or aircraft) via a datalink system. The acoustic data is also routed to a spectrum analyzer
for processing and display onboard the aircraft. It is possible to receive and demodulate signals from
sonobuoy units at the same time. The operator can select any of the channels for aural monitoring.
A typical sonobuoy receiver system can use anywhere from four to twenty individual receivers. Each
of the receivers can operate independently on a channel selected by an operator or a computer.
Additionally, the receivers are capable of being tuned to any of the 99 available sonobuoy
transmission channels. Analog and digital RF signals received from sonobuoys are applied to the
receiver modules where they are tuned and filtered. The signals are then amplified, filtered, and
mixed to produce an audio output. The audio output is then routed to a spectrum analyzer and the
aircraft data link system. The spectrum analyzer processes the signals which allow the operator to
monitor the data.
ARR-78(V) Advanced Sonobuoy Communication Link Receiver Set
The ARR-78(V) advanced sonobuoy communication link (ASCL) receiver set is installed in the Patrol
(P)-3 Orion aircraft. The ASCL consists of the following components:
•
RF preamplifier
•
Receiver assembly
•
Indicator-control unit
•
RF status panel
•
On top position indicator (OTPI) control unit
4-12
Radiofrequency Preamplifier
The RF preamplifier assembly contains two identical preamplifier modules that are capable of driving
two receiver assemblies. Each preamplifier accepts and amplifies FM signals in the VHF bands with
signal levels between 0.5 and 100,000 microvolts.
Receiver Assembly
The receiver assembly consists of the following components:
•
Receiver chassis assembly
•
20 synthesizer receivers
•
Built-in-test equipment modules
•
Dual power supplies
•
Automatic direction finder preamplifier/amplifier/multicoupler
•
Reference oscillator
•
Clock generator
•
Computer interface
Each acoustic receiver is identical and is capable of receiving FM or frequency shift key (FSK)
modulated RF signals. Additionally, the receivers are capable of producing outputs for audio
monitoring, RF monitoring, and OTPI.
Indicator-Control Unit
The indicator-control unit provides the operator with a centralized control and display of the selected
receiver modes.
Radiofrequency Status Panel
The RF status panel continuously displays the control mode (computer or manual), RF channel
assignment, and the intermediate frequency level for the active processing acoustic receiver.
On Top Position Indicator Control Unit
The OTPI uses the
ARC-143 radio control
set to the interface with
the OTPI receiver. The
OTPI system operates
in conjunction with the
direction finder system
to provide sonobuoy
bearing in relation to
aircraft position (relative
bearing). The operator
can manually tune the
OTPI receiver (Figure 414) to any of the
selectable VHF
channels.
Figure 4-14 — OTPI receiver control.
4-13
ACOUSTIC PROCESSING SYSTEM
Acoustic processing systems take the data received from the deployed sonobuoys and extracts and
converts the information into a usable format. A typical acoustic processing system processes the
received audio in active and passive modes to provide long range search, detection, localization, and
identification of targets. The processed signals are converted and sent to displays and recorders for
use by the operator. Additionally, a typical acoustic processing system generates audio command
tones to control active sonobuoys.
UYS-1 Single Advanced Signal Processor System
The UYS-1 Single Advanced Signal Processor (SASP) system is installed in the P-3 Orion aircraft. It
is important to note that while there are number of versions of the SASP in use they all operate in a
similar manner. The SASP consists of the following components:
•
Spectrum analyzer
•
Power supply
•
Control-indicator
Spectrum Analyzer
The spectrum analyzer is a high-speed processor that extracts acoustic target information from the
received signals of active and passive sonobuoys. The spectrum analyzer determines the frequency,
amplitude, bearing, Doppler, and range of the acoustic targets.
Power Supply
The power supply converts 115 volts alternating current (ac) into 120 volts direct current (dc)
operating voltages. The dc power is further converted into low level voltages used to operate
individual circuits. The power supply has a power interrupt unit installed to protect against the loss of
target data during transient power interruptions that can occur during operation.
Control-Indicator
The control-indicator (Figure 4-15) is used to provide the SASP system with power control options
and monitoring. The control-indicator also contains a caution section that will display the appropriate
thermal warning when an overheat condition exists in the system.
Figure 4-15 — SASP control-indicator.
4-14
AIRBORNE SONAR SYSTEM
A typical sonar dipping set is a lightweight, echo ranging systems installed in a helicopter. They are
used to detect, track, and classify moving and stationary underwater objects. Additionally, a typical
sonar dipping set can provide the capabilities for underwater voice communication, bathythermograph
recordings, and echo-ranging. Airborne sonar dipping sets are normally installed in helicopters.
A typical sonar dipping set consists of the following components:
•
Azimuth-range indicator
•
Sonar receiver
•
Sonar data computer
•
Multiplexer
•
Dome control
•
Reeling machine
•
Cable and reel assembly
•
Sonar transducer
Azimuth-Range Indicator
The azimuth-range indicator
(Figure 4-16) is typically installed
at the sensor operator station. It is
used to provide a visual
representation of target range and
bearing information. Typical
azimuth-range indicators contain
controls that are used to adjust
display settings, audio settings,
target range thresholds, and
initiate operational tests.
Figure 4-16 — Typical azimuth-range indicator.
Sonar Receiver
The sonar receiver generates the transmit signal and receives and processes sonic signals from the
transducer for display on the azimuth range indicator. The sonar receiver also provides the audio
output for aural monitoring of acoustic signals.
Sonar Data Computer
The sonar data computer is a programmed array processor that provides operation of the dipping
sonar. Additionally, the sonar data computer processes signals received from passive and active
sonobuoys.
Multiplexer
The multiplexer provides the electrical interface between the sonar set units and the sonar
transducer.
4-15
Dome Control
The dome control provides the operator with the controls
for raising and lowering the sonar transducer. Additionally,
the dome control provides indicators for monitoring the
sonar transducer and reeling machine.
Reeling Machine
The reeling machine is a hydraulic hoist is used to raise
and lower the sonar transducer. A typical reeling machine
operates at a pressure of 3,000 pounds per square inch
(PSI).
Cable and Reel Assembly
The cable and reel assembly (Figure 4-17) houses the
sonar cable that is normally between 1,500 to 1,600 feet in
length. A typical sonar cable uses a jacketed cable with a
metal armor braid used as the strength component.
Electrical wiring is installed inside the cable assembly and
is used to route signals between the transducer and
multiplexer.
Figure 4-17 — Typical cable and reel
assembly.
Sonar Transducer
The sonar transducer (Figure 4-18) generates and transmits sonar pulsed
energy or voice signals under the water. The transducer also acts as a listening
device and converts the received sound energy into electrical signals. The
transducer is attached to the cable and reel assembly. There is a tail assembly
installed on the transducer that provides hydrodynamic stability when being
raised and lowered into the water. The sonar transducer is the most important
component in a dipping sonar system.
Modes of Operation
A typical sonar set offers the following modes of operation:
•
Dipping sonar-active – commands the transducer to actively ping to
locate, identify, and track a target.
•
Dipping sonar-passive – commands the transducer to listen for target
sounds.
•
Sonobuoy-active – interfaces with deployed DICASS sonobuoys to
actively locate, identify, and track targets.
•
Sonobuoy-passive – interfaces with DIFAR and VLAD sonobuoys to
locate targets by noise signatures.
•
Underwater voice communication – uses the sonar transducer to transmit
and receive voice signals to and from other similarly equipped units.
•
Bathythermograph recording – commands the transducer to record the
differences in water temperature versus depth. This mode can be used to
interface with deployed BT sonobuoys.
4-16
Figure 4-18 —
Typical sonar
transducer.
ASQ-22 Airborne Low Frequency Sonar
The Navy currently uses the
ASQ-22 Airborne Low
Frequency Sonar (ALFS)
system (Figure 4-19), which is
installed in the Multi-Mission
Helicopter (MH)-60R Seahawk
helicopter. The ALFS provides
longer detection ranges and
improved detection capabilities
over previous sonar dipping
sets. The improvements are
provided by the use of lower
frequencies, less signal
attenuation, longer pulse
lengths, and increased
transmission power. The
system also uses an enhanced
modular signal processor for
improved sonobuoy processing
capabilities.
Figure 4-19 — MH-60R Seahawk using the ALFS system.
MAGNETIC ANOMALY DETECTION
Modern submarines rely on stealth to accomplish their missions while operating in open waters.
Operating using stealth can make locating a submarine a difficult endeavor even with the use of
enhanced radar, thermal, and acoustics systems. However, nature has provided an advantage. The
earth is covered in a magnetic field also known as the geomagnetic field. A MAD system provides
another option in detecting a submerged submarine. Detection is accomplished by aircraft using
specialized equipment designed to identify a disturbance (anomaly) in the geomagnetic field.
Principles of Magnetic Detection
Light, radar, and sound energy cannot pass from air into water and return to the air in any degree that
is useful in the airborne detection of submarines. However, the magnetic lines of force are able to
transition through both mediums nearly undisturbed because the magnetic permeability of water and
air are fundamentally the same. The lines of force in the geomagnetic field pass through the surface
of the ocean unchanged and undiminished in strength. Therefore, an object under the water can be
detected from a position in the air above if the object has magnetic properties that distort the
geomagnetic field. A submarine with sufficient ferrous mass and electrical equipment can cause an
anomaly in the geomagnetic field. The function of MAD equipment is to detect this anomaly.
Magnetic Anomaly
The lines comprising the natural geomagnetic field do not always run straight north and south. If the
lines of force are traced along a typical 100 mile path they twist at places to the east and west, and
assume different angles in the horizontal. The angles of change in the east-west direction are known
as variation angles. The angles between the lines of force and the horizontal are known as dip angles
and are shown in Figure 4-20.
The relationship between the Earth’s surface and the magnetic lines of force, at any given point
between the equator and the magnetic poles, is between 0 and 90 degrees. Dip angle was
4-17
determined by drawing an imaginary line
tangent to the Earth’s surface and to the point
at where the line of force intercepts the surface
of the Earth. It is important to note that dip
angles are considerably steeper in the extreme
northern and southern latitudes than they are
near the equator.
If the same lines are traced only a short
distance (short-trace), for example 300 feet,
their natural variation and dip over this distance
are almost impossible to measure. However, in
the area of a large mass of ferrous material,
short-trace and dip can be measured by using a
highly sensitive anomaly detector.
The angular direction at which the natural lines
of magnetic force enter and leave the Earth is
shown in Figure 4-21, View A. An area of
undisturbed natural magnetic strength is show
in Figure 4-21, View B. The submarine is
shown distorting the natural magnetic field in
Figure 4-21, View C and Figure 4-21, View D.
The natural dip angle is also affected, but only
very slightly.
Figure 4-20 — Dip angles.
Figure 4-21 — Simplified comparison of natural field density and a submarine anomaly.
4-18
Submarine Anomaly
The maximum range at which a submarine may
be detected is a function of both the intensity of
its magnetic anomaly and the sensitivity of the
detector. A submarine’s magnetic moment
(magnetic intensity) (Figure 4-22) determines
the intensity of the anomaly. It is dependent
mainly on the alignment of the submarine in the
geomagnetic field, the latitude at which it is
detected, its size, and the degree of its
permanent magnetization.
Although MAD equipment is designed to be very
sensitive, a submarine’s anomaly, even at short
distances is normally very weak. The strength of
the complex magnetic field varies as the inverse
cube of the distance from the anomaly. If the
detectable field strength of the anomaly has a
given value at a given distance and that
distance is doubled, the detectable strength of
the anomaly will be one-eighth of its former value.
Figure 4-22 — Submarine magnetic moment.
Based on the above information, two things are clear. First, MAD equipment must be operated at a
very low altitude to have the best chance to detect a submarine. Second, the searching aircraft
should fly a predetermined route and follow a clear search pattern. This pattern will ensure that a
systematic approach is used to reduce the chance of missing existing anomalies.
Anomaly Strength
Up to this point, the inferred strength of a submarine anomaly has been exaggerated for purposes of
explanation. Its actual value is usually so small that MAD equipment must be capable of detecting a
distortion of approximately 1 part in 60,000. It is important to understand that that the direction of
alignment of the earth’s magnetic lines of force is rarely changed more than one-half of one degree
by a submarine anomaly.
A contour map displaying the degree of anomaly caused by a submarine is shown in Figure 4-23,
View A. The straight line, which is approximately 800 feet, represents the flight path of an aircraft
searching the area. If a submarine was not present in the area the undisturbed magnetic area, due to
natural characteristics, would be 60,000 gamma. (The gamma, which is symbolized by the Greek
letter, γ, is a measure of magnetic intensity). All the variations in the magnetic field, when the
submarine is present, would be above or below the natural intensity. The 60,000γ measurement is
displayed in Figure 4-23, View C as the zero reference drawn on the moving paper by the recording
device shown in Figure 4-23, View B.
Any noise or disturbance in the aircraft or its equipment that could produce a signal on the recorder is
classified as a magnetic noise.
In an aircraft there are many sources of magnetic fields, such as engines, struts, control cables,
equipment, and ordnance. Many of these fields are of sufficient strength to seriously impair the
operation of MAD equipment. Some means must be employed to compensate for magnetic noise
fields. Magnetic noise sources fall into two major categories: maneuver noises and dc circuit noises.
4-19
Figure 4-23 — Contour map and anomaly indications.
Maneuver Noises
The magnetic field of the aircraft is changed when an aircraft maneuvers, which causes a change in
the total magnetic field at the detecting element. The major frequencies that are generated by aircraft
maneuvers are significant enough to be built into bandpass components of MAD equipment.
Maneuver noises may be caused by induced magnetic fields, eddy current field, or the permanent
field.
When the aircraft changes heading it induces a magnetic field that is detected by the magnetometer
(detecting head). The change in heading causes the aircraft to present a varying size to the
geomagnetic field, and only the portion of the aircraft parallel to the field is available for magnetic
induction.
Eddy current fields produce maneuver noise because of the electrical current that flow in the skin of
the aircraft and structural members. An eddy current flow is caused by the aircraft maneuvers and it
generates a magnetic field. If the aircraft maneuvers at a slow rate the effect of the eddy current field
in negligible.
When an aircraft’s maneuver causes an eddy current flow, a magnetic field is generated. The eddy
current field is a function of the rate of the maneuver. If the maneuver is executed slowly, the effect of
the eddy current field is negligible.
The structural parts of the aircraft exhibit permanent magnetic fields, and, as the aircraft maneuvers,
its composite permanent field remains aligned with it. The angular displacement between the
permanent field and the detector magnetometer during a maneuver produces a changing magnetic
field, which the detector magnetometer is designed to detect.
4-20
Direct Current Circuit Noise
The dc circuit noise in an aircraft comes from the standard practice in aircraft design of using a singlewire dc system, with the aircraft skin and structure as the ground return. The resulting current loop
from generator to load to generator serves as a large electromagnet that generates a magnetic field
similar to a permanent magnetic field. Whenever the dc electrical load of the aircraft is abruptly
changed, there is an abrupt change in the magnetic field at the detector.
Compensation
A magnetic field may be defined in three axial coordinates (longitudinal, lateral, and vertical)
regardless of its source, strength, or direction. That is, it must act through all or any of the three
possible directions in relation to the magnetometer.
Induced fields and eddy current fields for a given type of aircraft are constant. There is little difference
between the magnetic fields from one aircraft to another of the same type. Magnetic noise must be
compensated to provide a magnetically clean environment so that detection systems are not limited
by the magnetic fields generated by an aircraft. The aircraft magnetic field can be expected to remain
constant, unless significant structural changes are made, throughout the life of the aircraft. Based on
this information, aircraft manufacturers provide compensation for the induced fields and eddy current
fields.
Eddy current compensation is normally achieved by placing the magnetometer in a relatively
magnetically quiet area of the aircraft. In some aircraft, the magnetometer is placed at least 8 feet
away from the fuselage of the aircraft. This can be done by placing the magnetometer in a fixed boom
(Figure 4-24, View A). In comparison, helicopters use a cable attached to the fuselage to tow a
magnetometer as shown in Figure 4-24, View B.
Figure 4-24 — Types of magnetometers.
Induced magnetic field compensation can be accomplished by using Permalloy strips. The magnetic
moment is measured by rotating the aircraft to different compass headings. The polarity and variation
of the magnetic moment are noted for each of the compass headings. Permalloy strips are placed
near the magnetometer to compensate for the field changes created by the magnetic rotation of the
aircraft. Additional compensation is required on the longitudinal axis and is provided by the
development of outrigger compensators of Permalloy strips near the detecting element.
Permanent field compensation must be done in all three dimensions. Compensation is accomplished
by three compensating coils mounted mutually perpendicular to one another (Figure 4-25). The
adjustments to the field strength are accomplished by controlling the amount of dc that flows through
a particular coil.
4-21
Compensation for the dc magnetic field is
achieved through the use of electromagnetic
compensating loops. The loops are arranged
to provide horizontal, vertical, and longitudinal
fields. The loops are adjusted to be equal and
opposite to the dc magnetic field caused by
the load current. The loops are connected
across a variable resistor in a particular load
center, and are adjusted to allow electrical
current flow that is proportional to the load
current for correct compensation. An aircraft
may have several sets of compensating loops
based on the number of electrical distribution
centers. Ground wires are used in newer
aircraft to minimize the loop size.
The procedure for the adjustment of the dc
compensation system makes use of aircraft
straight and level flight on the four cardinal
headings (north, south, east, and west). For
example, the actuation of a cowl flap will
cause dc field changes representative of
Figure 4-25 — Arrangement of compensating
those caused by any nacelle load. When the
coils.
load is energized, the size and the polarity of
the signal are noted, and the compensation control is adjusted. The process is then repeated and the
compensation control is re-adjusted. This process continues until the resulting signals from the dc
field are minimized.
Under ideal conditions, all magnetic fields that act on the magnetometer would be completely
counterbalanced. In this state, the effect on the magnetometer is the same as if there were no
magnetic fields at all. This state could only exist if the following conditions exist:
•
The aircraft is flying through a magnetically quiet geographical area.
•
Electrical and electronic circuits are not turned on or off during compensation.
•
The proper intensity and direction of dc voltages has been set to flow through the
compensation coils, so that all stray fields are balanced.
The compensation of MAD equipment is normally performed in flight and at sea to approximate the
above conditions.
The objective of compensation is to gain a state of total magnetic force balance around the
magnetometer. If there are any sudden shifts in one of the balanced forces (the geomagnetic field) it
will upset the total balance. This sudden shift will be indicated by MAD recording equipment along
with any shift in a balanced magnetic force. Shift in any of the forces other than the geomagnetic field
are regarded as noise.
4-22
End of Chapter 4
Antisubmarine Warfare
Review Questions
4-1.
What term describes equipment that transmits and receives sound energy propagated through
water?
A.
B.
C.
D.
4-2.
What characteristic of a sound can be determined by counting the number of wavelengths that
occur per second?
A.
B.
C.
D.
4-3.
Rip
Surface
Coastal
Longshore
How many times faster do sound waves travel through water than through air?
A.
B.
C.
D.
4-6.
Medium
High
Very high
Ultra high
Which of the following ocean currents can contribute to greater sound loss?
A.
B.
C.
D.
4-5.
Amplitude
Polarity
Frequency
Propagation
What type of pressure is created by the outward movement of a transducer diaphragm?
A.
B.
C.
D.
4-4.
Sonar
Radar
Sounding
Depth testing
2
4
6
8
What total number of factors can cause sound wave transmission loss?
A.
B.
C.
D.
3
5
7
9
4-23
4-7.
Sound waves will travel in what direction from the surface of the ocean?
A.
B.
C.
D.
4-8.
Sound will travel at what speed, in feet per second, near sea level?
A.
B.
C.
D.
4-9.
Up
Down
Straight
Horizontal
1,020
1,040
1,060
1,080
What type of thermal gradient occurs when the surface temperature is cooler than the layers
beneath it?
A.
B.
C.
D.
Positive
Negative
Neutral
Transverse
4-10. What term describes a constant water temperature layer?
A.
B.
C.
D.
Epipelagic
Isothermal
Hadalpelagic
Thermocline
4-11. Sonar equipment uses what total number of basic sounds?
A.
B.
C.
D.
One
Two
Three
Four
4-12. What term describes sound waves generated by sonar equipment?
A.
B.
C.
D.
Pong
Ping
Beep
Ring
4-13. What total length is a typical sonobuoy, in feet?
A.
B.
C.
D.
3
5
7
9
4-24
4-14. What typical sonobuoy component modulates the received signals?
A.
B.
C.
D.
Transmitter
Synchronizer
Oscillator
Modulator
4-15. Electronic function select capable sonobuoys have what total number of selectable channels?
A.
B.
C.
D.
66
77
88
99
4-16. What radiofrequency band does a typical sonobuoy use to transmit data?
A.
B.
C.
D.
High
Very high
Ultrahigh
Super high
4-17. Other than type, what number will be stamped on the end of each non-electronic function
select sonobuoy?
A.
B.
C.
D.
Lot
Series
Model
Channel
4-18. What minimum number of sonobuoys is typically used in a tactical search pattern?
A.
B.
C.
D.
Two
Three
Four
Five
4-19. What part of the tactical pattern is affected when rotochute and parachute sonobuoys are
mixed?
A.
B.
C.
D.
Speed
Depth
Spacing
Arrangement
4-20. A sonobuoy will start transmitting in what total time, in minutes?
A.
B.
C.
D.
1
3
5
7
4-25
4-21. What type of suspension cable isolates the hydrophone from wave action?
A.
B.
C.
D.
Rigid
Elastic
Electrical
Composite
4-22. Most sonobuoys are equipped with what type of battery?
A.
B.
C.
D.
Thermal
Lithium
Seawater
Nickel cadmium
4-23. The directional frequency analysis and recording sonobuoy provides what type of bearing?
A.
B.
C.
D.
Magnetic
Visual
Radar
Relative
4-24. The directional frequency analysis and recording sonobuoy amplifies what type of wave into an
electronic signal?
A.
B.
C.
D.
Modulated
Pressure
Compressed
Sinusoidal
4-25. The vertical line array directional frequency and recording sonobuoy uses what type of
technology to detect sounds?
A.
B.
C.
D.
Array forming
Wave forming
Terraforming
Beamforming
4-26. What type of data does a typical sonobuoy receiver relay to other units?
A.
B.
C.
D.
Electrical
Acoustic
Digital
Analog
4-26
4-27. The radiofrequency preamplifier in a sonobuoy receiver accepts signals at what maximum
number of microvolts?
A.
B.
C.
D.
100,000
200,000
300,000
400,000
4-28. Other than frequency modulated, what other frequency signals are sonobuoy receivers
capable of receiving?
A.
B.
C.
D.
Single key
Silent key
Shift key
Sliding key
4-29. What component displays the operating mode of a sonobuoy receiver?
A.
B.
C.
D.
Receiver assembly
Indicator-control unit
Radiofrequency preamplifier
Radiofrequency status panel
4-30. What component of a sonobuoy receiver consists of a clock generator?
A.
B.
C.
D.
Receiver assembly
Indicator-control unit
Radiofrequency preamplifier
Radiofrequency status panel
4-31. What component of a sonobuoy receiver accepts frequency modulated signals in the very high
frequency bands?
A.
B.
C.
D.
Receiver assembly
Indicator-control unit
Radiofrequency preamplifier
Radiofrequency status panel
4-32. The single advanced signal processor system power supply converts 115 volts alternating
current into what number of volts direct current?
A.
B.
C.
D.
105
110
115
120
4-27
4-33. Which type of warning is the single advanced processor signal system control-indicator
capable of providing to the operator?
A.
B.
C.
D.
Electrical
Acoustic
Thermal
Proximity
4-34. A typical sonar dipping set consists of what total number of components?
A.
B.
C.
D.
Eight
Nine
Ten
Eleven
4-35. What typical sonar dipping set component uses a programmed array processor?
A.
B.
C.
D.
Multiplexer
Sonar receiver
Sonar data computer
Azimuth-range indicator
4-36. What typical sonar dipping set component provides the audio output for aural acoustic signal
monitoring?
A.
B.
C.
D.
Multiplexer
Sonar receiver
Sonar data computer
Azimuth-range indicator
4-37. What typical sonar dipping set component provides the electrical interface between units and
the transducer?
A.
B.
C.
D.
Multiplexer
Sonar receiver
Sonar data computer
Azimuth-range indicator
4-38. A typical dipping sonar reeling machine operates at how many pounds per square inch?
A.
B.
C.
D.
1,000
2,000
3,000
4,000
4-28
4-39. What typical sonar dipping assembly provides for the hydrodynamic stability of the transducer?
A.
B.
C.
D.
Tail
Tether
Rein
Lead
4-40. What is another term used to describe a disturbance in the magnetic field?
A.
B.
C.
D.
Variance
Anomaly
Irregularity
Abnormality
4-41. What angles are between the magnetic lines of force and the horizontal?
A.
B.
C.
D.
Dip
Force
Variation
Magnetic
4-42. Other than the sensitivity of the detector, what characteristic of a magnetic anomaly will affect
the maximum detection range?
A.
B.
C.
D.
Depth
Speed
Intensity
Wavelength
4-43. The difference between the Earth’s surface and the magnetic lines of force at the equator and
the magnetic poles is 0 and what maximum number of degrees?
A.
B.
C.
D.
40
30
60
90
4-44. At what altitude should magnetic anomaly detection equipment be operated to improve the
odds of detecting anomalies?
A.
B.
C.
D.
Very low
Low
High
Very high
4-29
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4-30
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CHAPTER 5
INDICATORS
Indicators are components used to display navigation, attack, and situational information to the
operator. However, many of the indicators in modern aircraft do more than to display information.
Multipurpose displays can provide the operator with control of other systems and subsystems. This
chapter provides an overview of the types of indicators installed in the Patrol (P)-3 Orion and
Fighter/Attack (F/A)-18 series aircraft.
LEARNING OBJECTIVES
When you have completed this chapter, you will be able to do the following:
1. Describe the operating principles of a typical aircraft navigation indicator.
2. Describe the operating modes of a typical aircraft head-up display (HUD).
3. Describe the operating principles of typical aircraft tactical displays.
AIRCRAFT NAVIGATION INDICATORS
The electronic flight display system (EFDS) is installed in the P-3 Orion and provides the operator
with the following information:
•
Aircraft course
•
Bearing
•
Heading
•
Distance
Additionally, the EFDS displays aircraft pitch and roll information and the steering commands
necessary to fly a designated course. The EFDS also displays indications that assist the operator
while using an instrument approach to land the aircraft. All of the indications and symbology for the
EFDS are displayed on the electronic horizontal situation indicator (EHSI).
Electronic Flight Display System Interfaces
The EFDS receives signals from the following systems:
•
Digital data computer
•
Navigation simulator
•
Tactical air navigation (TACAN) set
•
Multi-mode receiver
•
Direction finder group
•
Global positioning system (GPS)
•
Inertial navigation system (INS)
•
Low frequency automatic direction finder group
5-1
Digital Data Computer
The digital data computer receives signals
from the INS and computes command course
to assist in tactical maneuvering and to
provide drift angle information.
Navigation Simulator
The navigation simulator (Figure 5-1) allows
the EFDS to operate when the aircraft is on
the ground by supplying power to relays in the
navigation interconnection box. When the
relays are engaged, the EFDS will display
simulated heading information to the operator.
Tactical Air Navigation Set
The TACAN set provides the EFDS with the
distance and bearing information to a
compatible station. Course deviation and tofrom information is computed internally and
displayed as symbology on the EHSI.
Figure 5-1 — Navigation simulator.
Multi-Mode Receiver
The multi-mode receiver incorporates signals received for the very high frequency (VHF)
omnidirectional radio range (VOR), instrument landing system (ILS), glideslope receiver, and marker
beacon systems. The signals collected by the multi-mode receiver are routed to EFDS when the
appropriate mode of operation is selected.
Direction-Finder Group
The direction-finder group consists of the ultrahigh frequency (UHF) direction-finder and the on-top
position indicator (OTPI) systems. When one of the systems is selected by the operator, the
appropriate symbology is displayed on the EHSI.
Global Positioning System
The aircraft GPS provides the following data to the EFDS:
•
Bearing
•
Latitude
•
Longitude
•
Waypoint
•
Altitude
•
Distance
•
Speed
5-2
Inertial Navigation System
The INS provides the EFDS with magnetic or true heading signals. Magnetic heading signals are
supplied to the EHSI in normal operating modes. When a tactical mode of operation is selected, the
aircraft true heading is supplied to and displayed on the EHSI.
Low Frequency Automatic Direction Finder Group
The low frequency automatic direction finder group routes signals through the navigation
interconnection box. The low frequency automatic direction finder signals will be displayed as either a
bearing pointer 1 or bearing pointer 2 on the EHSI.
Electronic Flight Director System Components
The EFDS uses the following components to operate and to display situational information to the
operator:
•
EFDS control
•
Multifunction display
Electronic Flight Director System Control
The EFDS control provides the operator
with the interface to select and change
the operational setting for the EFDS.
The EFDS control is illustrated in Figure
5-2.
Multifunction Display
There are five multifunction displays
installed in the P-3 Orion aircraft. Each
of the multifunction displays provides
the operator with the interfaces to select
the following indicator display modes:
•
EHSI
•
EHSI map mode
•
Electronic flight director indicator (EFDI)
•
Primary flight display
Figure 5-2 — EFDS control box.
NOTE
In addition to the EFDS, the P-3 Orion multifunction display
provides the operator with control and display of numerous
avionics systems and subsystems installed within the
aircraft.
5-3
Figure 5-3 — EHSI symbology.
The following numbered items provide an overview of the EHSI (Figure 5-3) and symbology.
1. Pilot heading – is controlled by the heading knob on the pilot EFDS control box. The pilot
heading bug is colored magenta.
2. Heading reference – indicates the heading reference used (magnetic or true) when the
selected navigation mode is the flight management system, VOR, or TACAN.
3. Track indicator – is colored green and rotates around the compass card to reflect the ground
track that is computed by the flight management system.
4. Heading index/readout – indicates the current heading of the aircraft with a digital readout.
5. Bearing pointer 1 – is associated with the bearing source selected on the pilot EFDS control
box. The bearing pointer 1 is colored magenta.
6. Copilot heading – is controlled by the heading knob on the copilot EFDS control box. The
copilot heading bug is colored cyan.
7. Bearing pointer 2 – is associated with the bearing source selected on the copilot EFDS control
box. The bearing pointer 2 is colored cyan.
5-4
8. Wind indicator – uses a modified Beaufort scale to show wind display and direction and is
colored green. The wind indicator rotates around the compass card to show the current wind
direction.
9. Flight management system navigation source – displays the current source of the navigation
solution.
10. Flight management system distance – is displayed regardless of the selected navigation
source. The distance resolution is 0.1 mile below 100 miles and 1.0 mile above 100 miles up to
999 miles.
11. Active waypoint identification – displays the active waypoint identifier and is displayed below
the flight management distance readout.
12. Course arrow – is a segmented white arrow that represents the desired track and is controlled
by an external source. A digital readout of the course arrow position is displayed in 1-degree
increments.
13. To-from indicator – is displayed towards the nose or tail of the aircraft. The indicator is a white
triangle-shaped symbol and is removed from the display when a localizer frequency is selected
by the operator.
14. Course deviation bar – indicates the deviation relative to the course arrow position. The
deviation is indicated by the course deviation bar deflecting across a four dot reference scale.
15. Navigation source – indicates the source of the course data.
16. Navigation source submode – displays the submode based on the localizer frequency and
back course conditions.
17. Course/Desired track indicator – indicates the current selected navigation source course or
desired track. A digital readout of the course arrow position is displayed in 1-degree
increments below the course/desired track label.
18. Assigned altitude – is processed and displayed in a digital numeric readout with a resolution of
100-foot increments when manually entered into the navigation system.
19. Compass card – is a full 360-degree compass with north, east, south, and west designating
the cardinal points and numerical marks at 30-degree intervals. Fixed cardinal marks are
displayed at 45-degree intervals around the perimeter of the compass card.
20. Bearing pointer 1 source – indicates the bearing pointer source selected by the pilot.
21. Bearing pointer 2 source – indicates the bearing pointer source selected by the copilot.
22. Command heading – displays the heading currently set by the heading knob on the EFDS
control box.
23. Wind – displays a digital readout of the wind direction and speed data received from the flight
management system.
24. Aircraft symbol – is stationary and is displayed in the center of the compass card.
25. Course deviation dots – indicate the course deviation in degrees relative to the course arrow
position.
26. TACAN channel – displays the selected TACAN channel.
27. TACAN distance measuring equipment – displays the distance from the current selected
station.
5-5
Figure 5-4 — EFDI symbology.
The following numbered items provide an overview of the EFDI (Figure 5-4) and symbology.
1. Sky/Ground pitch and attitude display – indicates the aircraft pitch and roll through the
relationship of the blue upper half and brown lower half of the display. Roll is a continuous 360degree display and pitch is a 90-degree display.
2. Heading tape – is a white heading readout showing current heading with 15 degrees displayed
on each side of the center area of the indicator.
3. Roll attitude index – indicates when a no-roll condition of the aircraft exists.
4. Roll attitude indicator – provides the positon of the moving roll pointer with reference to the
bank scale.
5-6
5. Pitch tape – provides the positon of the pitch tape with reference to the nose of the aircraft.
6. Marker beacon annunciation – represents the outer, middle, and inner instrument landing
beacons when the discrete signal is detected.
7. Crosshair indicator – is used as a pilot/copilot centering cue during a TACAN/VOR/ILS
localizer approach and is green in color.
8. Pitch and roll command bar – moves up and down in 15-degree increments and rotates 45
degrees about the center of the display. The pitch and roll command bars are magenta with
shading and black outline.
9. Horizon – displays the aircraft pitch and roll attitude in relation to the horizon.
10. Aircraft symbol – is the reference source for the pitch and roll indicators.
11. Navigation source – indicates the selected navigation source.
12. Navigation source submode annunciations – displays the submode of the selected navigation
source.
13. Course/Localizer deviation indicator and scale – is located on the bottom center of the display
and consists of a green pointer that moves a maximum of 2.5 dots. The scale consists of two
white dots on both sides of a white center index.
14. Rate-of-turn indicator and scale – displays the calculated rate-of-turn based on the rate of
change of the aircraft heading.
15. Glideslope deviation indicator and scale – consists of a center horizontal bar and a series of
vertical white dots. Each of the dots above and below the center bar represents ¼-degree
displacement from the center of the glideslope beam.
16. Glideslope annunciation – displays when the pilot has selected a compatible navigation mode
and the signal is valid and reliable.
HEAD-UP DISPLAY
The F/A-18 series HUD is a primary flight instrument that displays essential flight and essential
weapons system information. The HUD projects symbology into the operator field-of-view through the
use of a combiner glass assembly. The HUD projects the following information:
•
Aircraft attitude
•
Steering cues
•
Navigation data
•
Air-to-air data
•
Air-to-ground data
•
Weapons data
Controls and Indicators
The F/A-18 series aircraft HUD uses the following controls and indicators (Figure 5-5):
•
HUD symbology normal/reject 1/reject 2 (HUD SYM-NORM/REJ 1/REJ 2) switch
•
HUD SYM-brightness (HUD SYM-BRT) control
•
HUD SYM DAY/AUTO/NIGHT switch
5-7
•
Altitude (ALT) switch
•
Attitude (ATT) switch
•
Course (CRS) set switch
•
Heading (HDG) set switch
Figure 5-5 — HUD control switches.
Head-Up Display Symbology Normal/Reject 1/Reject 2 Switch
The HUD SYM NORM/REJ 1/REJ 2 is a three-position toggle switch. Symbology is provided to the
HUD when the switch is in the NORM positon. The REJ 1 and REJ2 positions do the following:
•
REJ 1 – removes the ground cue, aircraft Mach number, airspeed box, altitude box, aircraft G
label and digits, and bank scale and bank scale indicator from the HUD field-of-view.
•
REJ 2 – removes all of the REJ 1 symbology and the heading scale, command heading,
heading box, heading caret, navigation range, bank angle scale, bank angle pointer, and time
window from the HUD field-of-view.
Head-Up Display Symbology Brightness Control
The HUD SYM-BRT control is used to turn the HUD to the on position. The HUD SYM-BRT control
also allows the operator to vary the intensity of the display to the ambient light.
Head-Up Display Symbology Day/Auto/Night Switch
The HUD SYM DAY/AUTO/NIGHT is a three-position toggle switch. When the switch is set to the
DAY position, the HUD control setting is set to the maximum symbol brightness. When the switch is
set to the AUTO position, the HUD contrast is controlled by the brightness control circuit. When the
switch is set to the NIGHT position, the HUD symbology is set to a reduced brightness level.
Altitude Switch
The ALT switch has two positions: barometric (BARO) and radio detection and ranging (radar) with
the position being labeled as RDR. When the switch is set to the BARO position, the aircraft displays
the computed barometric altitude on the HUD. When the switch is set to the RDR position, the aircraft
displays the radar altitude that is computed by the electronic altimeter set on the HUD.
Attitude Switch
The ATT switch has three positions: INS, automatic (AUTO), and standby (STBY). Each setting
designates a different primary data source to compute attitude. In the INS position, unfiltered INS
data is used; in the AUTO position, filtered INS data is used; and in the STBY position, the aircraft
attitude reference indicator is used.
5-8
Course Set Switch
The CRS set switch is used by the operator to manually set the aircraft course that will displayed on
the HUD.
Heading Set Switch
The HDG set switch is used by the operator to manually set the aircraft heading that will be displayed
on the HUD.
Modes of Operation
The F/A-18 series aircraft uses three master mode of operation: navigation, air-to-air, and air-toground.
Navigation Master Mode
The navigation master mode is the default mode of operation for the F/A-18 aircraft. When the
navigation master mode is selected, it provides the operator with basic flight data, steering/landing
data, and advisory data displayed on the HUD. The optical center of the HUD is placed, in height,
between the Mach number and the aircraft gravitational forces (G) value. The following numbered
items provide an overview of the navigation master mode (Figure 5-6) and symbology.
Figure 5-6 — Navigation master mode HUD symbology.
1. Heading scale – displays either the magnetic or true heading through the use of a movable 30degree heading scale.
5-9
2. True heading reference – When true heading is selected, a “T” is displayed below the heading
scale.
3. Vertical velocity – displays the aircraft vertical velocity, in feet per minute, above the attitude
navigation box when the navigation master mode is selected by the operator. The descent of
the aircraft is displayed in negative numbers.
4. Altitude – is displayed on the right-hand side of the HUD. The displayed altitude can be either
the barometric or radar altitude.
5. Barometric setting – displays the barometric setting used by the aircraft air data computer. The
barometric setting display is available in all master modes of operation.
6. Closing velocity – is displayed, in knots, on the HUD when a valid closing velocity exists.
7. Range window – displays the target range when it is available.
8. Ghost velocity vector – is displayed when the velocity vector is caged on the right-hand side of
the HUD.
9. Flight path pitch ladder – displays the aircraft position referenced to the velocity vector to
provide both pitch and flight path information.
10. Bank scale – is displayed at the bottom of the HUD with tick marks at 5 degrees, 15 degrees,
30 degrees, and 45 degrees. The bank angle scale is not displayed in the air-to-air and air-toground master modes.
11. Peak aircraft G’s – are displayed anytime the aircraft exceeds 4.0 G’s.
12. Aircraft G’s – display the normal acceleration of the aircraft below the Mach number indicator.
13. Mach number – displays the aircraft Mach immediately below the digital angle of attack
indicator.
14. Angle of attack – the true angle of attack is displayed at the left center of the HUD in degrees.
15. Required ground speed cue – is displayed when sequential steering and time on target has
been selected by the operator. If a pointer is displayed to the right of the reference mark, the
aircraft is flying too fast. If a pointer is displayed to the left of the reference mark, the aircraft is
flying too slow.
16. Air speed – displays the calibrated air speed that is calculated by the air data computer.
Air-to-Air Master Mode
The air-to-air master mode is highly automated to reduce the amount of operator tasks in selecting
air-to-air weapons, managing sensors, and selecting attack modes. The air-to-air master mode is
optimized for the effective beyond-visual-range, head-down attack capability.
The air-to-air mode additionally provides for the short-range attack capability using the aircraft guns,
and short- to medium-range missiles. The automatic features of the air-to-air mode allow the operator
to concentrate on the primary requirement of air-to-air combat. If the air-to-air mode is deselected by
the operator, the aircraft will default to the navigation master mode of operation. The following
numbered items provide an overview of the air-to-air master mode (Figure 5-7) and symbology.
1. Target locator line – assists the operator in quickly locating a target designation box or a
designation diamond.
2. Shoot cue – indicates that the selected weapon has acquired an acceptable firing solution.
5-10
Figure 5-7 — Air-to-air master mode HUD symbology.
3. Multiple target cue – indicates that multiple targets exist in the target designation box line-ofsight window.
4. Target designator – is a 25-milliradian square that identifies the line-of-sight to the selected
target. The target designator is displayed for all air-to-air weapons modes.
5. Sensor – indicates the selected sensor being employed for air-to-air weapons launch and
steering data.
6. Target aspect cue – provides a head-up indication of the launch and steering target aspect
angle.
7. Target range rate – indicates the target range in knots whenever the target data is valid.
8. Target range – is displayed only for air-to-air missiles whenever the target data is valid. The
target range is displayed to the nearest 10th of a nautical mile.
9. Selected weapon/count – is used to display the selected weapon and the quantity installed on
the aircraft.
10. Master arm cue – displays an “X” through the selected weapon when the aircraft master arm
switch is placed in the safe position.
11. Alternate line-of-sight – displays a small “x” that represents a second designated target’s lineof-sight.
5-11
12. Breakaway “X” – indicates to the operator when to break off the engagement or to alter the
attack position to achieve a positive weapons delivery solution. The breakaway “X” is displayed
for all air-to-air weapons when the range to the target is less than the minimum computed
range for the selected weapon.
13. Steering dot – is displayed on the HUD whenever an air-to-air missile is selected and a target
has been designated and is located within 76 degrees of the aircraft boresight.
Air-to-Ground Master Mode
The air-to-ground master mode is used for delivering conventional and laser-guided bombs, GPS
weapons, mines, guided weapons, and rockets. Weapons delivery is assured through the use of
backup features and redundant fail-safe systems. The focal point for air-to-ground weapons delivery
is the aircraft stores management system.
The aircraft mission computer and the stores management system control the air-to-ground weapons
delivery and weapons programming while providing vital advisory data and cueing to assist in an
attack. The following numbered items provide an overview of the air-to-ground master mode (Figure
5-8) and symbology.
1. Steering pointer – is displayed on the HUD heading scale when the air-to-ground mode is
activated by the operator. The pointer provides a visual steering cue to a selected waypoint or
offset aim point. When a target is designated, the steering cue is replaced by a diamond that
indicates the designation status.
Figure 5-8 — Air-to-ground master mode HUD symbology.
5-12
2. Pull-up cue – is displayed on the HUD when the selected air-to-ground weapon is a mine,
conventional bomb, or rocket. The distance between the velocity vector and the pull-up cue
provides the operator with a relative indication of ground avoidance or the dud altitude.
3. Breakaway “X” – is displayed when the pull-up cue intersects with the velocity vector. When
this condition occurs, the breakaway “X” flashes on the HUD.
4. Delta (Δ) time-of-fall cue – is displayed when the weapons time-of-fall exceeds 128 seconds.
The Δ time-of-fall cue indicates that the mission computer is unable to accurately determine
the impact point of the weapon.
5. Dud cue – is displayed when the bomb time-of-fall is less than the dud time for the fuze code
that is entered into the stores management system with the stores fuze option selected. The
dud cue is also displayed when any of the aircraft fuzing options are not selected.
6. Navigation designation range – is displayed when a steering mode or offset aim point is
selected by the operator. The navigation designation range is displayed to the nearest 10th of
a nautical mile.
7. Continuously computed impact point – indicates the impact point of the selected weapon if the
weapon release was immediately pressed by the operator. If the current weapon impact point
is not in the HUD field-of-view, the continuously computed impact point will not be displayed.
8. Displayed impact line (continuously computed impact point) – provides the operator with a
steering cue to position the continuously computed impact point cross onto the selected target.
AIRCRAFT TACTICAL DISPLAYS
The F/A-18 series of aircraft multipurpose display group (MDG) displays all the information required
by the operator to carry out the mission. Maintenance technicians also use the MDG to view the
status of various aircraft systems and to troubleshoot and isolate system discrepancies.
Multipurpose Display Group
The MDG (Figure 5-9) system provides the displays for
the following aircraft functions:
•
Aircraft attitude
•
Navigation
•
Air-to-air
•
Air-to-ground
•
Warnings, cautions, and advisories
•
Aircraft checklists
•
Built-in tests
The MDG receives digital data signals from the mission
computer system and the radar system. The digital data
is used by the MDG system to produce the symbology
and indications required for the selected display. The
MDG system also receives the composite video from
the aircraft radar system. Video is provided from the
armament computer to the MDG to display forwardlooking infrared (FLIR) and compatible weapons video.
5-13
Figure 5-9 — Typical multipurpose
display group.
The MDG provides the required digital or analog interface with the following systems:
•
Mission computer
•
Radar
•
Stores management
•
Flight incident recording and monitoring
•
Video recording
The physical components used by the MDG to display information are as follows:
•
Left digital data indicator (LDDI)
•
Right DDI (RDDI)
•
Multipurpose color display (MPCD)
•
HUD
Digital Data Indicators
The purpose of both digital data indicators (DDIs) is to display color alphanumeric symbology, a
variety of raster video inputs, deflection voltages, raster/stroke video, and digital serial data to other
displays. The DDIs contain circuits that generate calligraphic stroke letters, numbers, and symbols on
the display area.
The DDIs receive command signals from the aircraft mission computer system via a dual avionics
multiplex bus. The DDIs also contain one channel that is used to display radar digital data, which is
under the control of the mission computer system. An interface is provided for discrete and analog
inputs and outputs. A composite video switch matrix accepts up to five external video inputs and one
internal test video input.
Left Digital Data Indicator
When the LDDI is operating in normal mode, it provides the operator with the following displays:
•
Stores status
•
Weapon video
•
Built-in test status
•
Aircraft engine monitoring
•
Cautions and advisories
The LDDI also can reproduce aircraft navigation information through an interface with the mission
computer system. The LDDI is also the main component to generate symbology for the HUD. The
LDDI and RDDI are physically and electrically identical; therefore, they are interchangeable.
Right Digital Data Indicator
When the RDDI is operating in normal mode, it provides the operator with radar and weapons video
displays. The RDDI is also capable of displaying the operator-requested information and provides the
interface between the HUD and the mission computer system. If the LDDI fails for any reason, the
RDDI is able to produce the symbology for the HUD. However, the RDDI will operate in a degraded
mode. A typical DDI is illustrated in Figure 5-10.
5-14
Figure 5-10 — Typical digital data indicator.
Multipurpose Color Display
When the MPCD is operating in normal mode, it provides the operator with steering and navigation
displays. The MPCD is also the main interface for the digital map system. The digital map system
provides the operator with a colored map overlay that displays the aircraft’s current position based on
the data received from the INS.
Head-Up Display
The HUD is the primary flight instrument that displays essential flight and tactical systems
information.
5-15
End of Chapter 5
Indicators
Review Questions
5-1.
What electronic flight display system interface allows the system to operate with the aircraft on
the ground?
A.
B.
C.
D.
5-2.
What electronic flight display system interface provides the bearing and distance to a
compatible station?
A.
B.
C.
D.
5-3.
Four
Five
Six
Seven
What color is the electronic horizontal situation indicator copilot heading symbol?
A.
B.
C.
D.
5-6.
Navigation simulator
Digital data computer
Tactical air navigation set
Multi-mode receiver
How many multifunction displays are installed in the P-3 Orion aircraft?
A.
B.
C.
D.
5-5.
Navigation simulator
Digital data computer
Tactical air navigation set
Multi-mode receiver
What electronic flight display system interface incorporates the signals from various navigation
systems?
A.
B.
C.
D.
5-4.
Navigation simulator
Digital data computer
Tactical air navigation set
Multi-mode receiver
Red
Green
Cyan
Magenta
What color is the electronic horizontal situation indicator pilot heading symbol?
A.
B.
C.
D.
Red
Green
Cyan
Magenta
5-16
5-7.
The electronic horizontal situation indicator assigned altitude is a numeric readout with a
resolution in increments of how many feet?
A.
B.
C.
D.
5-8.
The electronic flight director roll attitude indicator provides the position of the roll pointer in
reference to what scale?
A.
B.
C.
D.
5-9.
100
150
200
250
Pitch
Attitude
Horizon
Bank
The head-up display control panel symbology switches both have how many selectable
positions?
A.
B.
C.
D.
Two
Three
Four
Five
5-10. What type of glass makes up the head-up display?
A.
B.
C.
D.
Acrylic
Ballistic
Combiner
Tempered
5-11. Other than barometric, what is the other head-up display altitude switch position?
A.
B.
C.
D.
Radar
Pressure
Indicated
Atmospheric
5-12. The head-up display attitude switch has what number of positions?
A.
B.
C.
D.
Two
Three
Four
Five
5-17
5-13. What head-up display mode of operation displays basic flight data?
A.
B.
C.
D.
Steering
Air-to-air
Navigation
Air-to-ground
5-14. What head-up display mode of operation is optimized for beyond-visual-range target
engagement?
A.
B.
C.
D.
Steering
Air-to-air
Navigation
Air-to-ground
5-15. What symbol is shown on the head-up display when an acceptable weapons solution has been
acquired?
A.
B.
C.
D.
Shoot cue
Target range cue
Target designator
Multiple target cue
5-16. The delta time-of-fall cue is displayed on the head-up display when the weapon time-of-fall
exceeds how many seconds?
A.
B.
C.
D.
108
118
128
138
5-17. What system is the focal point for air-to-ground weapons delivery?
A.
B.
C.
D.
Radar
Navigation
Communication
Stores management
5-18. The digital data indicator contains circuits that generate what type of letters?
A.
B.
C.
D.
Digitized
Interlaced
Calligraphic
Multiplexed
5-18
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5-19
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CHAPTER 6
INFRARED
The term infrared (IR) is a Latin word that means beyond the red. The process of detecting or sensing
IR radiation from a target without being in physical contact with that target is known as remote
sensing. Active and passive systems are both used for remote sensing.
Active systems send a signal to the target and receive a return signal. A radar set is an example of an
active system because it requires a return signal to process target data. Passive systems detect a
signal or disturbance originating at the target. The signal may be emitted by either the target or
another source. Photography using natural light is an example of a passive system.
LEARNING OBJECTIVES
When you have completed this chapter, you will be able to do the following:
1. Recognize the functions of IR imaging.
2. Identify the characteristics of IR imaging.
3. Recognize the components of IR imaging.
4. Describe the operating principles of IR imaging.
5. Recognize the components of a typical Forward Looking Infrared (FLIR) system.
6. Describe the operating principles of a typical FLIR system.
ELECTROMAGNETIC SPECTRUM
Humans can see only a small part of the entire
electromagnetic spectrum. However, there are
other parts of the spectrum that contain useful
information. The IR band exists in a small
portion of the electromagnetic spectrum, and IR
radiation is a form of electromagnetic energy. IR
waves have certain characteristics similar to
those of light and radio frequency waves. These
characteristics include reflection, refraction,
absorption, and speed of transmission. IR
waves differ from light, radio frequency, and
other electromagnetic waves only in
wavelengths and frequency of oscillation.
The IR frequency range is from about 300
gigahertz (GHz) to 400 terahertz (THz). Its place
in the electromagnetic spectrum (Figure 6-1) is
between visible light and the microwave region
used for high-definition radar. The IR region of
the electromagnetic spectrum lies between
wavelengths of 0.72 and 1,000 micrometers
(µm) Discussion of the IR region is usually in
terms of wavelength rather than frequency.
Figure 6-1 — Electromagnetic spectrum.
6-1
THERMAL IMAGING
IR radiation is also known as thermal or heat radiation. Most materials emit, absorb, and/or reflect
radiation in the IR region of the electromagnetic spectrum. For example, an aircraft parked on a sunlit
runway absorbs and radiates varying amounts of IR radiation. After the sun sets, the aircraft
continues to radiate the absorbed heat, making detection at night possible. Even if the aircraft is
moved, detection is possible because the runway surface, which was directly below the aircraft, will
be cooler than the surrounding runway.
Thermal imaging is referenced in terms of temperature instead of reflectivity (radar) or color (visible
light). Variations of the temperature in a scene tend to correspond to details that can be visually
detected. The IR imaging system processes this information and converts it into information that the
system operator can use. Currently, the types of imaging systems generally used are mechanical
scanning, fast-framing devices. They use a frame rate (information update rate) that is similar to
television. These devices are commonly known as Forward Looking Infrared (FLIR) systems.
Before a target can be detected, it must exchange energy with its environment, be self-heating, have
emissivity differences, and reflect other sources. The FLIR system uses thermal sensitivity, image
sharpness, spectral response, contrast, and magnification to produce a visual image of the thermal
scene. The operator of the system uses training, experience, and image interpretation skills to detect
and identify targets.
INFRARED RADIATION
The atmosphere is a poor transmitter of IR radiation because of the absorption properties of carbon
dioxide (CO2), water (H2O), and ozone (O3). IR radiation is grouped into four regions by wavelength,
as shown in Table 6-1. The transmission spectrum of the atmosphere is shown in Figure 6-2. The
best transmission areas for IR radiation are between 3 and 5 µm, and between 8 and 14 µm. The
range between these wavelengths is known as a window. IR imaging devices are designed to operate
in one of these two windows, usually the 8 to 14 µm window.
Table 6-1 — Characteristics of IR Radiation
NAME
ACRONYM
WAVELENGTH
Near Infrared
NIR
Middle Infrared
MIR
Far Infrared
FIR
0.72 – 3 µm
Extreme Infrared
XIR
Infrared Radiation Sources
3 – 6 µm
6 – 15 µm
15 – 1000 µm
All matter whose temperature is above absolute zero (-273 degrees Celsius (°C) or -460 degrees
Fahrenheit (°F)) emits IR radiation. The amount of the radiation emitted is a function of heat. The
emissivity of various objects is measured on a scale of 0 to 1. Theoretically, a perfect emitter is a
black body with an emissivity of 1. Realistically, the best emissivity is somewhere closer to 0.98. The
total energy emitted by an object at all wavelengths is directly dependent upon its temperature. If the
temperature of a body is increased 10 times, the IR radiation emitted by the body is increased 10,000
times. If the energy emitted by a black body and its wavelength is plotted on a graph, a hill-shaped
curve results (Figure 6-3). The graph shows that the energy emitted by short wavelengths is low. As
the wavelength size increases, the amount of energy increases until it reaches a peak amount. After
the peak is reached, the energy emitted by the body drops off sharply with a further increase in
wavelength.
6-2
Figure 6-2 — Transmission spectrum of the atmosphere.
Infrared Optics
Many of the materials commonly used in visible
light optics are opaque at IR frequencies.
Therefore, these materials would not be
suitable for IR imaging systems. The optical
material used in IR imaging systems should
have a majority of the following qualities:
•
Be transparent at the wavelengths on
which the system is operating
•
Be opaque to other wavelengths
•
Have a zero coefficient of thermal
expansion to prevent deformation and
stress problems in optical components
•
Have high surface hardness to prevent
scratching the optical surfaces
•
Have high mechanical strength to allow
the use of thin lenses (high-ratio
diameter to thickness)
•
Have low volubility with water to prevent
damage to optical components by
atmospheric moisture
•
Be compatible with antireflection
coatings to prevent separation of the
coating from the optical component
Figure 6-3 — Black body radiation.
6-3
None of the materials currently used for IR optics have all of these qualities. However, silicon,
germanium, zinc selenide, and zinc sulfide have many of them.
Infrared Detectors
The detector is the most important component of the IR imaging system. There are many types of
detectors, each having a distinct set of operating characteristics. Bolometers, Golay cells, mercurydoped germanium, lead sulfide, and phototubes are the most commonly used types of detectors.
Detectors can be characterized by their optical configuration or by the energy-matter interaction
process. There are two types of optical configurations: elemental and imaging.
Elemental Detectors
Elemental detectors average the portion of the image of the outside scene falling on the detector into
a single signal. To detect the existence of a signal in the field-of-view (FOV), the detector builds up
the picture by sequentially scanning the scene. Therefore, the elemental detector requires time to
develop the image because the entire scene must be scanned.
Imaging Detectors
Imaging detectors yield the image directly. Each of the detectors responds to a discrete point on the
image. Therefore, the imaging detector produces the entire image instantaneously. A good example
of an imaging detector is photographic film.
Energy-Matter Interaction
There are two basic types of energy-matter interaction. They are the thermal effect and the photon
effect.
Thermal Effect
The thermal effect type of energy-matter interaction involves the absorption of radiant energy in the
detector. Absorption results in a temperature increase in the detector element. Radiation is detected
by monitoring the temperature increase in the detector. Both the elemental and imaging forms of
detectors use the thermal effect.
Photon Effect
In the photon effect type of energy-matter interaction, the photons of the radiant energy interact
directly with the electrons in the detector material. Usually, detectors using the photon effect are
made out of semiconductor materials. There are three specific types of photon effect detection. They
are photoconductivity, photoelectric, and photo-emissive.
•
Photoconductivity is the most widely used photon effect. Radiant energy changes the electrical
conductivity of the detector material. An electrical circuit is used to measure the change in the
conductivity.
•
In the photoelectric effect (also referred to as photovoltaic), an electric potential difference
across a semiconductor P material and N material (PN) junction is caused by the radiant
signal. The photocurrent (current generated by light) is added to the dark current (current that
flows with no radiant input). The total current is proportional to the amount of light that falls on
the detector.
•
The photo-emissive effect is also known as the external photo effect. The action of the
radiation causes the emission of an electron from the surface of the photocathode to the
6-4
surrounding space. The electron is photo-excited from the
Fermi level above the potential barrier at the surface of the
metal.
Infrared Imaging Systems
An IR imaging system has the following components: detectors, a
scene dissection system, front end optics, a refrigeration system,
and an image processing system.
Detectors
Detectors convert the IR radiation signal into an electrical signal
that is processed into information used by the operator. Detectors
can be arranged in many different configurations for their use in an
IR imaging system.
Detector Array
Only a small portion of the image scene is needed by a detector (or
detectors) to achieve maximum resolution. A large number of
detector elements can be grouped together to form an array
(Figure 6-4, View A). The elements of this array are packed closely
together in a regular pattern. Therefore, the image of the scene is
spread across the array like a picture or a mosaic. Each detector
element views a small portion of the total scene. The disadvantage
of this type of system is that each detector element requires a
supporting electronic circuit to process the information that it
provides. In addition, each detector element requires a preamplifier
to boost the signal to a usable level.
Single Detector
Another method that is used to provide the operator with
information is the single detector (Figure 6-4, View B). Here, there
is one detector requiring one set of supporting circuitry. In this type
of system, the detector is scanned across the image so that the
detector can see the whole image. An optical system is required
that can supply the scanning. This type of system is adequate if
real-time information is not needed, or if the object of interest is
stationary or not moving quickly.
Scene Dissection System
The scene dissection system is used to scan the scene image.
Many types of scanning mechanisms are associated with each
type of detector array. When a single detector with one axis of fast
scan and one axis of slow scan is used, the scene is scanned
rapidly in the horizontal direction and slowly in the vertical
direction. As a result, the line is scanned horizontally; then the next
line is scanned horizontally, and so on.
A vertical linear array is scanned rapidly in the horizontal direction
(Figure 6-4, View C). One detector element scans one line of the
6-5
Figure 6-4 — Detector arrays.
image. In the linear array, there is a space, one element wide, between each element. The scan
pattern is one axis with an interlace. A vertical linear array is scanned rapidly in the horizontal
direction. After each horizontal scan, the mechanism shifts the image upward or downward one
detector element width so that on the next scan, the lines that were missed are covered.
Each system has an optimum configuration of detector array and image dissection. If the number of
elements in the detector increases, the system becomes more complicated. In addition, the cost of
the system increases, while the reliability of the system decreases. If the number of detectors
decreases, the amount of information that can be processed is reduced. A compromise between a
large number of elements (increased cost) and a smaller number of elements (reduced information) is
the linear array that scans in one direction only. Each detector scans one line of the scene image.
The complexity of the electronics is reduced, and the amount of information that is processed is
increased. Therefore, the size of the scene to be viewed and the detail increases.
Many types of mechanisms can be used to scan the scene. When you scan with two axes, the two
scanning motions must be synchronized. The electronic signal that controls the sampling of the
detectors must also be synchronized with the scanning motions.
Front-End Optics
The front-end optics collects the incoming radiant
energy and focuses the image at the detectors. An
example of front-end optics on a targeting pod is
shown in Figure 6-5. The optics may be reflective
or refractive, or a combination of both. Many
systems offer a zoom capability, allowing a
continuous change in magnification of the image
without changing the focus. Spectral filters are
used to restrict the wavelength of light entering the
system. Spectral filters prevent unwanted
wavelengths of light from reaching the detector and
interfering with the imaging process.
Refrigeration System
A refrigeration system is needed in imaging
systems because many types of IR detectors
require low temperatures to properly operate. The
two types of detector cooling systems that are used
are the open-cycle and the closed-cycle types.
Figure 6-5 — Front-end optics.
In the open-cycle type of cooling, a reservoir of liquefied cryogenic gas is provided. The liquid is
forced to travel to the detector, where it is allowed to revert to a gas. As it changes from a liquid to a
gas, a great deal of heat is absorbed from the surrounding area and the detector.
In the closed-cycle type of cooling, the gas is compressed, and the heat generated by the
compression is radiated away through the use of a heat exchanger. The gas is then returned to the
compressor, and the cycle repeats itself.
Image Processing Systems
The image processing system is used to convert the data collected by the detectors into a video
display. Data from the detectors is multiplexed so that it can be handled by one set of electronics. The
data is then processed so that the information coming from the detectors is in the correct order of
serial transference to the video display. At this point, any other information that is to be displayed is
6-6
added. The signals from the detectors in many image processing systems are amplified and sent to
light emitting diode (LED) displays.
FORWARD LOOKING INFRARED SYSTEM
The AN/ASQ-228 Advanced Targeting Forward Looking Infrared (ATFLIR) system (Figure 6-6)
provides the operator with real-time, passive thermal and visible imagery during day and night
operations. The ATFLIR system can be used to detect, classify, track, and designate both air-to-air
and air-to-surface targets of interest that would be concealed from either visual observation or radar
detection. The system was designed to give the operator the ability to deliver precision-guided
ordnance at a standoff distance outside of anti-air weapon envelopes. The ATFLIR system scans an
operator-selected portion of the terrain along the aircraft’s flight path and displays a televised image
of the IR and visible patterns of the terrain. In addition, the ATFLIR system does not emit
transmissions that can be detected by enemy forces. Although various types of FLIR systems used in
the Navy, the ATFLIR system is a good example of the components and operational capabilities of
other systems currently in use.
Figure 6-6 — AN/ASQ-228 ATFLIR system.
ATFLIR System Components
The ATFLIR system consists of 25 different Weapons Replaceable Assemblies (WRAs). The WRAs
are listed below and described in the following paragraphs:
•
Electro-optical sensor unit (EOSU)
•
Environmental control valve (ECV)
•
Eurocard modules
•
Laser electronics unit
•
Laser transceiver unit
6-7
•
Advanced Navigation Forward Looking Infrared (ANFLIR) sensor
•
Pod adapter unit
•
Pod electronics housing
•
Power interrupt protector
•
Roll drive amplifier
•
Roll drive motor
•
Roll drive unit
Electro-Optical Sensor Unit
The EOSU (Figure 6-7) is a self-contained
component designed to protect and seal the
optics and laser equipment from moisture,
contaminants, and electromagnetic interference.
Housed within the EOSU are the ATFLIR
midwave IR receiver, gimbal-mounted telescope,
laser spot tracker, and visible electro-optical
(EO) camera. All optical components are
mounted on a one-piece, beryllium aluminum
optical bench. The bench was designed to
eliminate alignment errors when individual
optical components are removed for
maintenance. The outer structure of the EOSU is
designed to withstand the wind loads of mach
plus velocities associated with high-speed
aircraft. The outer structure includes the
windscreen, multispectral, and laser spot tracker
windows. The optical bench is suspended in the
outer structure on four vibration isolators and
gimbals. The EOSU interfaces with many of the
power supply and processor Eurocard modules.
Figure 6-7 — ATFLIR electro-optical sensor
unit.
Environmental Control Valve
The environmental control valve (ECV) regulates the aircraft cooling air for the installed components
within the ATFLIR pod. In addition, the ECV enables airflow for the pod when the pod is operated on
the ground. The ECV is a vital component to the ATFLIR system, especially in warmer operating
areas.
Eurocard Modules
Eurocard modules (Figure 6-8) are individual circuit cards that are responsible for managing and
routing a variety of signals to control the operational functions of the ATFLIR system. Some examples
of the signals being routed and exchanged are pod control, temperature management, and video
signal correction. The Eurocard modules are mounted in a cooled card cage within the pod
electronics housing for easier maintenance access.
6-8
Laser Electronics Unit
The laser electronics unit is the primary interface between the laser transceiver unit, the aircraft, and
the pod. The laser electronics unit interfaces with the aircraft for discrete laser arming signals. The
laser electronics unit contains three functional subunits for interface and power.
Laser Transceiver
Unit
The laser
transceiver unit
provides the
energy for laser
generation, which
enables the
operator to deliver
precision-guided
ordnance on
target, the first
time. This
component is
purged with dry air
and sealed to
protect against
contamination. The
laser transceiver
unit provides a
Figure 6-8 — ATFLIR Eurocard modules.
boresight
reference source in
the form of a laser diode, which produces a low-power
signal that is precisely aligned to be parallel with the main
beam output wavelengths. The unit delivers laser energy
at repetition rate of 20 hertz (Hz) at a wavelength of
1.064 µm. The actual power output level of the laser
energy being generated by the transceiver unit is
classified information.
Advanced Navigation Sensor
The ANFLIR sensor is a self-contained FLIR imaging
system that provides IR imagery (Figure 6-9) used by the
operator to maneuver and navigate safely at low altitudes
and high air speeds. The imagery delivered by the
ANFLIR sensor is comparable to flying during daylight
operations while operating at night.
Pod Adapter Unit
The pod adapter unit provides the mounting and interface
for the aircraft, pod electronics housing, and ANFLIR
sensor. When a pod is installed on the aircraft, the pod
adapter unit provides the connection point for power,
signal routing, and cooling air for the ATFLIR system.
6-9
Figure 6-9 — ANFLIR video.
Pod Electronics Housing
The pod electronics
housing (Figure 6-10)
provides mounting and
interface for the pod
adapter unit, laser
transceiver, laser
electronics unit, and
environmental control valve.
In addition, the pod
electronics housing
provides interface and
mounting for the roll drive
unit, roll drive amplifier, and
Eurocard module cooled
card cage and backplane.
The pod electronics
housing contains a singlepanel maintenance door for
access to WRAs.
Power Interrupt Protector
Figure 6-10 — ATFLIR pod electronics housing.
The power interrupt protector provides the ATFLIR system with three-phase, 400 Hz rectified power
for 50 milliseconds when power from the aircraft is interrupted.
Roll Drive Amplifier
The roll drive amplifier (Figure 6-11, View A) is attached to the pod electronics housing and to the roll
drive motor. The roll drive amplifier provides the drive power to the roll drive motor.
Roll Drive Motor
The roll drive motor (Figure 6-11, View B) is mounted to the roll drive unit. It is a brushless motor with
an integral tachometer. Position readout is received with anti-backlash gearing and measuring pinion
and ring gear position. The roll drive motor electrical interface is provided by the pod electronics
housing.
Figure 6-11 — ATFLIR roll drive amplifier and motor.
6-10
Roll Drive Unit
The roll drive unit is the mechanical and electrical attachment between the EOSU and the pod
electronics housing. Roll drive unit mechanical aspects include a cooling air path for the EOSU and
ring gear drive. Roll axis rotation, and radial and axial alignment are also provided to the EOSU by
the roll drive unit.
ATFLIR Operational Capabilities
The subsystems listed and described
below will help you understand the
operational capabilities of the ATFLIR
system:
•
IR video
•
EO video
•
FOV and zoom
•
Point control
•
Track control
•
Laser and FLIR align
•
Laser energy
•
Laser range
•
Eyesafe
•
Laser spot tracker
•
ANFLIR
•
IR marker
•
Pod ECV
•
Built-in test
Figure 6-12 — IR video.
Infrared Video
This subsystem provides the IR video (Figure 6-12) for the tactical aircrew display. IR, visible, and
laser energy enters the telescope and is relayed off the pitch gimbal to beam splitters on the optical
bench. The separated IR energy passes through the relay, the derotation mechanism, and then
through the imager to the 640 X 480 element array. Nonuniformities in the raw image are corrected
by the digital nonuniformity and scene-based digital nonuniformity modules before reticules are added
by the video processor (VP). The VP also provides manual and automatic gain, level, and polarity
control and then converts the digital video to standard RS-170 analog video for display in the cockpit.
Electro-Optical Video
This subsystem provides visible imagery for use by the operator. The EO camera is boresighted to
the FLIR and laser optical path to ensure accuracy. Visible energy is separated from the laser and IR
spectrums by beamsplitters and routed to a charge coupling device (CCD) camera. The CCD camera
contains a mechanism to ensure the image being displayed maintains the correct horizon orientation.
Video for the CCD camera is digitally corrected before being routed to the VP, where reticules are
6-11
added and control functions implemented before being converted to RS-170 analog video. The EO
output utilizes the same video lines to the cockpit displays as the IR video subsystem.
Field of View and Zoom
There are three levels of optical FOV available for the operator using the ATFLIR system. They are
the wide, medium, and narrow FOVs. The wide FOV is optically fixed at 1X magnification. The
medium and narrow FOVs are optically fixed at 1X with a 2X magnification zoom capability. All three
FOVs are implemented in the reflective telescope of the EOSU with switch in mirrors.
Point Control
The pointing and stabilization functions for the ATFLIR system are provided by the line of sight
stabilization mirrors and the inertial measurement unit. These components interact with servos and
servo controllers to enable the operator to point the ATFLIR system optics (IR, visible, and laser) at a
designated area.
Track Control
The track control functions include both air-to-air and air-to-surface autotracking functions. The signal
processor and pod controller WRAs command the line of sight through the point control and
stabilization subsystem to maintain the tracked target where designated. Figure 6-13 shows an
example of the ATFLIR system using track control.
Laser and FLIR Align
The laser and FLIR align is the autoalignment element in the point control and
stabilization function. The ATFLIR contains
alignment sources to each of the FLIR
detector arrays, the CCD camera, and the
laser line of sight. Auto-alignment occurs on
a continual basis to ensure that the laser,
FLIR, and CCD camera are co-aligned to the
ATFLIR telescope line of sight. This process
is vital to the precision delivery of guided
ordnance.
Laser Energy
This subsystem controls when the laser
energy is started and stopped by the laser
transceiver. In addition, the subsystem
manages the laser energy shutter to facilitate
the built-in sampling of laser energy output
parameters.
Laser Range
The laser range function provides target
distances to the operator.
Figure 6-13 — ATFLIR track control function.
6-12
Eyesafe
Eyesafe enables the operator to place the laser transceiver into a training mode of operation. The
training mode of laser operation simulates all of the tactical aspects of laser employment without
emitting any laser energy. The training mode can be used in both the air-to-air and air-to-surface
modes of operation.
Laser Spot Tracker
The laser spot tracker subsystem detects and receives ground or “buddy” designated laser energy.
Advanced Navigation
The ANFLIR subsystem (Figure 614) is a separable WRA that mounts
inside the pod adaptor unit. The
ANFLIR WRA provides the operator
with the navigation capabilities that
were described earlier. When
installed, the WRA receives power
and cooling air from the pod adaptor
unit. This subsystem uses a
dedicated RS-170 connection to
provide navigational video.
Infrared Marker
The function of the IR marker is to
provide a laser reference whose
return energy can be seen by
personnel equipped with night vision
goggles. This function makes the
infrared marker useful for night
attacks where personnel on the
ground can confirm that the correct
target is being designated.
Pod Environmental Control Unit
Figure 6-14 — ANFLIR weapons replaceable
The pod ECV regulates the airflow
from the aircraft while in flight and
assembly.
allows the ground cooling fan to
operate when the aircraft is on the ground. In addition, closed-loop cooling is provided by an air-to-air
heat exchanger to the sealed optics in the EOSU and the laser assemblies.
Built-In Test
The built-in test (Figure 6-15) subsystem provides the operator with the ability to test the functionality
of the ATFLIR system and components. Three separate built-in test functions are listed below:
•
Operational readiness test (ORT)
•
Initiated built-in test (IBIT)
•
Periodic built-in test (PBIT)
6-13
Figure 6-15 — Typical built-in test and fail code displays.
Operational Built-In Test
ORT occurs automatically when power is applied to the ATFLIR system. ORT is a test of system
readiness that, when completed, will provide the operator with an overall status of the ATFLIR.
Initiated Built-In Test
IBIT provides the operator with a detailed end-to-end test of the ATFLIR system. The purpose of IBIT
is to aid in isolation of suspected faulty component(s).
Periodic Built-In Test
PBIT is done continuously during the tactical operation of the ATFLIR system. However, PBIT will not
start until the pod cool-down cycle is complete. Any failures detected during the PBIT cycle will be
recorded and can be used in isolating faulty components.
6-14
End of Chapter 6
Infrared
Review Questions
6-1.
Natural light photography is an example of what type of remote sensing?
A.
B.
C.
D.
6-2.
What is the infrared frequency range?
A.
B.
C.
D.
6-3.
Temperature
Reflectivity
Visible light
Color
Infrared energy is separated into how many regions?
A.
B.
C.
D.
6-6.
1.00 and 7,200 nanometers
1.00 and 7,200 micrometers
0.72 and 1,000 nanometers
0.72 and 1,000 micrometers
In what terms is thermal imaging referenced?
A.
B.
C.
D.
6-5.
300 megahertz to 400 gigahertz
400 megahertz to 300 gigahertz
300 gigahertz to 400 terahertz
400 gigahertz to 300 terahertz
The infrared region exists between what electromagnetic spectrum?
A.
B.
C.
D.
6-4.
Active only
Passive only
Inactive
Active and passive
One
Two
Three
Four
Matter emits infrared radiation above what temperature?
A.
B.
C.
D.
-273 degrees Celsius
-273 degrees Fahrenheit
0 degrees Celsius
0 degrees Fahrenheit
6-15
6-7.
Which of the following qualities is desired in optical material used in infrared imaging systems?
A.
B.
C.
D.
6-8.
What component in an infrared imaging system is the most important?
A.
B.
C.
D.
6-9.
Transparent to visible light
High coefficient of thermal expansion
Low mechanical strength
High surface hardness
Detectors
Optics
Receiver
Sensor
Photographic film is an example of what type of detector?
A.
B.
C.
D.
Elemental
Imaging
Photon
Thermal
6-10. What type of energy-matter interaction involves the absorption of radiant energy in the
detector?
A.
B.
C.
D.
Thermal effect
Photon effect
Elemental
Imaging
6-11. What type of photon effect occurs when radiant energy changes the detector materials
electrical conductivity?
A.
B.
C.
D.
Photo-emissive
Photoelectric
Photoconductivity
Photon effect
6-12. What type of photon effect occurs when the radiant signal causes a difference of potential
across a P material and N material (PN) semiconductor junction?
A.
B.
C.
D.
Photo-emissive
Photon effect
Photoconductivity
Photoelectric
6-16
6-13. What component collects the incoming energy and focuses the image at the detectors?
A.
B.
C.
D.
Scene dissection system
Front end optics
Image processing system
Detectors
6-14. What component converts the data collected by the detectors into a video display?
A.
B.
C.
D.
Scene dissection system
Front end optics
Image processing system
Detectors
6-15. What type of detector cooling systems uses a heat exchanger and a compressor?
A.
B.
C.
D.
Single cycle
Quad cycle
Closed cycle
Open cycle
6-16. What is the nomenclature of the Advanced Targeting Forward Looking Infrared system?
A.
B.
C.
D.
AN/ASQ-228
AN/ASQ-328
AN/ASQ-441
AN/ASQ-501
6-17. What component is described by the EOSU acronym?
A.
B.
C.
D.
Electrically operated sensor unit
Electro-optical sensor unit
Environment oxygen siphon unit
Element oxidizing separating unit
6-18. Other than the midwave infrared receiver, gimbal-mounted telescope, and laser spot tracker,
what component does the electro-optical sensor unit house?
A.
B.
C.
D.
Environmental control valve
Eurocard modules
Roll drive unit
Power interrupt protector
6-19. The optics bench is made from what type of material?
A.
B.
C.
D.
Titanium
Carbon steel
Aluminum
Iron
6-17
6-20. What component is responsible for managing and routing pod control and video correction
signals?
A.
B.
C.
D.
Gimbal-mounted telescope
Laser transceiver unit
Pod adapter unit
Eurocard modules
6-21. Energy for precision ordnance guidance is provided by what component?
A.
B.
C.
D.
Pod adapter unit
Laser transceiver unit
Eurocard module
Windscreen
6-22. What component provides three-phase, 400 hertz rectified power to the pod when power flow
is interrupted?
A.
B.
C.
D.
Eurocard module
Roll drive amplifier
Laser transceiver
Power interrupt protector
6-23. What component provides power to the roll drive motor?
A.
B.
C.
D.
Power interrupt protector
Eurocard module
Roll drive unit
Roll drive amplifier
6-24. What subsystem generates visible imagery for use by the operator?
A.
B.
C.
D.
Infrared/video
Electro-optical/video
Point control
Infrared marker
6-25. What subsystem auto-aligns the pod optics to ensure the accuracy of target designation?
A.
B.
C.
D.
Infrared/video
Electro-optical/video
Laser/Forward Looking Infrared align
Track control
6-18
6-26. What subsystem provides a laser reference that can be seen by personnel using night vision
goggles?
A.
B.
C.
D.
Infrared/video
Electro-optical/video
Point control
Infrared marker
6-27. What Weapons Replaceable Assembly can be installed into the pod to provide the operator
with low-level navigation imagery?
A.
B.
C.
D.
Point control
Electro-optical/video
Advanced Navigation Forward Looking Infrared
Pod environmental control valve
6-28. What type of built-in test is initiated by the operator?
A.
B.
C.
D.
Periodic
Operational
System
Initiated
6-29. What type of built-in test continually occurs after pod cool-down is complete?
A.
B.
C.
D.
Periodic
Operational
System
Initiated
6-30. Other than the periodic built-in test, what test can help isolate a suspected faulty component?
A.
B.
C.
D.
Periodic
Operational
System
Initiated
6-19
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6-20
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CHAPTER 7
WEAPONS SYSTEMS
As a result of major developments in current aircraft design and computer technology, modern aircraft
are able to deliver sophisticated weapons to a target automatically and with unprecedented accuracy.
Aircraft are designed and built as a completely integrated weapons system. In other words, the
weapons subsystems are interconnected and dependent on each other or on other aircraft systems.
When aviation electronics technicians are testing, troubleshooting, or performing maintenance on an
avionics system, they must be aware of the effects the system can have on ordnance. To illustrate
this fact, this chapter will provide you with some examples of the types of weapons being employed in
the fleet. In addition, three different types of aircraft armament systems and controls will be
discussed. They are the Fighter/Attack (F/A)-18E/F Super Hornet, the Patrol (P)-3 Orion, and the
Multi-Mission Helicopter (MH)-60R Seahawk. The three platforms represent aircraft being used to
support the strike, fighter, Antisubmarine Warfare (ASW), and Anti-Surface Warfare (ASUW) mission
areas.
LEARNING OBJECTIVES
When you have completed this chapter, you will be able to do the following:
1. Identify the different homing-missile guidance systems.
2. Recognize the common weapons being employed in the fleet.
3. Recognize the armament systems and subsystems used in strike fighter aircraft.
4. Describe the functions of strike fighter aircraft armament systems and subsystems.
5. Recognize the armament systems and subsystems used in ASW and ASUW aircraft.
6. Describe the functions of ASW and ASUW aircraft armament systems and subsystems.
COMMON WEAPONS
Aviation electronics technicians are routinely tasked with performing armament release and control
checks. Therefore, it is important to identify some basic concepts about weapon guidance, and to
recognize some common weapons in order to better understand armament control systems.
Guidance and Control
Missile guidance systems include electronic sensing equipment that initiates the guidance orders and
the control system that carries them out. Homing-type, air-launched, guided missiles are currently
used. A homing guidance system is one in which the missile seeks out the target, guided by some
physical indication from the target itself. Homing systems are classified as active, semi-active, and
passive.
Active
In the active homing system (Figure 7-1), target illumination is supplied by a component carried in the
missile, such as a radar transmitter. The radar signals transmitted from the missile are reflected off
the target and back to the receiver in the missile. These reflected signals give the missile information
such as the target's distance and speed. This information lets the guidance section compute the
correct angle of attack to intercept the target. The control section that receives electronic commands
7-1
Interaction Available
from the guidance section controls the missile’s
angle of attack. Mechanically manipulated wings,
fins, or canard control surfaces are mounted
externally on the body of the weapon. They are
actuated by hydraulic, electric, or gas generator
power, or combinations thereof, to alter the missile's
course.
Semi-Active
In the semi-active homing system (Figure 7-2), the
missile gets its target illumination from an external
source, such as a transmitter carried in the
launching aircraft. The receiver in the missile
receives the signals reflected off the target,
computes the information, and sends electronic
commands to the control section. The control
section functions in the same manner as previously
discussed.
Interaction Available
Interaction Available
Figure 7-1 — Active homing system.
Figure 7-3 — Passive homing system.
Figure 7-2 — Semi-active homing system.
Passive
In the passive homing system (Figure 7-3), the directing intelligence is received from the target.
Examples of passive homing include homing on a source of infrared rays (such as the hot exhaust of
jet aircraft) or radar signals (such as those transmitted by ground radar installations). Like active
homing, passive homing is completely independent of the launching aircraft. The missile receiver
receives signals generated by the target, and then the missile control section functions the same.
7-2
Air-to-Air Weapons
The following paragraphs provide an overview of the Air-launched, Aerial Intercept Guided Missile
(AIM)-9, AIM-7, and AIM-120 air-to-air (A/A) missiles.
AIM-9 Sidewinder Series
AIM-9M Sidewinder missiles are supersonic, A/A weapons with passive infrared target detection,
proportional navigation guidance, and torque-balanced control systems. The AIM-9M offers improved
defense against infrared countermeasures and enhanced background discrimination capability. The
latest variant of the Sidewinder missile is the AIM-9X (Figure 7-4). The AIM-9X is a supersonic, A/A,
short-range guided weapon that is capable of both offensive and defensive counter-air missions in
day/night operations. The AIM-9X provides extremely high off-boresight acquisition and launch
envelopes, enhanced maneuverability, and improved target acquisition ranges.
Figure 7-4 — AIM-9X Sidewinder.
AIM-7 Sparrow
The AIM-7 Sparrow is a radar-guided, A/A missile that contains a high-explosive warhead. The AIM-7
has all-weather, all-altitude operational capability and uses a semi-active guidance system to seek
out and destroy a target. Semi-active guidance systems are dependent on interface and input from a
host aircraft for target information and intercept guidance.
AIM-120 Advanced Medium-Range Air-to-Air Missile
The AIM-120 Advanced Medium-Range Air-to-Air Missile (AMRAAM) (Figure 7-5) is an all-weather
weapon that has beyond-visual-range targeting capability. The AIM-120 was designed and produced
to serve as follow-on to the AIM-7 Sparrow missile series. The AIM-120 uses semi-active guidance
until it approaches its target. When the missile is close enough, it switches to an internal radar system
(active guidance) to intercept the target. The proximity active guidance capability allows an AIM-120compatible aircraft to engage several targets simultaneously.
Figure 7-5 — AIM-120 AMRAAM.
7-3
Air-to-Ground Weapons
The following paragraphs provide an overview of guided bomb units (GBUs), the High-Speed AntiRadiation Missile (HARM), the Maverick missile, the Hellfire missile, and torpedoes.
Guided Bomb Units
The Navy employs a variety of precision GBUs to disable and destroy enemy targets. Most GBUs are
general-purpose bombs that are retrofitted with a guidance package. Examples of the variety of
GBUs being employed operationally are described below.
•
The GBU-10/12/16 series employs laser guided, general-purpose bombs outfitted with a
computer control group and guidance fins.
•
The GBU-24 Paveway III series employs 2,000-pound laser-guided bombs designed to be
hard target penetrators. The GBU-24 is a general-purpose bomb outfitted with a computer
control group and guidance fins.
•
The Joint Direct Attack Munition (JDAM) (Figure 7-6) series bombs are general-purpose
weapons outfitted with an inertial navigation system and global positioning system guidance
sets. The JDAM is used for precision strike capabilities in all weather conditions.
Figure 7-6 — Joint Direct Attack Munition.
AGM-88 High-Speed Anti-Radiation Missile
The Air-Launched, Surface Attack, Guided Missile (AGM)-88 HARM (Figure 7-7) is a supersonic, airto ground, guided missile. The HARM is used to detect, attack, and destroy enemy radar systems.
The HARM uses a proportional guidance system to target and destroy enemy radar sites.
Figure 7-7 — AGM-88 HARM.
7-4
AGM-65 Maverick
The AGM-65 Maverick is an air-to-surface tactical missile designed for close air support, interdiction,
and defense suppression. The AGM-65 is effective against a wide range of tactical targets, including
armor, air defenses, ships, ground transportation, and fuel storage facilities. The AGM-65 missile
variants use laser or infrared guidance.
AGM-114 Hellfire
The AGM-114 Hellfire (Figure 7-8) missile is an air-to-ground (A/G), laser-guided, subsonic missile
with significant antitank capacity. The AGM-114 missile can be employed against tanks, structures,
bunkers, and slow-moving aircraft. An AGM-114 missile can be guided to a target either from inside
the aircraft or by laser energy outside the aircraft.
Figure 7-8 — AGM-114 Hellfire.
Torpedoes
The Navy employs three types of torpedoes as the primary weapons for ASW operations. They are
the Mark (MK) 46, MK 50, and MK 54.
•
The MK 46 torpedo is a dual-speed, active or active/passive weapon with enhanced target
acquisition, and improved maintainability and reliability.
•
The MK 50 torpedo is a highly capable weapon designed to counter the fast, deep-diving,
double-hulled nuclear submarine threat. MK 50 torpedoes offer increased lethality, speed,
depth, and endurance characteristics.
•
The MK 54 torpedo uses existing torpedo hardware and software from the MK 46, MK 50, and
MK 48 (used by submarines) torpedo programs and integrates state-of-the-art digital signalprocessing technology.
F/A-18E/F SUPER HORNET
The F/A-18 series of aircraft are all-weather, multirole fighter/attack aircraft. The Navy tactically uses
five variants of the F/A-18 series (Figure 7-9). They are the F/A-18A/C/E/F and the EA-18G. There is
commonality of weapons systems, avionics, and software among F/A-18 variants. Therefore, the
following paragraphs focus on the armament systems and subsystems of the F/A-18E/F. The F/A18E/F Super Hornet provides significant improvements in combat range, payload, and survivability in
comparison to legacy F/A-18 aircraft.
Armament System Basic Controls
The following paragraphs provide an overview of the F/A-18E/F armament system. The armament
system basic controls consist of the following components: armament system circuit breakers, landing
7-5
gear control panel,
armament safety
override switch, mission
computers (MCs),
armament computer,
and signal data
convertor.
Interaction Available
Armament System
Circuit Breakers
The armament system
circuit breakers are
located on the power
distribution panels
behind the right- and
left-hand maintenance
access doors.
Landing Gear Control
Panel
The landing gear control
handle in the DOWN
Figure 7-9 — F/A-18 variants.
position disables normal
weapons release, launch, and fire signals. In the UP position, 28 volts direct current is directed from
the main landing gear weight-off-wheels relay to the master arm circuit breaker.
Armament Safety Override Switch
The armament safety override switch is on the nose wheel well maintenance panel. In the
OVERRIDE position, it provides a parallel path for master arm power for ground operations of the
armament release and control systems.
Mission Computers
Two digital data computers
make up the MC system and
control the avionics systems.
They interface with the
armament computer and allow
power routing to signal data
convertor controls for weapon
release. Power to the digital data
computers is controlled by the
MC switch on the MC/hydraulic
isolation (MC/HYD ISOL) panel.
Armament Computer
The armament computer (Figure
7-10) interfaces with and is
controlled by the MC. The
armament computer interfaces
Figure 7-10 — Armament computer.
7-6
with and controls the weapon station signal data control converters; monitors and controls gun fire
rates; and provides electric fuzing voltage.
The armament computer contains the digital weapon insertion panel (WIP) used to enter the weapon
type and fuzing requirements for each station loaded.
The weapon-type code entered for each loaded station must match the weapon loaded, and the
nose/tail fuze code entered must be compatible. Otherwise, the armament computer will not allow it to
release normally. For weapons without nose/tail fuzes, the codes in the armament computer must still
match the weapon loaded. In addition, the quantity of rounds loaded in the M61 gun system is also
entered using the WIP.
Signal Data Converter Control
The signal data converter control provides interface with the armament computer and weapons
loaded. The seven pylon converter controllers are identical. The two fuselage converter controllers
are identical and also provide interface to the wing tip launchers. In addition, the signal data converter
controllers provide release voltage and weapons/rack/launcher status to the armament computer.
Cockpit Basic Controls
The following paragraphs provide a brief overview of the basic controls and displays used to control
armament systems in the F/A-18E/F.
Digital Display Indicators
Cockpit digital display indicators (DDIs) are located on the main instrument panel (left and right). DDIs
are identical and display the same information, although not at the same time. The stores
management system (SMS) uses the DDIs to display weapon, function, and option. The operator
makes a selection on the DDIs by using the 20 pushbuttons around the edge of the display screen
and by using the up-front control display
(UFCD) for quantity, multiple, and interval
selection. Upon initiation of the stores display,
the number, station, master arm status, and
type of weapons loaded are shown in the wing
form display.
The wing form (Figure 7-11) is an outline of the
aircraft that identifies type, station, number,
and status of weapons loaded on the aircraft.
A weapon is identified by entering a code on
the armament computer WIP. Data is
transmitted to the MC system, which displays
the entered code as an acronym. The acronym
is displayed in the wing form for the station in
which the code was entered.
The operator makes a weapons selection for
A/G weapons by pressing the pushbutton
switch next to the acronym of the desired
weapon. When this switch is pressed, a box
appears around the weapon acronym,
indicating that weapon is selected.
Figure 7-11 — Typical wing form display.
7-7
Up-Front Control Display
UFCD is a touch-sensitive display that provides the keypad, option select, scratchpad, and option
displays. The option select display allows selection of quantity (QTY), multiple (MULT), and interval
(INT) options. After selecting an option, the operator uses the keypad option to enter a number, which
will be displayed on the scratchpad display. After verifying the number on the scratchpad display as
correct, the operator presses the keypad option enter (ENT) to transmit the number to the MC
system. The MC provides the data to the armament computer for storage and display on the DDIs.
Head-Up Display
Located on the pilot’s main instrument panel, the head-up display (HUD)
allows for weapon displays and visual markers.
Master Arm Control Panel
The master arm control panel (Figure 7-12) assembly allows the operator
to select the A/A, A/G, and MASTER modes. The panel also contains the
emergency jettison (EMRG JETT) and push to jettison (PUSH TO JETT)
switches.
Rear Cockpit Basic Controls
An overview of the rear cockpit armament basic controls of the F/A-18F
series aircraft is described in the following paragraphs.
Digital Display Indicators
The DDIs are located on the rear cockpit instrument panel. The rear DDIs
provide independent displays but are also capable of providing the same
display as the cockpit.
Rear Advisory and Threat Warning Indicator Panel
The rear advisory and threat warning indicator panel assembly contains the
A/A and A/G switches, and on lot numbers 166449 and up, the MASTER
ARM annunciator and LASER arm annunciator.
Left- and Right-Hand Controllers
The rear left- and right-hand controllers contain numerous switches for
weapons control, and on lot numbers 166449 and up, they contain
selection, launch, and release of weapons.
Armament Subsystems
Figure 7-12 —
Master arm
control panel.
The next section of this chapter provides an overview of the armament subsystems associated with
the F/A-18E/F and will include the following systems: air-air missile, air-to-ground weapons control,
jettison, gun control, and integrated defensive electronic countermeasures dispensing.
7-8
Air-to-Air Missile Control Systems
The A/A missile control systems provide the ability to
select and launch A/A missiles, including the AIM-7
Sparrow, AIM-9 Sidewinder, and AIM-120 AMRAAM.
Some of the A/A missile controls are located on the aircraft
controller grip, as shown in Figure 7-13. The cockpit
switches associated with the A/A weapons system are
described below.
•
The A/A weapons select switches are four-position
switches used to select the A/A weapons loaded on
the aircraft.
•
The CAGE/UNCAGE switch is used to control the
selected AIM-9M seeker head position.
•
The A/A missile trigger switch is a two-position
switch. The first detent initiates the HUD camera,
and the second detent initiates A/A weapons
launch.
•
The A/A weapons release switch is located on the
rear cockpit right-hand controller of the F/A-18F and
is a single pushbutton switch used to initiate A/A
missile launch.
•
The infrared cool (IR COOL) switch is a threeposition switch that controls the flow of
coolant/high-pressure pure air to the AIM/CATM-9M
seeker head.
•
The weapon (WPN) volume control is used to control the volume of the AIM-9 lock-on tone.
•
The radar control switch controls power to the radar system. The radar system is used to
interface and control the AIM-7 and AIM-120 missiles.
Figure 7-13 — Aircraft controller grip.
Air-to-Ground Weapons Control System
The A/G weapons control system provides the ability to select, launch, fire, or release A/G missiles,
bombs, and rockets. Some of the A/G weapons controls are on the left and right throttle grips, shown
in Figure 7-14. Cockpit switches and displays used in the A/G weapons subsystem are described
below.
•
The CAGE/UNCAGE switch is used to control the seeker head functions of the Maverick
missile system. The switch can also be used to initiate functions of the HARM missile.
•
The throttle designator control (TDC) switch is used to control the position of video-capable
weapons targeting crosshairs.
•
The designator control switch is used to control the positon of video-capable weapons
targeting crosshairs in the F/A-18F rear cockpit.
•
The HARM sequence/forward looking infrared field-of-view/raid (FLIR FOV/RAID) switch is
used to switch the sequences between HARM targets.
7-9
•
The multi-function switch is a three-position
switch used for weapons control. The forward
position sequences between HARM targets.
The aft position cages/uncages selected
seekers. The down position functions as the
RAID/FLIR switch.
•
The A/G weapons release switch initiates
launch, firing, or release of all selected A/G
weapons.
•
An UFCD is used to enter the quantity, multiple,
and interval options for A/G weapons data for
the MC system.
•
The electrical fuzing system provides the
voltage to arm electrically fuzed A/G weapons.
The system supplies the selected proximity
(VT), instantaneous (INST), delay 1 (DLY 1), or
delay (DLY 2) voltage when the bomb rack
hooks open for weapons release.
Figure 7-14 — Left and right throttle
grips.
Jettison System
The Jettison system provides a method of jettisoning
weapons/stores from the aircraft. The following
paragraphs describe controls and indicators of the
jettison system.
•
Emergency jettison is a mode of jettisoning all
weapons/stores from the seven pylon stations.
o The EMERG JETT PUSH TO JETT switch
(Figure 7-15) initiates emergency jettison
from all pylon stations.
•
Selective jettison is a mode of individually
jettisoning the left fuselage missile, right fuselage
missile, racks, launchers, and stores.
o The SELECT JETT switch is a five-position
switch used to select the station or type of
jettison needed.
o The JETT STATION SELECT switches are
seven pushbutton switch/indicators that
correspond to the aircraft left outboard
(LO), left midboard (LM), left inboard (LI),
center (CTR), right inboard (RI), right
midboard (RM), and right outboard (RO),
and are used to select the pylon station for
selective jettison or auxiliary release.
7-10
Figure 7-15 — Typical emergency
jettison switch.
•
Auxiliary release is a gravity mode of jettison used on selected pylon stations when emergency
and selective jettison fails.
o The auxiliary release (AUX REL) switch is a two-position switch used to enable or inhibit
auxiliary release. The ENABLE position enables auxiliary release. The normal (NORM)
position inhibits auxiliary release.
o The SELECT JETT, JETT switch initiates select jettison or auxiliary release of the
selected stations.
Gun System Controls
The gun system provides the means to select, arm, and fire the M61 gun in A/A and A/G modes.
Firing voltage, round count, and rate of fire are all controlled by the armament computer. Cockpit
controls for the gun system are described below.
•
The A/A weapons select switch is a four-position switch used to select A/A weapons. The aft
position of the switch selects the gun.
•
The A/A missile trigger switch is a two-position switch. When the gun has been selected, the
switch initiates the HUD camera at the first detent and fires the gun at the second detent.
Integrated Defensive Electronic Countermeasures (IDECM) Dispensing Systems
The integrated defensive electronic countermeasures (IDECM) dispensing systems include the
AN/ALE-47 and AN/ALE-50A integrated countermeasures system. The systems used in the IDECM
are described below.
•
The AN/ALE-47 dispensing system provides for threat-adaptive, reprogrammed computer- or
manual-controlled dispenses of decoys to confuse and jam enemy electronic tracking, missile
guidance, and homing systems. The system ejects expendable payloads of chaff, flares, or
radio-frequency (RF) jammers from four dispenser magazines located on the lower fuselage
aft of the engine intakes.
•
The AN/ALE-50A
dispensing system
provides for
reprogrammable,
computer- or
manual-controlled
dispenses of an
active RF
transmitting towed
decoy (Figure 7-16).
The magazine with
three decoys is
installed in the lower
fuselage between
the main landing
gear doors.
Figure 7-16 — AN/ALE-50 towed decoy.
7-11
P-3 ORION
The P-3 Orion (Figure 7-17) is a four-engine,
low-wing aircraft designed for patrol and
ASW. The armament system consists of
equipment for loading, carrying, and
releasing weapons and search stores.
Weapons include bombs, mines, torpedoes,
missiles, and rocket launchers. Search
stores include sonobuoys, parachute flares,
smoke markers, bathythermograph buoys,
and signal underwater sound (SUS).
Armament Systems Basic Controls
The basic P-3 ASW weapons system
consists of the equipment and accessories
necessary for carrying and releasing kill
stores and search stores. Armament basic
controls consist of the following components:
pilot armament control panel, armament control box,
weapons release switches, armament safety circuit
safety disable switch, forward interconnection box, aft
interconnection box, and armament circuit breaker
panel.
Figure 7-17 — P-3 Orion.
Pilot Armament Control Panel
The pilot armament control panel (Figure 7-18) provides
the pilot with control of all kill and search stores. The
switches and controls that are found on the armament
control panel are as follows:
•
The ARM HAZARD warning light warns the pilot
of a malfunction of any of the 18 weapon release
buffer relays.
•
The MASTER ARM switch controls power for
enabling arming and normal release of the wing
and bomb bay stores.
•
The MASTER ARM cue light advises pilot to
change the position of the MASTER ARM switch
in response to action by the tactical coordinator
(TACCO) or computer.
Figure 7-18 — Pilot armament control
panel.
•
The BOMB BAY door switch controls opening and closing of the bomb bay doors.
•
The BOMB BAY cue light advises the pilot to change position of the BOMB BAY door switch in
response to action by the TACCO or computer.
•
The search power (SRCH PWR) switch allows the pilot final control over the release of all
search stores; the computer monitors the position of this switch.
7-12
•
The SRCH PWR cue light, when illuminated, tells the pilot to turn the search power switch ON;
it lights only when the switch must be moved from OFF to ON; there is no offline function of
this light.
•
The KILL READY cue light advises the pilot that preparations are completed for release of the
weapon/store.
•
The JETTISON switch initiates release of all wing and bomb bay weapons/stores in a safe
(unarmed) condition.
•
The manual armament select (MANUAL ARMT SEL) panel provides the TACCO with controls
necessary for manual mode of operation.
Armament Control Box
In some series of P-3 Orion aircraft, the pilot armament control panel, wing jettison, and special
weapon armament panel have been replaced by an armament control box (ACB). The ACB is located
on the center pedestal at the flight station. The ACB combines the functionality of the two panels and
provides the pilot with command control of all kill and search stores.
Weapon Release Switches
Both the pilot and copilot have switches for the release of weapons. The switches are located on the
inboard side of the control wheels and are labeled stores release (STORES REL). Weapons release
can also be made by depressing the release (REL) switch located on the TACCO manual armament
select panel.
Armament Safety Circuit Disable Switch
The armament safety circuit disable switch is a momentary contact switch used to bypass the landing
gear lever switch to permit operation of the weapons system when the aircraft is on the ground.
Forward Interconnection Box A395
The forward interconnection box A395 contains eight subassemblies that provide control circuitry for
selection, arming, torpedo presetting, and release of weapons loaded in the bomb bay and jettison of
weapons loaded at bomb bay and wing stations.
Aft Interconnection Box A269
The aft interconnection box A269 contains four subassemblies that provide control circuitry for
selection, arming, and release of weapons loaded at wing stations.
Armament Circuit Breaker Panel
The armament circuit breakers on the forward load center supply power to the armament circuit
breakers located on the forward electronics circuit breaker panel.
Armament Subsystems
The following paragraphs provide general information on the aircraft armament subsystems,
components, and armament subsystems, to include torpedo system, Harpoon system, Maverick
system, jettison system, and defensive countermeasure systems.
7-13
Torpedo System Basic Controls
The aircraft’s torpedo system consists of the following
basic controls:
•
The torpedo presetter (TORP Presetter) panel
provides the controls and indicators for manual
or automatic preset of Mk 46, Mk 50, and Mk 54
torpedoes.
•
Torpedo MK 50 heater control panel provides
selection of Mk 50 heater power.
•
DIRECTED SEARCH MODE selector panel
(Figure 7-19) provides directed search capability
for Mk 46, Mk 50, and Mk 54 torpedoes.
Figure 7-19 — DIRECTED SEARCH
MODE selector panel.
Harpoon System Basic Controls
The Harpoon missile system basic controls are described below.
•
The Harpoon aircraft command launch control (HACLC) panel provides power application,
controls, and displays for the Harpoon missile. The controls and displays are used for manually
defining missile selection/deselection, target range, relative bearing, attack seeker modes,
aircraft true airspeed, and altitude inputs.
•
The data processor computer is a general-purpose, stored program, digital computer that
provides the digital communications link between the HACLC and the Harpoon missile. The
data processor computer serves as an interface unit to obtain control and data information
from existing aircraft systems. It performs the launch interlocks and prelaunch computations for
missile initialization and control of the launch sequence.
Maverick Missile Control System Basic Controls
The Maverick missile control system (MMCS) provides the
capability to individually identify and track up to four separate
targets with missiles loaded on wing stations 10, 11, 16, and 17.
The MMCS is composed of the following basic controls.
•
The missile interface box is the heart of the MMCS and is
the one component through which all signals used to
control the MMCS are routed.
•
The missile armament panel (Figure 7-20) provides the
TACCO with the status of the MMCS and allows the
TACCO to control various missile functions. The TACCO
can select up to four missiles to enter the launch mode
(land or ship), initiate missile cooling, and activate the
missile.
•
The missile/infrared detection set (IRDS) status panel
provides missile and IRDS control status indicators.
•
The missile controllers are two identical and
interchangeable joysticks used to provide missile and
IRDS turret controls to the missile interface box.
7-14
Figure 7-20 — Missile
armament panel.
Jettison System
All kill stores on the aircraft will be jettisoned in an unarmed condition when the pilot places the
JETTISON switch on the pilot armament control panel in the ACTUATED position. Kill stores are
jettisoned from the aircraft within a 20-second period. Components and functions of the jettison
system are described below.
•
The wing jettison and special weapon armament panel provides the pilot with a means of
jettisoning stores from wing stations only in an emergency and secondary release of bomb bay
stations 2C, 4C, and 8C.
•
The secondary rack lock panel, 962046-10, is used to unlock bomb bay racks at stations 2C,
4C, and 8C. The panel is used with the wing jettison and special weapon armament panel.
Defensive Countermeasures
The AN/ALE-39 and AN/ALE-47 countermeasures dispensing systems and controls are described
below.
•
The AN/ALE-39 countermeasures dispensing system, in conjunction with the AN/AAR-47
missile warning set (MWS), is designed to protect the aircraft from infrared guided missiles.
The countermeasures dispenser (CMD) system installed in this aircraft was designed to only
dispense flare payloads.
o The CMD control panel provides the functional interface to the ALE-39
countermeasures dispensing system.
o The AN/ALE-39 CMD programmer generates control signals for programmed or single
ejection of payload sequences controlled by the CMD control and initiated manually or
automatically by the MWS.
•
The AN/ALE-47 countermeasures dispensing system, in
conjunction with the AN/AAR-47 MWS, is designed to
protect the P-3C Anti-Surface Warfare Improvement
Program (AIP) aircraft from surface-to-air and air-to-air
missiles. The AN/ALE-47 system has the capability to
automatically dispense a combination of chaff, flare, or
jammer payloads. An example of the ALE-47 cockpit
controls is shown in Figure 7-21.
o The dispenser housings are located underneath
the aircraft and are designed to remain installed in
the aircraft for quick loading and unloading of the
magazine assemblies.
o The magazine assemblies are loaded into each
dispenser housing. Each magazine is partitioned
into two sections, tubes 1 through 10 and tubes
11 through 30.
MH-60R SEAHAWK
Figure 7-21 — AN/ALE-47
cockpit controls.
The MH-60R Seahawk (Figure 7-22) helicopter primary mission areas are ASW and ASUW.
Secondary missions include fleet support, surveillance, search and rescue, medical evacuation
logistics, vertical replenishment, and communication relay. The following paragraphs provide a brief
description of the aircraft armament systems and jettison systems.
7-15
Armament System Basic Controls
The MH-60R armament system basic controls
consist of the following components: weight-onwheels (WOW) switch, disabling switch for
armament safety circuit, data handling system,
primary mission/flight computer, SMS, and
processing interface units.
Weight-on-Wheels Switch
The WOW switch functions as a safety interlock
by disabling release and jettison circuits while
the aircraft is on deck.
Disabling Switch for Armament Safety Circuit
This switch functions as an override to disable
the WOW switch when the aircraft is on deck.
The purpose of this switch is to allow operational
testing of the armament system.
Figure 7-22 — MH-60R Seahawk.
Data Handling System
The data handling system provides for the operator interface, processing, and display of all avionics
and weapons systems.
Primary Mission/Flight Computer
The primary mission/flight computer is a digital computer that interfaces with all weapons and
avionics systems and performs all processing for displays, built-in-test (BIT), and armament system
functions.
Stores Management System
The SMS provides for the interface, control, and release functions of weapons and stores from the
aircraft weapon stations and launchers.
Processing Interface Units
The processing interface units provide the interface
between the weapons/stores and the primary
flight/mission computer and other onboard avionics
systems.
Cockpit Basic Controls
The following paragraphs provide a brief overview of
the armament displays, controls, and components to
include armament control indicator, mission displays,
and control indicators.
Armament Control Indicator
Figure 7-23 — Armament control
indicator.
The armament control indicator (ACI) panel (Figure 7-23) is located on the lower console and is a
component of the SMS. The ACI contains the covered MASTER ARM and ARM SAFE indicators. In
7-16
addition, the ACI contains control functions for the jettison, sonobuoy, and Hellfire armament
subsystems.
Mission Displays
The mission displays are located on both pilot and copilot instrument panels and are components to
the data handling system. The displays provide BIT, caution/advisory indications, and other SMS
selectable information. Information and data are selectable with the 22 pushbutton switches located
around the display bezel.
Control Indicators
Control indicators are located on both the pilot and copilot lower console and are components to the
data handling system. Control indicators consist of three keyboards and are used to interface with
aircraft avionics systems.
Sensor Operator Station Basic Controls
The following paragraphs provide a brief overview of the displays located at the sensor operator
station.
Mission Display
The sensor operator mission display is located on the sensor operator console. The display performs
the same functions as the pilot/copilot display.
Control Indicator
The sensor operator control indicator is located on the sensor operator console and oriented
horizontally instead of vertically. This component provides interaction with avionics systems from the
sensor operator console.
Armament Subsystems
This section discusses the armament subsystems associated with the MH-60R platform. This section
discusses the armament subsystems associated with the MH-60R platform and describes the
following subsystems: torpedo release system, sonobuoy launch system, AGM-114 Hellfire missile
system, defensive countermeasures, and jettison system.
Torpedo Release System
The torpedo release system is capable of controlling and releasing up to four torpedoes. Torpedo
system station and type selection, moding, and all other presetter functions are performed through
the use of indications and alerts displayed by the data handling subsystem control indicators and
mission displays. The torpedo release system consists of the following components:
•
The signal data convertor provides MK 50 torpedo heater power.
•
The hand control unit contains the RELEASE CONSENT switch that enables the release of
torpedoes.
Sonobuoy Launch System
The sonobuoy launch system is capable of controlling and launching up to 25 sonobuoys. The system
consists of the following components:
•
The sonobuoy launcher provides a housing and launch platform for 25 sonobuoys.
7-17
•
The pneumatic supply module and manifold consists of a pressure bottle, pressure gauge,
manual dump valve, and a SAFE/ARM lever. The supply module provides the pneumatic
charge that ejects the selected sonobuoy.
•
The distribution module connects the compressed air supply with the selected launcher tube
by way of a rotary valve. Stepper motor drives the rotary valve to the selected tube and is
stopped by a position
potentiometer. A selection
knob on the distribution
module provides manual
selection of a sonobuoy
tube. A distribution valve
lock allows the rotary valve
to be locked in any tube or
vent position and indicator
window.
•
The signal data converter
is a component of the SMS
that provides power to the
sonobuoy launch system.
•
The BUOY LAUNCH RDY
AWAY switch and indicator
are used to manually
launch a sonobuoy from a
loaded launch tube. An
example of the MH-60R
sonobuoy launch system is
shown in Figure 7-24.
Figure 7-24 — Sonobuoy launch system.
AGM-114 Hellfire Missile Control System
The AGM-114 Hellfire missile control system provides for the carriage and launch of the AGM-114
Hellfire missile. The Hellfire missile system consists of the following basic components and controls:
•
The extended pylon is located on the port side aft of the aircraft and provides for the carriage
of the Hellfire missile.
•
The AN/AAS-44 FLIR subsystem provides the capability to detect targets, determine target
range, and laser designate the target for Hellfire guidance. FLIR system displays are provided
on the mission displays.
•
The rotor overspeed and FLIR switch assembly panel contains the LASER and GIMBLE
ENABLE/DISABLE switches. The switches either enable or inhibit laser firing and FLIR turret
slewing. The FLIR laser can also be enabled and disabled from the sensor operator utility light
panel.
•
The hand control unit provides the operator interface for the FLIR and to launch Hellfire
missiles.
•
The signal data converter provides the power control and interface for the M299 Hellfire
launcher.
7-18
•
The M299 Hellfire launcher is installed on the extended pylon and is used to mount and launch
the Hellfire missile.
Jettison System
The system is capable of jettisoning all weapons/stores or selected weapons/stores. The jettison
system will be armed when the aircraft is in a weight-off-wheels condition or by engaging the
armament safety bypass circuit. Activating the emergency jettison panel ALL STORE JETT switch will
jettison all weapons/stores with the exception of jettisonable AN/ALE-47 countermeasures dispensing
system expendables. Selecting the MASTER ARM switch on the ACI, then selecting the appropriate
weapon station or system, and actuating the SELECT JETTISON switch selectively jettisons
weapons, stores, or AN/ALE-47 countermeasures dispensing system expendables.
Defensive Countermeasure System
The MH-60R uses the AN/ALE-47 countermeasures dispensing system (Figure 7-25) to protect the
aircraft against anti-air threats. The AN/ALE-47 countermeasures dispensing system provides for
threat-adaptive, reprogrammable, computer-controlled dispensing of decoys to confuse and jam
enemy electronic tracking, missile guidance, and homing systems. The system ejects expendable
payloads consisting of chaff, flares, or RF jammers in manual, semiautomatic, or automatic modes
based on software-controlled programs from two 32-round dispenser magazines located on the tail
pylon. The AN/ALE-47 consists of the following components:
•
The AN/ALE-47 programmer functions as the central processor for the AN/ALE-47 system; it
contains dispense programming software and controls dispensing for all modes of operation.
•
The dispenser magazine identification (ID) switches consist of two four-position (A–D and 1–4)
rotary switches that indicate specific expendable payload load outs for decoding and to be
used by the programmer.
•
The AN/ALE-47 safety switch/pin is opened by inserting AN/ALE-47 safety pin, which inhibits
AN/ALE-47 dispenses.
Figure 7-25 — AN/ALE-47 countermeasures dispensing system.
7-19
End of Chapter 7
Weapons Systems
Review Questions
7-1.
What type of homing-missile guidance uses a component inside the missile to illuminate a
target?
A.
B.
C.
D.
7-2.
What type of homing-missile guidance uses directing intelligence received from the target?
A.
B.
C.
D.
7-3.
AIM-7 Sparrow
AIM-9M Sidewinder
AIM-120 Advanced Medium-Range Air-to-Air Missile
AIM-9X Sidewinder
What air-to-air missile offers improved defense against infrared countermeasures?
A.
B.
C.
D.
7-6.
Active only
Semi-active
Passive only
Active and passive
What air-to-air missile provides for an extremely high off-boresight target acquisition window?
A.
B.
C.
D.
7-5.
Active only
Semi-active
Passive only
Active and passive
What type of homing-missile guidance receives target illumination from an external source?
A.
B.
C.
D.
7-4.
Active only
Semi-active
Passive only
Active and passive
AIM-7 Sparrow
AIM-9M Sidewinder
AIM-120 Advanced Medium Range Air-to-Air Missile
AIM-9X Sidewinder
What guided bomb unit series are 2,000 pounds and designed to penetrate hard targets?
A.
B.
C.
D.
10
12
16
24
7-20
7-7.
What air-to-ground missile is designed for close air support and defense suppression?
A.
B.
C.
D.
7-8.
What air-to-ground missile can be used to target and destroy slow-moving aircraft?
A.
B.
C.
D.
7-9.
AGM-65 Maverick
AIM-9M Sidewinder
AGM-88 High Speed Anti-Radiation Missile
AGM-114 Hellfire
AIM-9M Sidewinder
AGM-65 Maverick
AGM-88 High Speed Anti-Radiation Missile
AGM-114 Hellfire
What F/A-18E/F basic armament component disables 28 volts direct current to master arm
circuits when in down position?
A.
B.
C.
D.
Armament system circuit breakers
Landing gear control panel
Mission computers
Armament safety override switch
7-10. What F/A-18E/F basic armament component is located on the nose wheel well maintenance
panel?
A.
B.
C.
D.
Armament safety override switch
Armament system circuit breakers
Landing gear control panel
Mission computers
7-11. What F/A-18E/F basic armament component provides release voltage and
weapons/rack/launcher status to the armament computer?
A.
B.
C.
D.
Landing gear control handle
Mission computers
Signal data converter control
Armament safety override switch
7-12. How many digital data computers in the F/A-18E/F make up the mission computer system?
A.
B.
C.
D.
One
Two
Three
Four
7-21
7-13. What panel is used to enter weapon-type codes and nose/tail fuze codes into the armament
computer?
A.
B.
C.
D.
Code insertion
Landing gear control
Master arm control
Weapon insertion
7-14. On the F/A-18E/F aircraft, what four-position switch selects the air-to-air weapons loaded?
A.
B.
C.
D.
CAGE/UNCAGE
Air-to-air weapons select
Air-to-air missile trigger
Air-to-air weapon release
7-15. What switch in the F/A-18E/F is used to control the selected AIM-9M seeker head position?
A.
B.
C.
D.
CAGE/UNCAGE
Air-to-air weapons select
Air-to-air missile trigger
Air-to-air weapon release
7-16. What type of display in the F/A-18E/F is used to enter the quantity, multiple, and interval of airto ground weapons?
A.
B.
C.
D.
Digital data
Head-up
Up-front control
Countermeasure
7-17. What system in the F/A-18E/F provides target data for the AIM-7 Sparrow and AIM-120
Advanced Medium Range Air-to-Air Missiles?
A.
B.
C.
D.
Communications
Electronic warfare
Navigation
Radar
7-18. In the F/A-18E/F, in addition to proximity and delay 1, the electrical fuzing supplies what
selected fuzing voltages?
A.
B.
C.
D.
Instantaneous and delay
Instantaneous and delay 2
Instantaneous, delay, and delay 2
Delay and delay 2
7-22
7-19. What light on the P-3 Orion pilot armament control panel warns the pilot of a malfunction in
one of the weapon release buffers?
A.
B.
C.
D.
KILL READY
ARM HAZARD
MASTER ARM
JETTISON
7-20. What P-3 Orion interconnection box contains eight subassemblies that provide circuitry
control?
A.
B.
C.
D.
Port
Starboard
Forward
Aft
7-21. On the P-3 Orion, what panel provides the controls for manual or automatic preset of MK 46,
MK 50, and MK 54 torpedoes?
A.
B.
C.
D.
TORP presetter
DIRECTED SEARCH MODE selector
Pilot armament control panel
Armament control box
7-22. What P-3 Orion component provides the digital communications link between the Harpoon
aircraft command launch control and the missile?
A.
B.
C.
D.
DIRECTED SEARCH MODE selector
Armament control box
Data processor computer
Missile interface box
7-23. How many separate targets can the Maverick missile control system individually identify and
track?
A.
B.
C.
D.
One
Two
Three
Four
7-24. What armament function(s) are disabled by the MH-60R weight-on-wheels switch when the
aircraft is on deck?
A.
B.
C.
D.
Weapon identification
Release only
Jettison only
Release and jettison
7-23
7-25. What MH-60R armament system provides the interface between the weapons/stores and the
primary flight/mission computer?
A.
B.
C.
D.
Data handling system
Processing interface units
Stores management system
Weight-on-wheels switch
7-26. What is the total number of pushbuttons located around the MH-60R mission display?
A.
B.
C.
D.
10
12
18
22
7-27. What component of the MH-60R consists of three keyboards and allows the aircrew to
interface with the avionics systems?
A.
B.
C.
D.
Control indicator
Mission displays
Armament control indicator
Processing interface units
7-28. How many sonobuoys is the MH-60R sonobuoy launch system capable of controlling?
A.
B.
C.
D.
11
13
15
25
7-24
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7-25
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CHAPTER 8
COMPUTERS
Computers are used in many facets of everyday life. This fact is especially true in the Navy and in
aviation. A basic computer can be described as an instrument used to perform mathematical
operations, such as addition, subtraction, and so on, at very high speeds. However, computers in
today’s world are used for more than mathematical calculations. Computers have ensured the
successful advances in military, scientific, and commercial applications. Modern aircraft use
advanced computer systems to perform high-level avionics system calculations to ensure the success
of the mission. As an aviation electronics technician (AT), you will be tasked to troubleshoot and
diagnose computer-related failures. This chapter will provide a basic overview on computers and their
relationship to avionics systems. Additionally, the typical mission computer system used in the
Fighter/Attack (F/A)-18 series aircraft will be provided as an example.
LEARNING OBJECTIVES
When you have completed this chapter, you will be able to do the following:
1. Describe computer hardware components.
2. Describe computer software.
3. Recognize the functions of a computer.
4. Identify the applications of a computer.
5. Recognize the types of computers.
6. Describe the methods of data transmission.
7. Recognize peripheral avionics systems.
8. Identify the integrated components in a typical mission computer system.
BASIC COMPUTERS
Many different models and sizes of computers are designed to perform various functions. However,
computers are, generally speaking, all functionally the same no matter what size or purpose they are
designed to meet. The speed and processing power of a computer is determined by the technology
(components) used within the computer. The following paragraphs will provide an overview of basic
computers.
General Terms
Two general terms are used to define the
makeup of a basic computer: hardware and
software.
Hardware
The electronic and physical components of
a computer are commonly called hardware
(Figure 8-1). Examples of computer
hardware are microchips, printed circuit
Figure 8-1 — Typical computer hardware.
8-1
cards, power supplies, and so on. All basic computers require the following hardware components:
•
Input device – allows the operator to enter
data into a computer system
•
Output device – displays data and other
information
•
Mass storage device – permanently stores
large amounts of data
•
Memory – temporarily stores data and
applications
•
Central processing unit (CPU) – serves as
the main component of the computer system
A basic computer block diagram is illustrated in
Figure 8-2.
Figure 8-2 — Basic computer block diagram.
Software
Computer software is a set of programs and procedures used by a computer to perform a particular
function. Software includes compilers, assemblers, operating systems, and so on. Compiler software
is used to transform the source code of one programming language into another computer program
language. Assembler software enables developers to access, manage, and alter computer hardware
architecture. Operating systems are designed to support a computer’s basic functions, such as
running applications or controlling input/output (I/O) devices. Advances in software have led to the
development of a wide variety of specialized programming languages such as C++, Java, and many
others. Specialized programming languages allow the operator to design and implement applications
to solve problems or to meet a specific need.
Perhaps the best use of software has been in the area of real-time processing. Real-time processing
is a situation where the data is submitted to a computer, and an immediate response is obtained. The
capability of an aircraft mission computer to perform real-time processing could determine the
success or failure of an assigned mission.
Computer
Functions
All computers can
perform the
following operations:
gather, process,
store, disseminate,
and display data
(Figure 8-3).
Figure 8-3 — Basic computer functional diagram.
Gather Data
A computer must first gather information before it can process the information. A computer can gather
data using one or a combination of the following methods:
•
Manual – information is inputted by an operator either directly or through the use of an external
device. The information is stored, disseminated, or displayed depending on the operational
program.
8-2
•
Automatic – information is received from another system, subsystem, or equipment. The
information is either immediately used by the computer or stored for future use.
NOTE
Many computer systems are designed to use a combination
of both methods to gather data.
Process Data
The processing of data is the main function of a computer system. Other components can collect data
for the system, but the computer is going to exclusively process the information. The CPU is the main
component in the computer system used to process data.
Store Data
Computer systems can store information either internally or externally. The computer uses memory to
store information internally. In contrast, a number of options can be used to store data externally. For
example, information can be transferred to an external hard drive to be archived for later use.
Disseminate Data
Computer systems use I/O sections to route data to other components such as printers, storage
devices, or displays.
Display Data
Computer systems normally display two general types of data: data related to the mission of the
system and information related to the operation of the system. Computers rely on external devices to
display the processed information.
Computer Application
The uses for a computer fall into a large variety of categories that are too numerous to realistically
cover in this chapter. Therefore, an overview of some of the common applications of a computer is
provided below.
Database
A computer can be used to index and retrieve information. The information is stored in the computer
system under a keyword or heading. When an operator enters that specific keyword or heading, the
application calls up the data and displays the information.
Simulation
Computer systems can be used to simulate the operation of any type of system being designed.
Simulations will identify shortfalls and flaws in the new system that can be corrected before building
the final product.
Business
Computers are designed to perform complex calculations at a high speed and accuracy. The ability to
perform complex calculations makes a computer the perfect choice for use in business applications.
Some examples of the applications of computers in business are accounting, payroll, and customer
support.
8-3
Process Control
Controlling a process in real-time is another good example of the application of a computer system.
When the system detects a change in the process, an immediate corrective action can be initiated.
The applications and functions of a computer are virtually endless. Computers enable people to do
more than they could do in the past. For example, computations that required years to be calculated
by human methods are now accomplished in a matter of moments by a modern computer.
Types of Basic Computers
In general, there are two basic types of
computers: analog and digital.
Analog Computers
Analog computers (Figure 8-4) are all
designed to meet a special purpose.
For example, an analog computer can
be used to measure continuous
electrical or physical conditions, such
as current, voltage, flow, temperature,
or pressure. The data collected by the
Figure 8-4 — Analog computer.
analog computer is converted into a
related mechanical or electrical quantity. Analog computers can be used to adjust the control of a
machine or to manage a process. To accomplish these applications an analog computer must be
capable of converting analog data to digital data, process the data, and reverse the conversion
process. The applications of analog computers are limited because of their dependence on a physical
connection to a device.
Digital Computers
Digital computers are devices that are used to solve problems by manipulating numerical equivalents
of information by using mathematical and logical processes. A typical digital computer may use binary
numbers, octal numbers, decimal numbers, etc. as the required numerical equivalent. An electronic
digital computer typically uses binary numbers that are expressed as a 0 (OFF) or 1 (ON). The 0 and
1 functions are adjusted within the logic circuits by the voltage value and current applied to the
computer hardware.
Digital computers are capable of accepting a wide variety of instructions and responding in a specific
manner. This process, in general terms, is called programming. Programming is the modification or
arrangement of instructions in a predictable manner to a given situation. Digital computers are more
versatile than their analog equivalents because they are easily altered to meet changing conditions.
There are two basic types of digital computers: special purpose and general purpose.
•
Special-purpose digital computers (Figure 8-5) are designed to follow a specific set of
instruction sequences that are fixed at the time they are manufactured. The actual construction
of a special-purpose computer must be changed to alter its operational purpose.
•
General-purpose digital computers (Figure 8-6) follow instruction sequences that are read into
and stored in memory prior to the calculation being performed. This type of computer operation
can be altered by inputting a different set of instructions. Since the operation of generalpurpose digital computers can be changed with relative ease, they provide far greater usage
flexibility than a special-purpose digital computer.
8-4
Figure 8-6 — General-purpose
digital computer.
Figure 8-5 — Specialpurpose digital computer.
Peripheral Devices
A peripheral device (Figure 8-7) is any device that can be connected to a computer for input, output,
or communication functions. Peripherals that are under the control of the computer are defined as
being online. In contrast,
devices that operate
independently or are not
under direct control of the
computer are defined as
being offline. The following is
a list of some of the common
computer peripherals:
•
Printer
•
Scanner
•
Keyboard
•
Mouse
•
Monitor
•
Speakers
DATA
TRANSMISSION
Figure 8-7 — Common computer peripheral devices.
Computers use I/O sections to communicate with peripheral devices. Data is transmitted to the
computer, processed, and transferred as output. The I/O process is accomplished through the use of
electrical or optical cables that carry data and signals to and from the device to the computer. The
exchange of data and signals occurs on an I/O channel. There are two general types of I/O channels:
simplex and duplex.
•
Simplex operations occur in one direction only. A device that uses simplex communication
would only be able to transmit or receive data, but not both. Because of this characteristic,
8-5
simplex peripheral devices are seldom used because a return path is normally required to
control information flow or to generate an error signal.
•
A duplex channel is capable of
both sending and receiving
information. There are two types
of duplex channels: half-duplex
and full-duplex.
o Half-duplex – is capable of
transmitting and receiving
signals but only in one
direction at a time
o Full-duplex – is capable of
simultaneously
transmitting and receiving
data
Figure 8-8 — Types of computer I/O channels.
An illustration of the types of I/O channels is shown in Figure 8-8.
Digital Data Transmission Methods
A number of different methods can be used to receive and transmit digital data. However, this
discussion will focus on the three methods that are typically used in Navy aircraft: serial, parallel, and
fiber optic.
Serial Mode
Serial mode uses three wires for transmission: one to transmit data, one to receive data, and one to
act as a ground wire. In a serial system, digital data is transmitted one bit at a time using one pair of
transmission lines. Serial data transmission can be a good option to use in circumstances where a
computer and a peripheral are separated by a long physical distance.
Parallel Mode
Interaction Available
Parallel mode uses a single
wire for each bit of
information that will be
transmitted or received.
The data is transmitted via
the wires simultaneously.
Based on this fact, it would
require six wires to transfer
six bits of information using
the parallel mode of
transmission. The serial
and parallel modes of
transmission are illustrated
in Figure 8-9.
Figure 8-9 — Digital transmission modes.
8-6
Fiber Optic
Fiber optic systems transmit light photons through a specially designed glass medium to send and
receive digital information. The light photons in a fiber optic system are created by either a light
emitting diode (LED) or a laser diode.
There are three basics functions of a fiber optic data link:
•
To convert an electrical input into an optical signal
•
To transmit the optical signal over an optic fiber
•
To convert the optic signal back into an electrical signal
A typical fiber optic system uses four main components: transmitter, optical fiber, connectors/splices,
and receiver.
•
Transmitter – coverts the electrical signal into an optical signal and sends it through the optical
fiber cabling. Fiber optic transmitters in aircraft are normally embedded into Weapons
Replaceable Assemblies (WRAs). The photo-emitters in the fiber optic transmitter are chosen
specifically to meet an application. The primary differences in the photo-emitters include the
type (laser or LED), infrared (IR) wavelength, output power, and optical launch. Optical launch
describes the transmitter’s ability to launch the light photons down the fiber optic cabling.
•
Optical fiber – is a three-part structure that includes a core, cladding, and a coating. The
optical transport layer of a fiber optic cable is made up of a glass strand that consists of a core
region surrounded by a cladding region. The protective layer in aircraft fiber optic cables is
typically a polyimide coating that is 10- to 20-micrometers thick.
•
Connectors/Splices – are used to physically connect the optical fiber cable to the transmitter
and receiver sections of the data link. The most common connector used in aircraft fiber optic
systems is the military specification (MIL)-DTL-38999
series-III connector (Figure 8-10). The MIL-DTL-38999
series-III connector is compatible with both electronic
and fiber optic pins and sockets.
Figure 8-10 — MIL-DTL-38999
series-III fiber optic connector.
Figure 8-11 — Light transmission through a fiber optic cable.
8-7
Interaction Available
• Receiver – converts the optical signal into an electrical
signal and routes the signal to the appropriate
equipment for processing. Fiber optic receivers, like
transmitters, are embedded into WRAs. The
photodetectors in an aircraft fiber optic system are
also chosen to meet the specific application. The
photodetectors vary by
size and sensitivity to
the IR wavelength
(near IR to mid IR).
The transmission path
of light through a fiber
optic cable is illustrated
in Figure 8-11.
A typical fiber optic system incorporates all of the above components into one unit that is called a
transceiver. Fiber optic systems in aircraft are designed to be more rugged than fiber optic systems
on land. Aircraft fiber optic cables are normally 300 feet or less, contain less than five cables, and
may be incorporated with other aircraft wiring systems. Fiber optic data systems are progressively
being used to replace traditional electrical data transmission systems in aircraft.
PERIPHERAL AVIONICS SYSTEMS
The aircraft computer is the most important avionics system component used to ensure the assigned
mission is completed successfully. However, the success of the computer depends upon the interface
with external sensors or other avionics systems. The quality of the input data from the peripheral
systems to the computer determines the quality of the output from the computer. The following
paragraphs will provide an overview of some of the typical avionics systems that interface with the
aircraft computer system. The systems are as follows: navigation, radio detection and ranging (radar),
weapons, and data link.
Navigation
Navigation systems are designed to constantly update the operator with the current position of the
aircraft in space. Measuring equipment is used to gather navigational data such as station reference
points and geographic location. The navigational data is routed to the aircraft computer system where
it is compared, processed, and outputted out to other systems. Examples of the general
classifications of navigation systems are as follows:
•
Global positioning
•
Inertial navigation
•
Tactical air navigation
•
Automatic direction finder
Radar
Radar systems are designed to provide the operator with enhanced situational awareness. A typical
radar system can determine whether a target is moving, stationary, a land mass, an aircraft, and
other situational data. The radar system maintains communication with the aircraft computer system
to provide the operator with a steady flow of real-time information. Examples of the general
classifications of radar systems are as follows:
•
Search
•
Intercept
•
Fire control
•
Navigation
•
Airborne early warning
•
Antisubmarine warfare
Weapons
Many of the advanced weapons employed today require detailed target information before being fired
or released from an aircraft. The detailed information is provided to the weapons via the aircraft
computer system and associated peripheral armament components. The use of computer systems
8-8
has significantly increased the chances of successfully destroying or disabling a target the first time.
Examples of the general classifications of weapons systems are as follows:
•
Precision bombs
•
Guided missiles
•
Antisubmarine warfare
Data Link
Modern aircraft use complex avionics equipment that is capable of providing the operator with realtime tactical information. The real-time information is received from outside sources via a data link
system and is processed by the aircraft computer and peripheral equipment. The real-time
information can provide the operator with a distinct tactical advantage while on an assigned mission.
Examples of the general classifications of data link systems are as follows:
•
Multifunctional information distribution
•
Instrument landing
•
Navigation
F/A-18 MISSION COMPUTER SYSTEM
The F/A-18 Hornet mission computer system is the heart of the aircraft and will be used as an
example of peripheral avionics systems interface. The mission computer system oversees the control
of aircraft subsystems, which, in turn, greatly increases the ability to accomplish a mission. The
following paragraphs will provide an overview of a typical mission computer system installed in the
F/A-18 Hornet series aircraft. The mission computer system enables the following processes:
•
Computes and controls the displays sent to the multi-purpose display system
•
Computes and produces missile launch and weapons release commands
•
Provides mode control and option select output for various avionics systems
•
Provides mode control and option select
output from the multi-purpose display
group to avionics systems for control and
computation
•
Outputs built-in-test (BIT) initiate signals to
various avionics systems and monitors the
status
System Components
The F/A-18 mission computer system consists of
the following components:
•
Digital data computer no. 1 (Figure 8-12)
•
Digital data computer no. 2 (Figure 8-12)
•
Control-convertor
•
Electronic equipment control
•
Mission computer (MC)/hydraulic isolation
Figure 8-12 — Digital data computer.
8-9
(HYD ISOL) control panel assembly
•
Right mux bus impedance matching network
•
Left mux bus impedance matching network
Digital Data Computers
The two digital data computers
(mission computers) are generalpurpose computers with core memory.
A typical computer core memory
consists of tiny doughnut-shaped rings
that are made out of ferrite (iron) and
Figure 8-13 — Typical aircraft mux bus system wiring.
are strung on a grid of very thin wires.
The digital data computers
communicate with other avionics equipment by using six independent avionics multiplex channels.
Each channel consists of two independent “X” and “Y” buses. The wiring used in a typical aircraft mux
bus system is illustrated in Figure 8-13. The “X” bus is the primary bus and is used to communicate
with all equipment on that particular avionics mux channel. If there is an equipment communication
failure on the “X” bus, all communications are switched to the “Y” bus. The redundancy is the same
with the avionics equipment on the “Y” bus. The digital data computers communicate with equipment
not on the mux bus network through the control-convertor. If one of the digital data computers fails for
any reason, the other automatically defaults to control the aircraft navigation functions.
Both digital data computer systems use 115 volts alternating current (vac), 400 hertz (Hz), and 3phase power to operate. The power is provided via the aircraft electrical or ground power systems.
Both digital data computers have internal self-protection modules installed to protect the computer
hardware during input power failures.
Both digital data computers are divided into four functional subsystems, which enable the control of
the operations between the aircraft avionics systems. The four functional subsystems of the digital
data computer are as follows:
•
Processor – is configured with two modules that are further divided into seven sections
•
Memory – contains the main data storage for the computers through the use of two core
memory modules
•
I/O – contains six independent channels to process both inputs and outputs
•
Power conversion – is used to convert 115 vac into direct current (dc) power used by the
digital data computer modules
Both digital data computers are installed with specific software suites that control various mission
functions of the aircraft. The following is a basic overview of the software suites installed in each
digital data computer.
Digital data computer no. 1 has software installed that controls the following:
•
Navigation
•
Navigation head-up display
•
Engine monitor
•
Avionics BIT
•
Data link
8-10
•
Navigation controls and displays (Figure 814)
•
Inflight monitor and recording
•
Non-avionics BIT
•
Support controls and displays
•
Display format manager
•
Math subroutines
•
Test support and monitoring
•
Instrumentation support and monitoring
Digital data computer no. 2 has software installed
that controls the following:
•
Air-to-air weapons
•
Weapon delivery head-up display
•
Air-to-ground weapons
•
Tactical controls and displays (Figure 8-15)
•
Display format manager
•
Self-test
•
Math subroutines
•
Test support and monitoring
•
Instrumentation support and monitoring
Figure 8-14 — Typical navigation display.
Control-Convertor
The control-convertor is the interface unit between
the following components:
•
Electronic equipment control
•
Digital computers no. 1 and no. 2
•
Non-mux avionics systems
The control-convertor contains a central
processing unit and a fixed software program,
which is controlled by the digital computers or the
electronic equipment control. The control-convertor
sends option, scratch pad (input display), and
communication display outputs to the electronic
equipment control in response to commands.
Commands transmitted from the electronic
equipment control or the digital computers are
decoded by the control-convertor for non-mux
capable avionics system control. The inputs
received from the digital computer are reformatted
8-11
Figure 8-15 — Typical tactical weapons
delivery status display.
and supplied to non-mux capable equipment as control-convertor outputs. The following signals are
reformatted and transmitted over the avionics mux bus by the control-convertor:
•
Synchro
•
Analog
•
Discrete
•
Status
•
Digital inputs
Electronic Equipment Control
The electronic equipment control (Figure 8-16) contains the switches and display functions required
to control the following systems:
•
Communication
•
Navigation
•
Identification
The electronic equipment control also provides
for the manual entry of program data and option
selection. The systems enabled by the function
select switch are as follows:
•
Electronic flight control
•
Identification friend or foe (IFF)
•
Tactical air navigation
•
Instrument landing
•
Data link
•
Radar beacon
Figure 8-16 — Typical electronic equipment
control.
The selected system is turned on and off via the ON/OFF switch on the electronic equipment control.
When the system is activated, the status is displayed on the electronic equipment control by two
alphanumeric characters. There are five preset options and a four-character alphanumeric display
associated with each selected system. The control and power for the electronic equipment control is
provided by the control-convertor. The electronic equipment control also provides for the selection of
voice communication channels and volume controls.
MC/HYD ISOL Control Panel Assembly
The MC switch on the panel assembly has three-positions and is electrically latched in either positon
other than center. Power is removed from digital data computer no. 1 when the switch is placed in the
1 OFF position. Further, power is removed from digital data computer no. 2 when the switched is
placed in the 2 OFF position. In the normal (NORM) position, power is applied to both digital data
computers.
Right and Left Mux Bus Impedance Matching Networks
The mux bus impedance matching networks are used to terminate the six dual bus avionics mux
channels in their characteristic impedance.
8-12
Mission Computer System Interface
Digital data computers no. 1 and no. 2 use six avionics mux channels, the control-convertor channel,
and the electronic equipment control interface to receive input and supply output data to avionics
components.
Avionics Mux Channel 1
Avionics mux channel 1interfaces with the following components:
•
Air data computer
•
Armament computer
•
High-Speed Anti-Radiation Missile (HARM) command launch computer
•
Control-convertor
•
Left digital display indicator
•
Communication (COMM) no. 1 receiver-transmitter
•
COMM no. 2 receiver-transmitter
•
Flight control computer (FCC) A
•
FCC B
•
Signal data computer
•
Signal data recorder
•
Aircraft instrumentation internal subsystem
Avionics Mux Channel 2
Avionics mux channel 2 interfaces with the following components:
•
Computer-power supply
•
Controller-processor
•
Inertial navigation group
•
Data link system receiver-transmitter-processor
•
Right digital display indicator
•
Electronic countermeasures computer
•
Advanced Targeting Forward Looking Infrared (ATFLIR) pod
•
Aircraft instrumentation internal subsystem
Avionics Mux Channel 3
Avionics mux channel 3 is used to interface and provide a direct communication line between digital
data computer no. 1 and digital data computer no. 2.
Avionics Mux Channel 4
Avionics mux channel 4 provides the interface to digital data computers no. 1 and no. 2 for the
mission data loader system. The mission data loader system allows the operator to automatically
populate mission-specific data into both digital data computers. For example, an operator can
8-13
configure all of the mission-specific radio frequencies onto a mission card that will load that
information into the digital data computers.
Avionics Mux Channel 5
Avionics mux channel 5 provides a communication path between digital computer no. 1, digital
computer no. 2, right digital display indicator, and the aircraft instrumentation internal subsystem.
Avionics Mux Channel 6
Avionics mux channel 6 provides a communication path between digital data computer no. 1, digital
data computer no. 2, left digital display indicator, and the digital map computer.
Control-Convertor Channel
The following components are interfaced through the control-convertor channel:
•
Embedded global positioning system (GPS)/inertial navigation system (INS)
•
Engine monitor indicator
•
Left hand (LH) advisory and threat warning indicator panel
•
Caution light indicator panel
•
Instrument landing system pulse decoder
•
Intercommunication amplifier-control
•
Antenna selector
•
Electronic equipment control
•
Head-up display unit
•
IFF receiver-transmitter
•
Lock/Shoot light assembly
•
IFF computer-transponder
•
Automatic direction finder system
•
Interference blanker
•
Attitude reference indicator
•
Radar beacon receiver-transmitter
•
Radar beacon receiver
•
Electronic altimeter height indicator
•
Electronic altimeter receiver-transmitter
•
Digital data computers no. 1 and no. 2
•
COMM 1 and COMM 2 receiver-transmitter
8-14
Electronic Equipment Control Interface
The electronic equipment control receives input data and supplies output data to the following
components:
•
Control-convertor
•
Antenna selector
•
IFF system receiver-transmitter
•
Cockpit electric light control
•
Intercommunication amplifier-control
A block diagram of the mission computer system and the six avionics mux channels is shown in
Figure 8-17.
Figure 8-17 — Mission computer system and avionics mux channels block diagram.
8-15
End of Chapter 8
Computers
Review Questions
8-1.
The speed and processing power of a computer is determined by what internal characteristic?
A.
B.
C.
D.
8-2.
What hardware component allows the operator to enter data into the system?
A.
B.
C.
D.
8-3.
Memory
Output device
Input device
Central processing unit
What type of software application processing could determine the success or failure of a
mission?
A.
B.
C.
D.
8-6.
Memory
Output device
Input device
Central processing unit
What hardware component is the most important part of the computer system?
A.
B.
C.
D.
8-5.
Memory
Output device
Input device
Central processing unit
What hardware component temporarily stores data and applications?
A.
B.
C.
D.
8-4.
Size
Power
Scope
Components
Static
Arithmetic
Real-time
Read-only
What component does a computer use to store information internally?
A.
B.
C.
D.
Input
Output
Memory
Processor
8-16
8-7.
C++ and Java are examples of what type of programming language?
A.
B.
C.
D.
8-8.
What type of software is used to transform the source code of a programming language?
A.
B.
C.
D.
8-9.
Localized
Specialized
Generalized
Randomized
Compiler
Assembler
Application
Operating system
What type of software is used to support a computer’s basic functions?
A.
B.
C.
D.
Compiler
Assembler
Application
Operating system
8-10. Other than manual, what method can a computer use to gather data?
A.
B.
C.
D.
Logical
Automatic
External
Semi-automatic
8-11. What is the main function of a computer?
A.
B.
C.
D.
Process data
Gather data
Display data
Disseminate data
8-12. What computer function involves the routing of data to external components?
A.
B.
C.
D.
Process data
Gather data
Display data
Disseminate data
8-13. What computer function is dependent on the use of peripheral devices?
A.
B.
C.
D.
Process data
Gather data
Display data
Disseminate data
8-17
8-14. What computer function occurs first?
A.
B.
C.
D.
Process data
Gather data
Display data
Disseminate data
8-15. What application of a computer is used to index and retrieve information?
A.
B.
C.
D.
Business
Database
Simulation
Process control
8-16. Design and testing of a system occurs using what application of a computer?
A.
B.
C.
D.
Business
Database
Simulation
Process control
8-17. The ability to perform high-speed and accurate calculations is most suitable for which of the
following applications?
A.
B.
C.
D.
Business
Database
Simulation
Process control
8-18. When a deficiency is encountered, what application of a computer enables the initiation of an
immediate corrective action?
A.
B.
C.
D.
Business
Database
Simulation
Process control
8-19. The two basic types of computers are analog and what other type?
A.
B.
C.
D.
Mission
Digital
Desktop
Electrical
8-18
8-20. Other than mechanical, the data collected by an analog computer is converted into what type
of quantity?
A.
B.
C.
D.
Sound
Electrical
Pressure
Temperature
8-21. Binary code uses what set to represent an ON and OFF signal respectively?
A.
B.
C.
D.
0 and 0
0 and 1
1 and 0
1 and 1
8-22. What term is used to describe the modifying of computer instructions based on a situation?
A.
B.
C.
D.
Operating
Manipulating
Disseminating
Programming
8-23. Binary code in computer hardware is adjusted by current and what other value?
A.
B.
C.
D.
Time
Voltage
Quotient
Numerical operator
8-24. The operation of what type of digital computer can be easily changed?
A.
B.
C.
D.
All-purpose
Multi-purpose
General-purpose
Special-purpose
8-25. Printers and keyboards are examples of what types of devices?
A.
B.
C.
D.
Internal
Peripheral
Dependent
Independent
8-26. A device using what type of data transmission will only be able to either receive or transmit?
A.
B.
C.
D.
Simplex
Duplex
Full-duplex
Half-duplex
8-19
8-27. A device using what type of data transmission can send and receive data at the same time?
A.
B.
C.
D.
Simplex
Multiplex
Full-duplex
Half-duplex
8-28. A device using what type of data transmission can transmit and receive signals, but in only one
direction at a time?
A.
B.
C.
D.
Simplex
Duplex
Full-duplex
Half-duplex
8-29. Data is transmitted one bit at a time using what mode of digital transmission?
A.
B.
C.
D.
Serial
Parallel
Fiber optic
Series-parallel
8-30. Data is transmitted simultaneously using what mode of digital transmission?
A.
B.
C.
D.
Serial
Parallel
Fiber optic
Series-parallel
8-31. Other than a laser diode, what type of diode can be used to generate photons in a fiber optic
system?
A.
B.
C.
D.
Gunn
Zener
Avalanche
Light-emitting
8-32. Fiber optic data link systems convert an electrical signal into what type of signal?
A.
B.
C.
D.
Visual
Optical
Acoustical
Mechanical
8-33. The protective layer of a fiber optic cable is typically how many micrometers thick?
A.
B.
C.
D.
10 to 20
20 to 30
30 to 40
40 to 50
8-20
8-34. Automatic direction finders are an example of what type of peripheral avionics system?
A.
B.
C.
D.
Radar
Weapons
Navigation
Data link
8-35. Radar systems provide the operator with what type of awareness?
A.
B.
C.
D.
Tactical
Situational
Operational
Environmental
8-36. The F/A-18 mission digital data computers use what type of memory?
A.
B.
C.
D.
Core
Logical
Volatile
Non-volatile
8-37. Each digital data computer multiplex channel consists of how many buses?
A.
B.
C.
D.
One
Two
Three
Four
8-38. If one digital data computer fails, the other will default to what mode of operation?
A.
B.
C.
D.
Radar
Weapon
Navigation
Communication
8-39. The F/A-18 digital data computer is divided into how many functional subsystems?
A.
B.
C.
D.
Three
Four
Five
Six
8-40. What avionics mux channel is reserved for digital computer-to-computer communication?
A.
B.
C.
D.
1
2
3
4
8-21
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8-22
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CHAPTER 9
AUTOMATIC CARRIER LANDING SYSTEM/INSTRUMENT
LANDING SYSTEM
One of the most demanding tasks facing aircrew is landing an aircraft onto an aircraft carrier. The
Automatic Carrier Landing System (ACLS) and Instrument Landing System (ILS) are great aids to the
aircrew to accomplish this task. In the fleet, aviation electronics technicians (ATs) routinely
troubleshoot discrepancies with the ACLS and ILS. Therefore, basic knowledge of the systems and
the carrier landing process is vital to the successful diagnosis and repair of the system. This chapter
will provide an overview of basic aerodynamics, ACLS carrier systems, ACLS aircraft systems, and
the ILS.
LEARNING OBJECTIVES
When you have completed this chapter, you will be able to do the following:
1. Recognize the basic forces that affect flight.
2. Recognize the components used in the ACLS.
3. Describe the operating principles of the ACLS.
4. Describe the aircraft carrier landing sequence.
AIRFOIL
An airfoil is defined as that part of an aircraft that produces lift or any other desirable aerodynamic
effect as it passes through the air. The wings and the propeller blades of a fixed-wing aircraft and the
rotor blades of a helicopter are examples of airfoils.
Airfoil Terminology
The shape of an airfoil and its relationship to the airstream are important. The following are some of
the common terms that are used to describe airfoils.
•
The leading edge is the front edge or
surface of the airfoil (Figure 9-1).
•
The trailing edge is the rear edge or
surface of the airfoil (Figure 9-1).
•
The chord line is an imaginary straight
line from the leading edge to the trailing
edge of an airfoil (Figure 9-1).
•
The camber is the curve or departure
from a straight line (chord line) from the
leading edge to the trailing edge of the
airfoil (Figure 9-1).
Figure 9-1 — Airfoil terminology.
9-1
•
Relative wind is the direction of the
airstream in relation to the airfoil (Figure 92).
•
Angle-of-attack (AOA) is the angle
between the chord line and the relative
wind (Figure 9-2).
FORCES AFFECTING FLIGHT
Figure 9-2 — AOA.
An aircraft in flight is in the center of a continuous
battle of forces. The conflict of these forces is the
key to all maneuvers performed in the air. There is nothing mysterious about these forces because
they are definite and known. The direction in which each of the forces acts can be calculated. The
aircraft is designed to take advantage of each force. These forces are lift, weight, thrust, and drag.
Lift
Lift is the force that acts in an upward direction to support the aircraft in the air. Lift counteracts the
effects of weight and must be greater than or equal to weight if flight is to be sustained.
Weight
Weight is the force of gravity acting downward on
the aircraft and everything in the aircraft, such as
crew, fuel, and cargo.
Thrust
Thrust is the force developed by the aircraft's
engine. Thrust acts in the forward direction and
must be greater than or equal to the effects of
drag for flight to begin or to be sustained.
Drag
Drag is the force that tends to hold an aircraft
back. Drag is caused by the disruption of the
airflow about the wings, fuselage, and all
protruding objects on the aircraft. Drag resists
motion as it acts parallel and in the opposite
direction in relation to the relative wind. The
direction in which these forces act in relation to
the aircraft is shown in Figure 9-3.
Figure 9-3 — Forces affecting flight.
ROTATIONAL AXES
Any vehicle, such as a ship, a car, or an aircraft, is capable of making three primary movements (roll,
pitch, and yaw). The vehicle has three rotational axes that are perpendicular (90 degrees) to each
other. The axes are referred to by their direction: longitudinal, lateral, and vertical.
9-2
Longitudinal Axis
The longitudinal axis is the pivot point about which
an aircraft rolls. The movement associated with
roll is best described as the movement of the wing
tips (one up and the other down). The longitudinal
axis runs fore and aft through the length (nose to
tail) of the aircraft. This axis is parallel to the
primary direction of the aircraft. The primary
direction of a fixed-wing aircraft is always forward.
The roll axis is shown in Figure 9-4, View A.
Interaction Available
Vertical Axis
The vertical axis runs from the top to the bottom
of an aircraft. The vertical axis runs perpendicular
to both the roll and pitch axes. The movement
associated with the vertical axis is yaw. Yaw is
best described as the change in aircraft heading
to the right or left of the primary direction of an
aircraft. The yaw axis is shown in Figure 9-4, View
B.
Lateral Axis
The lateral axis is the pivot point about which the
aircraft pitches. Pitch can best be described as
the up and down motion of the nose of the
aircraft. The pitch axis runs from the left to the
right of the aircraft (wingtip to wingtip). The pitch
axis is perpendicular to and intersects the roll axis
and is shown in Figure 9-4, View C.
AUTOMATIC CARRIER LANDING
SYSTEM COMPONENTS
Figure 9-4 — Motion about the axes.
The ACLS consists of multiple components installed in the aircraft and systems located onboard an
aircraft carrier. The following paragraphs will provide an overview of both the typical ACLS aircraft
carrier and aircraft components and systems.
Aircraft Carrier Automatic Carrier Landing System Components
Aircraft carriers are equipped with two radar systems that provide landing aircraft with critical
information and guidance during the landing cycle. There are the SPN-41 Instrument Carrier Landing
System (ICLS) and the SPN-46(V)3 Precision Approach Landing System (PALS).
SPN-41 Instrument Carrier Landing System
The ICLS radar transmits the glidepath pulse-coded under the K frequency band (Ku) information
from the aircraft carrier to the aircraft. The ICLS is located on the carrier and uses two antennas. One
antenna is used to transmit azimuth information, and the other transmits elevation information. Both
signals are processed by the receiver-decoder group on the aircraft.
9-3
SPN-46(V)3 Precision Approach Landing System
The PALS (Figure 9-5) was designed to be an
automatic landing system but it has the capability to
operate in manual modes. The PALS uses two modes
to receive and transmit data: display and voice. The
PALS operates in three modes: mode I, mode II, and
mode III.
•
Mode I is the automatic control mode of
operation. The PALS transmits command and
error signals to the aircraft via the aircraft data
link system. The approaching aircraft receives
command and error signals and automatically
corrects the approach to remain in the narrow
flight envelope.
•
Mode II is a manual control mode with
information relayed to aircraft displays. The
operator is provided with cockpit visual
indications of command and error signals relayed
by the PALS.
•
Figure 9-5 — SPN-46(V)3 PALS antenna.
Mode III is a manual control mode with voice communications. The PALS provides a voice link
for ship-to-aircraft voice communications to provide talkdown guidance.
Aircraft Automatic Carrier Landing System Components
Aircraft ACLS systems do not use one system or one component. The aircraft ACLS is an integration
of multiple aircraft systems that work together to guide the aircraft safely to a carrier landing. The
following paragraphs will describe a typical aircraft ACLS system and its components.
Instrument Landing System
The ILS (Figure 9-6) provides the data
for visual steering commands that
assist the aircrew for the last 25 miles
before carrier touchdown. The ILS
interacts with the ICLS and decodes
the azimuth and elevation signals. The
decoded signals are provided to the
aircrew via the head-up display (HUD)
and the standby attitude reference
indicator (ARI). The ILS consists of the
following components: radio receiver,
pulse-decoder, Ku-band antenna, and
Ku-band waveguide assembly.
•
The radio receiver mixes,
detects, and amplifies azimuth
and elevation microwave
signals from the ICLS to
provide a coded-pulse train to
the pulse-decoder.
Figure 9-6 — Typical instrument landing aircraft-toaircraft-carrier communication.
9-4
•
The pulse-decoder receives and decodes the coded-pulse train and uses the signal to route
the elevation and azimuth errors to the HUD and ARI.
•
The Ku-band antenna receives the Ku-band azimuth and elevation signals transmitted from the
ICLS.
•
The Ku-band waveguide assembly provides the path to route the azimuth and elevation signals
from the Ku-band antenna to the radio receiver.
Standby Attitude Reference Indicator
A typical standby ARI (Figure 9-7) is designed to
assist the aircrew in determining the attitude of the
aircraft in instances where the natural horizon is
not visible. A typical standby ARI uses a miniature
representation of an aircraft that represents the
nose (pitch) and wing (bank) attitude. The bank
pointer on the indicator face shows the degree of
aircraft bank in the following manner:
•
10-degree increments up to 30 degrees
•
30-degree increments up to 90 degrees
The upper half of the indicator is a light color that
represents the sky. The bottom half of the
indicator is a dark color that is used to represent
the ground. Calibration marks on the sphere are
used to represent the pitch of the aircraft in 5- to
10-degree increments. Every attitude reference
indicator consists of a control to adjust the pitch
trim adjustment or a pull-to-cage knob which the
operator uses to center the artificial horizon as
necessary.
Figure 9-7 — Typical standby attitude
reference indicator.
The standby ARI automatically displays ILS steering when the ILS system is turned on by the
operator. The ILS steering cues use the miniature representation of the aircraft as a reference. The
horizontal needle indicates an ILS approach that is above or below the glideslope. The vertical needle
indicates an ILS approach that is left or right of the glideslope. The aircraft is at the optimal approach
conditions when the horizontal and vertical needles are centered on the standby ARI. A typical
standby ARI uses pitch and roll information obtained via the aircraft inertial navigation system. The
sphere inside the standby ARI is gimbal-mounted and capable of 360 degree rotation.
Automatic Flight Control System
A typical automatic flight control system (AFCS) is made up of a number of components and systems.
A typical AFCS is used to provide the interface between the correction signals received from the data
link and the aircraft flight control surfaces. The AFCS provides switching and signal conditioning,
engage logic, command signal limiting, and failsafe interlocks. The failsafe interlocks are required to
couple and process data link signals to the pitch and bank channels of the AFCS. Automatic
synchronization is provided in all three axes.
9-5
Automatic Throttle Control
Similar to the AFCS, the automatic throttle control (ATC) system encompasses a number of different
components and subsystems. The ATC system is used during the landing sequence to maintain the
appropriate AOA by electrically adjusting the output power of the engines. The ATC also manipulates
the engine controls to keep the aircraft traveling at a constant rate of airspeed.
Head-up Display
The aircraft HUD displays the same cues as the
standby ARI but in a digital format. The ILS
steering cues on the HUD are referenced to
velocity vector (center of the display) and the
artificial horizon. The elevation deviation bar
(Figure 9-8) indicates an ILS approach that is
above or below the glideslope. The azimuth
deviation bar (Figure 9-8) indicates an ILS
approach left or right of the glideslope. The
aircraft is at the optimum approach conditions
when both the elevation and azimuth bar are
centered within the velocity vector and the
artificial horizon.
Receiving-Decoding Group
A typical receiving-decoding group converts the
Figure 9-8 — HUD ILS steering display.
glidepath error signals received from the ship’s
ICLS and converts the signals into visual indications for the operator. The receiving-decoding group is
also used for the airborne monitoring of ACLS mode I and mode II aircraft carrier approaches.
Radar Beacon
The radar beacon has two modes of operation: normal and automatic carrier landing (ACL). The
normal mode is used to extend the range of the surface tracking radar. When in the ACL mode the
radar beacon receives conically scanned above the K frequency band (Ka) signals from the SPN-46
radar system. The signals are used to derive the range, angle tracking, and position error for aircraft
data link guidance. There are five components to the radar beacon system:
•
The radar receiver is used during both the
normal and ACL modes. The radar receiver
detects when the aircraft is out of position.
The radar receiver produces an amplitude
modulated (AM) envelope called spin error.
The amplitude of the spin error is directly
proportional to the amount of position error.
The spin error signal is then applied to the
radar receiver-transmitter.
•
The radar receiver-transmitter (Figure 9-9)
receives the X-band signals that are
transmitted by the SPN-46 PALS. The main
purpose of the radar receiver-transmitter is to
improve the aircraft tracking while operating
in the ACL mode. When the radar receiver9-6
Figure 9-9 — Radar beacon receivertransmitter.
transmitter receives the spin error signal from the radar receiver it produces X-band reply
signals. The SPN-46 PALS additionally uses the X-band replies for aircraft angle tracking and
range information.
•
The Ka-band antenna receives the Ka frequency band signals and routes the signals to the
radar receiver.
•
The X-band antenna receives the X-band signals and routes the signals to the radar receivertransmitter.
•
The Ka-band coaxial cable and waveguide assembly is used to route the received Ka-band
signals to the radar receiver.
Angle-of-Attack Indexer
The AOA indexer is located on the left hand side of the HUD in the Fighter/Attack (F/A)-18 series
aircraft. The AOA indexer uses lighted symbols to visually indicate the aircraft AOA.
AUTOMATIC CARRIER LANDING SYSTEM OPERATION
The all-weather combination AFCS and ACLS provides the automatic, semiautomatic, or manual
operation for aircraft carrier landings with minimum use of airborne electronic subsystems. The
aircraft control commands are generated by shipboard computers so that the necessary pitch and
bank signals can be transmitted to the aircraft AFCS via the one-way data link system. This closedloop operation between aircraft and aircraft carrier can provide the aircraft with automatic control from
approach to touchdown. The ACLS is the final approach and landing medium for carrier-based
aircraft during daylight or darkness, severe weather and sea states, and in low ceiling and low
visibility conditions.
There are three selectable modes of operation for the ACLS: mode I, mode II, and, mode III.
•
Mode I is a fully automatic approach from entry point to touchdown on the flight deck.
•
Mode II requires manual control of the aircraft. In this mode, the aircrew controls the aircraft by
observing the crew station displays.
•
Mode III is manual aircrew control with talkdown guidance by a shipboard controller that
provides verbal information for aircrew control to visual minimums.
NOTE
The operator can use full mode I capability with mode II and
mode III as backups.
Landing Sequence
The following paragraphs will provide an overview of the mode I landing sequence. The landing
sequence (Figure 9-10) begins when the aircraft is at the marshaling point under control of the Carrier
Air Traffic Control Center (CATCC). The sequence has two phases: approach and descent.
•
Approach consists of the flight of the aircraft from the marshaling point to the radar acquisition
window.
•
Descent consists of the flight of the aircraft from the radar acquisition window until landing on
the aircraft carrier flight deck.
9-7
The transition from the approach phase
to the descent phase is accomplished
with minimal crew station switching
operations. The minimal switching
operations are intended to reduce the
task loading during the landing
sequence.
Mode I Landing Operation
The aircraft is held at a marshalling
point by CATCC, before transitioning
into a mode I landing approach. The
aircraft will remain at the marshal point
until CATCC has determined the landing
priorities. When the aircraft is selected
to begin its approach, CATCC assigns a
data link channel, which is entered into
the aircraft data link system by the
aircrew. The aircrew is cleared for
approach to the aircraft carrier when the
landing check (LDG CHK) indicator
illuminates in the crew station of the
aircraft.
At this point in the sequence the
Figure 9-10 — Carrier landing sequence.
operator ensures all required mode I
landing systems are in the correct mode
of operation. The aircraft then begins the initial descent towards the aircraft carrier. When the aircraft
passes the acquisition radar window (approximately 4 miles astern of the aircraft carrier) the ACL
ready (ACL RDY) indicator will illuminate in the crew station.
The PALS system begins to transmit lateral and vertical error signals after the aircraft passes the
acquisition radar system window. The lateral and vertical signals represent the actual position of the
aircraft in comparison to the approach path to the aircraft carrier. Next, the PALS transmits a
COUPLE discrete signal to the aircraft. The COUPLE discrete signal indicates that the AFCS system
is being provided with pitch and roll commands. The pitch and roll commands are transmitted by the
AFCS to the aircraft control surfaces.
The aircrew places the aircraft into landing configuration and ensures the aircraft is within aircraft
carrier landing approach parameters. The ICLS sends a 10 second discrete message (10 SEC) when
the aircraft is approximately 12 seconds away from landing on the aircraft carrier flight deck. The 10
SEC discrete message informs the operator that the motion of the flight deck is being added to the
glideslope commands. The ICLS freezes the transmission of compensation messages when the
aircraft is approximately 1.5 seconds from touchdown. At the same time, the AFCS in combination
with the ATC holds the aircraft altitude.
Safety Provisions
The ACLS was designed with the safety of the aircrew and aircraft as a core component. The ACLS
uses the following provisions to ensure safety:
9-8
•
The ICLS uses an independent monitoring link to ensure the aircraft is within a safe glidepath
position. Additionally, the monitoring link allows the operator to monitor the position of the
aircraft in relation to the transmitted glidepath.
•
The COUPLE discrete message transfer is terminated any time the aircraft exceeds the control
envelope. The operator can continue the landing approach to the aircraft carrier but only in
ACLS modes II or III.
If at any point during the coupled landing sequence the aircraft requires a large maneuver to get back
on course and into the flightpath, an automatic WAVEOFF signal is generated. The automatic
WAVEOFF signal automatically disengages the aircraft ACLS to allow the operator to execute the
waveoff maneuver.
The ACLS mode I approach is illustrated in Figure 9-11.
Figure 9-11 — ACLS mode I approach.
9-9
End of Chapter 9
Automatic Carrier Landing System/Instrument Landing System
Review Questions
9-1.
Which of the following terms describe the part of an aircraft that produces lift as it passes
through the air?
A.
B.
C.
D.
9-2.
What term describes an imaginary line from the leading edge to the trailing edge of an airfoil?
A.
B.
C.
D.
9-3.
Camber
Chord line
Trailing edge
Leading edge
What force is defined as gravity acting downward on an aircraft?
A.
B.
C.
D.
9-6.
Camber
Chord line
Trailing edge
Leading edge
What term describes the curve from the leading edge to the trailing edge of an airfoil?
A.
B.
C.
D.
9-5.
Camber
Chord line
Rotational
Longitudinal
What term describes the front edge of an airfoil?
A.
B.
C.
D.
9-4.
Airfoil
Engines
Fuselage
Landing gear
Lift
Drag
Thrust
Weight
What force is developed by an aircraft’s engine?
A.
B.
C.
D.
Lift
Drag
Thrust
Weight
9-10
9-7.
What force has the tendency to hold an aircraft back?
A.
B.
C.
D.
9-8.
What force acts in an upward direction to support an aircraft in the air?
A.
B.
C.
D.
9-9.
Lift
Drag
Thrust
Weight
Lift
Drag
Thrust
Weight
What rotational axis runs from the top to the bottom of an aircraft?
A.
B.
C.
D.
Lateral
Vertical
Diagonal
Longitudinal
9-10. What rotational axis is the pivot point around which an aircraft pitches?
A.
B.
C.
D.
Lateral
Vertical
Diagonal
Longitudinal
9-11. What rotational axis is the pivot point around which the aircraft rolls?
A.
B.
C.
D.
Lateral
Vertical
Diagonal
Longitudinal
9-12. What frequency band does the SPN-41 radar use to transmit information to an aircraft?
A.
B.
C.
D.
K
X
K-over
K-under
9-13. The precision approach landing system has how many modes of operation?
A.
B.
C.
D.
Two
Three
Four
Five
9-11
9-14. What modes can the precision approach landing system use to receive and transmit data?
A.
B.
C.
D.
Analog and digital
Input and output
Display and voice
Electrical and mechanical
9-15. What system provides the data for visual steering commands at about 25 miles away from the
aircraft carrier?
A.
B.
C.
D.
Weapons
Communication
Global positioning
Instrument landing
9-16. What does the upper half of a typical attitude reference indicator represent?
A.
B.
C.
D.
Sky
Ground
Bank
Pitch
9-17. Calibration marks on a typical attitude reference indicator represents aircraft pitch in
increments of how many degrees?
A.
B.
C.
D.
5 to 10
5 to 20
5 to 30
5 to 40
9-18. What system provides the interface between data link signals and aircraft control surfaces?
A.
B.
C.
D.
Radar beacon
Automatic throttle
Receiving-decoding
Automatic flight control
9-19. What system is used to keep the aircraft traveling at a constant speed?
A.
B.
C.
D.
Radar beacon
Automatic throttle
Receiving-decoding
Automatic flight control
9-20. What radar beacon component detects when the aircraft is out of position?
A.
B.
C.
D.
Receiver
Antenna
Receiver-transmitter
Coaxial cable
9-12
9-21. How many selectable modes are in an automatic carrier landing system?
A.
B.
C.
D.
Two
Three
Four
Five
9-22. What are the two phases in the aircraft carrier landing sequence?
A.
B.
C.
D.
Marshal and descent
Marshal and approach
Transition and approach
Approach and descent
9-23. The aircrew will begin the approach to the aircraft carrier when what indicator illuminates?
A.
B.
C.
D.
COUPLE
WAVEOFF
LDG CHK
AUTOMATIC CARRIER LANDING
9-24. The acquisition radar window is approximately how many miles astern of the aircraft carrier?
A.
B.
C.
D.
3
4
5
6
9-25. What signal is generated when an aircraft requires a large maneuver to get back into the safe
glideslope?
A.
B.
C.
D.
COUPLE
WAVEOFF
LDG CHK
AUTOMATIC CARRIER LANDING
9-13
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9-14
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CHAPTER 10
ELECTROSTATIC DISCHARGE
The electrical noise generated in a radio or radar receiver is often confused with electrical noise
generated external to and coupled into the receiver. The internally generated noise is the result of
circuit deficiencies in the receiver itself, and can be eliminated by replacing the defective component
or replacing the entire receiver. Electrical noise produced external to the receiver enters the receiver
by various means. The noise causes interference in the receiver, as well as poor reception.
In early naval aircraft, electrical noise interference was not a major problem because there were
fewer external sources of electrical noise. Receiver sensitivities were low, and the aircraft control
components were manually operated. In today’s aircraft, however, there are considerably more
sources of externally generated electrical noise. The aircraft now contains numerous receivers with
higher sensitivities, and aircraft controls are operated by various electrical and/or mechanical devices.
These devices include control surface drive motors, fuel and hydraulic boost pumps, alternating
current (ac) inverters, and cabin pressurization systems. In addition, pulsed electronic transmitters,
such as Tactical Air Navigation (TACAN), radar, and Identification Friend or Foe (IFF), can be
sources of electrical noise interference. Listening to electrical noise interference in the output of a
radio receiver can cause nervous fatigue in aircrew personnel. Electrical noise may also reduce the
performance (sensitivity) of the receiver. For these reasons, electrical noise should be kept at the
lowest possible level.
The overall objective of this chapter is to assist you in recognizing various types of electrical/
electronic noise, their effects on radio and radar receivers, and what the electrostatic discharge
program means to you as an aviation electronics technician (AT). This chapter also provides you
with information for keeping electrical noise interference as low as possible in electronic equipment
aboard naval aircraft.
LEARNING OBJECTIVES
When you have completed this chapter, you will be able to do the following:
1. Recognize the effects of natural electrical interference.
2. Recognize the effects of man-made electrical interference.
3. Identify the sources of electrical noise.
4. Recognize the effects of electrical noise.
5. Identify various types of electrical interference caused by coupling.
6. Describe methods to reduce electrical interference caused by coupling.
7. Identify components that are used to reduce radio interference caused by electrical noise.
8. Describe the purpose of bonding.
9. Identify the hazards to electrostatic discharge sensitive devices.
10. Identify materials used to package and protect electrostatic discharge sensitive devices.
11. Explain the proper handling techniques when packaging electrostatic discharge sensitive
devices.
10-1
TYPES AND EFFECTS OF RECEIVER NOISE INTERFERENCE
The types of electrical noise interference that enter aircraft receivers are broadly categorized as
natural interference and man-made interference.
Natural Interference
Radio interference caused by natural electrical noise is separated into three types: atmospheric static,
precipitation static, and cosmic noise. Each type is discussed below.
Atmospheric Static
Atmospheric static is a result of the electrical
breakdown between masses (clouds) of
oppositely charged particles in the
atmosphere. An extremely large electrical
breakdown between two clouds or between
the clouds and ground is called lightning
(Figure 10-1). Atmospheric static is completely
random in nature, both as to rate of
recurrence and as to intensity of individual
discharges. Atmospheric static produces
irregular popping and crackling in audio
outputs and false indications on visual output
devices. Its effects range from minor
annoyance to complete loss of receiver
usefulness. Atmospheric interference is
seldom of a crippling intensity at frequencies
from 2 to 30 megahertz (MHz). Above 30
MHz, the noise intensity decreases to a very
low level. At frequencies below 2 MHz, natural
static is the principal limiting factor on usable
receiver sensitivity.
Figure 10-1 — Example of atmospheric static.
The intensity of atmospheric static varies with location, season, weather, time of day, and the
frequency to which the receiver is tuned. It is most intense at the lower latitudes, during the summer
season, during weather squalls, and at the lower radio frequencies. Many schemes have been
devised to minimize the effects of atmospheric static. However, the best technique is to avoid those
frequencies associated with intense static, if possible.
Precipitation Static
Precipitation static is a type of interference that occurs during dust, snow, or rain storms. The
principal cause of precipitation static is the corona discharge of high voltage charges from various
points on the airframe. These charges may reach several hundred thousand volts before discharge
occurs. The charge can be built up in two ways. First, an electrostatic field existing between two
oppositely charged thunderclouds induces bipolar (positive and negative) charges on the surfaces of
the aircraft as it passes through the charged clouds. Second, a high unipolar charge on the entire
airframe occurs from frictional charging by collision of atmospheric particles (low altitudes) or fine ice
particles (high altitudes) with the aircraft’s surface. The effects of corona discharge vary with
temperature. The effects increase as altitude and airspeed increase. Doubling airspeed increases the
effect by a factor of about 8; tripling airspeed increases the effect by a factor of about 27.
10-2
The effect of precipitation static is a loud hissing or frying noise in the audio output of a
communication receiver and a corresponding false indication on a visual output device. The radio
frequency range affected by precipitation static is nearly the same as for atmospheric static. When
present, precipitation interference is severe, and often totally disables all receivers tuned to the low
and medium frequency bands.
Cosmic Noise
Cosmic noise is usually heard in the ultrahigh frequency band and above, but it is occasionally heard
at frequencies as low as 10 MHz. Cosmic noise is a byproduct of the radiation of stars. Although its
effect is generally unnoticed, at peaks of cosmic activity, cosmic noise interference could conceivably
be a limiting factor in the sensitivity of navigational and height finder radar receivers.
Man-Made Interference
Man-made interference is generally categorized according to the spectrum of its influence, such as
broadband and narrow band. Each type of man-made interference is discussed below.
Broadband Interference
Broadband interference is generated when the current flowing in a circuit is interrupted or varies at a
rate that departs radically from a sinusoidal rate. A current whose waveform is a sine wave is capable
of interfering only at a single frequency. Any other waveform contains harmonics of the basic
frequency. The steeper the rise or fall of current, the higher the upper harmonic frequency will be. A
perfect rectangular pulse contains an infinite number of odd harmonics of the frequency represented
by its pulse recurrence rate. Typical types of electrical disturbances that generate broadband
interference are electrical impulses, electrical pulses, and random noise signals.
For purposes of this discussion, impulse is the term used to describe an electrical disturbance, such
as a switching transient that is an incidental product of the operation of an electrical or electronic
device. The impulse recurrence rate may or may not be regular. Pulse is the term used to describe an
intentional, timed, momentary flow of energy produced by an electronic device. The pulse recurrence
rate is usually regular.
Switching transients or impulses result from the make or break of an electrical current. They are
extremely sharp pulses. The duration and peak value of these pulses depend upon the amount of
current and the characteristics of the circuit being opened or closed. The effects are sharp clicks in
the audio output of a receiver and sharp spikes on an oscilloscope trace. The isolated occasional
occurrence of a switching transient has little or no significance. However, when repeated often
enough and with sufficient regularity, switching transients are capable of creating intolerable
interference to audio and video circuits, and degradation of receiver performance. Typical sources of
sustained switching transients are ignition timing systems, commutators of direct current (dc) motors
and generators, and pulsed navigational lighting.
Pulse interference is normally generated by pulsed electronic equipment. This type of interference is
characterized by a popping or buzzing in the audio output device and by noise spikes on an
oscilloscope. The interference level depends upon the pulse severity, repetition frequency, and
regularity of occurrence. Pulse interference can trigger beacons and IFF equipment and cause false
target indications on the radar screens. In certain types of navigational beacons, these pulses cause
complete loss of reliability.
Random noise consists of impulses that are of irregular shape, amplitude, duration, and recurrence
rate. Normally, the source of the random noise is a variable contact between brush and commutator
bar or slip ring, or an imperfect contact or poor electrical isolation between two surfaces.
10-3
Narrow Band Interference
Narrow band interference is almost always caused by oscillators or power amplifiers in receivers and
transmitters. In a receiver, the cause is usually a poorly shielded local oscillator stage. In a
transmitter, several of the stages could be at fault. The interference could be at the transmitter
operating frequency, a harmonic of its operating frequency, or at some spurious frequency. A
multichannel transmitter that uses crystal-bank frequency synthesizing circuits can produce
interference at any of the frequencies present in the synthesizer. Narrow band interference in a
receiver can range in severity from a heterodyne whistle in the audio output to the complete blocking
of received signals. Narrow band interference affects single frequencies or spots of frequencies in the
tuning range of the affected receiver.
SOURCES OF ELECTRICAL NOISE
Any circuit or device that carries a varying electrical current is a potential source of receiver
interference. The value of the interference voltage depends upon the amount of voltage change. The
frequency coverage depends upon the abruptness of the change. The principal sources of man-made
interference in aircraft include rotating electrical machines, switching devices, pulsed electronic
equipment, propeller systems, receiver oscillators, nonlinear elements, and ac power-lines. Each of
these sources of noise is discussed in the following sections.
Rotating Electrical Machines
Rotating electrical machines are a major source of receiver interference because of the large number
of electric motors used in the aircraft. Rotating electrical machines used in aircraft may be divided into
three general classes: dc motors, ac motors and generators, and inverters.
Direct Current Motors
Modern aircraft use dc motors in great numbers, such as in flight control actuators, armament
actuators, and flight accessories. Most electronic equipment on the aircraft include one or more dc
motors for driving cycling mechanisms, compressor pumps, air circulators, and antenna mechanisms.
Each of these motors can generate voltages capable of causing radio interference over a wide band
of frequencies. Types of interfering voltages generated by dc motors are as follows:
•
Switching transients generated as the brush moves from one commutator bar to another
(commutation interference)
•
Random transients produced by varying contact between the brush and the commutator
(sliding contact interference)
•
Audio frequency hum (commutator ripple)
•
Radio frequency and static charges built up on the shaft and the rotor assembly
The dc motors used in aircraft systems are of three general types: the series-wound motor, the shuntwound motor, and the compound type. The field windings of both series- and shunt-wound motors
afford some filter action against transient voltages generated by the brushes. The compound motor
has the characteristics of both series and shunt dc motors. The size of a dc motor has little bearing
upon its interference-generating characteristics. The smallest motor aboard the aircraft can be the
worst offender.
Alternating Current Generators and Motors
The output of an ideal ac generator is a pure sine wave. A pure sine wave voltage is incapable of
producing interference except at its basic frequency. However, a pure waveform is difficult to
10-4
produce, particularly in a small ac generator (Figure 10-2). Nearly all types of ac generators used in
naval aircraft are potential sources of interference at frequencies other than the output power
frequency. Interference voltages are produced by the following sources:
•
Harmonics of the power frequency. Generally,
the harmonics are caused by poor waveform.
•
Commutation interference. This condition
originates in a series-wound motor.
•
Sliding-contact interference. This condition
originates in an alternator and in a serieswound motor.
Generally, an ac motor without brushes does not
create interference.
Inverters
An inverter (Figure 10-3) is a dc motor with armature
taps brought out to slip rings to supply an ac voltage.
The ac output contains some of the interference
voltages generated at the dc end, as well as the
brush interference at the ac end of the inverter.
Figure 10-2 — Brush type, three-phase ac
generator.
Switching Devices
A switching device makes abrupt changes in
electrical circuits. Such changes are
accompanied by transients capable of
interfering with the operation of radio and other
types of electronic receivers. The simple
manual switch (occasionally operated) is of
little consequence as a source of interference.
Examples of switching devices (frequently
operated) capable of causing appreciable or
serious interference are the relay and the
thyratron.
Relays
A relay is an electromagnetically operated
remote control switch. Its main purpose is to
switch high current, high voltage, or other
critical circuits. Since the relay is used almost
exclusively to control large amounts of power
with relatively small amounts of power, the
relay is always a potential source of
Figure 10-3 — Typical aircraft inverter.
interference. This is especially true when the
relay is used to control an inductive circuit.
Relay actuating circuits should not be overlooked as possible interference sources. Even though the
actuating currents are small, the inductances of the actuating coils are usually quite high. It is not
unusual for the control circuit of a relay to produce more interference than the controlled circuit.
10-5
Thyratrons
A thyratron is a gas-filled, grid-controlled, electronic switching tube used mainly in radar modulators.
The current in a thyratron is either on or off; there is no in between. Since the time required to turn a
thyratron on is only a few microseconds, the current waveform in a thyratron circuit always has a
sharp leading edge. As a result, the waveform is rich in radio interference energy. The voltage and
peak power in a radar modulator are usually very high, and the waveforms are intentionally made as
sharp and flat as possible. Although these factors are essential for proper radar operation, they also
increase the production of interference energy.
Pulsed Electronic Equipment
Pulse interference is generated by pulsed electronic equipment. Types of systems that fall within this
category include radar, transponders, coded-pulse equipment, and beacons.
Radar
In radar equipment, range resolution depends largely on the sharpness of the leading and trailing
edges of the pulse. The ideal pulse is a perfect square wave. Target definition is also dependent on
the narrowness of the pulse. Both the steepness and the narrowness of a pulse determine the
number and amplitudes of harmonic frequencies. With respect to the shape of a radar pulse, the
better the radar is working, the greater the interference it is capable of producing. Most of the
interference is produced at frequencies other than those leaving the radar antenna, except in
receivers operating with the radar band.
Radar interference at frequencies below the antenna frequency severely affects all receivers in use.
Principal sources of such interference are the modulator, pulse cables, and transmitters.
Transponders, Coded-Pulse Equipment, and Beacons
This group includes IFF, beacons, TACAN,
teletype, and other coded-pulse equipment.
The interference energy produced by this
group is the same as that produced by radarpulsing circuits. The effects of this interference
energy are lessened because the equipment is
usually self-contained in one shielded case,
and uses lower pulse power. The effects are
increased because the radiating frequencies
are lower, which allows fundamental
frequencies and harmonics to fall within the
frequency bands used by other equipment.
Each piece of equipment is highly capable of
producing interference outside the aircraft
where it can be picked up by receiver
antennas.
Propeller Systems
Propeller systems, whether hydraulically or
electrically operated, are potent generators of
radio interference (Figure 10-4). The sources
of interference include propeller pitch control
motors and solenoids, governors and
Figure 10-4 — Typical propeller system.
10-6
associated relays, synchronizers and associated relays, deicing timers and relays, and inverters for
synchro operation.
Propeller control equipment generates clicks and transients as often as 10 per second. The audio
frequency envelope of commutator interference varies from about 20 to 1,000 hertz (Hz). The
propeller deicing timer generates intense impulses at a maximum rate of about 4 impulses per
minute.
Values of current in the propeller system are relatively high; consequently, the interference voltages
generated are severe. They are capable of producing moderate interference at frequencies below
100 kilohertz (kHz) and at frequencies above 1 MHz. However, the interference voltages can cause
severe interference at intermediate frequencies.
Receiver Oscillators
Either directly or through frequency multipliers or synthesizers, the local oscillator in a
superheterodyne receiver generates a radio frequency signal at a given frequency. The local
oscillator signal is mixed with another radio frequency signal to produce an intermediate frequency
signal. Depending on receiver design, the frequency of the local oscillator signal is either above or
below the frequency of the radio frequency signal by a frequency equal to the intermediate frequency.
The amount of interference leaving the receiver through its antenna is roughly proportional to the ratio
of the tuned input frequency to the intermediate frequency. For any tuning band on the receiver,
oscillator leakage is highest at the low end of the band. In addition, the lower the intermediate
frequency is, the greater the leakage probability.
Although the receiver antenna is the principal outlet of oscillator leakage, leakage can occur from
other points. Any path capable of introducing interference into a receiver is also capable of carrying
internally generated interference out of the receiver. The paths of entry are discussed in more detail
later in this chapter.
Oscillator leakage from a single communications receiver in an aircraft is not likely to be a direct
source of interference, except in a very large aircraft where two or more frequencies in the same
band are used simultaneously. However, high order harmonics of the oscillator frequency can
become problematic in the very high frequency band and above.
Oscillator leakage from a swept-tuning receiver can produce interference in any receiver aboard the
aircraft. This is done directly (on harmonics) or by nonlinear mixing, as shown in the following
example:
•
Receiver A, operating at a frequency of 2,100 kHz, with an intermediate frequency of 500 kHz,
has oscillator leakage at 2,600 kHz (or 1,600 kHz).
•
Receiver B, operating at 150 MHz, with an intermediate frequency of 10 MHz, has oscillator
leakage at 160 MHz (or 140 MHz).
•
Receiver C, sweeping a frequency band from 200 to 300 MHz, with an intermediate frequency
of 30 MHz, has oscillator leakage across the band 170 to 270 MHz (or 230 to 330 MHz).
Each receiver is capable of interfering with the other receivers at the oscillator frequency and its
harmonics. In addition, with the presence of a nonlinear detector, the leakage signals from the three
receivers can be mixed and interfere with the following frequencies:
•
Receivers A and B, after nonlinear mixing, can produce interference at 160 ± 2.6 MHz.
•
Receivers A and C can similarly produce interference at any frequency from 200 ± 2.6 MHz to
300 ± 2.6 MHz; receivers B and C between 200 ± 160 MHz to 300 ± 160 MHz.
10-7
Nonlinear Elements
A nonlinear element is a conductor, semiconductor, or solid state device whose resistance or
impedance (opposition to current flow) varies with the voltage applied across it. Consequently, the
resultant voltage is not proportional to the original applied voltage. Typical examples of nonlinear
elements are metallic oxides, certain non-conducting crystal structures, semiconductor devices, and
electron tubes. Nonlinear elements that could cause radio interference in aircraft systems are
overdriven semiconductors, oxidized or corroded joints, cold solder joints, and unsound welds.
In the presence of a strong signal, a nonlinear element acts like a detector or mixer. It produces sum
and difference frequencies and any harmonics from the signal applied to it. These spurious
frequencies are called external cross-modulation. The external cross-modulations can be expected to
cause interference problems when the combined products of their field strength exceed 1 millivolt.
A common example of this action is the entry of a strong off radio frequency voltage into the mixer
stage of a superheterodyne receiver. By the time the interfering signal has passed through the preselector stages of the receiver, it has undergone distortion by clipping. Therefore, the interfering
signal is essentially a rectangular wave that is rich in harmonics. Frequency components of the wave
beat both above and below the local oscillator frequency and its harmonics, and produce, at the
output of the mixer, signals that are acceptable to the intermediate frequency amplifier.
Power- Lines
Alternating current power sources have already been briefly discussed as broadband interference.
Even though they are conducting a nearly sinusoidal waveform, ac signals on power-lines are
capable of interfering with audio signals in receivers. In such cases, only the power-line frequency
appears. However, where multiple sources of ac power are present, these signals are capable of
being mixed in the same manner as discussed under receiver oscillators. Sum and difference
frequencies will appear.
In ac-powered equipment, ac hum can appear at the power frequency or at the rectification ripple
frequency. The rectification ripple frequency is twice the power frequency times the number of
phases. Normally, aircraft systems use only single- and three-phase sources at a nominal frequency
of 400 Hz. Full-wave rectification with single-phase 400 Hz power gives a ripple frequency of 800 Hz.
A three-phase source would give a 2,400 Hz ripple. This ripple produces interference varying from
problematic to complete unreliability of equipment, depending upon the severity and its coupling to
susceptible elements.
INTERFERENCE COUPLING
Openings in the outer shields of equipment are necessary for the entrance of power leads, control
leads, mechanical linkages, ventilation, and antenna leads. Interference entering these openings is
amplified by various amounts, depending upon the point of entry into the equipment’s circuits.
Coupling between the entry path and the sensitive points of the receiver can be in any form.
Conductive Coupling
Interference is often coupled from its source to a receiver by metallic conduction. Normally, this is
done by way of mutual impedance, as shown in Figure 10-5. Note in the figure that “A” is the power
source (the battery), “B” the receiver, and “C” the interference source. The interference is greatest at
(C) and attenuates rapidly to a relatively low value at (A). This occurs because of the very low
impedance of the battery. It is apparent from the size of the arrows that the nearer the current flow of
(B) to (C), the greater the amplitude of interfering current in the “BC” loop.
10-8
Interaction Available
Figure 10-5 — Path of conducted interference.
Inductive-Magnetic Coupling
Every current-carrying conductor is surrounded by a magnetic field whose intensity variations are
faithful reproductions of variations in the current in the conductor. When another parallel conductor is
cut by the lines of force of this field, the conductor has a current induced into it. The amplitude of the
induced current depends upon the following factors:
•
The strength of the current in the first conductor
•
The nearness of the conductors to each other
•
The angle between the conductors
•
The length through which the conductors are exposed to each other
The amount of the variation in the current that directly affects variation in the magnetic field
surrounding the conductor depends upon the nature of the current. When the conductor is a power
lead to an electric motor, all the frequencies and amplitudes associated with broadband interference
are present in the magnetic field. When the lead is an ac power lead, a strong sinusoidal magnetic
field is present. When the lead is carrying switched or pulsed currents, extremely complex broadband
variations are present. As the magnetic field cuts across a neighboring conductor, a voltage replica of
its variation is induced into the neighboring wire. This causes a current to flow in the neighboring wire.
When the neighboring wire leads to a sensitive point in a susceptible receiver, serious interference
with that receiver’s operation can result. Similarly, a wire carrying a steady, pure dc of high value sets
up a magnetic field capable of affecting the operation of equipment whose operation is based upon
the earth’s magnetic field.
Shielding a conductor against magnetic induction is both difficult and impractical. Nonferrous
shielding materials have little or no effect upon a magnetic field. Magnetic shielding that is effective at
low frequencies is prohibitively heavy and bulky.
In aircraft wiring, the effect of induction fields should be minimized. This can be done by use of the
proper spacing and coupling angle between wires. The degree of magnetic coupling diminishes
rapidly with distance. Interference coupling is least when the space between active and passive leads
is at a maximum, and when the angle between the leads approaches a right angle.
10-9
Inductive-Capacitive Coupling
Capacitive (electric) fields are voltage fields. Their effects depend upon the amount of capacitance
existing between exposed portions of the noisy circuit and the noise-free circuit. The power transfer
capabilities are directly proportional to frequency. Thus, high-frequency components are more easily
coupled to other circuits. Capacitive coupling is relatively easy to shield out by placing a grounded
conducting surface between the interfering source and the susceptible conductor.
Coupling by Radiation
Almost any wire in an aircraft system can, at some particular frequency, begin to act like an antenna
through a portion of its length. Inside an airframe, however, this occurs only at very high frequencies.
At high frequencies, all internal leads are generally well shielded against pickup of moderate levels of
radiated energy. Perhaps the only cases of true inside-the-aircraft radiation at high frequency and
below occur in connection with unshielded or inadequately shielded transmitter antenna leads.
Complex Coupling
Some examples of interference coupling involve more than one of the types (conduction, induction, or
radiation) just discussed. When more than one coupling occurs simultaneously, corrective actions,
such as bonding, shielding, or filtering, used to correct one type of coupling can increase the coupling
capabilities of another type. The result may be an increase in the transfer of interference. For
example, an unfiltered dc motor can transfer interference to a sensitive element by conduction,
inductive coupling, capacitive coupling, and radiation. Some frequencies are transmitted
predominately by one form of coupling and some frequencies by others. At still other frequencies, all
methods of transmission are equally effective. On the motor used in the example above, bonding
almost always eliminates radiation from the motor shell. It also increases the intensity in one of the
other methods of transmission, usually by conduction. The external placement of a low-pass filter or a
capacitor usually reduces the intensity of conducted interference. At the same time, it may increase
the radiation and induction fields. This occurs because the filter appears to interference voltages to be
a low-impedance path across the line. Relatively high interference currents then flow in the loop
formed between the source and the filter. For complex coupling problems, multiple solutions may be
required to prevent the interference.
RADIO INTERFERENCE REDUCTION COMPONENTS
Radio interference reduction at the source may be accomplished to varying degrees by one or more
of the following methods: short-circuiting, dissipation, open-circuiting, or a combination of all three.
Discrete components are normally used to achieve interference reduction at the source. Capacitors,
resistors, and inductors are used to short-circuit, dissipate, and open-circuit the interference,
respectively.
Capacitors
Short-circuiting of interference is done by using capacitors connected across the source. The perfect
capacitor looks like an open-circuit to dc or the power frequency, and progressively as a short-circuit
to ac as the frequency is increased.
Function
The function of a capacitor in connection with radio interference filtering is to provide a lowimpedance radio frequency path across the source. When the reactance of the capacitor is lower than
the impedance of the power-lines to the source, high-frequency voltages see the capacitor as a
10-10
shorter path to ground. The capacitor charges to the line voltage. It then tends to absorb transient
rises in the line voltage and to provide energy for canceling transient drops in the line voltage.
Limitations
The efficiency of a perfect capacitor in bypassing radio interference increases in indirect proportion to
the frequency of the interfering voltage, and in direct proportion to the capacitance of the capacitor.
All capacitors have both inductance and resistance. Any lead for connecting the capacitor has
inductance and resistance as a direct function of lead length and inverse function of lead diameter.
Some resistance is inherent in the capacitor itself in the form of dielectric leakage. Some inductance
is inherent in the capacitor, which is usually proportional to the capacitance.
The effect of the inherent resistance in a high-grade capacitor is negligible as far as its filtering action
is concerned. The inherent inductance, plus the lead inductance, seriously affects the frequency
range over which the capacitor is useful. The bypass value of a capacitor with inductance in series
varies with frequency.
At frequencies where inductive reactance is much less than capacitive reactance, the capacitor looks
very much like pure capacitance. As the frequency approaches a frequency at which the inductive
reactance is equal to the capacitive reactance, the net series reactance becomes smaller until the
resonant frequency, a point of zero impedance, is reached. At this point, maximum bypass action
occurs. At frequencies above the resonant frequency, the inductive reactance becomes greater than
the capacitive reactance. The capacitor then exhibits a net inductive reactance, whose value
increases with frequency. At frequencies much higher than the resonant frequency, the value of the
capacitor as a bypass becomes lost.
The frequency at which the reversal of reactance occurs is controlled by the size of the capacitor and
the length of the leads. For instance, the installation of a very large capacitor frequently requires the
use of long leads. Table 10-1 is representative of a typical 4-microfarad (µF) capacitor whose inherent
inductance is 0.0129 henrys.
Table 10-1 — Lead Length Changes
LEAD LENGTH
CROSSOVER FREQUENCY
1 inch
0.47 MHz
2 inches
0.41 MHz
3 inches
0.34 MHz
4 inches
0.30 MHz
6 inches
0.25 MHz
Note that for the 4 µF capacitor, each additional inch of lead causes the capacitance-inductance
crossover point to be reduced.
Notice in Figure 10-6 the capacitance-to-inductance crossover frequencies for various lead lengths of
a 0.05 µF capacitor. Also, notice the difference in the crossover frequencies for the 3-inch lead for the
4 µF capacitor, discussed above, and for the 3-inch lead for the 0.05 µF capacitor, shown in Figure
10-6.
Coaxial Feedthrough Capacitors
Coaxial feedthrough capacitors are available with capacitances from 0.00005 to about 2 µF. These
capacitors work well up to frequencies several times those at which capacitors with leads become
useless. The curves in Figure 10-7 compare the bypass value of a feedthrough capacitor of 0.05 µF
with that of a hypothetically perfect capacitor of the same capacitance. The feedthrough capacitor
10-11
differs from the capacitor with leads in that the feedthrough capacitor type forms a part of both the
circuit being filtered and the shield used to isolate the filtered source. Lead length has been reduced
to zero. The center conductor of the feedthrough capacitor must carry all the current of the filtered
source and must have an adequate current rating to ensure against dc loss or power frequency
insertion loss. The internal constructions of feedthrough and conventional capacitors are shown in
Figure 10-8. Notice the differences in the two types.
Figure 10-6 — Crossover frequency of a 0.05 µF capacitor with varied lead lengths.
Figure 10-7 — Crossover frequency of a 0.05 µF feedthrough capacitor.
10-12
Figure 10-8 — Internal construction of feedthrough and conventional capacitor.
Selection of Capacitors
Capacitors used for filtering circuits in aircraft should be selected for characteristics such as physical
size, high temperature and humidity tolerances, and physical ruggedness. The capacitors should
have an adequate voltage rating (at least twice that of the circuit to be filtered), and should be
installed with minimum lead length.
Application of Capacitive Filters
Every circuit carrying an unintentionally varying voltage or current capable of causing radio
interference should be bypassed to ground by suitable capacitors. When the nature of the variations
is such that interference is caused at both high and low frequencies, a capacitor should be chosen
and installed to provide an adequate insertion loss at the lowest frequency where interference exists.
When the overall capacitance required at low frequency provides inadequate insertion loss at high
frequencies, it should be bridged in the shortest and most direct manner possible by a second
capacitor.
A capacitive filter should be installed as near as possible to the actual source of interference. Lead
length should be held to an absolute minimum for two reasons. First, the lead to the capacitor carries
interference that must not be allowed to radiate. Second, the lead has inductance that tends to lower
the maximum frequency for which the capacitor is an effective bypass.
To the extent possible, a filter capacitor should be installed to make use of any element of the filtered
circuit that provides a better filtering action. The use of filter capacitors is shown in Figure 10-9.
Capacitive Filtering in an Alternating Current Circuit
The radio interference generated in slip ring ac motors and generators is a transient caused by sliding
contacts plus high-frequency energy from other internal sources. For this reason, filtering should be
aimed at reducing high-frequency and very-high-frequency noise components with the use of lowcapacitance, high-grade capacitors. Wherever possible, feedthrough capacitors should be used.
Capacitances should be chosen low enough in value to represent high impedance at the power
frequency and to avoid resonance with the internal inductances of the filtered unit. Voltage ratings
should be at least twice the peak voltage across the capacitors.
10-13
Figure 10-9 — Capacitive filtering of a three-phase attenuator.
In a four-wire electrical system, the neutral lead carries all three phases; a large quantity of the third
harmonic of the power frequency is present. This frequency must be considered in setting
capacitance limits and in filtering the return lead. Normal values of capacitance for filtering 400 Hz
leads vary from 0.05 to 0.1 µF.
Capacitive Filtering of Switching Devices
Normally, a capacitor should not be used by itself as a filter on a switch in a dc system. In the open
position, the capacitor bridging the switch assumes a charge equal to the line voltage. When the
switch closes, the capacitor discharges at such a rapid rate that it generates a transient energy,
whose interference value exceeds that caused by the opening of the unfiltered circuit. The capacitor
across a switch should have enough series resistance to provide a slow discharge when the capacitor
is shorted by the switch.
Resistive-Capacitive Filters
A resistive-capacitive (RC) filter is an effective
arc and transient absorber. The RC filter reduces
interference in two ways: by changing the
waveform of transients and by dissipating
transient energy. An example of a RC filter
connected across a switch is shown in Figure 1010.
Without the RC filter, the voltage appearing
across the switch at the instant the switch is
opened is equal to the sum of the line voltage
and an inductive voltage of the same polarity.
The amplitude of the inductive surge depends
upon the inductance of the line and the amplitude
of the closed-circuit current.
Figure 10-10 — RC filter connected across a
switch.
When the sum of the voltages appearing across the switch is great enough, arcing occurs. When the
capacitance is large enough, the capacitor absorbs sufficient transient energy to reduce the voltage to
below arcing value. During the charging time of the capacitor, the resistor is passing current and
dissipating some of the transient energy.
For maximum absorption of the circuit opening transients, resistance should be small and
capacitance should be large. Good representative values are resistance = 1/5 load resistance and
capacitance = 0.25 µF.
10-14
Two RC filters used to absorb the transient interference resulting from the opening of a relay field are
shown in Figure 10-11. In circuit “A,” the value of “Ra” should be low enough to provide a resistance
path to ground less than the line impedance and high enough to lower the value of the charge (Q)
sufficiently. The capacitor should be at least 0.25 µF with a voltage rating several times the lone
voltage. Circuit “B” has the advantages of reducing the capacitor and coil leads to absolute minimum
and reducing the relay field current. It has the disadvantage of carrying the dc coil current. Normal
values of each resistance (Rb) in circuit “B” is 5 percent of the dc resistance of the coil. The capacitor
is normally 0.25 µF. Circuit “B” serves as both a damping load and a high-loss transmission line.
Figure 10-11 — Methods for using RC filters in relay circuits.
Inductive-Capacitive Filters
Filtering of radio interference is done by means of an inductor inserted in series with the ac power
source. The inductor offers negligible impedance to the ac or power- line frequency and an
increasingly high impedance to transient interference as frequency is increased. Combinations of
inductance and capacitance are widely used to reduce both broadband and narrow band interference.
Filters come in a large variety of types and sizes. Filters are classified as to their frequency
characteristics such as low-pass, high-pass, bandpass, and band-rejection filters.
Filters are also classified as to their applications,
such as power-line, antenna, and audio filters. The
type most often used in aircraft is the low-pass,
power-line filter.
Low-Pass Filters
A low-pass filter is used in an aircraft to power
leads coming from interference sources. The filter
prevents the transmission of interference voltages
into the wiring harness, and blocks transmission or
reception of radio-frequency energy above a
specified frequency.
The ideal low-pass filter has no insertion loss at
frequencies below its cutoff frequency, but has
infinite insertion loss at all higher frequencies.
Practical filters fall short of the ideal in three ways.
First, a filter of acceptable physical size and
weight has some insertion loss, even under dc
conditions. Second, because of the lack of a pure
10-15
Figure 10-12 — Insertion loss curve of a
low-pass power-line filter.
inductor, the transition from low to high impedance is
gradual instead of abrupt. Third, the impedance is
held to a finite value for the same reason. The
insertion loss of a typical low-pass filter as compared
to a hypothetical ideal filter is shown in Figure 10-12.
The arrangement and typical parameters of a lowpass filter that has a design cutoff frequency of 100
kHz is shown in Figure 10-13. Inductor “L” must
carry load current. It must be wound of wire large
enough that its dc insertion loss is negligible.
Therefore, filters are rated to maximum current. In
addition, the capacitors “C1” and “C2” must
withstand the line voltage. Therefore, filters are also
rated as to maximum voltage.
Figure 10-13 — Low-pass filter circuit.
At frequencies immediately below cutoff, the filter
looks capacitive to both the generator and the load.
Inductive reactance has very little influence, and no filtering action takes place. However, at
frequencies above cutoff, the series reactance of coil “L” becomes increasingly higher. The series
reactance of coil “L” is limited only by the resistance of the coil and its distributed capacitance. Coil “L”
then functions as a high-frequency disconnect. The bypass values of both capacitors “C1” and “C2”
become increasingly higher, and are limited only by the inductance of the capacitors and their leads.
As a result of these two actions, high-frequency isolation between points “A” and “B” is achieved.
High-Pass Filters
In almost all radio transmitters operating at high
frequencies and above, the master oscillator signal
is generated at a submultiple of the output
frequency. By using one or more frequency
multipliers, the basic oscillator frequency is raised to
the desired output frequency. At the input to the
antenna, an overdriven output amplifier may output
the output frequency and harmonics of the output
frequency. A high-pass filter is very effective in
preventing the undesired harmonics from reaching
the antenna and being radiated.
High-pass filters are also useful for isolating a highfrequency receiver from the influence of energy of
Figure 10-14 — Schematic diagram of a highsignals of lower frequencies. A typical high-pass
pass filter section.
filter being used to reduce radio noise interference
is shown in Figure 10-14. In symmetrical high-pass
filter sections, the total opposition to current flow in is equal to the total opposition to current flow out.
The series combination of “C1” and “L” should resonate at √2 times the desired cutoff frequency. The
impedance and current flow ratio that is chosen should have a square root equal to the terminal
impedance.
Bandpass Filters
Bandpass filters provide very high impedance above and below a desired set of frequencies within
that band.
10-16
Bandpass filters find their greatest application in the following manners:
•
Decoupling the receiver from shock and overload by transmitters operating above and below
the receiver band
•
Multiplexing and decoupling two or more receivers or transmitters using the same antenna
A bandpass filter can be one of many forms and configurations, depending upon its application. For
filtering antennas, a bandpass filter normally consists of one or more high-pass filter sections,
followed by one or more low-pass filter sections. The configuration of sections is normally selected so
the upper limit of the pass band approaches or exceeds twice the frequency of the lower limit of the
pass band. Typical arrangements for bandpass filters are shown in Figure 10-15.
Figure 10-15 — Examples of bandpass filter circuits.
Band-Rejection Filters
A band-rejection (band-stop) filter is used to reject or block a band of frequencies from being passed.
This filter allows all frequencies above and below this band to be passed with little or no attenuation.
The band-stop filter circuit consists of inductive and capacitive networks combined and connected to
form a definite frequency response characteristic. The band-stop filter is designed to attenuate a
specific frequency band and to permit the passage of all frequencies not within this specific band. The
frequency range over which attenuation or poor transmission of signals occurs is called the
attenuation band. The frequency range over which the passage of signals readily occurs is called the
bandpass. The lowest frequency at which the attenuation of a signal starts to increase rapidly is
known as the lower cutoff frequency. The highest frequency at which the attenuation of a signal starts
to increase rapidly is known as the upper cutoff frequency. The basic configurations into which the
band-reject filter elements can be arranged or assembled are known as the half-section, the pisection, and the T-section configurations. These configurations are illustrated in Figure 10-16.
BONDING
Aircraft electrical bonding is defined as the process of obtaining the necessary electrical conductivity
between all the metallic component parts of the aircraft. Bonding successfully brings all items of
empennage and internal conduction objects to essentially the same dc voltage level appearing on the
basic structure of the fuselage. However, bonding for radio frequencies is not quite so simple. Only
direct bonding between affected components can accomplish the desired results at all frequencies.
Only when direct bonding is impossible or operationally impracticable should bonding jumpers be
10-17
Figure 10-16 — Examples of band-reject filter circuits.
used. Regardless of its dc resistance, any length of conductor has inductive reactance that increases
directly with frequency. At a frequency for which the length of a bond is a quarter wavelength, the
bond becomes high impedance. The impedance of such a resonant lead becomes greater without
limit as the dc resistance becomes lower. Multiple bonding using the same length of bonding jumper
increases the impedance at the resonant frequency, but also tends to sharpen the high impedance
area around the resonant frequency. This sharpening is done by the rapid fall of impedance on each
side of resonance.
Purposes of Bonding
Bonding must be designed and executed to obtain the following results:
•
Protect the aircraft and personnel from hazards associated with lightning discharges
•
Provide power-current and fault-current return paths
•
Provide sufficient uniformity and stability of conductivity for radio frequency currents affecting
transmission and reception
•
Prevent development of ac potentials on conducting frames, enclosures, cables of electrical
and electronic equipment, and conducting objects adjacent to unshielded transmitting antenna
lead-ins
•
Protect personnel from the shock hazard resulting from equipment that experiences an internal
power failure
•
Prevent the accumulation of static charges that could produce radio interference or be an
explosion hazard due to periodic spark discharge
Bonding for Lightning Protection
Close-riveted skin construction that divides any lightning current over a number of rivets is considered
adequately bonded to provide a lightning discharge current path. Control surfaces and flaps should
have a bonding jumper across each hinge. A typical bonding arrangement on an aircraft surface is
shown in Figure 10-17. To protect the control cables and levers, additional jumpers should be
connected between the control surface and the structure. The length of a discharge path through the
control system should be at least 10 times the length of the path of the jumper or jumpers.
10-18
All external electrically isolated
conducting objects (except
antennas) should have a bonding
jumper to the aircraft to ensure a
low-impedance path. This is done
so the voltage drop developed
across the jumper system by the
lightning discharge is minimized.
The bonding jumpers must be kept
as short as possible. When
practical, a bonding jumper should
not exceed 3 inches.
ELECTROSTATIC
DISCHARGE
Figure 10-17 — Typical aircraft bonding arrangement.
The sensitivity of electronic devices and components to electrostatic discharge (ESD) has recently
become clear through use, testing, and failure analysis. The construction and design features of
current microtechnology have resulted in devices being destroyed or damaged by ESD voltages as
low as 20 volts. An
example of the type of
damage caused by
ESD is shown in
Figure 10-18.
Technologies are
trending toward
greater complexity,
increased packaging
density, and thinner
dielectrics between
active elements.
Ultimately, this will
result in devices
becoming more
sensitive to ESD. It is
highly important that
Figure 10-18 — ESD damaged components.
you learn the effects of
ESD because limiting the effects is critical to naval aviation.
Various devices and components are susceptible to damage by electrostatic voltage levels commonly
generated in production, test, and operation, and by maintenance personnel. The devices and
components include the following:
•
All microelectronic and most semiconductor devices, except various power diodes and
transistors
•
Thick and thin film resistors, chips and hybrid devices, and crystals
All subassemblies, assemblies, and equipment containing these components and devices without
adequate protective circuitry are ESD sensitive (ESDS). You can protect ESDS items by
implementing simple, low-cost ESD controls. Lack of implementation has resulted in high repair costs,
excessive equipment downtime, and reduced equipment effectiveness. The operational
characteristics of a system may not normally show these failures. However, under internal built-in test
10-19
monitoring in a digital application, they become pronounced. For
example, the system functions normally on the ground, but when placed
in an operational environment, a damaged component might further
degrade, causing its failure. Normal examination of these parts will not
detect the damage unless you use a curve tracer to measure the signal
rise and fall times, or check the parts for reverse leakage current.
Table 10-2 — List of
Triboelectric
Substances
TRIBOELECTRIC
SUBSTANCES
Acetate
Static Electricity
Glass
Static electricity is electrical energy at rest. Some substances readily give
up electrons while others accumulate excessive electrons. When two
substances are rubbed together, are separated, or flow relative to one
another (such as gas or liquid over a solid), one substance becomes
negatively charged and the other positively charged. An electrostatic field
or lines of force emanate between a charged object and an object at a
different electrostatic potential or ground. Objects entering this field will
receive a charge by induction.
Human hair
Nylon
Wool
Fur
Aluminum
Polyester
Paper
The capacitance of the charged object relative to another object or
ground also has an effect on the field. If the capacitance is reduced, there
is an inverse linear increase in voltage since the charge must be
conserved. As the capacitance decreases, the voltage increases until a
discharge occurs via an arc.
Cotton
Wood
Steel
Acetate fiber
Nickel, copper, silver
Causes of Static Electricity
Generation of static electricity on an object by rubbing is known as the
triboelectric effect. A list of substances in the triboelectric series is shown
in Table 10-2. The list is arranged in such an order that when any two
substances in the list contact one another and then separate, the
substance higher on the list assumes a positive charge.
Brass, stainless steel
The size of an electrostatic charge on two different materials is
proportional to the separation of the two materials. Electrostatic voltage
levels generated by nonconductors can be extremely high. However, air
will slowly dissipate the charge to a nearby conductor or ground.
The more moisture in the air, the faster a charge will dissipate. The
typical measured charges generated by personnel in a manufacturing
facility are shown in Table 10-3. Note the decrease in generated voltage
with the increase in humidity levels of the surrounding air.
Rubber
Acrylic
Polystyrene foam
Polyurethane foam
Saran
Polyethylene
Polypropylene
PVC (vinyl)
KEL-F
Teflon®
Table 10-3 — Typical Measured Electrostatic Voltages
VOLTAGE LEVEL @ RELATIVE HUMIDITY
MEANS OF STATIC GENERATION
LOW 10-20%
HIGH 65-90%
WALKING ACROSS CARPET
35,000
1,500
WALKING OVER VINYL FLOOR
12,000
250
WORKER AT BENCH
6,000
100
VINYL ENVELOPS FOR WORK INSTRUCTIONS
7,000
600
COMMON POLY BAG PICKED UP FROM BENCH
20,000
1,200
WORK CHAIR PADDED WITH URETHANE FOAM
18,000
1,500
10-20
Effects of Static Electricity
The effects of ESD are not easily recognized. Failures due to ESD are often analyzed as being
caused by electrical overstress due to transients other than static. Many failures, often classified as
other, random, or unknown, are actually caused by ESD. Misclassification of the defect is often
caused by not performing failure analysis to the proper depth.
Component Susceptibility
Some solid state devices with the exception of various power transistors and diodes are susceptible
to damage by discharging electrostatic voltages. The discharge may occur across their terminals or
through subjection of these devices to electrostatic fields.
Latent Failure Mechanisms
ESD overstress can produce a dielectric breakdown of a self-healing nature when the current is
unlimited. When this occurs, the device may retest good, but contain a hole in the gate oxide. With
use, metal will eventually migrate through the puncture, resulting in a shorting of this oxide layer.
Another structure mechanism involves highly limited current dielectric breakdown from which no
apparent damage is done. However, this reduces the voltage at which subsequent breakdown occurs
to as low as one-third of the original breakdown value. ESD damage can result in a lowered damage
threshold at which a subsequent lower voltage ESD will cause further degradation or a functional
failure.
ESD Elimination
The heart of an ESD control program is the ESD protected work area and ESD grounded work
station. When you handle an ESDS device outside of its ESD protective packaging, you need to
provide a means to reduce generated electrostatic voltages below the levels at which the item is
sensitive. The greater the margin between the levels at which the generated voltages are limited and
the ESDS item sensitivity level, the greater the probability of protecting that item.
Prime Generators
All common plastics and other generators should be prohibited in the ESD protected work area.
Carpeting should also be prohibited. If you must use carpet, it should be of a permanently antistatic
type. It is important to perform weekly static voltage monitoring where carpeting is in use to lower the
risk of an ESD incident.
PERSONAL APPAREL AND GROUNDING
An essential part of the ESD program is grounding personnel and their apparel when handling ESDS
material. Means of doing this are described in this section.
Smocks
Personnel handling ESDS items, such as circuit cards and individual electronic components, should
wear long sleeve, ESD protective smocks (Figure 10-19). They should also wear short sleeve shirts
or blouses so that ESD protective gauntlets can be banded to the bare wrist and extend toward the
elbow. If these items are not available, use other antistatic material (such as cotton) that will cover
sections of the body that could contact an ESDS item during handling.
10-21
Personnel Ground Straps
Personnel ground straps should have a
minimum resistance of 250,000 ohms. Based
upon limiting leakage currents to personnel to 5
milliamperes, this resistance will protect
personnel from shock from voltages up to 125
volts rms. The wrist, leg, or ankle bracelet end
of the ground strap should have some metal
contact with the skin. Bracelets made
completely of carbon-impregnated plastic may
burnish around the area in contact with the skin,
resulting in the impedance to ground being too
high.
ESD PROTECTIVE MATERIALS
There are two basic types of ESD protective
material, conductive and antistatic. Conductive
materials protect ESD devices from static
discharges and electromagnetic fields. Antistatic
materials are nothing more than a non-staticgenerating material. Therefore, antistatic
materials do not offer any other protection to
ESD devices other than not generating static.
Figure 10-19 — ESD protective smocks.
Conductive ESD Protective Materials
Conductive ESD protective materials consist of metal, metal-coated, and metal-impregnated
materials. The most common conductive materials used for ESD protection are steel, aluminum, and
carbon-impregnated polyethylene and nylon. The latter two are opaque, black, flexible, heat sealable,
electrically conductive plastics. These plastics are composed of carbon particles, impregnated in the
plastic, that provide volume conductivity throughout the material.
Antistatic ESD Protective Materials
Antistatic materials are normally plastic-type materials (such as polyethylene, polyolefin,
polyurethane, and nylon) that are impregnated with an antistatic substance. The antistatic substance
migrates to the surface and combines with the humidity in the air to form a conductive sweat layer on
the surface. This layer is invisible, and although highly resistive, it is amply conductive to prevent the
buildup of electrostatic charges by triboelectric methods in normal handling. Simply stated, the
primary asset of an antistatic material is that it will not generate a charge on its surface. However, this
material will not protect an enclosed ESD device if it comes into contact with a charged surface.
This material is of a pink tint, which is a symbol of it being antistatic. Antistatic materials are designed
to be used as the inner wrapping packaging. However, antistatic materials are not used unless
components and/or assemblies are contained in conductive packaging.
Hybrid ESD Protective Bags
Lamination of different ESD protective material is available. This combination of conductive and
antistatic materials provides the advantages of both types in a single bag.
10-22
ESDS DEVICE HANDLING
The following are general guidelines applicable to the handling of ESDS devices:
•
Make sure that all containers, tools, test equipment, and fixtures used in ESD protected areas
are grounded before and during use.
•
Personnel handling ESDS items must avoid physical activities that are friction producing in the
vicinity of ESDS items. Some examples are putting on or removing smocks, wiping feet, and
sliding objects over surfaces.
•
Personnel handling ESDS items must wear cotton smocks and/or other antistatically treated
clothing.
•
Avoid the use or presence of plastics, synthetic textiles, rubber, finished wood, vinyl, and other
static-generating materials where ESDS items are handled out of their ESD protective
packaging.
•
Place the ESD protective material containing the ESDS item on a grounded work bench
surface to remove any charge before opening the packaging material.
•
Personnel must ground themselves before removing ESDS items from their protective packing
by attaching their personnel ground straps to an approved grounding location.
•
Remove ESDS items from ESD protective packaging with fingers or metal grasping tools only
after grounding, and place on the ESD grounded work bench surface.
•
Make periodic electrostatic measurements in accordance with local procedures or applicable
maintenance instructions at all ESD protected areas. This assures the ESD protective
properties of the work station and all equipment contained have not degraded.
•
Perform periodic continuity checks of personnel ground straps, ESD grounded work station
surfaces, conductive floor mats, and other connections to ground in accordance with local
procedures or applicable maintenance instructions.
ESDS DEVICE PACKAGING
Before an ESDS item leaves an ESD protected area, package the item in one of the following ESD
protective materials:
•
Ensure shorting bars, clips, or non-corrective conductive materials are correctly inserted in or
on all terminals or connectors.
•
Package ESDS items using only approved packaging materials and prepare the items for
shipment as per MIL-HDBK-773.
•
Mark the packaged unit with the ESD symbol and caution as shown in Figure 10-20 as
required.
10-23
Figure 10-20 — ESDS symbols.
10-24
End of Chapter 10
Electrostatic Discharge
Review Questions
10-1. During what season is atmospheric interference the greatest?
A.
B.
C.
D.
Spring
Summer
Fall
Winter
10-2. Other than dust or snow, what type of natural event can create precipitation static?
A.
B.
C.
D.
Rain
Wind
Hail
Sleet
10-3. Corona discharge can occur at what voltage level from the airframe of an aircraft?
A.
B.
C.
D.
Low
Negative
High
Positive
10-4. Cosmic noise can be heard on what frequency band?
A.
B.
C.
D.
Very high
Ultra high
Low
Voice
10-5. What type of radar receiver other than navigational can be potentially limited by cosmic noise?
A.
B.
C.
D.
Height finder
Fire control
Search
Doppler
10-6. The two general types of man-made interference are broadband and what other type?
A.
B.
C.
D.
Medium band
Low band
Narrow band
High band
10-25
10-7. Broadband interference is generated by impulses, pulses and what other type of electrical
disturbance?
A.
B.
C.
D.
Fixed noise
Random noise
Linear noise
Cosmic noise
10-8. What type of electronic equipment can generate pulse interference?
A.
B.
C.
D.
Impulse
Transient
Mixed
Pulsed
10-9. Pulse interference can trigger beacons and what other avionics system?
A.
B.
C.
D.
Identification Friend or Foe
Tactical Air Navigation
Radar
Automatic Direction Finder
10-10. What type of motor commutators can cause sustained switching transients?
A.
B.
C.
D.
Hydraulic
Pneumatic
Alternating current
Direct current
10-11. What type of direct current motor has the characteristics of both the series and shunt types?
A.
B.
C.
D.
Hybrid
Compound
Complex
Fusion
10-12. When uninstalled, which component of alternating current motors should NOT cause
interference?
A.
B.
C.
D.
Coils
Brushes
Commutator
Slip rings
10-13. What type of dc motor is capable of supplying ac voltage?
A.
B.
C.
D.
Inverter
Convertor
Transformer
Modifier
10-26
10-14. What type of switching device is made out of a gas-filled, electronic switching tube?
A.
B.
C.
D.
Relay
Remote
Thyratron
Transistor
10-15. What characteristic of harmonic frequencies determines the narrowness of radar pulses?
A.
B.
C.
D.
Bandwidth
Voltage
Current
Amplitude
10-16. Other than Identification Friend or Foe and beacons what other type of equipment uses codedpulses?
A.
B.
C.
D.
Teletype
Intercommunication systems
Telephone
Radio transmitter
10-17. What high electrical value generates severe interference voltages in propeller systems?
A.
B.
C.
D.
Resistance
Capacitance
Current
Impedance
10-18. Nonlinear elements include semiconductors, solid state devices and what other devices?
A.
B.
C.
D.
Conductors
Resistors
Capacitors
Inductors
10-19. What type of signal on power-lines is capable of interfering with audio signals?
A.
B.
C.
D.
Analog
Digital
Alternating current
Direct current
10-20. What method of conduction often couples a source to a receiver?
A.
B.
C.
D.
Inductive
Metallic
Thermal
Magnetic
10-27
10-21. It is difficult and impractical to shield conductors against what type of induction?
A.
B.
C.
D.
Metallic
Thermal
Magnetic
Electrical
10-22. What frequency band components are most easily coupled to other circuits?
A.
B.
C.
D.
Low
High
Ultra high
Super high
10-23. When externally placed, what type of filter normally reduces the intensity of conducted
interference?
A.
B.
C.
D.
High-pass
Low-pass
Bandpass
Band-stop
10-24. When frequency is increased in an alternating current component, a perfect capacitor would
appear as what circuit malfunction?
A.
B.
C.
D.
Open-circuit
Short-circuit
Closed-circuit
Parallel-circuit
10-25. At resonant frequency, the bypass value of which of the following components is lost?
A.
B.
C.
D.
Resistor
Conductor
Transistor
Capacitor
10-26. What distance should a capacitive filter be installed from a source of interference?
A.
B.
C.
D.
Far as possible
Middle distance
Near as possible
Opposite side
10-27. In a four-wire electrical system, what wire carries all three phases of power?
A.
B.
C.
D.
Neutral
Phase A
Phase B
Phase C
10-28
10-28. What should a capacitor NOT be used for in a direct current system?
A.
B.
C.
D.
Resistor
Inductor
Semiconductor
Filter
10-29. What type of capacitor is an effective arc and transient absorber?
A.
B.
C.
D.
Inductive-capacitive
Resistive-capacitive
Low-pass
High-pass
10-30. What type of filter has no insertion loss at frequencies below cutoff but infinite loss at higher
frequencies?
A.
B.
C.
D.
Low-pass
Bandpass
High-pass
Band-rejection
10-31. What other configuration can a band-rejection filter be besides half-section and pi-section?
A.
B.
C.
D.
I-section
U-section
R-section
T-section
10-32. What type of filter provides very high impedance above and below a desired set of
frequencies?
A.
B.
C.
D.
Bandpass
High-pass
Low-pass
Band-rejection
10-33. What process brings all metal and internal components of an aircraft to essentially the same
direct current voltage level?
A.
B.
C.
D.
Mixing
Compounding
Potting
Bonding
10-34. A bond becomes high impedance at what frequency size?
A.
B.
C.
D.
One-quarter
One-third
One-fifth
One-half
10-29
10-35. What length of bonds will increase the impedance at the resonant frequency?
A.
B.
C.
D.
One-quarter
One-half
Same
Varied
10-36. Which of the following aircraft components does NOT require electrical isolation by a bonding
jumper?
A.
B.
C.
D.
Flap
Slat
Landing gear
Antenna
10-37. Bonding must be designed to protect personnel against shock from what type of equipment
failure?
A.
B.
C.
D.
Sensitivity
Control
Power
Input
10-38. Sensitive electronic devices are susceptible to what type of hazard?
A.
B.
C.
D.
Electrostatic absorption
Electrostatic discharge
Electrostatic induction
Electrostatic repulsion
10-39. What type of field emanates from a charged object to an object that has a different electrical
potential?
A.
B.
C.
D.
Reactive
Electrostatic
Inductive
Magnetic
10-40. Misclassification of Electrostatic Discharge damage is often caused by NOT performing what
type of analysis to the proper depth?
A.
B.
C.
D.
Design
Cost
Failure
Statistical
10-30
10-41. What common type of material is considered a prime generator of static electricity?
A.
B.
C.
D.
Wood
Glass
Metal
Plastic
10-42. Personnel ground straps are designed to protect workers from exposure to what maximum
voltage level?
A.
B.
C.
D.
25 volts root mean square
50 volts root mean square
75 volts root mean square
125 volts root mean square
10-43. The most common conductive materials are steel, aluminum, carbon-impregnated
polyethylenes, and what other material?
A.
B.
C.
D.
Cotton
Nylon
Rayon
Teflon®
10-44. What color material is identified as being antistatic?
A.
B.
C.
D.
Yellow
Red
Pink
Orange
10-45. Prior to being used in an Electrostatic Discharge protected area, tools and equipment must go
through what process?
A.
B.
C.
D.
Inventory
Inspection
Grounding
Replacement
10-31
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10-32
APPENDIX I
GLOSSARY
A/A—Air-to-air.
A/G—Air-to-ground.
ABSOLUTE ZERO—Measured at -273 degrees Celsius or -460 degrees Fahrenheit.
ABSORPTION—In IR systems, the loss of energy that is turned into heat, which results in a
temperature increase in a detector element. In sonar, sound energy that is absorbed while passing
through the water. The absorption of sound can depend on the sea state. When the winds are high
enough to produce whitecaps and a concentration of bubbles at the surface level, the absorption level
of sound energy will be higher. In addition, the absorption of sound energy is greater at higher
frequencies.
AC—Alternating current—An electrical current that encompasses a constant change in amplitude and
regular intervals of change in polarity.
ACB—Armament control box.
ACCELERATION—The increase in the rate or speed of an object.
ACCELEROMETERS—A device that used to produce a voltage proportional to the aircraft
acceleration input. Accelerometers provide output signals proportional to the total accelerations
experienced along the three axes of the stable element.
ACCURACY—In radar, the ability of a radar system to determine the correct range, bearing, and in
some cases, altitude of a target.
ACI—Armament control indicator—Installed in the MH-60R Seahawk helicopter and contains the
control functions for the jettison, sonobuoy, and Hellfire armament subsystems.
ACL RDY—Automatic carrier landing ready.
ACLS—Automatic carrier landing system—Consists of multiple components installed in the aircraft
and systems located onboard an aircraft carrier. Aircraft carriers are equipped with two radar systems
that provide landing aircraft with critical information and guidance during the landing cycle. Aircraft
ACLSs do not use one system or one component; they are an integration of multiple aircraft systems
that work together to guide the aircraft safely to a carrier landing.
ACOUSTIC—Pertaining to sound or the study of sound.
ACTIVE SONAR—Equipment that depends on a transmitted sound wave and the return of an echo.
ADF—Automatic direction finder—Provides a bearing to a selected station by using a specific
frequency to transmit and receive signals that are processed by compatible equipment. In some
cases ADF systems are incorporated as an operational mode of aircraft radio communications
systems.
ADVANCED NAVIGATION SENSOR—See ANFLIR.
AF—Audio frequency.
AFCS—Automatic flight control system—In ACLS, is made up of a number of components and
systems. A typical AFCS is used to provide the interface between the correction signals received from
the datalink and the aircraft flight control surfaces. The AFCS provides switching and signal
conditioning, engage logic, command signal limiting, and failsafe interlocks. The failsafe interlocks are
AI-1
required to couple and process data link signals to the pitch and bank channels of the AFCS.
Automatic synchronization is provided in all three axes.
AGM—Air-launched, surface attack, guided missile.
AIM—Air-launched, aerial intercept, guided missile.
AIP—Anti-surface warfare improvement.
AIRFOIL—A part of an aircraft that produces lift or any other desirable aerodynamic effect as it
passes through the air.
ALFS—Airborne low frequency system—A sonar dipping set that is installed in the MH-60R Seahawk
helicopter. The ALFS provides longer detection ranges and improved detection capabilities over
previous sonar dipping sets.
ALIGNMENT, CARRIER—An INS process that uses SINS to provide aircraft with reference data.
SINS data is supplied to the aircraft via a cable assembly or by aircraft data link. See also SINS.
ALIGNMENT, GROUND—An INS process that analyzes latitude and longitude data manually
entered into the aircraft.
ALIGNMENT, INFLIGHT—An INS process that uses inputs and reference data from avionics
systems to either preserve an existing alignment or to start a new alignment. During the inflight
alignment, air data dead reckoning is used for navigation and for maintaining the current existing
position.
ALPHA ANGLE—The angular difference between an INS platform heading and true north.
ALTIMETER, ABSOLUTE—Uses pulse range-tracking RF energy that measures the surface of
terrain clearance below the aircraft. Absolute altimeters are reliable in the altitude range of 0 to 5,000
feet. Absolute altimeters are also known as radar altimeters.
ALTIMETER, PRESSURE—An aneroid barometer calibrated to indicate feet of altitude instead of
pressure using pointers that are connected by a mechanical linkage to a set of aneroid cells.
ALTITUDE, ABSOLUTE—The height above terrain that is computed by subtracting terrain elevation
from true altitude.
ALTITUDE, CALIBRATED—The indicated altitude corrected for installation or positional error.
ALTITUDE, DENSITY—The pressure altitude corrected for temperature.
ALTITUDE, INDICATED—The value of altitude that is displayed on the pressure altimeter.
ALTITUDE, PRESSURE—The height of the aircraft above the standard datum plane.
ALTITUDE, TRUE—The actual vertical distance above mean sea level, measured in feet.
ALTITUDE—The vertical distance of a level, a point, or an object measured from a given surface.
AM—Amplitude modulation—Any method of varying the amplitude of an electromagnetic carrier to
maintain a constant amplitude in the output waveform.
AMBIENT NOISE—The naturally occurring noise in the sea and the noise resulting from man’s
activity, but excluding self-noise and reverberation.
AMPLIFICATION—The process of enlarging a signal, such as voltage or current. Also, the ratio of
output magnitude to input magnitude in a device that is intended to produce an output that is an
enlarged reproduction of its input.
AMPLITUDE—The size of a signal as measured from a reference line to a maximum value above or
below the line. Generally used to describe voltage, current, or power.
AI-2
AMRAAM, AIM-120—Advanced medium-range air-to-air missile—An all-weather weapon that has
beyond-visual-range targeting capability that uses a semi-active guidance system.
ANALOG COMPUTER—A type of computer that is designed to meet a special purpose. For
example, an analog computer can be used to measure continuous electrical or physical conditions,
such as current, voltage, flow, temperature, or pressure.
ANFLIR—Advanced navigation forward looking infrared—A self-contained FLIR imaging system that
provides IR imagery used by the operator to maneuver and navigate safely at low altitudes and high
air speeds.
ANGLE-OF-ATTACK—The angle between the chord line and the relative wind.
ANOMALY—In magnetic detection systems, a disturbance in the natural magnetic field.
ANTENNA, RADAR—Routes the RF energy from the transmitter and radiates the energy in a highly
directional beam. The return or received RF energy is routed to the receiver for processing.
ANTENNA—A conductor or system of conductors used to collect or radiate RF energy.
ANT-SEL—Antenna select—A panel installed in the F/A-18 series aircraft. The ANT-SEL panel is
used to electrically change the transmitting/receiving antenna position.
ARI—Attitude reference indicator—Designed to assist the aircrew in determining the attitude of the
aircraft in instances where the natural horizon is not visible. A typical standby ARI uses a miniature
representation of an aircraft that represents the nose (pitch) and wing (bank) attitude. The standby
ARI automatically displays ILS steering when the ILS system is turned on by the operator. The ILS
steering cues use the miniature representation of the aircraft as a reference. The horizontal needle
indicates an ILS approach that is above or below the glideslope. The vertical needle indicates an ILS
approach that is right or left of the glideslope. The aircraft is at optimal approach conditions when the
horizontal and vertical needles are centered on the standby ARI.
ARMAMENT COMPUTER—Installed in the F/A-18 series aircraft. The armament computer provides
for the control and release of weapons and is controlled by the mission computer system.
ARMAMENT CONTROL PANEL, PILOT—Installed in the P-3 Orion aircraft and provides the pilot
with control of all the kill and search stores installed on the aircraft.
ARRAY, DETECTOR—A large number of elements closely grouped together to form an array. The
elements of this array are packed closely in a regular pattern. This allows the image of the scene to
spread across the array like a picture or mosaic. Each detector in the array views a small portion of
the scene. The main disadvantage to a detector array is that each element requires a supporting
electronic circuit to process the information that the element provides.
ASCL—Advanced sonobuoy communication link receiver set—Sonobuoy receiver system that is
installed in the P-3 Orion aircraft.
ASTROLABE—An inaccurate navigation device that was used by early explorers.
ASUW—Anti-surface warfare.
ASW—Antisubmarine warfare—Operations conducted against submarines; their supporting forces,
and bases.
ATC—Automatic throttle control—In ACLS, encompasses a number of different components and
subsystems. The ATC system is used during the landing sequence to maintain the appropriate angleof-attack by electrically adjusting the output power of the engines. The ATC also manipulates the
engine controls to keep the aircraft traveling at a constant rate of airspeed.
AI-3
ATFLIR—Advanced targeting forward looking infrared—Provides the operator with real-time, passive
thermal and visible imagery during day and night operations. The ATFLIR system is used to detect,
classify, track, and designate both air-to-air and air-to-surface targets of interest. The ATFLIR system
also provides the ability to deliver precision-guided ordnance at a stand-off distance outside anti-air
weapons envelopes.
ATMOSPHERIC STATIC—The result of the electrical breakdown between two masses of oppositely
charge particles in the atmosphere.
ATTENUATION—The reduction of radio signal strength due to atmospheric or system loss
conditions.
AUX REL—Auxiliary release.
AXIS—A straight line, either real or imaginary, passing through a body, around which the body
revolves.
AZIMUTH—Angular position or bearing in a horizontal plane, usually measured clockwise from true
north. Azimuth and bearing are often used synonymously.
AZIMUTH-RANGE INDICATOR—In airborne sonar systems, provides a visual representation of
target range and bearing information. In addition, azimuth-range indicators contain controls that are
used to adjust display settings, audio settings, and target range thresholds, and initiate operational
tests.
BAND—The radio frequencies existing between two definite limits and used for a definite purpose; for
example, the standard broadcast band extending from 550 to 1600 kHz.
BANDWIDTH—The total frequency width of a channel or band of frequencies.
BATHYTHERMOGRAPH—A recording thermometer for obtaining a permanent graphical record of
water temperature in degrees Fahrenheit or Celsius at different water depths, in feet, as it is lowered
or dropped into the ocean. See also SONOBUOY, BATHYTHERMOGRAPH.
BATTERY—A device for converting chemical energy into electrical energy.
BEACON—A radio or radar signal station that provides navigation and interrogation information for
ships and aircraft.
BEAMWIDTH—The width of an electromagnetic beam, measured in degrees on an arc that lies in a
plane along the axis of propagation, between points of equal field strength. It may be measured in the
horizontal or vertical plane.
BEARING, RELATIVE—Measured in a clockwise direction using the centerline of the measuring
device (antenna, aircraft, etc.) as a reference point.
BEARING, TRUE—The angle between true north and the reference line pointed directly at a target.
True bearing is measured in the horizontal plane in a clockwise direction from true north.
BEARING—Horizontal direction from one point to another, usually measured clockwise from true
north. See also AZIMUTH.
BINARY—A number system that uses two digits, a 1 and 0, that define a characteristic such as a
selection or condition in which there are only two possibilities.
BINARY CODE—A method of representing one of the two possible conditions, such as on or off, high
or low, or one or zero.
BIT—Built-in-test.
AI-4
BLACKBODY—An ideal object that absorbs all incident light, and therefore appears perfectly black
at all wavelengths.
BOLOMETER—A small resistive element used in the measurement of low and medium RF power. It
is characterized by a large temperature coefficient of resistance that is capable of being properly
matched to a transmission line.
BONDING, ELECTRICAL—Process of obtaining the necessary conductivity between the metallic
component parts of an aircraft. Bonding successfully brings all items of empennage and internal
conduction objects to essentially the same dc voltage level appearing on the basic structure of the
fuselage. Bonding is designed to protect aircraft and personnel from the hazards associated with
lightning discharges, provide power-current and fault-current return paths, provide stable conductivity
for RF currents, prevent the development of ac potentials, prevent shock hazards and reduce the
accumulation of static electricity.
BONDING, JUMPER—A device used on an aircraft surface, such as control surfaces or flaps, that
provides a lightning discharge current path.
BOTTOM BOUNCE—That form of sonar sound transmission in which sound rays strike the ocean
bottom in deep water at steep angles and are reflected back to the surface and returned, which
allows the obtaining of target information at long distances.
BOX, ARMAMENT CONTROL—Installed in some P-3 Orion aircraft and incorporates the functions of
the pilot armament control panel, wing jettison, and special weapon armament panel.
BOX, INTERCONNECTION AFT—Installed in the P-3 Orion aircraft and contains four subassemblies
that provide control circuitry for the selection, arming, and release of weapons loaded on wing
stations.
BOX, INTERCONNECTION FORWARD—Installed in the P-3 Orion aircraft and contains eight
subassemblies that provide control circuitry for the selection, arming, torpedo presetting, and release
of weapons.
BRIDGE CIRCUIT—Any one of a variety of electric circuit networks, one branch of which, the “bridge”
proper, connects two points of equal potential, and hence carries no current when the circuit is
properly adjusted or balanced.
BRUSHES—Sliding contacts, usually made from carbon, that make the electrical connection to the
rotating part of a motor or generator.
BUS—System that is used to transfer data between components by using low voltage electrical
signals.
CABLE AND REEL ASSEMBLY—In airborne sonar systems, houses the sonar cable, which is
normally between 1,500 to 1,600 feet in length. A typical sonar cable uses a jacketed cable with a
metal armor braid as the strength component. Electrical wiring is installed inside the cable assembly
and is used to route signals between the transducer and multiplexer.
CAMBER—The curve or departure from a straight line (chord line) from the leading edge to the
trailing edge of the airfoil.
CAPACITANCE—The property of an electrical current that opposes changes in voltage.
CAPACITIVE REACTANCE—The opposition, expressed in ohms, offered to the flow of an
alternating current by capacitance.
CAPACITOR, COAXIAL FEEDTHROUGH—A type of capacitor that works well up to high
frequencies.
AI-5
CAPACITOR—A device that can be used to short-circuit interference, when it is connected across
the source. The function of a capacitor in connection with radio interference is to provide to a lowimpedance radio frequency path across the source. When the reactance of the capacitor is lower than
impedance of the power-lines to the source, high-frequency voltages see a capacitor as a shorter
path to ground.
CARRIER SIGNAL, L1 AND L2—In GPS, are used to transmit position, velocity, and time signals for
use by compatible equipment. The L1 carrier signal operates in the 1575.42 MHz frequency range.
The L2 carrier signal operates in the 1227.6 MHz frequency range.
CAS—Close air support—A mission conducted by aircraft in support of friendly forces on the ground.
CATCC—Carrier air traffic control center.
CATHODE—A negative electrode.
CCA—Carrier-controlled approach—A type of approach radar system used on board aircraft carriers
to guide aircraft to safe landings in poor visibility conditions.
CCD—Charge coupled device—A light-sensitive integrated circuit that stores and displays the data
for an image so that each picture element is converted into an electrical charge that relates to the
intensity of a color in the color spectrum.
CENTRAL PROCESSING UNIT, COMPUTER—Serves as the main component of the computer
system.
CENTRIPETAL FORCE—Force that acts on an object moving in a circular path and is directed
toward the center around which the object is moving.
CFS—Command function selection—In sonobuoys, allows the operator to turn the system on or off,
change modes of operation, adjust depths, and change RF channels.
CHANNEL—A carrier frequency assignment, usually with a fixed bandwidth.
CHORD LINE—An imaginary straight line from the leading edge to the trailing edge of an airfoil.
CIRCUIT—The complete path of an electric current.
CLADDING—Material used in fiber optics to reduce the loss of light for the core into the surrounding
air, reduce scattering loss at the surface of the core, protect fiber from absorbing surface
contaminants, and add mechanical strength.
CMD—Countermeasures dispenser.
CODER-SYNCHRONIZER, IFF—Synchronizes the reception of IFF responses and radar signals so
that they will not occur at the same time.
COMM CONT—Communications control—Installed in the F/A-18 series of aircraft. The COMM CONT
panel is used to provide ground crews with the ability to communicate with the aircrew in the cockpit.
COMM—Communications.
COMMUTATOR BAR—A device in a dc motor used to change the direction or frequency of the
current flow through the windings.
COMMUTATOR—A mechanical device that reverses armature connections in motors and generators
at the proper instant so that current continues to flow in only one direction.
COMPASS ROSE—A circle that is used to represent the horizon and is divided into 360 degrees.
COMPOSITE VIDEO—The total video signal that consists of picture information, blanking pulses, and
sync pulses.
AI-6
COMPRESSION—In sonar, describes the action that occurs when a transducer diaphragm moves
outward creating a high-pressure wave.
COMPUTER CODE—Code by which data is represented within a computer system; for example,
binary coded decimal.
COMPUTER, ANALOG—See ANALOG COMPUTER.
COMPUTER, DIGITAL—See DIGITAL COMPUTER.
COMPUTER—A mechanism or device that performs mathematical operations. There are many
different models and sizes of computers designed to perform various functions. However, computers
are, generally speaking, all functionally the same no matter what size or purpose they are designed to
meet. See also ANALOG COMPUTER and DIGITAL COMPUTER.
CONTINUOUS WAVE—Method of transmission that directs a continuously transmitted wave of RF
energy at a target. A shift in the frequency when a target moves toward or away from the transmitted
RF energy. The shift in frequency is known as the Doppler effect. See also DOPPLER EFFECT.
CONTROL SEGMENT—Part of the global positioning network that is responsible for tracking,
monitoring, and managing the satellite constellation.
CONTROL, GUN SYSTEM—Installed in the F/A-18 series aircraft and provides the means to select,
arm, and fire the M61 gun system in A/A and A/G modes.
CONTROL, SIGNAL DATA CONVERTOR—Installed in the F/A-18 series aircraft and provides the
interface between the armament computer and the loaded weapons and stores.
CORE MEMORY, COMPUTER—Consists of tiny doughnut-shaped rings that are made out of ferrite
(iron) and are strung on a grid of very thin wires.
CORIOLIS FORCE—A false acceleration caused by the Earth rotating around its polar axis as
related to inertial space.
CORONA DISCHARGE—An electrical discharge brought on by ionization.
COSMIC NOISE—The byproduct of the radiation of the stars. Cosmic noise is usually heard in the
ultrahigh frequency range and above.
COUNTERMEASURES—Devices and/or techniques intended to impair the operational effectiveness
of enemy activity.
COUPLING, COMPLEX—Interference coupling that is caused by more than one of the following
types of transfer: conduction, induction, or radiation. When more than one coupling occurs at the
same time, corrective actions, such as shielding, or filtering, can increase the coupling capabilities of
another type.
COUPLING, CONDUCTIVE—Interference that is coupled from a source to a receiver by metallic
conduction. Normally, conductive coupling occurs by way of mutual impedance.
COUPLING, INDUCTIVE-CAPACITIVE—Interference caused by high-frequency components that
occurs based on the amount of capacitance. The effect of inductive-capacitive coupling depends on
the amount of capacitance existing between exposed portions of a noisy circuit and a noise-free
circuit. The power transfer capabilities are directly proportional to frequency.
COUPLING, INDUCTIVE-MAGNETIC—Interference caused by the variations in a magnetic field.
When another parallel conductor is cut by the lines of force of this field, the conductor has a current
induced into it. The amount of variation in the current that directly affects variation in the magnetic
field surrounding the conductor depends on the nature of the current. As a magnetic field cuts across
AI-7
another conductor a voltage replica of its variation is induced into that conductor. Inductive-magnetic
coupling can result in serious interference.
COUPLING, RADIATION—Interference caused when aircraft wiring acts like an antenna by directing
RF energy. Inside-the-aircraft radiation at high frequency and below normally occurs in unshielded or
inadequately shielded transmitter antenna leads.
COURSE—The intended horizontal direction of travel.
CRT—Cathode-ray tube—An electron tube that has an electron gun, a deflection system, and a
screen. A CRT is used to display visual electronic signals.
CRYSTAL—A natural substance, such as quartz or tourmaline, that is capable of producing a voltage
when under physical stress or a physical movement when a voltage is applied.
CURRENT—The movement of electrons past a reference point. Also, the passage of electrons
through a conductor, which is measured in amperes.
DARK CURRENT—Current that flows without any radiant input.
DATA HANDLING SYSTEM—Is installed in the MH-60R helicopter and provides for the operator
interface, processing, and display of all avionics and weapons systems.
DATA LINK—A system that is used for the electronic exchange of secure data between two capable
and participating units.
DATABASE—Application of a computer that can be used to index and retrieve information. When an
operator enters a specific keyword or heading, the computer system calls up the data and displays
the information.
DC—Direct current—An electric current that flows in one direction only.
DCS—Digital communication system—Used to lower the workload of the operator during CAS
missions by visually displaying mission information in a text format.
DDIs—Digital data indicators—Are installed in the F/A-18 series of aircraft and used to display
tactical and situational information to the operator.
DEAD RECKONING—Determining the position of an aircraft by estimating the direction and the
speed data relative to a previous position.
DECIBEL—Unit used to measure the intensity of sound or the power level of an electrical signal.
DETECTION—The separation of low frequency (audio) intelligence from the high frequency carrier.
DETECTOR—In IR systems, converts the IR radiation signal into an electrical signal that is
processed into information used by the operator.
DETECTOR, SINGLE—A single detector is scanned across an image so that the detector can view
the whole image. A single detector requires one set of supporting circuitry. The single detector
system is adequate if real-time information is not needed, or the object of interest is stationary or not
moving quickly.
DETECTORS, ELEMENTAL—Type of IR detector that averages the portion of the image outside the
scene that falls on the detector into a single signal.
DETECTORS, IMAGING—Type of IR detector that yields the image directly by responding to a
discrete point on the image.
DETECTORS, INFRARED—Thermal devices for observing and measuring IR radiation, such as the
bolometer, thermopile, pneumatic cell, photocell, photographic plate, and photoconductive cell. IR
AI-8
detectors convert IR radiation signals into electrical signals that are processed into information that is
used by the operator.
DEVICES, SWITCHING—Make abrupt changes in electrical circuits that create transients capable of
interfering with operation of radio and other electronic receivers. Examples of switching devices
capable of causing serious interference are the relay and the thyratron.
DICASS—Directional command activated sonobuoy system—An active sonobuoy that provides
active sonar ranging, bearing, and Doppler information on a submerged target.
DIELECTRIC—An electrical insulator.
DIFAR—Directional frequency analyzing and recording—An improved passive sonobuoy acoustic
sensing system that is programmed prior to deployment using EFS circuitry. DIFAR sonobuoys use a
directional or omnidirectional antenna to detect sound waves.
DIFFUSION—The spread of energy or particles from high concentration to low concentration due to
random velocity and scattering.
DIGITAL COMPUTER—A type of computer that is used to solve problems by manipulating numerical
equivalents of information by using mathematical and logical processes. A typical digital computer
may use binary numbers, octal numbers, decimal numbers, etc. as the required numerical equivalent.
DIGITAL COMPUTER, GENERAL-PURPOSE—Follows instruction sequences that are read into and
stored in memory prior to a calculation being performed. General-purpose digital computers can be
altered by inputting a different set of instructions. Since the operation of general-purpose digital
computers can be changed with relative ease, they provide far greater usage flexibility than a specialpurpose digital computer.
DIGITAL COMPUTER, SPECIAL-PURPOSE—Designed to follow a specific set of instruction
sequences that are fixed at the time that they are manufactured. The actual construction of a specialpurpose digital computer must be changed to alter its operational purpose.
DIODE—An electron tube that contains two electrodes: a cathode and a plate. Diodes are primarily
used as switching devices.
DIP ANGLE—In magnetic anomaly detection, is determined by drawing an imaginary line tangent to
the Earth’s surface to the point at which the line of force intercepts the surface of the Earth.
DIRECTION—Is the position of one point in space relative to another without reference to the
distance between them.
DISABLING SWITCH FOR ARMAMENT SAFETY CIRCUIT—Installed in the MH-60R Seahawk
helicopter and functions as a safety interlock by disabling release and jettison circuits while the
aircraft is on deck.
DISPLAY, MISSION—Installed in the MH-60R Seahawk helicopter and provides BIT,
caution/advisory, and other situation information to the aircrew.
DISTANCE—The spatial separation between two points, measured by the length of a line joining
them.
DISTORTION—The production of an output waveform that is not a true reproduction of the input
waveform. Distortion may consist of irregularities in amplitude, frequency, phase, etc.
DIVERGENCE—Energy loss caused by the spreading of a sound wave in all directions. The farther a
target is from a sonar transducer, the weaker the sound waves will be when they reach that target.
DLY—Delay.
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DME—Distance measuring equipment—A transponder-based radio navigation technology used in
TACAN that measures slant range distance by timing the propagation delay of an RF signal.
DOME CONTROL—In airborne sonar systems, provides the operator with the controls for raising and
lowering the sonar transducer. Additionally, the dome control provides indicators for monitoring the
sonar transducer and reeling machine.
DOPPLER EFFECT—An apparent change in the frequency of a sound wave or electromagnetic
wave reaching a receiver when there is relative motion between the source and the receiver. When
the frequency of the received waves increases, the target is moving towards the transmitter or
transducer. If the frequency of the waves decreases, the target is moving away from the transmitter or
transducer. If the frequency remains the same, the target may be stationary or passing through the
transmitted wave at a right angle.
DRAG—The force that tends to hold an aircraft back. Drag is caused by the disruption of the airflow
about the wings, fuselage, and all protruding objects on the aircraft. Drag resists motion as it acts
parallel and in the opposite direction in relation to the relative wind.
DRIFT—Net change in characteristics of electronic components or parameters, resulting from
external or incidental conditions.
DROGUE—In sonobuoys, a termination mass that is used to stabilize a hydrophone at a selected
depth.
DUPLEX—Data transmission method that is capable of both sending and receiving information. See
also HALF-DUPLEX and FULL-DUPLEX.
DUPLEXER, RADAR—An electronic switch that allows a radar system to use the same antenna to
alternate between transmitting and receiving RF energy. A duplexer must be capable of switching
between the two cycles rapidly to improve the detection of short range targets.
ECHO—In sonar, a sound wave that strikes a target. Or, the RF signal reflected back from a radar
target.
ECV—Environmental control valve—Used to regulate the aircraft cooling air for the installed
components with the ATFLIR pod system.
EDDY CURRENT—Induced circulating currents in a conducting material that are caused by a varying
magnetic field.
EFDS—Electronic flight display system—Installed in the P-3 Orion aircraft and provides the operator
with aircraft course, bearing, heading, and distance. The EFDS also displays aircraft pitch and roll
commands necessary for the operator to fly a designated course.
EFFECT, PHOTOELECTRIC—The electric potential difference across a semiconductor that is
caused by a radiant signal. The total current is proportional to the amount of light that falls on a
detector.
EFFECT, PHOTO-EMISSIVE—The action of radiation that causes the emission of an electron from
the surface of the photocathode to the surrounding space.
EFFECT, PHOTON—A type of energy-matter interaction in which photons of radiant energy interact
directly with the electrons of IR detector material.
EFFECT, THERMAL—A type of energy-matter interaction that involves the absorption of radiant
energy in an IR detector.
EFFECT, TRIBOELECTRIC—Describes the process of generating static electricity by rubbing an
object.
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EFS—Electronic function select—A system that provides a sonobuoy with 99 selectable channels, 50
life settings, and 50 depth settings.
EHF—Extremely high frequency—The band of frequencies from 30 to 300 GHz.
EHSI—Electronic horizontal situation indicator.
ELECTRODE—The terminal at which electricity passes from one medium into another, such as in an
electrical cell where the current leaves or returns to the electrolyte.
ELECTROLYTE—A solution of a substance that is capable of conducting electricity. A typical
electrolyte may be in the form of a liquid or a paste.
ELECTROMAGNETIC FIELD—The combination of an electric and a magnetic field.
ELECTROMAGNETIC RADIATION—The radiation of radio waves into space.
ELECTROMAGNETIC SPECTRUM—The range of wavelengths and frequencies over which
electromagnetic radiation extends.
ELECTROMAGNETIC—Of or relating to the interrelation of electric currents or fields or magnetic
fields.
ELECTRONIC SWITCH—A circuit that causes a start and stop action or a switching action by
electronic means.
ELEMENTS, NONLINEAR—Conductors, semiconductors, or solid state devices whose resistance or
impedance varies with the voltage that is applied across the device.
ELF—Extremely LF—The band of frequencies up to 300 Hz.
EMERG—Emergency.
EMISSIVITY—The ratio of the energy radiated from a material’s surface to that radiated from a
blackbody at the same temperature and wavelength under the same viewing conditions.
EMRG JETT—Emergency jettison.
EO—Electro-optical—An electronic device that is used to emit, modulate, transmit, or sense light or
other wavelengths.
EOSU—Electro-optical sensor unit—In the ATFLIR system, a self-contained component designed to
protect and seal the ATFLIR optics and laser equipment from moisture, contaminants, and
electromagnetic interference.
EQUATOR—A great circle that is located midway between the north and south poles.
ERROR, HYSTERESIS—In pressure altimeters, a lag in attitude indication due to the elastic
properties of the material within the altimeter. This can occur when the aircraft makes a large, rapid
altitude change.
ERROR, INSTALLATION/POSITION—In pressure altimeters, is caused by airflow around the static
pressure measuring ports on an aircraft. The error varies with the type of aircraft, airspeed, and
altitude.
ERROR, MECHANICAL—In pressure altimeters, is caused by misalignments in gears and levers that
transmit the aneroid cell expansion and contraction to the pointers in the altimeter.
ERROR, REVERSAL—In pressure altimeters, is caused by inducing false static pressure into the
system that can occur during abrupt or huge pitch changes.
ERROR, SCALE—In pressure altimeters, is caused by the irregular expansion of the aneroid cells.
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ESD—Electrostatic discharge—A transfer of electrostatic charge between objects at different
potentials caused by direct contact or induced by an electrostatic field.
ESDS—Electrostatic discharge sensitive—Used to describe components or devices that are sensitive
to electrostatic discharge.
EXTERNAL PHOTO EFFECT—See EFFECT, PHOTO-EMISSIVE.
EYESAFE—In ATFLIR systems, enables the operator to place the laser transceiver into a training
mode that simulates all of the tactical aspects of laser employment without emitting any laser energy.
The training mode can be used in both air-to-air and air-to-surface modes of operation.
F/A—Fighter/Attack.
FAC—Forward air controller—An operator on the ground that directs a combat aircraft onto a specific
target or location.
FACSIMILE—A process, commonly called fax, used to transmit photographs, charts, and other
graphic information electronically. Images are scanned by a photoelectric cell and transmitted to the
receiver. At the receiver, a signal operates a recorder the reproduces the scanned images. Fax
signals may be transmitted by landline or radio.
FADING—The variation of signal strength at a receiver due to the difference in phase relationships.
FARAD—The basic unit of capacitance.
FEEDBACK NETWORK—A component of an oscillator that is used to route parts of the signal back
to the frequency determining network to maintain oscillation.
FEEDBACK—The return of a portion of the output of a circuit stage to the input of that stage or a
preceding stage, such that there is either an increase (regeneration) or a reduction (degeneration) in
amplification, depending on the relative phase of the returned signal with the input.
FERMI LEVEL—The top of the collection of electron energy levels at absolute zero.
FERRITE—A hard and brittle crystalline substance made from a mixture of powdered materials,
including iron oxides; it has special magnetic properties of particular value in computers and in many
other applications.
FERROUS—A material that is related to or contains the element iron.
FIBER OPTIC CORE—Located in the center of the optical fiber along the longitudinal axis and is
bound by the cladding. The core is the region with the highest index of refraction and is the light
photon conducting part of the fiber.
FIBER OPTIC—System that transmits light photons through a specifically designed glass medium to
send and receive digital information. The light photons in a fiber optic system are created by either a
light emitting diode or a laser diode.
FIDELITY—The extent to which a system, or a portion of a system, accurately reproduces at its
output the essential characteristics of the signal that is impressed upon its input.
FILTER, BANDPASS—Used to provide a very high impedance above and below a desired set of
frequencies within a specified band. Bandpass filters can be used to decouple the receiver from
shock and overload by transmitters operating above and below the receiver band. In addition,
bandpass filters are used in multiplexing or to decouple two or more receivers or transmitters using
the same antenna.
FILTER, BAND-REJECTION—Used to reject or block a band of frequencies from being passed with
little to no attenuation. A band-rejection filter consists of inductive and capacitive networks combined
and connected to form a definite frequency response characteristic. A band-rejection filter is designed
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to attenuate a specific frequency band and to permit the passage of all frequencies not within this
specific band. Band-rejection filters can be arranged as half-section, pi-section and T-section
configurations.
FILTER, HIGH-PASS—Used to prevent the undesired harmonics from reaching an antenna and
being radiated. High-pass filters are useful for isolating high-frequency receiver from the influence of
energy of signals of lower frequencies. In symmetrical high-pass filters sections, the total opposition
to current flow in is equal to the total opposition to current flow out.
FILTER, INDUCTIVE-CAPACITIVE—Are widely used components to reduce both broadband and
narrow band interference. Inductive-capacitive filters come in a large variety of types and sizes.
FILTER, LOW-PASS—Used in aircraft to power leads coming from interference sources. The lowpass filter prevents the transmission of interference voltages into a wiring harness, and blocks
transmission or reception of RF energy above a specified frequency.
FILTER, RESISTIVE-CAPACITIVE—An effective arc and transient absorber. A resistive-capacitive
filter reduces interference in two ways: by changing the waveform of transients and by dissipating
transient energy.
FILTER, SPECTRAL—In imaging systems, are used to restrict the light wavelength from reaching an
IR detector.
FILTER—A selective network of resistors, capacitors, and inductors that offer little opposition to
certain frequencies, while blocking or attenuating other frequencies.
FIR—Far IR.
FIXED NOTCH FILTER—A component of the MIDS that limits the number of transmitted TACAN
channels by the upper antenna.
FLIR—Forward Looking IR.
FLOAT—In sonobuoys, the buoyant section of a sonobuoy that follows the motion of the waves.
FLUX DENSITY—The number of magnetic lines of force passing through a given area.
FM—Frequency modulation—Angle modulation in which the modulating signal causes the carrier
frequency to vary. The amplitude of the modulating signal determines how far the frequency changes,
and the frequency of the modulating signal determines how fast the frequency changes.
FOV—Field-of-view.
FREQUENCY DETERMING NETWORK—A component of an oscillator that is an inductive or
capacitive circuit containing a natural or man-made crystal.
FREQUENCY MODULATION—Radiates RF energy whose frequency increases and decreases from
a fixed reference frequency. In radar, the frequency of the returned signal differs from the radiated
signal by the amount of time it takes for the signal to travel to the target and return.
FREQUENCY SHIFT KEYING—Frequency modulation somewhat similar to continuous-wave keying
in AM transmitters. The carrier is shifted between two differing frequencies by opening and closing a
key.
FREQUENCY, SOUND WAVE—Determined by counting the number of wavelengths that occur per
second.
FREQUENCY—The number of Hz (cycles per second) of ac.
FULL-DUPLEX—Data transmission method that is capable of transmitting and receiving data
simultaneously.
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FUNCTIONS, COMPUTER—All computers can perform the following operations: gather, process,
store, disseminate, and display data.
G—Gravitational force—A measurement of the type of acceleration that indirectly causes weight.
GAMMA—A measure of magnetic intensity.
GBU—Guided bomb unit—General-purpose bombs that are retrofitted with a precision guidance
package.
GCA—Ground-controlled approach—A type of approach radar system that is used in land-based
applications.
GENERATORS, PRIME—Common plastics and other materials that should be prohibited in an ESD
protected work area.
GEOMAGNETIC FIELD—The natural magnetic field that surrounds the entire Earth.
GHz—Gigahertz.
GIGA—A prefix meaning one billion.
GIMBAL—A frame in which the gyro wheel spins that allows the gyro wheel to have certain freedom
of movement. It permits the gyro rotor to incline freely and retain that position when the support is
tipped or repositioned.
GPS—Global positioning system—A space-based radio navigation system that provides continuous,
all-weather, passive operation anywhere in the world.
GRADIENT, NEGATIVE THERMAL—Describes the colder temperatures that occur with the increase
in the depth of water. A negative thermal gradient will cause a sound wave to be refracted in a
downward angle.
GRADIENT, POSITIVE THERMAL—Occurs when the surface temperature of a body of water is
cooler than the layers beneath it. This condition rarely occurs, but when a positive thermal gradient
occurs it will cause a sound wave to travel at a sharp upward angle.
GRADIENT, THERMAL—The direction and the rate of temperature changes in a particular location.
GREAT CIRCLE—A plane that intersects through the center of a sphere.
GREENWICH MERIDIAN—The prime meridian that passes through Greenwich, England and is used
to measure longitude from east or west.
GROUND STRAPS, PERSONNEL—Used to ground personnel; should have a minimum resistance
of 250,000 ohms and should protect personnel from shock voltages up to 125 volts root mean square.
GUIDANCE, ACTIVE—Uses an internal component, such as a radar transmitter, to illuminate a
target to provide target distance and speed.
GUIDANCE, PASSIVE—Uses the information from the target to determine distance and speed.
GUIDANCE, SEMI-ACTIVE—Uses the information from an external source to provide the distance
and speed of a target.
GYROSCOPE—Mechanical device that contains a spinning mass that is universally mounted
allowing it to assume any position in space. Gyroscopes are also commonly known as gyros.
HACLC—Harpoon aircraft command launch control—Installed in the P-3 Orion aircraft and is used to
provide power, control, and display for the Harpoon missile.
HALF-DUPLEX—Data transmission method that transmits or receives data in one direction at a time.
HARDWARE, COMPUTER—Electronic and physical components that make up a computer system.
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HARM, AGM-88—High-speed anti-radiation missile—A supersonic, A/G, guided missile designed to
detect, attack, and destroy enemy radar systems.
HARMONICS—The multiples of the basic or fundamental frequency. Harmonics can be even and
odd numbers. Harmonics are expressed as the fundamental frequency times an even or odd number.
HAVEQUICK—Mode that provides line-of-sight, jam resistant, ultrahigh frequency, and amplitude
modulated band voice communications.
HEADING—Horizontal direction in which an aircraft is pointed.
HELLFIRE, AGM-114—An A/G, laser guided, subsonic missile with significant antitank capacity. The
Hellfire missile was designed to be employed against tanks, structures, bunkers, and slow-moving
aircraft.
HENRY—The electromagnetic unit of inductance or mutual inductance.
HETERODYNE—To mix two different frequencies in the same circuit; they are alternately additive
and subtractive, thus producing two beat frequencies, which are the sum of, and difference between,
the two original frequencies.
HF—High frequency—The frequency bands from 3 to 30 MHz.
HORIZONTAL PLANE—A horizontal plane is tangent to the surface of the earth. Every plane parallel
to the horizontal plane is likewise a horizontal plane.
HUD—Head-up display—In ACLS, displays the same steering cues as the standby ARI but in digital
format. The ILS steering cues are referenced to the velocity vector (center of the display) and the
artificial horizon. The elevation deviation bar indicates an ILS approach that is above or below the
glideslope. The azimuth deviation bar indicates an ILS approach left or right of the glideslope. The
aircraft is at the optimum approach conditions when both the elevation and azimuth bar are centered
within the velocity vector and the artificial horizon.
HYDROPHONE—An acoustic device that receives and converts underwater sound energy into
electrical energy.
Hz—Hertz—A unit of frequency equal to 1 cycle per second.
I/O CHANNEL—The line of communication that carries data into a computer and out to an output or a
peripheral device; may be simplex or duplex. See also SIMPLEX and DUPLEX.
I/O—Input/Output—Process of transmitting data to a computer, processing the data, and transferring
the data to an output or peripheral device.
I/P—Identification of positon.
IAC—Intercommunication amplifier-control—Installed in the F/A-18 series of aircraft. The IAC is used
to amplify audio outputs and to provide the aircrew with communication-, navigation-, and
identification-related warnings and advisories.
IBIT—Initiated BIT.
ICLS—Instrument carrier landing system—In ACLS, the radar system that transmits the glidepath
pulse-coded under the K frequency band (KU)-band information from the aircraft carrier to the aircraft.
The ICLS is located on board the aircraft carrier and it uses two antennas. One antenna is used to
transmit azimuth information, and the other antenna transmits elevation information. Both signals are
processed by the receiver-decoder group on the aircraft.
IDECM—Integrated defensive electronic countermeasures.
IFF—Identification friend or foe—Provides a means for identifying friendly aircraft from enemy aircraft.
AI-15
IF—Intermediate frequency—A lower frequency to which an RF echo is converted for ease of
amplification.
ILS—Instrument landing system—Provides the data for visual steering commands that assist the
aircrew for the last 25 miles before touchdown onto the aircraft carrier. The ILS interacts with the
ICLS and decodes the azimuth and elevation signals. The decoded signals are provided to the
aircrew via the HUD and the standby ARI.
IMAGING PROCESSING SYSTEMS—Used to convert the data collected by the detectors into a
video display. Data from the detectors is multiplexed so that it can be handled by one set of
electronics. The data is then processed so that the information coming from the detectors is in the
correct order of serial transference to the video display. The signals from the detectors in many
imaging processing systems are amplified and sent to light emitting diode (LED) displays.
IMAGING, THERMAL—The use of specialized heat-sensing equipment to detect targets.
IMPEDANCE—Measure of electrical opposition in a circuit when current of voltage is applied.
INDICATOR, CONTROL—Installed in the MH-60R Seahawk helicopter and is the main interface to
access the data handling system.
INDICATOR—Provides the operator with a visual display of the returned echo signals that show the
bearing, range, or the altitude of a target.
INDUCTANCE—The property of a circuit that tends to oppose a change in the existing current flow.
INDUCTIVE REACTANCE—The opposition to the flow of an alternating current caused by the
inductance of a circuit, expressed in ohms.
INERTIA—The physical tendency of a body in motion to remain in motion and a body at rest to
remain at rest unless acted upon an outside force.
INFRARED MARKER—In ATFLIR, provides a laser reference whose return energy can be seen by
personnel equipped with night vision goggles. The IR marker function makes it useful for night attacks
where personnel on the ground can confirm that the correct target is being designated.
INPUT DEVICE, COMPUTER—Allows an operator to enter data into a computer system.
INS—Inertial navigation system—Detects the motion of an aircraft and provides acceleration, velocity,
present position, pitch, roll, and true heading data. The INS continuously measures aircraft
accelerations to compute aircraft velocity and change in present position.
INST—Instantaneous.
INTELLIGENCE—The message or information conveyed, as by a modulated radio wave.
INTERFACE—A concept involving the specification of the interconnection between equipment or
systems. The specifications include the type, quantity, and function of signals to be interchanged via
those circuits. Also a device that converts or translates any type of information from one given
medium into signals of another given medium; for example, electrical signals to fluidic signals, fluidic
signals to electronic signals, etc.
INTERFERENCE, BROADBAND—Generated when the current flowing in a circuit is interrupted or
varies at a rate that departs radically from a sinusoidal rate.
INTERFERENCE, COMMUTATION—A condition that occurs in a series-wound motor.
INTERFERENCE, NARROW BAND—Caused by oscillators or power amplifiers in receivers and
transmitters that have a poorly shielded local oscillator stage. Narrow band interference can range in
severity from a heterodyne whistle in audio output to completely blocked signals. Narrow band
AI-16
interference affects single frequencies or spots of frequencies in the tuning range of the affected
receiver.
INTERFERENCE, SLIDING-CONTACT—A condition that occurs in an alternator and in a serieswound motor.
INTERROGATOR, IFF—Responds to coded pulse signals from a challenger. The challenger can be
another aircraft, ship, or ground station.
INU—Inertial navigation unit.
INVERTER—A dc motor with armature taps brought out to slip rings to supply an ac voltage. The
alternating output contains some of the interference voltages generated at the direct current end, as
well as brush interference at the ac end of the inverter.
IONIZATION—Process by which an atom or molecule loses or gains electrons, which results in
creation of an electrical charge or change to an existing charge.
IONOSPHERE—A layer of electrically charged particles at the top of the Earth’s atmosphere that
result from strong solar radiation.
IR—Infrared—A Latin word that means “beyond the red”. IR is invisible waves in the portion of the
electromagnetic spectrum lying between visible light and radio frequencies. The IR frequency range is
from about 300 GHz to 400 THz and between wavelengths of 0.72 and 1,000 micrometers.
ISOTHERMAL—A condition where the temperature gradient is equal throughout a layer of a body of
water.
ISOTHERMAL LAYER—A layer of water in which there is no appreciable change of temperature with
depth.
JDAM—Joint direct attack munition—General-purpose weapons that are outfitted with INS and GPS
guidance sets. The JDAM is used for precision strike capabilities in all weather conditions.
KALMAN FILTERING—A statistical estimation that is used by INS to obtain an alignment. The INS
platform outputs and reference data are compared to external reference data inputs. Kalman filtering
estimates the errors in the compared data to correct platform heading, velocity, and attitude.
KHz—Kilohertz.
KILO—A prefix meaning one thousand.
KNOT—Nautical miles per hour.
LASER SPOT TRACKER—In ATFLIR, a subsystem that detects and receives ground or “buddy”
designated laser energy.
LASER—Light amplification by the stimulated emission of radiation.
LATERAL AXIS—The pivot point about which the aircraft pitches.
LATITUDE—Angular distance measured north or south of the equator along a meridian, 0 through 90
degrees.
LDDI—Left digital data indicator.
LDG CHK—Landing check.
LEADING EDGE—The front edge or surface of the airfoil.
LED—Light emitting diode—A P material and N material (PN)-junction diode that emits visible light
when it is forward biased.
LF—Low frequency—The band of frequencies from 30 to 300 kHz.
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LIFT—The force that acts in an upward direction to support an aircraft in the air. Lift counteracts the
effects of weight and must be greater than or equal to weight if flight is to be sustained.
LINE OF FORCE—A line in an electric or magnetic field that shows the direction of the force.
LOGIC CIRCUITS—Digital computer circuits used to store information signals and/or to perform
logical operations on those signals.
LONGITUDE—The angular distance east or west of the Greenwich meridian, measured in the plane
of the equator or of a parallel from 0 to 180 degrees.
LONGITUDINAL AXIS—The pivot point about which an aircraft rolls. The longitudinal axis runs fore
and aft through the length of the aircraft and is parallel to the primary direction of the aircraft. The
primary direction of an aircraft is always forward.
LOOP ANTENNA—One or more complete turns of wire used with a radio receiver. Loop antennas
are also used with direction-finding equipment.
LOS—Line-of-sight—The straight-line distance from a reference point to the horizon. Line-of-sight
represents the radio and radar VHF and UHF transmission range limits under normal conditions.
MACH—The ratio of the speed of a body to the speed of sound in the surrounding medium. Mach is
normally used to indicate the speed of sound.
MAD—Magnetic anomaly detection—The detection of slight distortions in the earth’s magnetic field.
MAGNETIC FIELD—The region in space in which a magnetic force exists, caused by a permanent
magnet or as a result of current flowing in a conductor.
MAGNETOMETER—A device that is used to detect anomalies in the geomagnetic field.
MAGNETRON—A microwave oscillator that uses an electron tube (consisting of a cathode and an
anode), a strong axial magnetic field, and resonant cavities.
MANUAL ARMT SEL—Manual armament select.
MASS STORAGE DEVICE, COMPUTERS—Used to permanently store large amounts of data.
MAVERICK, AGM-65—An air-to-surface tactical missile designed for close air support, interdiction,
and defense suppression.
MC/HYD ISOL—Mission computer/hydraulic isolation—A panel installed in the F/A-18 series aircraft.
The MC/HYD ISOL panel is used to turn the power off to either mission computer (1 or 2) installed in
the aircraft.
MC—Mission computer—Oversees the control and interface of aircraft subsystems and peripheral
components. A typical mission computer controls displays, produces weapons launch and release
commands, and provides control and option select for various avionics systems.
MDG—Multipurpose display group—Installed in the F/A-18 series aircraft and displays all the
information required by the operator to carry out the mission. The MDG also is used by maintenance
technicians to view the status of various aircraft systems to troubleshoot and isolate system
discrepancies. The MDG is made up of the LDDI, RDDI, MPCD, and HUD.
MEAN SEA LEVEL—The average of the sea levels of high and low water.
MEGA—A prefix meaning one million.
MEMORY UNIT—In computers, a device used for storing data for possible use in computation.
MEMORY, COMPUTER—Used to temporarily store data and applications in a computer system.
MERIDIAN—A great circle drawn through the north and south poles.
AI-18
MF—Medium frequency—The band of frequencies from 300 kHz to 3 MHz.
MH—Multi-mission helicopter.
MHz—Megahertz.
MICRO—A prefix meaning one-millionth.
MICROMETER—A unit of length equal to 1 millionth of a meter.
MICROWAVES—Electromagnetic waves of extremely high frequency (between 300 MHz and 300
GHz).
MIDS—Multifunctional information distribution system—Is designed to improve the situational
awareness of aircrew and to improve the effectiveness of command and control centers. The MIDS
uses secure digital communications to display the location and status of friendly air and surface units.
MILE, RADAR—The time it takes for a RF pulse to travel from a radar antenna to a target and back.
A radar mile is normally expressed as the time interval of 12.36 microseconds.
MILLI—A prefix meaning one-thousandth.
MILLIRADIAN—One-thousandth of a radian.
MIR—Middle IR.
MMCS—Maverick missile control system—Installed in the P-3 Orion aircraft and provides the
capability to identify and track up to four separate targets when Maverick missiles are installed on the
aircraft.
MMR—Multi-mode radar.
MODE 1—In IFF systems, provides for the general identification of military aircraft only; has 32
different codes.
MODE 2—In IFF systems, identifies specific military aircraft; has 4,096 different codes.
MODE 3/A—In IFF systems, is used by both military and civilian air traffic control to identify aircraft;
has 4,096 different codes.
MODE 4—In IFF systems, a classified secure mode of operation used only by military aircraft.
MODE 5—In IFF systems, a secured cryptological mode that uses two methods of data transmission,
level 1 and level 2.
MODE I—In ACLS, the automatic control mode of operation from aircraft entry point to touchdown on
the flight deck. The PALS transmits command and error signals to the aircraft via the aircraft data link
system. The approaching aircraft receives command and error signals and automatically corrects the
approach to remain in the narrow flight envelope.
MODE II—In ACLS, the manual control mode with information relayed to aircraft displays. The
operator is provided with cockpit visual indications of command error signals relayed by the PALS. In
mode II, the aircrew controls the aircraft by observing the crew station displays.
MODE III—In ACLS, a manual control mode with voice communications. The PALS provides a voice
link for ship-to-aircraft voice communications to provide talkdown guidance.
MODE SELECTIVE INTERROGATION (S)—In IFF systems, a civilian air traffic control capability that
reduces the number of unwanted IFF replies. Each aircraft is assigned a unique and permanent mode
S address that allows air traffic control to direct interrogations and to send data messages to the
desired aircraft.
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MODULATION—The process of varying the amplitude or frequency of a carrier wave in accordance
with other signals to convey intelligence. The modulating signal may be an audiofrequency signal, a
video signal (as in television), or even electrical pulses or tones to operate relays.
MODULATOR—A device that varies the amplitude, frequency, or phase of an ac signal.
MODULE—In electronic terminology, a group or cluster of circuits/components usually mounted
together.
MODULES, EUROCARD—In ATFLIR, are individual circuit cards that are responsible for managing
and routing a variety of signals to control the operational functions of the system. For example, some
of eurocard modules manage temperature and correct video signals. Eurocard modules are mounted
in a cooled card cage within the pod electronics housing.
MOTOR, ALTERNATING CURRENT—Can be a source of interference at frequencies other than the
output power frequency.
MOTORS, DIRECT CURRENT—Can generate voltages that are capable of causing radio
interference over a wide band of frequencies. There are three types of dc motors generally used in
aircraft: series-wound, shunt-wound, and the compound type.
MPCD—Multipurpose color display—In the F/A-18 series aircraft, it is a color display that provides the
operator with steering and navigation displays. The MPCD is also the main interface for the digital
map system, which provides the operator with a colored map overlay displaying the current position
of the aircraft.
MULTIPLEXER—In sonar, provides the electrical interface between the sonar set units and a sonar
transducer. Or, a system that converts analog and digital signals and transmits the converted signal
using a single line or wire. Also known as mux.
MULTIPLEXING—A method for simultaneous transmission of two or more signals over a common
carrier.
MWS—Missile warning set.
NATOPS—Naval air training and operating procedures standardization.
NATURAL INTERFERENCE—Radio interference caused by natural electrical noise that is separated
into atmospheric static, precipitation static, and cosmic noise.
NAUTICAL MILE—Distance of measurement that is equivalent to 6,076.10 feet.
NAVIGATION, RELATIVE—MIDS mode of operation that improves the navigational accuracy of a
host aircraft. Relative navigation compares the location of other MIDS network participants to the
current aircraft location by measuring the time it takes for a participant to receive a message.
NIR—Near IR.
NOISE—Any undesired disturbance within the useful frequency band; also, that part of the
modulation of a received signal (or an electrical or electronic signal within a circuit) representing an
undesirable effect of transient conditions.
NOISE, RANDOM—Consists of impulses that are of irregular shape, amplitude, duration, and
recurrence rate. Normally, the source of the random noise is a variable contact between brush and
commutator bar or slip ring, or an imperfect contact or poor electrical isolation between surfaces.
NULL—A point or position where a variable-strength signal is at its minimum value (or zero).
NUTATING—Moving an antenna feed point in a conical pattern so that polarization of the beam does
not change.
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OHM—The unit of electrical resistance.
OMNIDIRECTIONAL—Transmitting or receiving a signal in all directions.
OPAQUE—In optics, not able to be seen through or not having the characteristic of being
transparent.
OPER—Operate.
OPERATING SYSTEM—In computers, are designed to support a computer’s basic functions, such
as running applications or controlling I/O devices.
OPTICAL FIBER—Consists of a thin cylindrical dielectric (non-conductive) waveguide used to send
light energy for communication. Optical fiber is a three-part structure in a fiber optic system that
includes a core, a cladding, and a coating. The choice of optical fiber materials and fiber design
depends on the operating conditions and the intended application.
OPTICAL FIBER COATING—Typically has a 10- to 20-micrometer-thick protective polyimide
coating. The coating tolerates extreme temperatures and protects the glass fiber from penetration by
moisture and other contaminants. The coating is softer than the glass fiber.
OPTICAL LAUNCH—The fiber optic transmitter’s ability to launch the light photons down the fiber
optic cabling.
OPTICS, FRONT-END—Used to collect the incoming radiant energy to focus an image at detectors.
The optics may be reflective, refractive, or a combination of both. Many systems offer a zoom
capability, allowing a continuous change in the magnification of an image without changing the focus.
Spectral filters are used on front-end optics to restrict the wavelength of light from reaching the
detector and interfering with the imaging process.
OPTICS, INFRARED—Materials that are specifically designed to filter out all electromagnetic
wavelengths in order to focus the reception of IR wavelengths.
ORT—Operational readiness test.
OSCILLATOR—A component that provides a constant frequency for radio transmitters and receivers.
OTPI—On top position indicator—A navigation system that provides the operator with the bearing of
a sonobuoy in relation to the aircraft.
OUTPUT DEVICE, COMPUTER—Displays computer data and other information to the operator.
OVHT—Overheat.
P—Patrol.
PALS—Precision approach landing system—Designed to be an automatic landing system but has
the capability to operate in manual modes. The PALS uses two modes to receive and transmit data:
display and voice. The PALS operates in three modes: mode I, mode II, and mode III.
PANEL, ARMAMENT CIRCUIT BREAKER—Installed in the P-3 Orion aircraft and supplies power to
the armament circuit breakers located on the forward electronics circuit breaker panel.
PANEL, KEYFILL—Located on an aircraft, a panel into which cryptological keys can be inputted to
allow access to secure functions and systems.
PANEL, LANDING GEAR CONTROL—Installed in the F/A-18 series aircraft. The landing gear
control panel acts as a safety interlock for the armament control system. When the landing gear is in
the down position, the armament release system is disabled.
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PANEL, MASTER ARM CONTROL—Installed in the F/A-18 series aircraft and allows the operator to
select the A/A, A/G MASTER modes of operation. The master arm control panel allows the operator
to arm the selected weapon and to jettison stores from the aircraft.
PARALLEL MODE—Digital transmission method that uses a single wire for each bit of data to be
transmitted or received. The data is transmitted via the wires simultaneously.
PARASITIC ELEMENT—The passive element of an array antenna array that is connected to neither
the transmission line nor the driven element.
PASSIVE SONAR—Equipment that uses the sound generated by the target as the source of the
echo.
PBIT—Periodic BIT.
PERIPHERAL DEVICE—Any device that can be connected to a computer for input, output, or
communication functions.
PERMALLOY—A material used for compensation of magnetic field changes created by the magnetic
rotation of an aircraft.
PHASE—The angular relationship between two alternating currents or voltages when the voltage or
current is plotted as a function of time. When the two are in phase, the angle is zero; both reach their
peak simultaneously. When the two are out of phase, one will lead or lag the other; that is at the
instant when one of the two is at its peak the other will not be at a peak value. This characteristic is
dependent on the phase angle and may differ in polarity as well as magnitude.
PHOTOCONDUCTIVITY—The most widely used photon effect. Radiant energy changes the
electrical conductivity of the detector element. An electrical circuit is used to measure the change in
conductivity.
PHOTOCURRENT—A term used to describe electrical current generated by light.
PHOTON—A particle of electromagnetic energy or a quantum of light.
PHOTOVOLTAIC—See EFFECT, PHOTOELECTRIC.
PIEZOELECTRIC EFFECT—Effect of producing a voltage by placing stress, either by compression,
expansion, or twisting, on a crystal and conversely, producing a stress in a crystal by applying a
voltage to it.
PING—A term used to describe the sound wave that is generated by sonar equipment.
PITCH—The up and down motion of the nose of the aircraft. The pitch axis runs from the left to the
right of the aircraft (wingtip to wingtip).
PLANES OF ALTITUDE—Are made up of indicated altitude, calibrated altitude, pressure altitude,
density altitude, true altitude, and absolute altitude.
POD ELECTRONICS HOUSING—In ATFLIR, provides the mounting and interface for the pod
adapter unit, laser transceiver, laser electronics unit, and environmental control valve.
POLARIZATION—In electronics, a term used in specifying the direction of the electric vector in a
linearly polarized electromagnetic wave as radiated from a transmitting antenna, or as picked up by a
receiving antenna.
POSITION—A location that is defined by stated or implied coordinates.
POWER SUPPLY, RADAR—Provides the radar system with the regulated voltages and signal
routing for operation.
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POWER—The rate of doing work or the rate of expending energy. The unit of electrical power is the
watt.
PRECESSION—The slow movement of the axis of a spinning body around another axis due to a
torque acting to change the direction of the first axis. Precession is seen in a circle slowly traced out
by the pole of a spinning gyroscope.
PRECIPITATION STATIC—A type of interference that occurs during dust, snow, or rain storms.
Precipitation static is caused by the corona discharge of high voltage charges from various points on
the airframe of an aircraft.
PRF—Pulse repetition frequency—In radar, the rate at which pulses are transmitted, given in Hz or
pulses per second. PRF is expressed as the reciprocal of PRT.
PROCESS CONTROL—Application of a computer that detects a change in a system or process and
initiates an immediate corrective action.
PROCESSING SYSTEM, ACOUSTIC—Takes the data received from deployed sonobuoys and
extracts and converts the information into a usable format.
PROGRAMMING LANGUAGE—Used by an operator to design and implement computer
applications to solve problems or to meet a specific need.
PROPAGATION—Extending the action of, transmitting, or carrying forward as in space or time or
through a medium (as the propagation of sound, light, or radio waves).
PRT—Pulse repetition time—In radar, the interval between the start of one pulse and the start of the
next pulse. PRT is expressed as the reciprocal of PRF.
PUBIT—Power-up BIT.
PULSE—A momentary sharp surge of electrical voltage, current, or energy.
PULSE INTEREFERENCE—Normally generated by pulsed electrical equipment. This type of
interference is characterized by a popping or buzzing in an audio output device or by the display of
noise spikes on an oscilloscope. The interference level depends upon the pulse severity, repetition
frequency, and regularity of occurrence. Pulse interference can cause complete loss of reliability in
certain types of navigational beacons.
PULSE MODULATION—A method of transmission that uses very short and powerful bursts of RF
energy. In radar, the time duration of pulse travel time is measured and used to calculate range.
PULSE WIDTH—In radar, the duration of time between the leading and trailing edges of a pulse.
PULSE-DOPPLER—Uses the Doppler effect to track the movement of a target by comparing the
transmitted and received frequencies.
PUSH TO JETT—Push to jettison.
PVT—Positon, velocity, and time.
Q—Figure of merit of efficiency of a circuit or coil. Or, the ratio of inductive reactance to resistance in
servos. Or, the relationship between stored energy (capacitance) and the rate of dissipation in certain
types of electric elements, structures, or materials.
QUANTUM—A quantity of energy that is proportional in magnitude to the frequency of the radiation
that it represents.
RADAR—Radio detecting and ranging—A system that operates by transmitting and receive an RF
pulse to determine the range, bearing, and altitude of a target.
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RADAR BEACON—In ACLS, receives conically scanned above-the-K-frequency band (Ka) signals
from the PALS. The received signals are used to derive the range, angle tracking, and position error
for aircraft data link guidance.
RADAR, AIR SEARCH—Is used to detect and determine the position, course, and speed of air
targets. There are two types of air search radar systems: two-dimensional and three-dimensional.
Two-dimensional air search radar systems provide the range and bearing of a target. Threedimensional air search radar systems provide the range, bearing, and altitude of a target.
RADAR, AIRBORNE—Is designed to meet the strict weight and space limitations necessary to be
installed into aircraft. Airborne radar systems have the same characteristics and performance as land
or ship-based systems.
RADAR, APPROACH—Used to guide aircraft to a safe landing in all weather conditions.
RADAR, MISSILE GUIDANCE—Used to guide a missile to a target. There are three basic type of
missile guidance radar: beam-rider, homing, and passive. Beam rider missiles follow a beam of
directed continuous wave of RF energy to intercept a target. Homing missiles detect the reflected
radar energy off of a target and use it to intercept a target. Passive missiles intercept a target by
using the energy radiated from the target.
RADAR, SEARCH—Designed to scan a volume of space in order to detect any target within that
space.
RADAR, SURFACE SEARCH—Used to determine the range and bearing of surface targets or lowflying aircraft. Surface search radar systems generate a pattern for all objects within a line-of-sight
distance from the antenna.
RADAR, SURFACE SEARCH HEIGHT FINDING—Used to provide accurate range, bearing, and
altitude of air targets detected by air search radar systems.
RADAR, TRACKING—Also known as fire control radar. Used to provide continuous positional data of
a target by using a narrow, circular RF beam.
RADIAN—A unit of plane angular measurement that is equal to the angle at the center of a circle
subtended by an arc whose length equals the radius or approximately 57.3 degrees.
RADIO TERMINAL UNIT—The main physical component of MIDS.
RADIOFREQUENCY SPECTRUM—The spectrum of electromagnetic frequencies that are used for
communications. The RF spectrum also includes frequencies that are used in radar and other
systems.
RADIOTELEGRAPH—Device that operates by opening and closing a switch to separate a
continuously transmitted wave into dots and dashes based on Morse code.
RADIOTELEPHONE—Device better known as a radio and one of the most useful methods of
communication in military applications. One of the key disadvantages to a radio is that effective
transmission and receiving range is limited.
RANGE—The distance of an object from an observer.
RANGE, MAXIMUM—In radar, maximum range is dependent on the signal carrier frequency, peak
power of the transmitted pulse, pulse repetition frequency, and the sensitivity of the receiver.
RANGE, MINIMUM—In radar, minimum range is dependent on the timing, pulse width, and recovery
time of the radar system.
RAREFACTION—In sonar, the action that occurs when a transducer diaphragm moves inward
creating a low-pressure wave.
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RASTER—The illuminated rectangular area scanned by the electron beam on a display.
RDDI—Right digital data indicator.
RDP—Radar data processor—A general purpose dual processor digital computer that functions as a
radar management control, data processor, and a performance monitor. A typical RDP provides
target information, display conditions, and BIT commands to the operator.
RECEIVER DETECTION—Occurs when the receiver separates an AF from the RF carrier signal by
using a detector circuit.
RECEIVER OSCILLATOR—A local oscillator in a superheterodyne receiver that generates an RF
signal at a given frequency. The local oscillator signal is mixed with another RF signal to produce an
IF signal. Depending on the receiver design, the frequency of the local oscillator signal is either above
or below the frequency of the RF signal by a frequency equal to the IF.
RECEIVER RECEPTION—Occurs when an RF wave passes through the receiver antenna and
induces a voltage level into the antenna.
RECEIVER REPRODUCTION—Process of converting the electrical signal into an audio output
signal.
RECEIVER SELECTION—Ability of a receiver to select a particular station frequency from the rest of
the frequencies.
RECEIVER, FIBER OPTIC—Converts optical signals into electrical signals and routes the signal to
the appropriate equipment for processing.
RECEIVER, RADAR—Amplifies the weak echoes returned by the target and reproduces the echoes
into a video pulse that is routed to an indicator. One of the primary functions of a radar receiver is to
convert the frequency of the echo into a lower frequency that is easier to amplify.
RECEIVER, RADIO—Equipment that has the capability to decode RF energy into a usable form.
RECEIVER, SONOBUOY—Uses radios to receive, demodulate, and amplify sonobuoy transmissions
in the very high frequency spectrum bands. A typical sonobuoy receiver system relays acoustic data
to other units (ships or aircraft) via a datalink system. The data from a sonobuoy receiver is routed to
a spectrum analyzer.
RECEIVING-DECODING GROUP—In ACLS, converts the glidepath error signals received from the
ship’s ICLS and converts the signals into visual indications for the operator. The receiving-decoding
group is also used for the airborne monitoring of ACLS mode I and mode II aircraft carrier
approaches.
RECOVERY TIME—In radar, the time interval between the end of a transmitted pulse and the time
when the echo signals are no longer attenuated by the transmission/reception gap.
REELING MACHINE—In airborne sonar systems, a hydraulic hoist that is used to raise and lower the
sonar transducer. A typical reeling machine operates at a pressure of 3,000 pounds per square inch.
REFLECTION, SOUND—Sound waves transmitted in the sea eventually reach either the surface or
the bottom. Since these boundaries are abrupt and very different in sound transmitting properties
from the water, sound energy along a path striking these boundaries will be returned (reflected)
through the water. Because the density of the water is 800 greater than the density of air nearly all
sound waves are reflected to the surface. See also BOTTOM BOUNCE.
REFRACTION—The deflection or change in the direction of a wave as they travel through space at
different speeds.
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REFRACTION, SOUND—The bending of a sound wave caused by the variations of temperature. A
sound beam would travel in a straight line if there were no temperature differences in the water. The
path of a sound wave will bend away from an area of high temperature and towards an area of lower
temperature. The characteristics of sound refraction can significantly lower the detection range of an
undersea target.
RELATIVE MOTION—The apparent movement of an object in relation to another object.
RELATIVE WIND—The direction of the airstream in relation to the airfoil.
RELAY—An electromagnetically operated remote control switch used to switch high current, high
voltage, or other critical circuits. Since the relay is used almost exclusively to control large amounts of
power with relatively small amounts of power, the relay is always a potential source of interference.
This is especially true when the relay is used to control an inductive circuit.
RESISTANCE—The opposition a device or material offers to the flow of current. The effect of
resistance is to raise the temperature of the material or device carrying the current.
RESISTOR—An electrical component that offers resistance to the flow of current. It may be a coil of
fine wire or a composition rod.
RESOLUTION—In radar, is the ability of a radar system to distinguish between targets.
RESOLUTION, BEARING—In radar, is the ability of a radar system to distinguish between two
targets that are at the same range but at different bearings.
RESOLUTION, RANGE—In radar, is the ability of a radar system to distinguish between two targets
that are on the same bearing but at different ranges.
RESOLUTION, TARGET—In radar, is the ability of a radar system to distinguish between two targets
that are close together in either range or bearing.
RESONANCE—The condition in a circuit containing inductance and capacitance, which is resonant
at one frequency.
REVERBERATION—Multiple reflections of a sound wave. In the ocean reverberations are caused by
irregularities in the ocean bottom, surface, and suspended natural matter. Each of the scattered
sound waves produces a small echo that may be returned to a transducer. The combinations of these
echoes from the cumulative disturbances are reverberations. Under these conditions, an emitted
sound wave maybe received as a muffled echo due to sound interference.
RF—Radiofrequency—Any frequency of electromagnetic energy capable of propagation into space.
The frequencies that fall between 3 kHz and 300 GHz are used for radio communications.
ROOT MEAN SQUARE—The most common method of defining the effective voltage or current of an
ac wave.
ROTOCHUTE—A rotating blade assembly that slows the descent of an airborne deployed sonobuoy
to reduce the water-entry shock to the device.
RTTY—Radio teletypewriter. See also TELETYPEWRITER.
SALINITY—The amount of salt content in seawater. Salinity can affect the travel of a sound wave
through a body of water. The higher the salt content, the faster the sound wave will travel through the
body of water.
SASP—Single advanced signal processor—An acoustic processing system that is installed in the P-3
Orion aircraft.
SCANNING SONAR—Sonar that transmits sound pulses in all directions simultaneously.
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SCANNING, BEAM—Consists of two methods: mechanical and electronic. Mechanical beam
scanning moves the entire antenna in a desired scanning pattern. Electronic beam scanning changes
the scanning pattern by electronically switching a multi-element array or by switching between a set
of energy sources.
SCANNING, STATIONARY-LOBE—The simplest form of scanning system, which uses a single
beam that is stationary in reference to the antenna.
SCATTERING—Reflection losses from foreign matter that is suspended in the water. Foreign matter
in the water scatters the sound beam and causes the loss of sound energy. The practical result of
scattering is the reduction of the echo strength especially at long ranges.
SCENE DISSECTION SYSTEM—Used to scan the scene image. Each system has an optimum
configuration of detector array and image dissection. Many types of mechanisms can be used to scan
the scene. When two axes are scanned, the two scanning motions must be synchronized. In addition,
the electronic signal that controls the sampling of the detectors must be synchronized with the
scanning motions.
SCHULER TUNING (LOOP)—In INS, torques the platform to a position normal to the gravity vector
by signals received from a computing loop. The Schuler-tuned loop is a closed loop circuit between
the accelerometer, velocity integrator, and stable element. The Schuler-tuned loop prevents large
velocity and distance errors caused by misalignment of the stable element.
SELECTIVITY—The degree of distinction that a receiver can make between the desired and
unwanted signals.
SEMI-SYNCHRONOUS ORBIT—An orbit with a period equal to half the average rotational period of
the body (Earth) being orbited, and in the same direction as that body’s rotation.
SENSITIVITY—The ability of a receiver to reproduce a weak input signal into a useable output signal.
In receivers, the greater the sensitivity, the weaker the signal can be reproduced.
SENSOR—A component that senses variables and produces a signal derived from that variable.
Some examples of sensors are temperature, sound, heat, and light.
SERIAL MODE—Digital data transmission method that transmits data one bit at time on a single
transmission line.
SHF—Super high frequency—The band of frequencies from 3 to 30 GHz.
SIDEWINDER, AIM-9 SERIES—Supersonic, A/A weapons with passive IR target detection,
proportional navigation guidance, and torque-balanced control systems.
SIMPLEX—Data transmission that occurs in one direction (transmit or receive) only.
SIMULATION—A computer application used to simulate the operation of any type of system being
designed.
SINE WAVE—The basic synchronous alternating waveform for all complex waveforms. Also known
as a sinusoidal wave.
SINGCARS—Single channel ground and airborne radio system—Mode that provides line-of-sight,
jam resistant, very high frequency, frequency-modulated band voice communications.
SINS—Ship’s INS—Provides ship’s velocity, position, and attitude data to aircraft via a cable
assembly or by an aircraft datalink system.
SINUSOIDAL—Having a magnitude that varies as the sine of an independent variable.
SLEW—To change the position of an indicator mark on a display.
AI-27
SMALL CIRCLE—Any intersection of a plane that does not pass through the center of a sphere.
SMS—Stores management system—Provides the interface for the selection, control, and release of
weapons and stores from aircraft weapons stations and launchers.
SOFTWARE—A set of programs and procedures used by a computer to perform a particular
function. Software includes compilers, assemblers, operating systems, and so on.
SOFTWARE, ASSEMBLER—Used to access, manage, and alter computer hardware architecture.
SOFTWARE, COMPILER—Used to transform the source code of one programming language into
another computer programming language.
SOFTWARE, REAL-TIME PROCESSING—Data is submitted to a computer, and an immediate
response is obtained.
SONAR—Sound navigation and ranging—Equipment that transmits and receives sound energy
propagated through water.
SONAR DATA COMPUTER—In airborne sonar systems, a programmed array processor that
provides the operator of the dipping sonar. Additionally, the sonar data computer processes signals
received from passive and active sonobuoys.
SONAR RECEIVER—In airborne sonar systems, generates the transmit signal and receives and
processes sonic signals from the transducer for display on the azimuth-range indicator. The sonar
receiver also provides the audio output for aural monitoring of acoustic signals.
SONAR SYSTEM, AIRBORNE—A lightweight sonar dipping set that is installed in ASW helicopters.
SONOBUOY—Cylindrical metal tubes that are about 3 feet in length and 5 inches in diameter and
can weigh from 20 to 39 pounds. Sonobuoys are expendable devices that are used to detect,
localize, and identify submarines. Sonobuoys fall into three general categories: active, passive, or
special purpose.
SONOBUOY REFERENCE SYSTEM—The system used to determine the position of deployed
sonobuoys relative to aircraft position.
SONOBUOY, ACTIVE—Uses a transducer to radiate a sonar pulse that is reflected back from the
target. Active sonobuoys use the Doppler effect to calculate both the range and the speed of a target.
SONOBUOY, BATHYTHERMOGRAPH—A special purpose sonobuoy that provides a continuous
reading of temperature versus depth. The bathythermograph sonobuoy uses a thermistor to provide
the operator with temperature data.
SONOBUOY, PASSIVE—Are listen-only devices.
SONOBUOY, SPECIAL PURPOSE—Are not designed for use in target detection, identification, or
localization of a target.
SOUND CHANNEL—Condition when two layers of water with near equal temperatures produce a
sound channel. Sound between the two layers is refracted by the layers, stays between them, and
travels for great distances.
SPACE SEGMENT—Consists of the global positioning system constellation that encompasses 21
operational and 3 spare satellites positioned approximately 12,550 miles high in a semi-synchronous
orbit around Earth. The satellites are in six orbital planes with three or four operational satellites in
each plane. There are a minimum of four satellites observable from anywhere in the world.
SPARROW, AIM-7—An all-weather, all-altitude missile that uses a semi-active guidance system to
seek out and destroy a target.
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SPECTRUM ANALYZER—In sonar, a high-speed processor that extracts acoustic information from
the received signals of active and passive sonobuoys. A spectrum analyzer determines the
frequency, amplitude, bearing, Doppler, and range of an acoustic target.
SPEED OF LIGHT—Measured at approximately 186,000 statute miles per second.
SPREAD SPECTRUM—A technique used by GPS satellites to improve the availability of transmitted
signals and to improve the resistance against jamming and natural interference.
SRCH PWR—Search power.
SSB—Single sideband.
STABLE ELEMENT—In INS, mounts in the gimbal structure of an INU unit so that, regardless of
aircraft maneuvers, the platform maintains the original orientation. Additionally, the stable element
serves as a level mount for the accelerometers.
STANDARD DATUM PLANE—A theoretical plane where the atmospheric pressure is 29.92 inches
of mercury (Hg) and the temperature is 15 degrees Celsius or 59 degrees Fahrenheit. The standard
datum plane is the zero-elevation level of an imaginary atmosphere known as the standard
atmosphere.
STANDARD LAPSE RATES—A list of altitudes, temperatures, and pressure that was determined by
the average readings obtained over a period of years.
STATIC ELECTRICITY—Electrical energy at rest.
STATUTE MILE—Measurement that is equivalent to 5,280 feet.
STBY—Standby.
SUBHARMONICS—The submultiple of the fundamental frequency. Subharmonics are expressed in
even or odd terms and as a fraction of a number (1/2, 1/4, etc.) of the fundamental frequency.
SUPPRESSION—The electrical elimination of an undesired portion of a radio signal.
SUS—Signal underwater sound.
SWITCH, ARMAMENT SAFETY CIRCUIT DISABLE—Installed in the P-3 Orion aircraft and is used
to bypass the landing gear lever switch to permit the operation of the weapons systems when the
aircraft is on the ground.
SWITCH, ARMAMENT SAFETY OVERRIDE—Installed in the F/A-18 series aircraft and is used to
enable the armament control system when the aircraft is on the ground.
SWITCHABLE NOTCH FILTER—A component of the MIDS that prevents interference between RF
transmissions.
SYNCHRONIZER, RADAR—Supplies the signals that time the transmitted pulses, the indicator, and
other associated circuits. A synchronizer sets the interval between transmitted pulses to ensure the
pulsed RF energy is the proper length.
SYSTEM, AIR-TO-AIR MISSILE CONTROL—Installed in the F/A-18 series of aircraft and provides
the ability to select and launch A/A missiles, such as the AIM-9 Sidewinder, AIM-7 Sparrow, and the
AIM-120 AMRAAM.
SYSTEM, AIR-TO-GROUND WEAPONS CONTROL—Installed in the F/A-18 series aircraft and
provides the ability to select, launch, fire, or release A/G missiles, bombs, mines, and rockets.
SYSTEM, DEFENSIVE COUNTERMEASURES—Used to protect the aircraft from anti-air threats by
dispensing flares, chaff, or RF jammers in manual, semiautomatic, or automatic modes of operation.
AI-29
SYSTEM, HELLFIRE MISSILE CONTROL—Installed in the MH-60R Seahawk helicopter and
provides for the carriage and launch of the AGM-114 Hellfire missile.
SYSTEM, JETTISON—Provides the interface and control to jettison selected stores from the aircraft.
The jettison system also provides for the selection of an emergency mode that will jettison all stores
from the aircraft.
SYSTEM, REFRIGERATION—In imaging systems, is required to keep IR detectors cooled to the low
temperatures required for effective operation. Refrigeration systems are either open-cycle or closedcycle types. Open-cycle systems require a reservoir of liquefied cryogenic gas. A closed-cycle system
recycles the compressed gases to cool the IR detectors.
SYSTEM, SONOBUOY LAUNCH—Installed in the MH-60R Seahawk helicopter and is capable of
launching and controlling up to 25 sonobuoys.
SYSTEM, TORPEDO RELEASE—Installed in the MH-60R Seahawk helicopter and provides for the
control and release of up to four torpedoes.
TACAN—Tactical Air Navigation—A polar coordinate type radio air-navigation system that provides
distance information and bearing information to a compatible station.
TACCO—Tactical coordinator.
TDC—Throttle designator control.
TELETYPEWRITER—A device that transmits and translates letters, figure, and symbols by landlines,
radio, or cable, that are entered using a keyboard similar to a typewriter keyboard.
TEMPERATURE—The most important factor that can affect the speed of a sound wave traveling in
seawater. One degree of temperature change can increase the speed of sound in seawater by 4 to 8
feet per second.
TERA—A prefix meaning one trillion.
THERMISTOR—A solid-state, semiconducting device whose resistance varies with temperature.
THERMOCLINE—The layer in a body of water where the temperature decreases continuously with
depth.
THRUST—The force developed by the aircraft’s engine or engines. Thrust acts in the forward
direction and must be greater than or equal to the effects of drag to begin or sustain flight.
THYRATRONS—A gas-filled, grid-controlled, electronic switching tube used mainly in radar
modulators. Since the time required to turn a thyratron on is only a few microseconds, the current
waveform in a thyratron circuit always has a sharp leading edge. As a result, the waveform is rich in
radio interference energy.
THz—Terahertz.
TIME—In air navigation, either the hour of the day or an elapsed interval.
TORPEDO, MK 46—Dual-speed active or active/passive weapon with enhanced target acquisition
and improved reliability.
TORPEDO, MK 50—A highly capable weapon designed to counter the fast, deep diving, doublehulled nuclear submarine threat.
TORPEDO, MK 54—Uses existing torpedo hardware and software and integrates state-of-the-art
digital signal processing.
TORP—Torpedo.
AI-30
TORQUE—A force tending to cause rotational motion; the product of the force applied times the
distance from the force to the axis of rotation.
TRAILING EDGE—The rear edge or surface of the airfoil.
TRANSCEIVER, FIBER OPTIC—Incorporates transmission and reception capabilities into one unit.
TRANSDUCER, SONAR—A device that converts an electrical signal into acoustical energy and vice
versa. Transducers are watertight and act in the same manner as a loudspeaker when used to
transmit a sound and as a microphone when receiving the transmitted echo. A typical transducer
uses a diaphragm to create areas of low and high pressure underwater. The mechanical action of the
diaphragm creates two types of sound waves: rarefaction and compression.
TRANSIENTS, SWITCHING—Result from the make or break of an electrical current and are
extremely sharp pulses. The duration and peak value of these pulses depend upon the amount of
current and the characteristics of the circuit being opened or closed. The effects of switching
transients are shape clicks in the audio output of a receiver and sharp spikes on an oscilloscope
trace. Typical sources of sustained switching transients are ignition timing systems, commutators of
dc motors, or pulsed navigational lighting.
TRANSMITTER, FIBER OPTIC—Converts electrical signals into optical signals and sends it through
optical fiber cabling.
TRANSMITTER, RADAR—Generates RF energy in the form of short and powerful pulses.
Transmitters use oscillators to turn a low-power RF signal into a high-power output signal.
TRANSMITTER, RADIO—Equipment that is responsible for generating the proper amount of RF
energy to transmit information from one point to another.
TRANSPONDER, IFF—Receives the challenge signals from an interrogator unit and transmits the
properly coded response.
TRIGGERING—In electronics, the initiation of starting action in another circuit; the triggered circuit
will then operate for a period of time under its own control.
TTY—Teletypewriter.
TUNED CIRCUIT—A tuned circuit acts as a filter in a radio communication system by allowing or
rejecting specific frequency ranges.
UFCD—Upfront control display—A touch sensitive display that provides the keypad, option select,
scratch pad, and option displays.
UHF—Ultrahigh frequency—The band of frequencies from 300 MHz to 3 GHz.
UNIT, LASER ELECTRONICS—In the ATFLIR system, the primary interface between the laser
transceiver unit, the aircraft, and the pod. The laser electronics unit interfaces with the aircraft for
discrete laser arming signals.
UNIT, LASER TRANSCEIVER—In the ATFLIR system, provides the energy for laser generation for
the system.
UNIT, POD ADAPTER—In the ATFLIR system, provides the mounting and interface for the aircraft,
the pod electronics housing, and the ANFLIR sensor.
UNIT, PROCESSING INTERFACE—Installed in the MH-60R Seahawk helicopter and provides the
interface between the weapons/stores and the primary flight/mission computer and other onboard
avionics systems.
USER SEGMENT—The equipment used to receive, decode, and process global positioning system
information.
AI-31
VARACTOR—Consists of a semiconductor diode whose capacitance is varied with the amount of
applied voltage. A varactor is used to vary the frequency output of an oscillator.
VARICAP—See VARACTOR.
VELOCITY—A vector quantity that includes both magnitude (speed) and direction in relation to a
given frame of reference.
VERTICAL AXIS—Runs from the top to the bottom of the aircraft. The vertical axis runs
perpendicular to both the roll and pitch axes. The movement associated with the vertical axis is yaw.
VERTICAL PLANE—A vertical plane is perpendicular to the horizontal plane, and is the reference
from which bearings are measured.
VF—Voice frequency.
VHF—Very high frequency—The band of frequencies from 30 to 300 MHz.
VLAD—Vertical line array directional frequency and recording—A passive directional sonobuoy that
deploys a vertical line array that consists of directional or omnidirectional hydrophones. VLAD
sonobuoys are normally deployed in areas that have high ambient noise.
VLF—Very LF—The band of frequencies from 3 to 30 kHz.
VOR—VHF omnidirectional radio range—A type of short-range radio navigation systems that uses a
series of radio beacons.
WAVE PROPAGATION—Radiation, as from an antenna, of RF energy into space, or of sound
energy into a conducting medium.
WAVEGUIDE—Metal tubes or dielectric cylinders capable of propagating electromagnetic waves
through their interiors. The dimensions of these devices are determined by the frequency to be
propagated. Metal guides are usually rectangular or circular in cross section; they may be evacuated,
air filled, or gas filled, and may or may not be pressurized. Dielectric guides consist of solid dielectric
cylinders surrounded by air.
WAVELENGTH—Distance traveled by a wave during the time interval of one complete cycle. It is
equal to the velocity divided by the frequency.
WEIGHT—The force of gravity that acts downward on the aircraft, and everything in the aircraft, such
as crew, fuel, and cargo.
WING FORM—A digital outline of an aircraft that identifies type, weapons station, number, and status
of weapons that are loaded on the aircraft.
WIP—Weapons insertion panel—Component of the F/A-18 armament computer that is used to enter
weapon type and fuzing codes for each loaded weapon station. The weapons code entered for each
loaded station must match the loaded weapon. In addition, the nose/tail fuze code must be
compatible. If these conditions are not met the aircraft will not allow the weapon to fire or release.
WOW—Weight-on-wheels—A switch that indicates that the aircraft is on the ground.
WPN—Weapon.
WRA—Weapons replaceable assembly.
XIR—Extreme IR.
YAW—The change in aircraft heading to the right or to the left of the primary direction of the aircraft.
ZERO COEFFICIENT—A lack of relationship between one property and another property.
AI-32
APPENDIX II
SYMBOLS, FORMULAS, AND TABLES
Figure AII-1 — Electrical symbols.
AII-1
Figure AII-1 — Electrical symbols (continued).
AII-2
Figure AII-1 — Electrical symbols (continued).
AII-3
Figure AII-1 — Electrical symbols (continued).
AII-4
Figure AII-1 — Electrical symbols (continued).
AII-5
Figure AII-1 — Electrical symbols (continued).
AII-6
Figure AII-1 — Electrical symbols (continued).
AII-7
Figure AII-1 — Electrical symbols (continued).
AII-8
Table AII-1 — Common Electrical Formula Symbols
Electrical Symbol
General Description
I
Current is measured in amperes
E
Voltage is measured in volts
R
Resistance is measured in ohms
P
Power is measured in watts
L
Inductance is measured in henrys
X
Reactance is measured in ohms
t
Measure of time
EP
Voltage in a transformer primary
ES
Voltage in a transformer secondary
NP
Number of turns in a transformer primary
NS
Number of turns in a transformer secondary
Eave
Value of average voltage
Emax
Value of maximum voltage
Eeff
Value of effective voltage
F
Measure of magnetomotive force
ᶲ (flux)
Measure of magnetic flow
R (reluctance)
Measure of magnetic opposition
H
Measure of magnetic force intensity
dB
Measure of intensity (sound or electrical)
AII-9
Figure AII-2 — Common electrical calculations formula wheel.
AII-10
Ohm’s Law for Direct Current Circuits
I=
E
P
P
= = �
R
E
R
E
P
E2
R= = 2=
I
I
P
E = IR =
P
= √PR
I
E2
P = EI =
= I2 R
R
Resistors in Series
R T = R1 + R 2 …
Resistors in Parallel
Two resistors:
R1 R2
RT = 1
R + R2
More than two:
1
1
1
=
+
+⋯
RT
R1 R 2
Resistive-Inductance (RL) Circuit Time Constant
L (in henrys)
= t (in seconds), or
R (in ohms)
L (in microhenrys)
= t (in microseconds)
R (in ohms)
Resistive-Capacitive (RC) Circuit Time Constant
R (ohms) × C (farads) = t (seconds)
R (megohms) × C (microfarads) = t (seconds)
R (ohms) × C (microfarads) = t (microseconds)
AII-11
R (megohms) × C (picofarads) = t (microseconds)
Capacitors in Series
Two capacitors:
CT =
C1 C2
C1 + C2
More than two:
1
1
1
=
+
+⋯
CT
C1 C2
Capacitors in Parallel
CT = C1 + C2 + ⋯
Capacitive Reactance
XC =
1
2πfC
Impedance in an RC Circuit (Series)
Z = �R2 + (XC )2
Inductor in Series
LT = L1 + L2 + ⋯ (No coupling between coils)
Inductors in Parallel
Two inductors:
LT =
L1 L2
(No coupling between coils)
L1 + L2
More than two:
1
1
1
=
+
+ ⋯ (No coupling between coils)
LT
L1 L2
AII-12
Inductive Reactance
XL = 2πfL
Q of a Coil
Q=
XL
R
Impedance of an RL Circuit (Series)
Z = �R² + (XL )²
Impedance with R, C, and L in Series
Z = �R² + (XL − XC )²
Parallel Circuit Impedance
Z=
Z1 Z2
Z1 + Z2
Sine-Wave Voltage Relationships
Average value:
Eave =
2
× Emax = 0.637Emax
π
Effective or rms value:
Eeff =
Emax
√2
=
Emax
= 0.707Emax = 1.11Eave
1.414
Maximum value:
Emax = �2 (Eeff) = 1.414Eeff = 1.57Eave
Voltage in an alternating circuit:
E = IZ =
P
I × PF
AII-13
Current in an alternating circuit:
I=
P
E
=
E × PF
Z
Power in Alternating Current Circuit
Apparent power: P = EI
True power: P = EI cos θ = EI × PF
Power factor:
P
= cos θ
EI
true power
cos θ =
apparent power
PF =
Transformers
Voltage relationship:
Np
Ep
Ns
=
or Es = Ep ×
Es
Ns
Np
Current relationship:
Ip
Ns
=
Is
Np
Induced voltage:
Eeff = 4.44 × BAfN × 10−8
Turns ratio:
Np
Zp
= �
Ns
Zs
Secondary current:
Is = Ip ×
AII-14
Np
Ns
Secondary voltage:
Es = Ep ×
Ns
Np
Three-phase Voltage and Current Relationships
With wye connected windings:
Eline = √3 (Ecoil ) = 1.732Ecoil
Iline = Icoil
With delta connected windings:
Eline = Ecoil
Iline = 1.732Icoil
With wye or delta connected winding:
Pcoil = Ecoil Icoil
Pt = 3Pcoil
Pt = 1.732Eline Iline
(To convert to true power, multiply by 𝐜𝐜𝐜𝐜𝐜𝐜 𝛉𝛉)
Resonance
At resonance:
XL = XC
Resonant frequency:
F0 =
1
2π√LC
Series resonance:
Z (at any frequency) = R + j (XL − XC )
Z (at resonance) = R
AII-15
Parallel resonance:
Zmax (at resonance) =
XL XC
XL2
L
=
= QXL =
CR
R
R
Bandwidth:
∆=
F0
R
=
Q
2πL
Tube Characteristics
Amplification factor:
∆ep
(i constant)
∆eg p
µ=
µ = g m rp
Alternating current plate resistance:
∆ep
(e constant)
∆ip g
rp =
Grid-plate transconductance:
gm =
∆ip
(e constant)
∆eg p
Decibels
NOTE
Wherever the expression “log” appears without a subscript
specifying the base, the logarithmic base is understood to
be 10.
Power ratio:
dB = 10 log
P2
P1
Current and voltage ratio:
dB = 20 log
AII-16
I2 �R 2
I1 �R1
dB = 20 log
E2 �R1
E1 �R 2
NOTE
When R1 and R2 are equal they may be omitted from the
formula.
When reference level is 1 milliwatt:
dBm = 10 log
P
(when P is in watts)
0.001
Synchronous Speed of a Motor
rpm =
120 × frequency
number of poles
Wavelength
wavelength (in meters) =
λ=
300
frequency (in megahertz)
300
f MHz
AII-17
BRIDGE CIRCUIT CONVERSION FORMULAS
Pi to Tee
R1′ =
R1 R 2
R1 + R 2 + R 3
R 3′ =
R2R3
R1 + R 2 + R 3
R 2′ =
Tee to Pi
R1 =
R2 =
R3 =
R1 R 3
R1 + R 2 + R 3
R1′ R 2′ + R 2′ R 3′ + R1′ R 3′
R3
R1′ R 2′ + R 2′ R 3′ + R1′ R 3′
R2
R1′ R 2′ + 𝑅𝑅2′ 𝑅𝑅3′ + 𝑅𝑅1′ 𝑅𝑅3′
R1
AII-18
Calculating RT for Bridge
1. Redraw.
2. Convert Pi network made up of resistors R3, R4, R5 to Tee network made up of R3’, R4’, R5’.
R 3′ =
R3R5
R3 + R4 + R5
R 5′ =
R3R4
R3 + R4 + R5
R 4′ =
R4R5
R3 + R4 + R5
AII-19
3. Redraw circuit.
4. Simplify circuit by combining.
5. Simplify again.
6. Solve for RT.
R1′ = R1 + R 3′
R 2′ = R 2 + R 4′
R 6′ =
R1′ R 2′
R1′ + R 2′
R T = R 6′ + R 5′
AII-20
Table AII-2 ─ Law of Exponents
Numbers
Powers of Ten
1012
1,000,000,000,000
9
1,000,000,000
10
1,000,000
106
Prefixes
Symbol
tera
T
giga
G
mega
M
10
3
kilo
k
100
10
2
hecto
h
10
10
deka
da
deci
d
1,000
-1
0.1
10
0.01
10-2
centi
c
10
-3
milli
m
10
-6
micro
µ
10
-9
nano
n
10
-12
pico
p
10
-15
femto
f
0.000000000000000001 10
-18
atto
a
0.001
0.000001
0.000000001
0.000000000001
0.000000000000001
To multiply like (with same base) exponential quantities, add the exponents. In the language of
algebra the rule is 𝐚𝐚𝐦𝐦 × 𝐚𝐚𝐧𝐧 = 𝐚𝐚𝐦𝐦 + 𝐧𝐧 .
𝟏𝟏𝟏𝟏𝟒𝟒 × 𝟏𝟏𝟏𝟏𝟐𝟐 = 𝟏𝟏𝟏𝟏𝟒𝟒 + 𝟐𝟐 = 𝟏𝟏𝟏𝟏𝟔𝟔
𝟎𝟎. 𝟎𝟎𝟎𝟎𝟎𝟎 × 𝟖𝟖𝟖𝟖𝟖𝟖. 𝟐𝟐 = 𝟑𝟑 × 𝟏𝟏𝟏𝟏−𝟑𝟑 × 𝟖𝟖. 𝟐𝟐𝟐𝟐𝟐𝟐 × 𝟏𝟏𝟏𝟏𝟐𝟐
= 𝟐𝟐𝟐𝟐. 𝟕𝟕𝟕𝟕𝟕𝟕 × 𝟏𝟏𝟏𝟏−𝟏𝟏 = 𝟐𝟐. 𝟒𝟒𝟒𝟒𝟒𝟒𝟒𝟒
To divide exponential quantities, subtract the exponents. In the language of algebra the rule is:
𝐚𝐚𝐦𝐦
= 𝐚𝐚𝐦𝐦−𝐧𝐧 𝐨𝐨𝐨𝐨 𝟏𝟏𝟏𝟏𝟖𝟖 ÷ 𝟏𝟏𝟏𝟏𝟐𝟐 = 𝟏𝟏𝟏𝟏𝟔𝟔
𝐧𝐧
𝟑𝟑, 𝟎𝟎𝟎𝟎𝟎𝟎 ÷ 𝟎𝟎. 𝟎𝟎𝟎𝟎𝟎𝟎 = 𝟎𝟎. 𝟎𝟎𝟎𝟎𝟎𝟎 = (𝟑𝟑 × 𝟏𝟏𝟏𝟏𝟑𝟑 ) ÷ (𝟏𝟏. 𝟓𝟓 × 𝟏𝟏𝟏𝟏−𝟐𝟐 )
= 𝟐𝟐 × 𝟏𝟏𝟏𝟏𝟓𝟓 = 𝟐𝟐𝟐𝟐𝟐𝟐, 𝟎𝟎𝟎𝟎𝟎𝟎
To raise an exponential quantity to a power, multiply the exponents. In the language of algebra:
(𝐱𝐱 𝐦𝐦 )𝐧𝐧 = 𝐱𝐱 𝐦𝐦𝐦𝐦
(𝟏𝟏𝟏𝟏𝟑𝟑 )𝟒𝟒 = 𝟏𝟏𝟏𝟏𝟑𝟑 ×𝟒𝟒 = 𝟏𝟏𝟏𝟏𝟏𝟏𝟏𝟏
𝟐𝟐, 𝟓𝟓𝟓𝟓𝟓𝟓𝟐𝟐 = (𝟐𝟐. 𝟓𝟓 × 𝟏𝟏𝟏𝟏𝟑𝟑 )𝟐𝟐 = 𝟔𝟔. 𝟐𝟐𝟐𝟐 × 𝟏𝟏𝟏𝟏𝟔𝟔 = 𝟔𝟔, 𝟐𝟐𝟐𝟐𝟐𝟐, 𝟎𝟎𝟎𝟎𝟎𝟎
Any number (except zero) raised to the zero power is 1. In the language of algebra:
𝐱𝐱 𝟎𝟎 = 𝟏𝟏
𝐱𝐱 𝟑𝟑 ÷ 𝐱𝐱 𝟑𝟑 = 𝟏𝟏
𝟏𝟏𝟏𝟏𝟒𝟒 ÷ 𝟏𝟏𝟏𝟏𝟒𝟒 = 𝟏𝟏
AII-21
Any base number with a negative exponent is equal to 1 divided by the base with an equal positive
exponent. In the language of algebra:
𝐱𝐱 −𝐚𝐚 =
𝟏𝟏
𝐱𝐱 𝐚𝐚
𝟏𝟏
𝟏𝟏
=
𝟐𝟐
𝟏𝟏𝟏𝟏
𝟏𝟏𝟏𝟏𝟏𝟏
𝟓𝟓
𝟓𝟓𝟓𝟓−𝟑𝟑 = 𝟑𝟑
𝐚𝐚
𝟏𝟏
(𝟔𝟔𝟔𝟔)−𝟏𝟏 =
𝟔𝟔𝟔𝟔
To raise a product to a power, raise each factor of the product to that power.
𝟏𝟏𝟏𝟏−𝟐𝟐 =
(𝟐𝟐 × 𝟏𝟏𝟏𝟏)𝟐𝟐 = 𝟐𝟐𝟐𝟐 × 𝟏𝟏𝟏𝟏𝟐𝟐
𝟑𝟑, 𝟎𝟎𝟎𝟎𝟎𝟎𝟑𝟑 = (𝟑𝟑 × 𝟏𝟏𝟏𝟏𝟑𝟑 )𝟑𝟑 = 𝟐𝟐𝟐𝟐 × 𝟏𝟏𝟏𝟏𝟗𝟗
To find the nth root of an exponential quantity, divide the exponent by the index of the root. Therefore,
𝐦𝐦
the nth root of 𝐚𝐚𝐦𝐦 = 𝐚𝐚 ⁄𝐧𝐧 .
𝟑𝟑
�𝐱𝐱 𝟔𝟔 = 𝐱𝐱
𝟔𝟔�
𝟐𝟐
= 𝐱𝐱 𝟑𝟑
�𝟔𝟔𝟔𝟔 × 𝟏𝟏𝟏𝟏𝟑𝟑 = 𝟒𝟒 × 𝟏𝟏𝟏𝟏 = 𝟒𝟒𝟒𝟒
Joint Electronics Type Designation System
The Joint Electronics Type Designation System (JETDS) was developed to standardize the
identification of electronic material and equipment. There is a three letter designation assigned to
complete sets of electronic equipment that describes where they are used, the type of equipment,
and purpose of that equipment. For example, the designator APG would represent piloted aircraft (A),
radar (P), fire control or searchlight directing (G), or an airborne fire control radar system. The three
letter system is provided as a reference to explain aircraft electronics systems designations and is
shown on the following page in Table AII-3.
AII-22
Table AII-3 — JETDS
Installation Class
Type of Equipment
Purpose
A
Piloted aircraft
A
Invisible light, heat
radiation
A
Auxiliary assembly
B
Underwater mobile,
submarine
B
Communications security
B
Bombing
C
Cryptographic
C
Carrier (electronic
wave/signal)
C
Communications (receiving
and transmitting)
D
Pilotless carrier
D
Radiac
D
Direction finder,
reconnaissance and
surveillance
F
Fixed ground
E
Laser
E
Ejection and/or release
G
General ground use
F
Fiber optics
G
Fire control or searchlight
directing
K
Amphibious
G Telegraph or teletype
H
Recording/reproducing
M
Mobile (ground)
I
Interphone and public
address
K
Computing
P
Portable
J
Electromechanical or
inertial wire covered
M
Maintenance/test
assemblies
S
Water
K
Telemetering
N
Navigational aids
T
Transportable (ground)
L
Countermeasures
Q Special or combination
U
General utility
M Meteorological
R
Receiving/passable
detection
V
Vehicular (ground)
N
Sound in air
S
Detecting/range and
bearing, search
W
Water surface and
underwater combined
P
Radar
T
Transmitting
Z
Piloted-pilotless airborne
vehicles combined
Q
Sonar and underwater
sound
W
Automatic flight or remote
control
R
Radio
X
Identification and
recognition
S
Special or combination
Y
Surveillance (search,
detect, and multiple target
tracking ) and control
T
Telephone (wire)
Z
Secure
V
Visual and visible light
W
Armament (peculiar not
already covered)
X
Facsimile or television
Y
Data processing or
computer
Z
Communications
AII-23
Table AII-4 — Greek Alphabet
Name
Capital
Lower Case
Designation
Alpha
Α
α
Angles, coefficient of thermal expansion
Beta
Β
β
Angles, flux density
Gamma
Γ
γ
Conductivity
Delta
Δ
δ
Variation of quantity, increment
Epsilon
Ε
ε
Base of natural logarithms (2.71828)
Zeta
Ζ
ζ
Impedance, coefficient, efficiency, magnetizing force
Eta
Η
η
Hysteresis coefficient, efficiency, magnetizing force
Theta
Θ
θ
Phase angle
Iota
Ι
ι
Kappa
Κ
κ
Dielectric constant, coupling constant, susceptibility
Lambda
Λ
λ
Wavelength (lower case)
Mu
Μ
μ
Permeability, micro, amplification factor
Nu
Ν
ν
Reluctivity
Xi
Ξ
ξ
Omicron
Ο
ο
Pi
Π
π
3.1416
Rho
Ρ
ρ
Resistivity (lower case)
Sigma
Σ
σ
Summation symbol (capital)
Tau
Τ
τ
Time constant, time-phase displacement
Upsilon
Υ
υ
Phi
Φ
φ
Chi
Χ
Χ
Psi
Ψ
Ψ
Dielectric flux, phase difference
Omega
Ω
ω
Ohms (capital), angular velocity (2 π f)
Angles, magnetic flux
AII-24
APPENDIX III
REFERENCES
NOTE
Although the following references were current when this NRTC was
published, their continued currency cannot be assured. When consulting these
references, keep in mind that they may have been revised to reflect new
technology or revised methods, practices, or procedures; therefore, you need
to ensure that you are studying the latest references.
If you find an incorrect or obsolete reference, please use the Rate Training
Manual User Update Form provided at the end of each chapter to contact the
CNATT Rate Training Manager.
Chapter 1
Interactive Electronic Technical Manual (IETM), A1-F/A-18A/B/C/D.
NATOPS Flight Manual, Navy Model, F/A-18E/F 165533 and Up Aircraft, A1-F18EA-NFM-000,
Commander, Naval Air Systems Command, Patuxent River, MD, 1 December 2012.
Navy Electricity and Electronics Training Series, Module 17—Radio-Frequency Communications
Principles, NAVEDTRA 14189A, Center for Surface Combat Systems, Dahlgren, VA, April 2013.
Chapter 2
Air Navigation, NAVAIR 00-80V-49, Office of the Chief of Naval Operations, Washington, DC, 15
March 1983.
Electronics Installation and Maintenance Book (EIMB), General, NAVSEA SE000-00-EIM-100,
Commander, Naval Sea Systems Command, Washington, DC, April 1983.
Interactive Electronic Technical Manual (IETM), A1-F/A-18A/B/C/D.
Navy Electricity and Electronics Training Series, Module 17—Radio-Frequency Communications
Principles, NAVEDTRA 14189A, Center for Surface Combat Systems, Dahlgren, VA, April 2013.
Chapter 3
Interactive Electronic Technical Manual (IETM), A1-F/A-18A/B/C/D.
Navy Electricity and Electronics Training Series, Module 18—Radar Principles, NAVEDTRA 14190A,
Center for Surface Combat Systems, Dahlgren, VA, April 2013.
Chapter 4
Aviation Electricity and Electronics, Undersea Warfare, NAVEDTRA 14340, Center for Naval Aviation
Technical Training, Pensacola, FL, April 2003.
Integrated Sensor Station 1 and 2, Update III and Block Mod Upgrade Program, Navy Model P-3C
Aircraft, NAVAIR 01-75PAC-2-15, Commander, Naval Air Systems Command, Patuxent River, MD, 1
May 1993, Change 16, 15 September 2013.
AIII-1
Maintenance Instructions, Organizational, Integrated Flight Station Systems, Navy Model P-3C
Aircraft, NAVAIR 01-75PAC-2-9, Commander, Naval Air Systems Command, Patuxent River, MD, 1
May 1993, Change 16, 1 September 2013.
Sonobuoys, Navy Models P-3 (Series), SH-60 (Series), S-3B, P-8A Aircraft and All Navy Vessels,
NAVAIR 28-SSQ-500-1, Commander, Naval Air Systems Command, Patuxent River, MD, Revision 2,
1 October 2011.
Chapter 5
Interactive Electronic Technical Manual (IETM), A1-F/A-18A/B/C/D.
Maintenance Instructions, Organizational, Integrated Flight Station Systems, Navy Model P-3C
Aircraft, NAVAIR 01-75PAC-2-9, Commander, Naval Air Systems Command, Patuxent River, MD, 1
May 1993, Change 16, 1 September 2013.
NATOPS Flight Manual, Navy Model, F/A-18E/F 165533 and Up Aircraft, A1-F18EA-NFM-000,
Commander, Naval Air Systems Command, Patuxent River, MD, 1 December 2012.
Chapter 6
Interactive Electronic Technical Manual (IETM), A1-F/A-18A/B/C/D.
Interactive Electronic Technical Manual (IETM), A1-F/A-18E/F/G.
NATOPS Flight Manual, Navy Model, F/A-18E/F 165533 and Up Aircraft, A1-F18EA-NFM-000,
Commander, Naval Air Systems Command, Patuxent River, MD, 1 December 2012.
Chapter 7
Airborne Weapons/Stores Loading Manual, Navy Model F/A-18E/F and EA-18G Aircraft, A1-F18EALWS-000, Commander, Naval Air Systems Command, Patuxent River, MD, 1 January 2014.
Airborne Weapons/Stores Loading Manual, Navy Model MH-60R Helicopter, A1-H60RA-LWS-000,
Commander, Naval Air Systems Command, Patuxent River, MD, 1 December 2014.
Airborne Weapons/Stores Loading Manual, Navy Model P-3 Aircraft, NAVAIR 01-75PAC-75,
Commander, Naval Air Systems Command, Patuxent River, MD, 1 September 2014.
Aviation Ordnanceman, NAVEDTRA 14313A, Center for Naval Aviation Technical Training,
Pensacola, FL, March 2011.
Chapter 8
Installation and Repair Practices, Aircraft Fiber Optic Cabling, NAVAIR 01-1A-505-4, TO 1-1A-14-4,
TM 1-1500-323-24-4, Commander, Naval Air Systems Command, Patuxent River, MD, 13 August
2012.
Interactive Electronic Technical Manual (IETM), A1-F/A-18A/B/C/D.
Navy Electricity and Electronics Training Series, Module 22—Digital Computing, NAVEDTRA
14194A, Center for Surface Combat Systems, Dahlgren, VA, May 2013.
Navy Electricity and Electronics Training Series, Module 24—Fiber Optics, NAVEDTRA 14196A,
Center for Surface Combat Systems, Dahlgren, VA, June 2014.
AIII-2
Chapter 9
Aeronautical Information Manual, U.S. Department of Transportation, Federal Aviation Administration,
Washington, DC, 3 April 2014.
CV NATOPS Manual, NAVAIR 00-80T-105, Commander, Naval Air Systems Command, Patuxent
River, MD, 15 September 2013.
Fundamentals of Aviation and Space Technology, Institute of Aviation, University of Illinois, Savoy, IL,
1974.
Interactive Electronic Technical Manual (IETM), A1-F/A-18A/B/C/D.
NATOPS Flight Manual, Navy Model, F/A-18A/B/C/D 161353 and Up Aircraft, A1-F18AC-NFM-000,
Commander, Naval Air Systems Command, Patuxent River, MD, 1 December 2012.
NATOPS Flight Manual, Navy Model, F/A-18E/F 165533 and Up Aircraft, A1-F18EA-NFM-000,
Commander, Naval Air Systems Command, Patuxent River, MD, 1 December 2012.
Chapter 10
Electronics Installation and Maintenance Book (EIMB), General Maintenance, NAVSEA SE000-00EIM-160, Commander, Naval Sea Systems Command, Washington, DC, January 1981.
Electronics Installation and Maintenance Book (EIMB), General, NAVSEA SE000-00-EIM-100,
Commander, Naval Sea Systems Command, Washington, DC, April 1983.
Installation and Repair Practices, Volume 1, Aircraft Electric and Electronic Wiring, NAVAIR 01-1A505, TO 1-1A-14, TM 1-1500-323-24-1, Commander, Naval Air Systems Command, Patuxent River,
MD, 15 April 2014.
AIII-3
APPENDIX IV
Answers to End of Chapter Questions
Chapter 1 ─ Communications
1-1.
B
1-13.
D
1-25.
B
1-2.
C
1-14.
A
1-26.
D
1-3.
D
1-15.
B
1-27.
A
1-4.
A
1-16.
A
1-28.
D
1-5.
B
1-17.
D
1-29.
C
1-6.
A
1-18.
B
1-30.
B
1-7.
C
1-19.
C
1-31.
A
1-8.
D
1-20.
B
1-32.
D
1-9.
A
1-21.
C
1-33.
D
1-10.
D
1-22.
D
1-34.
A
1-11.
B
1-23.
A
1-35.
C
1-12.
C
1-24.
C
1-36.
C
Chapter 2 ─ Navigation
2-1.
B
2-8.
A
2-15.
D
2-2.
C
2-9.
C
2-16.
C
2-3.
A
2-10.
D
2-17.
B
2-4.
D
2-11.
A
2-18.
C
2-5.
C
2-12.
C
2-19.
A
2-6.
B
2-13.
B
2-20.
C
2-7.
D
2-14.
C
AIV-1
Chapter 3 ─ Radar
3-1.
C
3-21.
D
3-41.
C
3-2.
B
3-22.
D
3-42.
A
3-3.
D
3-23.
A
3-43.
D
3-4.
A
3-24.
C
3-44.
A
3-5.
B
3-25.
D
3-45.
D
3-6.
D
3-26.
A
3-46.
C
3-7.
C
3-27.
B
3-47.
A
3-8.
C
3-28.
C
3-48.
B
3-9.
A
3-29.
B
3-49.
C
3-10.
B
3-30.
A
3-50.
A
3-11.
D
3-31.
D
3-51.
C
3-12.
A
3-32.
A
3-52.
B
3-13.
C
3-33.
D
3-53.
A
3-14.
D
3-34.
C
3-54.
D
3-15.
C
3-35.
A
3-55.
D
3-16.
A
3-36.
C
3-56.
C
3-17.
D
3-37.
D
3-57.
B
3-18.
B
3-38.
B
3-58.
D
3-19.
C
3-39.
A
3-59.
C
3-20.
B
3-40.
B
AIV-2
Chapter 4 ─ Antisubmarine Warfare
4-1.
A
4-16.
B
4-31.
C
4-2.
C
4-17.
D
4-32.
D
4-3.
B
4-18.
B
4-33.
C
4-4.
A
4-19.
C
4-34.
A
4-5.
B
4-20.
B
4-35.
C
4-6.
C
4-21.
B
4-36.
B
4-7.
B
4-22.
C
4-37.
A
4-8.
D
4-23.
A
4-38.
C
4-9.
A
4-24.
B
4-39.
A
4-10.
B
4-25.
D
4-40.
B
4-11.
C
4-26.
B
4-41.
A
4-12.
B
4-27.
A
4-42.
C
4-13.
A
4-28.
C
4-43.
D
4-14.
C
4-29.
D
4-44.
A
4-15.
D
4-30.
A
Chapter 5 ─ Indicators
5-1.
A
5-7.
A
5-13.
C
5-2.
C
5-8.
D
5-14.
B
5-3.
D
5-9.
B
5-15.
A
5-4.
B
5-10.
C
5-16.
C
5-5.
C
5-11.
A
5-17.
D
5-6.
D
5-12.
B
5-18.
C
AIV-3
Chapter 6 ─ Infrared
6-1.
B
6-11.
C
6-21.
B
6-2.
C
6-12.
D
6-22.
D
6-3.
D
6-13.
B
6-23.
D
6-4.
A
6-14.
C
6-24.
B
6-5.
D
6-15.
C
6-25.
C
6-6.
A
6-16.
A
6-26.
D
6-7.
D
6-17.
B
6-27.
C
6-8.
A
6-18.
B
6-28.
D
6-9.
B
6-19.
C
6-29.
A
6-10.
A
6-20.
D
6-30.
D
Chapter 7 ─ Weapons Systems
7-1.
A
7-11.
C
7-21.
A
7-2.
C
7-12.
B
7-22.
C
7-3.
B
7-13.
D
7-23.
D
7-4.
D
7-14.
B
7-24.
D
7-5.
B
7-15.
A
7-25.
B
7-6.
D
7-16.
C
7-26.
D
7-7.
A
7-17.
D
7-27.
A
7-8.
D
7-18.
B
7-28.
D
7-9.
B
7-19.
B
7-10.
A
7-20.
C
AIV-4
Chapter 8 ─ Computers
8-1.
D
8-15.
B
8-29.
A
8-2.
C
8-16.
C
8-30.
B
8-3.
A
8-17.
A
8-31.
D
8-4.
D
8-18.
D
8-32.
B
8-5.
C
8-19.
B
8-33.
A
8-6.
C
8-20.
B
8-34.
C
8-7.
B
8-21.
C
8-35.
B
8-8.
A
8-22.
D
8-36.
A
8-9.
D
8-23.
B
8-37.
B
8-10.
B
8-24.
C
8-38.
C
8-11.
A
8-25.
B
8-39.
B
8-12.
D
8-26.
A
8-40.
C
8-13.
C
8-27.
C
8-14.
B
8-28.
D
Chapter 9 ─ Automatic Carrier Landing System/Instrument Landing System
9-1.
A
9-10.
A
9-19.
B
9-2.
B
9-11.
D
9-20.
A
9-3.
D
9-12.
D
9-21.
B
9-4.
A
9-13.
B
9-22.
D
9-5.
D
9-14.
C
9-23.
C
9-6.
C
9-15.
D
9-24.
B
9-7.
B
9-16.
A
9-25.
B
9-8.
A
9-17.
A
9-9.
B
9-18.
D
AIV-5
Chapter 10 ─ Electrostatic Discharge
10-1.
B
10-16.
A
10-31.
D
10-2.
A
10-17.
C
10-32.
A
10-3.
C
10-18.
A
10-33.
D
10-4.
B
10-19.
C
10-34.
A
10-5.
A
10-20.
B
10-35.
B
10-6.
C
10-21.
C
10-36.
D
10-7.
B
10-22.
B
10-37.
C
10-8.
D
10-23.
B
10-38.
B
10-9.
A
10-24.
B
10-39.
B
10-10.
D
10-25.
D
10-40.
C
10-11.
B
10-26.
C
10-41.
D
10-12.
B
10-27.
A
10-42.
D
10-13.
A
10-28.
D
10-43.
B
10-14.
C
10-29.
B
10-44.
C
10-15.
D
10-30.
A
10-45.
C
AIV-6
INDEX
A
A/A weapons, 7-3
AIM-120 advanced medium-range air-to-air missile (AMRAAM), 7-3
AIM-7 Sparrow, 7-3
AIM-9 Sidewinder series, 7-3
A/G weapons, 7-4
AGM-114 Hellfire, 7-5
AGM-65 Maverick, 7-5
AGM-88 high-speed anti-radiation missile, 7-4
guided bomb units, 7-4
torpedoes, 7-5
Absorption and scattering, 4-3
Accelerometers, 2-15
Acoustic processing , 4-14 to 4-15
Active and passive sonar, 4-1
Active sonobuoys, 4-12
Advanced targeting forward looking infrared (ATFLIR) operational capabilities, 6-11
advanced navigation, 6-13
built-in test, 6-13
electro-optical video, 6-12
eyesafe, 6-13
field of view and zoom, 6-12
infrared marker, 6-13
infrared video, 6-11
initiated built-in-test, 6-14
laser and FLIR align, 6-12
laser energy, 6-12
laser range, 6-12
laser spot tracker, 6-13
operational built-in test, 6-14
periodic built-in test, 6-14
pod environmental control unit, 6-13
point control, 6-12
track control, 6-12
Airborne navigation systems, 2-11 to 2-17
Airborne radar, 3-10
Airborne sonar system, 4-15 to 4-18
azimuth-range indicator, 4-16
cable and reel assembly, 4-17
dome control, 4-16
modes of operation, 4-17
multiplexer, 4-16
reeling machine, 4-17
sonar data computer, 4-16
sonar receiver, 4-16
sonar transducer, 4-17
Aircraft automatic carrier landing system components, 9-4
Index-1
angle-of-attack indicator, 9-7
automatic flight control system, 9-6
instrument landing system, 9-4
radar beacon, 9-7
receiving-decoding group, 9-7
standby attitude reference indicator, 9-5
Aircraft carrier automatic carrier landing system components, 9-4
SPN-41 instrument carrier landing system, 9-4
SPN-46 (V) 3 precision approach landing system, 9-4
Aircraft communications systems, 1-12 to 1-17
Aircraft global positioning systems, 2-13
Aircraft identification friend or foe systems, 3-18
Aircraft radar systems, 3-10 to 3-17
Aircraft tactical displays, 5-13
Airfoil, 9-1 to 9-2
airfoil terminology, 9-1
Air-to-air (A/A) master mode, 5-10
Air-to-ground (A/G) master mode, 5-9
Altimeters, 2-8
absolute (radar) altimeters, 2-10
pressure altimeter, 2-9
Altitude and atmosphere, 2-6
planes of altitude, 2-8
standard datum plane, 2-6
Amplitude modulated receiver, 1-10
Amplitude modulated transmitter, 1-6
Anomaly strength, 4-21
Antisubmarine warfare, 4-1
APG-73 radar system, 3-10
components, 3-10
controls and indicators, 3-11
modes of operation, 3-12
APN-234 color weather radar system, 3-16
components, 3-16
controls and indicators, 3-16
modes of operation, 3-16
Application of capacitive filters, 10-13
bandpass filters, 10-16
band-rejection filters, 10-17
capacitive filtering in an alternating current circuit, 10-13
high-pass filters, 10-16
inductive-capacitive filters, 10-15
low-pass filters, 10-15
resistive-capacitive filters, 10-14
Approach radar, 3-9
APX-123(V) IFF transponder system, 3-18
components, 3-18
modes of operation, 3-18
ARC-210 communication system, 1-12
antenna selector, 1-13
ANT-SEL COMM 1 switch, 1-13
Index-2
communications antennas, 1-13
VHF/UHF receiver/transmitter no. 1 and no. 2, 1-12
ARR-78(V) advanced sonobuoy communication link receiver set, 4-13
indicator-control unit, 4-14
on top position indicator control unit, 4-14
radiofrequency preamplifier, 4-13
radiofrequency status panel, 4-14
receiver assembly, 4-13
ASQ-22 airborne low frequency sonar, 4-18
ATFLIR system components, 6-7
advanced navigation sensor, 6-9
electro-optical sensor unit, 6-8
environmental control valve, 6-8
eurocard modules, 6-8
laser electronics unit, 6-9
laser transceiver unit, 6-9
pod adapter unit, 6-9
pod electronics housing, 6-10
power interrupt protector, 6-10
roll drive amplifier, 6-10
roll drive motor, 6-10
roll drive unit, 6-11
Atmospheric static, 10-2
Automatic carrier landing system, 9-1
components, 9-4 to 9-8
operation, 9-8 to 9-11
Automatic direction finder, 2-11
B
Basic computers, 8-1 to 8-6
analog, 8-5
digital, 8-5
Basic transmitter and receiver terms, 1-4
antenna, 1-4
attenuation, 1-5
fading, 1-5
harmonics,
microphone, 1-5
oscillator, 1-5
speaker, 1-5
subharmonics, 1-6
suppression, 1-5
tuned circuits, 1-5
varactors, 1-5
Beam scanning, 3-8
Bonding, 10-17 to 10-19
bonding for lightning protection, 10-18
purpose of bonding, 10-18
Broadband interference, 10-3
Index-3
C
Capacitive filter, application, 10-13
Capacitor selection, 10-13
Capacitors, 10-10
coaxial feedthrough capacitors, 10-11
function, 10-10
limitation, 10-11
Common weapons, 7-1
Communications, 1-1
Complex coupling, 10-10
Computer applications, 8-4
business, 8-4
database, 8-4
process control, 8-4
simulation, 8-4
Computer functions, 8-3
display data, 8-4
disseminate data, 8-4
gather data, 8-3
process data, 8-4
store data, 8-4
Computer terms, 8-1
Computers, 8-1
Conductive coupling, 10-8
Continuous wave, 3-7
Control segment, 2-14
Cosmic noise, 10-3
Coupling by radiation, 10-10
D
Data link, 1-16
A507 data terminal set communications interface 2, 1-17
C-7790A data terminal set control-monitor, 1-17
CV-2528 data terminal set convertor-control, 1-17
PP-6140 data terminal set power supply, 1-17
Data transmission, 8-7 to 8-10
Detectors, 6-4
elemental detectors, 6-4
imaging detectors, 6-4
Digital communications system, 1-14
Digital data indicators, 5-14
Digital data transmission, 8-8
fiber optic, 8-9
parallel mode, 8-9
serial mode, 8-8
Direction, 2-2, 2-5
Direction-finder group, 5-2
Distance, 2-2, 2-5
Divergence, 4-5
Doppler effect, 3-7, 4-7
Index-4
Doppler effect and sonar, 4-7
Drag, 9-2
E
Earth's size and shape, 2-2 to 2-11
Electrical communications, 1-1
facsimile, 1-2
radiotelegraph, 1-1
radiotelephone, 1-2
teletypewriter, 1-2
Electrical noise, 10-4 to 10-8
nonlinear elements, 10-8
power-lines, 10-8
sources of, 10-4 to 10-8
Electromagnetic spectrum, 6-1
Electronic flight director system components, 5-3
electronic flight director systems control, 5-3
multifunction displays, 5-3
Electronic flight display system, 5-1 to 5-7
Electronic flight display system interfaces, 5-1 to 5-3
Electronic horizontal situation indicator, 5-1
digital data computer, 5-2
direction finder group, 5-2
global positioning system, 5-2
inertial navigation system, 5-2
low frequency automatic direction finder group, 5-2
multi-mode receiver, 5-2
navigation simulator, 5-2
tactical air navigation set, 5-2
Electrostatic discharge, 10-1, 10-19 to 10-21
Electrostatic discharge elimination, 10-21
Electrostatic discharge protective materials, 10-22
antistatic electrostatic discharge protective materials, 10-22
conductive electrostatic discharge protective materials, 10-22
hybrid electrostatic discharge protective materials, 10-22
Electrostatic discharge sensitive device handling, 10-23
Electrostatic discharge sensitive device packaging, 10-23
Energy-matter interaction, 6-4
alternating current generators and motors, 10-4
direct current motors, 10-4
inverters, 10-5
photon effect, 6-4
propeller systems, 10-6
pulsed electrical equipment, 10-6
radar, 10-6
receiver oscillators, 10-7
relays, 10-5
rotating electrical machines, 10-4
switching devices, 10-5
thermal effect, 6-4
thyratrons, 10-6
Index-5
transponders, coded-pulse equipment, and beacons, 10-6
F
F/A-18 mission computer system, 8-12 to 8-19
control-convertor, 8-14
digital data computers, 8-13
electronic equipment control, 8-15
MC/HYD ISOL control panel assembly, 8-16
right and left mux bus impedance matching networks, 8-16
systems components, 8-12
F/A-18E/F Super Hornet, 7-5 to 7-11
A/A missile control systems, 7-9
A/G weapons control systems, 7-9
armament computer, 7-6
armament safety override switch, 7-6
armament subsystems, 7-8
armament system basic controls, 7-5
armament system circuit breakers, 7-6
cockpit basic controls, 7-7
digital display indicators, 7-7, 7-8
gun systems controls, 7-11
head-up display, 7-8
integrated defensive electronic countermeasures dispensing systems, 7-11
jettison systems, 7-10
landing gear control panel, 7-6
left- and right-hand controllers, 7-8
master arm control panel, 7-8
mission computers, 7-6, 8-12 to 8-19
rear advisory and threat warning indicator panel, 7-8
rear cockpit basic controls, 7-8
signal data converter control, 7-7
up-front control display, 7-8
Facsimile, 1-2
Factors affecting the sound wave, 4-3
Forces affecting flight, 9-2
drag, 9-2
lift, 9-2
thrust, 9-2
weight, 9-2
Forward looking infrared system, 6-7 to 6-14
Frequency modulated receiver, 1-11
Frequency modulated transmitter, 1-7
Frequency modulation, 3-7
Front-end optics, 6-6
G
General computer terms, 8-1
hardware, 8-1
software, 8-2
Global positioning system, 2-13, 5-2
aircraft GPS, 2-14
Index-6
control segment, 2-14
space segment, 2-13
user segment, 2-14
Great circles, 2-2
H
Head-up display, 5-7 to 5-13
altitude switch, 5-8
attitude switch, 5-8
controls and indicators, 5-7
course set switch, 5-8
day/auto/night switch, 5-8
heading set switch, 5-8
modes of operation, 5-8
symbology brightness control, 5-8
symbology normal/reject 1/reject 2 switch, 5-8
I
Identification friend or foe, 3-17 to 3-19
modes of operation, 3-17
system components, 3-17
systems principles, 3-17 to 3-19
Image processing system, 6-6
Indicators, 5-1
Inductive-capacitive coupling, 10-10
Inductive-magnetic coupling, 10-9
Inertial navigation system, 2-14, 5-3
accelerometers, 2-15
alignment, 2-16
basic components, 2-14
inertial corrections, 2-15
Infrared, 6-1
Infrared imaging systems, 6-5
detector array, 6-5
detectors, 6-5
front-end optics, 6-6
image processing system, 6-6
refrigeration system, 6-6
scene dissection system, 6-5
single detector, 6-5
Infrared radiation, 6-2 to 6-7
optics, 6-3
sources, 6-2
Instrument landing system, 9-1
Intercommunication system, 1-15
COMM CONT panel, 1-16
intercommunication amplifier-control, 1-16
Interference coupling, 10-8 to 10-10
Index-7
L
Landing sequence, 9-8
mode I landing operation, 9-9
safety provisions, 9-10
Lateral axis, 9-3
Latitude, 2-3
direction, 2-5
distance, 2-4
latitude, 2-3
longitude, 2-3
Left digital data indicator, 5-14
Lift, 9-2
Longitude, 2-3
Longitudinal axis, 9-3
Low frequency automatic direction finder group, 5-3
M
Magnetic anomaly, 4-19
Magnetic anomaly detection, 4-19 to 4-25
Magnetic detection principles, 4-19
Maneuver noises, 4-22
Man-made interference, 10-3
broadband interference, 10-3
narrow band interference, 10-4
MH-60R Seahawk, 7-15 to 7-19
AGM-114 Hellfire missile control system, 7-18
armament control indicator, 7-16
armament subsystems, 7-17
armament system basic controls, 7-16
cockpit basic controls, 7-16
control indicator, 7-17
data handling system, 7-16
defensive countermeasure system, 7-19
disabling switch for armament safety circuit, 7-16
jettison system, 7-19
mission displays, 7-17
primary mission and flight computer, 7-16
processing interface unit, 7-16
sensor operator station basic controls, 7-17
sonobuoy launch system, 7-17
stores management system, 7-16
torpedo release system, 7-17
weight-on-wheels switch, 7-16
Missile guidance radar, 3-9
Mission computer system interface, 8-16
avionics mux channel 1, 8-16
avionics mux channel 2, 8-16
avionics mux channel 3, 8-17
avionics mux channel 4, 8-17
avionics mux channel 5, 8-17
Index-8
avionics mux channel 6, 8-17
control-convertor channel, 8-17
electronic equipment control interface, 8-18
Multifunctional information distribution system, 1-14
fixed notch filter, 1-15
radio terminal unit, 1-14
remote power supply, 1-15
switchable notch filter, 1-15
Multi-mode radar system, 3-14
components, 3-14
controls and indicators, 3-15
modes of operation, 3-15
Multi-mode receiver, 5-2
Multipurpose color display, 5-15
Multipurpose display group, 5-13
N
Narrow band interference, 10-4
Natural interference, 10-2
atmospheric static, 10-2
precipitation static, 10-2
cosmic noise, 10-3
Navigation, 2-1
Navigation master mode, 5-9
Navigation simulator, 5-2
Navigational terms, 2-1 to 2-2
direction, 2-2
distance, 2-2
position, 2-1
time, 2-2
Navy frequency band use, 1-2 to 1-4
medium frequency (MF) and high frequency (HF) band communications, 1-3
very high frequency (VHF) and ultrahigh frequency (UHF) band communications, 1-4
very low frequency (VLF) and low frequency (LF) band communications, 1-3
Nonlinear elements, 10-8
P
P-3 Orion, 7-12 to 7-15
aft interconnection box A269, 7-13
armament circuit breaker panel, 7-13
armament control box, 7-13
armament safety circuit disable switch, 7-13
armament subsystems, 7-13
armament systems basic controls, 7-12
defensive countermeasures, 7-15
forward interconnection box A395, 7-13
harpoon system basic controls, 7-14
jettison system, 7-15
maverick missile control system basic controls, 7-14
pilot armament control panel, 7-12
torpedo system basic controls, 7-14
Index-9
weapons release switch, 7-13
Passive sonobuoys, 4-11
Peripheral avionics systems, 8-11
data link, 8-12
navigation, 8-11
radar, 8-11
weapons, 8-11
Peripheral devices, 8-6
Personal apparel and grounding, 10-21 to 10-22
personnel ground straps, 10-22
smocks, 10-22
Planes of altitude, 2-8
Position, 2-1
Power-lines, 10-8
Precipitation static, 10-2
Prime generators, 10-21
Principles of magnetic detection, 4-19
anomaly strength, 4-21
compensation, 4-23
direct current circuit noise, 4-23
magnetic anomaly, 4-19
maneuver noises, 4-22
submarine anomaly, 4-21
Propeller systems, 10-6
Pulse modulation, 3-7
Pulsed electrical equipment, 10-6
radar, 10-6
transponders, coded-pulse equipment, and beacons, 10-6
Pulse-doppler, 3-7
R
Radar, 3-1
Radar accuracy, 3-4
atmospheric conditions, 3-4
pulse shape, 3-4
Radar altimeters, 2-10
Radar bearing, 3-3
relative bearing, 3-4
true bearing, 3-4
Radar principles and operation, 3-1 to 3-10
Radar range, 3-2
maximum range, 3-3
minimum range, 3-3
Radar resolution, 3-4
bearing resolution, 3-4
range resolution, 3-4
target resolution, 3-4
Radar system components, 3-5
antenna, 3-6
duplexer, 3-6
indicator, 3-6
Index-10
power supply, 3-6
receiver, 3-6
synchronizer, 3-5
transmitter, 3-6
Radio communications, 1-1
Radio interference reduction components, 10-10 to 10-16
application of capacitive filters, 10-13
bandpass filters, 10-16
band-rejection filters, 10-17
capacitive filtering in an alternating current circuit, 10-13
capacitors, 10-10
coaxial feedthrough capacitors, 10-11
high-pass filters, 10-16
inductive-capacitive filters, 10-15
low-pass filters, 10-15
resistive-capacitive filters, 10-14
selection of capacitors, 10-13
Radio receiver characteristics and components, 1-9
characteristics, 1-9
components, 1-9
Radio receiver types, 1-10 to 1-11
amplitude modulation receiver, 1-10
frequency modulation receiver, 1-11
Radio receivers, 1-9
detection, 1-9
reception, 1-9
reproduction, 1-9
selection, 1-9
Radio transmitter and receiver fundamentals, 1-4
Radio transmitter types, 1-6 to 1-8
amplitude modulation transmitter, 1-6
frequency modulation transmitter, 1-7
single sideband transmitter, 1-7
Radiofrequency transmission methods, 3-6
continuous wave, 3-7
frequency modulation, 3-7
pulse modulation, 3-7
pulse-doppler, 3-7
Radiotelegraph, 1-1
Radiotelephone, 1-2
Receiver noise, 10-2 to 10-4
Receiver oscillators, 10-7
Reflection, 4-3
Refraction, 4-6
Refrigeration system, 6-6
Reverberation, 4-4
Right digital data indicator, 5-14
Rotating electrical machines, 10-4
alternating current generators and motors, 10-4
direct current motors, 10-4
inverters, 10-5
Index-11
Rotational axes, 9-3
lateral axis, 9-3
longitudinal axis, 9-3
vertical axis, 9-3
S
Salinity, 4-6
Scanning methods, 3-8
beam scanning, 3-8
stationary-lobe scanning, 3-8
Scene dissection system, 6-5
Search radar, 3-8
Selection of capacitors, 10-13
Single detector, 6-5
Single sideband transmitter, 1-7
Small circles, 2-2
Sonar principles, 4-1 to 4-8
absorption and scattering, 4-3
active and passive sonar, 4-1
divergence, 4-5
Doppler effect, 4-7
Doppler effect and sonar, 4-7
factors affecting the sound wave, 4-3
reflection, 4-3
refraction, 4-6
reverberation, 4-4
salinity, 4-6
temperature, 4-5
transducers, 4-2
Sonobuoy classifications, 4-11
active sonobuoys, 4-12
passive sonobuoys, 4-11
special-purpose sonobuoys, 4-13
Sonobuoy receivers, 4-13 to 4-14
Sonobuoys, 4-8 to 4-13
deployment, 4-10
description and components, 4-8
external markings, 4-9
frequency channels, 4-9
operating life, 4-11
principles of operation, 4-9
water entry and activation, 4-10
Sound wave, 4-3
Space segment, 2-13
Special-purpose sonobuoys, 4-13
Standard datum plane, 2-6
Static electricity, 10-20
causes of static electricity, 10-20
component susceptibility, 10-21
effects of static electricity, 10-21
latent failure mechanisms, 10-21
Index-12
Stationary-lobe scanning, 3-8
Submarine anomaly, 4-21
Switching devices, 10-5
relays, 10-5
thyratrons, 10-6
T
Tactical air navigation, 2-11
bearing and distance information, 2-12
radiation pattern, 2-12
tactical air navigation principles, 2-12
tactical air navigation pulse-pairs, 2-12
Tactical air navigation set, 5-2
Teletypewriter, 1-2
Temperature, 4-2
Thermal imaging, 6-2
Thrust, 9-2
Time, 2-2
Tracking radar, 3-9
Transducers, 4-2
Transmitter and receiver fundamentals, 1-4 to 1-12
U
User segment, 2-14
UYS-1 single advanced signal processor system, 4-14
control-indicator, 4-15
power supply, 4-15
spectrum analyzer, 4-15
V
Vertical axis, 9-3
W
Weapons guidance and control, 7-1
active, 7-1
passive, 7-2
semi-active, 7-2
Weapons systems, 7-1
Weight, 9-2
Index-13
End of Book Questions Chapter 1
Communications
1-1.
What type of communication is relatively slow and requires experienced operators?
A.
B.
C.
D.
1-2.
What type of communication is susceptible to wave propagation characteristics?
A.
B.
C.
D.
1-3.
Teletypewriter
Radiotelephone
Facsimile
Radiotelegraph
Other than commercial broadcasting stations, what other frequencies are included in the
medium and high frequency bands?
A.
B.
C.
D.
1-6.
Photoreactive
Photoemissive
Photoelectric
Photoconductive
What type of communication system is used for high-speed automatic communications across
oceans?
A.
B.
C.
D.
1-5.
Teletypewriter
Radiotelephone
Facsimile
Radiotelegraph
What type of cell is used by a facsimile system to scan an image?
A.
B.
C.
D.
1-4.
Teletypewriter
Radiotelephone
Facsimile
Radiotelegraph
Guard receive
International distress
Radio telegraphy
Frequency broadcasting
Other than very low frequency, what frequency band was originally used for radio telegraphy?
A.
B.
C.
D.
High
Low
Very low
Ultra low
1-7.
Other than medium frequency, what frequency band includes international distress
frequencies?
A.
B.
C.
D.
1-8.
At what distance above the earth does the ionosphere begin, in miles?
A.
B.
C.
D.
1-9.
Low
High
Very high
Ultra high
17
27
37
47
The characteristics of the ionosphere vary the most during what hours?
A.
B.
C.
D.
Day
Evening
Twilight
Night
1-10. What characteristic of a facsimile scanning cell is varied according to the light and dark areas
of an image?
A.
B.
C.
D.
Thermal
Photo
Electrical
Mechanical
1-11. What component must have the ability to filter unwanted transmissions?
A.
B.
C.
D.
Transmitter
Receiver
Antenna
Speaker
1-12. What term describes the variation of signal strength at the receiver?
A.
B.
C.
D.
Suppression
Attenuation
Varactor
Fading
1-13. What device converts sound energy into electrical energy?
A.
B.
C.
D.
Speaker
Microphone
Antenna
Oscillator
1-14. What component is a semiconductor diode used to vary frequency outputs?
A.
B.
C.
D.
Varactor
Antenna
Oscillator
Crystal
1-15. What frequency is also known as the fundamental frequency?
A.
B.
C.
D.
Advanced
Combined
Basic
Single
1-16. What type of transmitter varies the radiofrequency output to the proportion of the modulating
signal?
A.
B.
C.
D.
Frequency modulating
Amplitude modulating
Single sideband
Radar
1-17. What component of a frequency modulating transmitter is used to vary the frequency of the
modulating signal?
A.
B.
C.
D.
Varactor
Oscillator
Antenna
Microphone
1-18. What single sideband transmitter component creates the upper sideband?
A.
B.
C.
D.
Amplifier
Multiplier
Generator
Filter
1-19. What frequency modulating transmitter component increases a signal to the desired
transmission output level?
A.
B.
C.
D.
Amplifier
Multiplier
Generator
Filter
1-20. What term can describe heterodyning?
A.
B.
C.
D.
Separating
Mixing
Isolating
Dividing
1-21. What process occurs when a receiver separates an audio signal from a radiofrequency signal?
A.
B.
C.
D.
Reception
Reproduction
Selection
Detection
1-22. What process occurs when a receiver converts an electrical signal into an audio signal?
A.
B.
C.
D.
Reception
Reproduction
Selection
Detection
1-23. What term describes a receiver’s ability to replicate an input signal?
A.
B.
C.
D.
Sensitivity
Noise
Fidelity
Selectivity
1-24. What component of an amplitude modulating receiver filters the intermediate frequency?
A.
B.
C.
D.
Detector
Amplifier
Mixer
Antenna
1-25. What component of a frequency modulating receiver combines the radiofrequency and local
oscillator signals?
A.
B.
C.
D.
Discriminator
Limiter
Mixer
Amplifier
1-26. What ARC-210 component is a radiofrequency switching unit?
A.
B.
C.
D.
Receiver-transmitter
Antenna selector
ANT-COMM 1 switch
Data link
1-27. What multifunctional information distribution system component limits the number of
transmitted tactical air navigation channels?
A.
B.
C.
D.
Remote power supply
Fixed notch filter
Switchable notch filter
Radio terminal unit
1-28. What multifunctional information distribution system component provides secure and plain
voice communications?
A.
B.
C.
D.
Remote power supply
Fixed notch filter
Switchable notch filter
Radio terminal unit
1-29. What frequency in megahertz is the guard frequency?
A.
B.
C.
D.
108.00
118.00
121.50
225.00
1-30. What ARC-210 frequency mode allows the operator to select 57 preset channels?
A.
B.
C.
D.
Fixed
Maritime
Anti-jam
Havequick
1-31. What ARC-210 frequency mode provides jam resistant ultrahigh frequency band
communications?
A.
B.
C.
D.
Havequick
Maritime
Fixed
Guard
1-32. What aircraft communications system is used to lower the operator’s workload during close air
support missions?
A.
B.
C.
D.
Analog communications
Digital communications
Voice communications
Multifunctional information distribution
1-33. A brief containing how many lines of text is provided to the operator to decrease
miscommunication during a close air support mission?
A.
B.
C.
D.
3
6
9
11
1-34. What multifunctional information distribution system function improves the navigation accuracy
of the host aircraft?
A.
B.
C.
D.
Secure data link
Secure voice
Tactical navigation
Relative navigation
1-35. What function of the multifunctional information distribution system allows participants to
exchange real time tactical data?
A.
B.
C.
D.
Data link
Secure voice
Relative navigation
Tactical air navigation
1-36. What system provides the intercommunication amplifier-control with secure voice audio?
A.
B.
C.
D.
Identification friend or foe
Landing gear
Stores management
Multifunctional information distribution
End of Book Questions Chapter 2
Navigation
2-1.
What is the navigational term for a location defined by stated or implied coordinates?
A.
B.
C.
D.
2-2.
At the equator, the diameter of the Earth is how many nautical miles?
A.
B.
C.
D.
2-3.
Two
Four
Six
Eight
Latitude is measured up to what maximum number of degrees?
A.
B.
C.
D.
2-6.
Axis
Quadrant
Apogee
Meridian
Meridians are divided into how many sections?
A.
B.
C.
D.
2-5.
6,750.25
6,864.57
6,887.91
6,950.78
What geographic term describes a great circle drawn through the north and south poles?
A.
B.
C.
D.
2-4.
Time
Position
Distance
Direction
30
60
90
180
Longitude is measured up to what maximum number of degrees?
A.
B.
C.
D.
30
60
90
180
2-7.
What unit is a subdivision of degree of arc?
A.
B.
C.
D.
2-8.
One minute of arc on the earth’s equator is equal to how many nautical miles?
A.
B.
C.
D.
2-9.
Nanoseconds
Minutes
Microseconds
Milliseconds
1
2
3
4
What factor determines the rate of change in position?
A.
B.
C.
D.
Height
Speed
Direction
Course
2-10. Compass roses are divided into how many degrees?
A.
B.
C.
D.
30
90
180
360
2-11. In the numerical system of navigation, what numerical value represents north?
A.
B.
C.
D.
000
090
180
270
2-12. What true direction is defined as the horizontal direction of one point to another?
A.
B.
C.
D.
Course
Heading
Bearing
Track
2-13. What true direction is defined as the horizontal direction in which an aircraft is pointed?
A.
B.
C.
D.
Course
Heading
Bearing
Track
2-14. What is the pressure, in inches of mercury, at 0 feet in the standard atmosphere?
A.
B.
C.
D.
26.82
27.82
28.86
29.92
2-15. What altitude reference plane is defined as pressure altitude corrected for temperature?
A.
B.
C.
D.
Calibrated
Density
Pressure
True
2-16. What altitude reference plane is defined as the actual vertical distance above mean sea level?
A.
B.
C.
D.
Calibrated
Density
Pressure
True
2-17. What measurement of altitude does the pointer position indicate on a pressure altimeter?
A.
B.
C.
D.
Feet
Meters
Yards
Acres
2-18. What are the altitude increments, in feet, indicated on the counter-pointer altimeter two-digit
display?
A.
B.
C.
D.
10
100
1,000
10,000
2-19. What category of pressure altimeter error is caused by the irregular expansion of aneroid
cells?
A.
B.
C.
D.
Scale
Installation
Mechanical
Hysteresis
2-20. What category of pressure altimeter error results in a lag of altitude indication?
A.
B.
C.
D.
Scale
Installation
Mechanical
Hysteresis
2-21. Radar altimeters are reliable up to what maximum feet in altitude?
A.
B.
C.
D.
1,000
3,000
5,000
7,000
2-22. Radar altimeter systems are in what condition when the aircraft is weight-on-wheels?
A.
B.
C.
D.
Enabled
Disabled
Synched
Stowed
2-23. What airborne navigation system detects bearing only?
A.
B.
C.
D.
Automatic direction finder
Global positioning
Inertial navigation
Tactical air navigation
2-24. What airborne navigation system detects bearing and range?
A.
B.
C.
D.
Automatic direction finder
Global positioning
Inertial navigation
Tactical air navigation
2-25. A tactical air navigation system uses how many two-way operating channels?
A.
B.
C.
D.
100
115
126
133
End of Book Questions Chapter 3
Radar
3-1.
Radiofrequency energy travels at approximately how many feet per microsecond?
A.
B.
C.
D.
3-2.
A radar mile equals how many total microseconds?
A.
B.
C.
D.
3-3.
Pulse repetition time
Pulse repetition width
Pulse repetition sensitivity
Pulse repetition frequency
What type of mile does the Navy use to calculate a radar mile?
A.
B.
C.
D.
3-6.
True
Inertial
Relative
Magnetic
What is the primary limiting factor when determining the maximum range of a radar system?
A.
B.
C.
D.
3-5.
10.36
11.36
12.36
13.36
What type of bearing is measured in a clockwise direction using the centerline of the radar
antenna?
A.
B.
C.
D.
3-4.
684
784
884
984
Statute
Nautical
Imperial
Standard
What typical radar system component supplies the signals that time the transmitted pulses?
A.
B.
C.
D.
Duplexer
Receiver
Transmitter
Synchronizer
3-7.
Most modern aircraft use what type of display to show radar data?
A.
B.
C.
D.
3-8.
Which of the following terms describes radiofrequency energy processed by a radar receiver?
A.
B.
C.
D.
3-9.
Adaptable
Versatile
Dedicated
Multipurpose
Echo
Eche
Ecru
Ecco
What characteristic of pulses is directly related to the pulse repetition frequency?
A.
B.
C.
D.
Width
Height
Timing
Duration
3-10. What type of radar lobe scanning is the simplest?
A.
B.
C.
D.
Single
Active
Parasitic
Stationary
3-11. Other than electronic, what other beam scanning method can be found in modern radar
systems?
A.
B.
C.
D.
Automatic
Stationary
Mechanical
Motorized
3-12. How many dimensions are indicated by target range and bearing?
A.
B.
C.
D.
Two
Three
Four
Five
3-13. What type of missile guidance radar uses energy radiated from the target?
A.
B.
C.
D.
Beam
Passive
Homing
Unguided
3-14. What APG-73 radar component uses a two-axis gimbal assembly?
A.
B.
C.
D.
Receiver
Transmitter
Antenna
Processor
3-15. What APG-73 radar component commands the position of the antenna?
A.
B.
C.
D.
Servo
Planar
Gimbal
Waveguide
3-16. What type of gain does the APG-73 radar planar array use when directing a radiofrequency
pencil beam?
A.
B.
C.
D.
Low
Medium
High
Truncated
3-17. The APG-73 radar receiver converts a radiofrequency signal into what type of signal?
A.
B.
C.
D.
Low
Intermediate
Modulated
Transitional
3-18. The APG-73 power supply converts aircraft power into what type of power for use by the
system?
A.
B.
C.
D.
Direct
Indirect
Ancillary
Immediate
3-19. How many radar switch positions are available on the sensor control panel?
A.
B.
C.
D.
Three
Four
Five
Six
3-20. The APG-73 radar system has how many main modes of operation?
A.
B.
C.
D.
Three
Four
Five
Six
3-21. What APG-73 air-to-ground sub mode of operation offers three different resolution options?
A.
B.
C.
D.
Real beam
Sea surface
Doppler beam
Precision velocity
3-22. What is the APG-73 radar default main mode of operation?
A.
B.
C.
D.
Air
Map
Ground
Navigation
3-23. What component of the multi-mode radar system radiates X-band radiation?
A.
B.
C.
D.
Antenna
Receiver
Transmitter
Interrogator
3-24. What component of the multi-mode radar system houses the Identification Friend or Foe
interrogator?
A.
B.
C.
D.
Dias
Platform
Pedestal
Support
3-25. What component of the multi-mode radar system interfaces with the mission computer
system?
A.
B.
C.
D.
Data director
Data handler
Data controller
Data processer
3-26. What multi-mode radar assembly directs the X-band energy to be radiated from the antenna?
A.
B.
C.
D.
Receiver
Processor
Waveguide
Transmitter
3-27. The multi-mode radar system has how many general modes of operation?
A.
B.
C.
D.
Three
Four
Five
Six
3-28. The multi-mode radar Identification Friend or Foe antenna uses what frequency band?
A.
B.
C.
D.
L
K
X
C
3-29. What multi-mode radar mode of operation is useful for low-visibility navigation?
A.
B.
C.
D.
Navigation
Target designate
Long-range search
Short-range search
3-30. What type of radar does the multi-mode radar system use to capture an image of a surface
target?
A.
B.
C.
D.
Natural aperture
Synthetic aperture
Genuine aperture
Artificial aperture
3-31. What aircraft uses the multi-mode radar system?
A.
B.
C.
D.
MH-60R Seahawk
P-3 Orion
F/A-18E Super Hornet
E-2 Hawkeye
3-32. What component of the APN-234 radar system is 10 inches and flat in shape?
A.
B.
C.
D.
Receiver-transmitter
Waveguide assembly
Data processor
Antenna assembly
3-33. In what frequency range, in hertz, does the APN-234 radar system transmit a constant level
pulse?
A.
B.
C.
D.
200 to 400
200 to 600
200 to 800
200 to 900
3-34. Other than target range, what information is displayed on the APN-234 indicator-controller?
A.
B.
C.
D.
Velocity
Bearing
Altitude
Attitude
3-35. What component of the APN-234 radar system processes received reflected microwave
pulses?
A.
B.
C.
D.
Antenna assembly
Waveguide assembly
Planar array
Receiver-transmitter
3-36. What information does the APN-234 radar system provide to the operator?
A.
B.
C.
D.
Altimetry
Weather
Guidance
Surveillance
3-37. What level of detected moisture will return high levels of microwave energy?
A.
B.
C.
D.
Low
Intermediate
Transitional
High
3-38. When the APN-234 detects open ground, what color is displayed on the indicator?
A.
B.
C.
D.
Red
Yellow
Blue
Green
3-39. What APN-234 mode of operation displays flashing red areas on the indicator?
A.
B.
C.
D.
Map
Search
Weather
Weather alert
3-40. What APN-234 mode of operation is used to track surface objects over water?
A.
B.
C.
D.
Map
Search
Weather
Weather alert
3-41. When the APN-234 is in map mode, what condition of water will NOT return a signal?
A.
B.
C.
D.
Calm
Rough
Shallow
Swirling
3-42. What component of an Identification Friend or Foe system times radiofrequency pulse to avoid
interference with radar?
A.
B.
C.
D.
Interrogator
Transponder
Search radar unit
Coder-synchronizer
3-43. What component of an Identification Friend or Foe system receives the challenge signals and
transmits a response?
A.
B.
C.
D.
Interrogator
Transponder
Search radar unit
Coder-synchronizer
3-44. What component of an Identification Friend or Foe system initiates the trigger pulse when an
unidentified aircraft has been detected?
A.
B.
C.
D.
Interrogator
Transponder
Search radar unit
Coder-synchronizer
3-45. What component of an Identification Friend or Foe system responds to coded-pulse signals?
A.
B.
C.
D.
Interrogator
Transponder
Search radar unit
Coder-synchronizer
3-46. What component of an Identification Friend or Foe system initiates a radar video signal?
A.
B.
C.
D.
Interrogator
Transponder
Search radar unit
Coder-synchronizer
3-47. A typical Identification Friend or Foe system has how many modes of operation?
A.
B.
C.
D.
Four
Five
Six
Seven
3-48. What Identification Friend or Foe mode is used by both military and civilian air traffic
controllers?
A.
B.
C.
D.
1
2
3/A
C
3-49. What Identification Friend or Foe mode provides for the general identification of only military
aircraft?
A.
B.
C.
D.
1
2
3/A
C
3-50. What Identification Friend or Foe mode has a total of 2,048 different code options?
A.
B.
C.
D.
1
2
3/A
C
3-51. What Identification Friend or Foe mode is used to identify a specific military aircraft?
A.
B.
C.
D.
1
2
3/A
C
3-52. Other than mode 3/A, what Identification Friend or Foe mode has a total of 4,096 different
code options?
A.
B.
C.
D.
1
2
3/A
C
3-53. Identification Friend or Foe mode 1 typically has what total number of code options?
A.
B.
C.
D.
32
42
52
62
3-54. What type of altimeter does mode C use to report altitude?
A.
B.
C.
D.
Radar
Density
Pressure
Compression
3-55. What APX-123(V) Identification Friend or Foe component is used to select system functions?
A.
B.
C.
D.
Antenna
Interrogator
Transponder
Control display units
3-56. What are APX-123(V) secure modes of operation?
A.
B.
C.
D.
1 and 3
2 and 4
3 and C
4 and 5
3-57. How many levels are available in mode 5?
A.
B.
C.
D.
Two
Three
Four
Five
3-58. The APX-123(V) has how many operational testing modes?
A.
B.
C.
D.
Two
Three
Four
Five
3-59. What APX-123(V) operational test automatically starts when the system is turned to the on
position?
A.
B.
C.
D.
Initiated
Periodic
Special
Power up
3-60. What APX-123(V) operational test provides the operator with up-to-date status indications?
A.
B.
C.
D.
Initiated
Periodic
Special
Power up
End of Book Questions Chapter 4
Antisubmarine Warfare
4-1.
What type of sonar equipment depends on a transmitted sound wave and a return echo?
A.
B.
C.
D.
4-2.
What characteristic can be determined by identifying the point of a reflected sound echo?
A.
B.
C.
D.
4-3.
Low
Medium
High
Very high
What transmission loss characteristic causes the reduction of echo strength at long ranges?
A.
B.
C.
D.
4-6.
Receiver
Transducer
Microphone
Loud speaker
What type of pressure is created by the inward movement of a transducer diaphragm?
A.
B.
C.
D.
4-5.
Range
Speed
Bearing
Wavelength
What typical sonar component is used to transmit and receive sound echoes?
A.
B.
C.
D.
4-4.
Active
Passive
Homing
Semi-active
Absorption
Scattering
Divergence
Reverberation
Water is how many more times denser than air?
A.
B.
C.
D.
200
400
600
800
4-7.
What transmission loss characteristic is caused when a sound wave hits an object?
A.
B.
C.
D.
4-8.
What transmission loss characteristic is described as the multiple reflections of a sound wave?
A.
B.
C.
D.
4-9.
Reflection
Scattering
Absorption
Divergence
Scattering
Absorption
Divergence
Reverberation
At depths greater than 450 feet, water can vary what total number of degrees, in Fahrenheit?
A.
B.
C.
D.
10
20
30
40
4-10. What transmission loss characteristic can be described as the bending of sound waves caused
by the variations in temperature?
A.
B.
C.
D.
Salinity
Refraction
Divergence
Reverberation
4-11. A typical sonobuoy is what diameter, in inches?
A.
B.
C.
D.
3
5
7
9
4-12. What NAVAIR technical manual provides detailed information on storing, handling, and setting
sonobuoys?
A.
B.
C.
D.
26-SSL-500-1
27-SSQ-500-1
28-SSQ-500-1
28-SSR-500-1
4-13. Other than spring, pneumatic, and free-fall, what method is used to deploy a sonobuoy from an
aircraft?
A.
B.
C.
D.
Casing
Cartridge
Container
Magazine
4-14. Sonobuoys can be deployed from an aircraft traveling up to what speed, in knots?
A.
B.
C.
D.
310
330
350
370
4-15. What component of a sonobuoy is used to stabilize the hydrophone at the selected depth?
A.
B.
C.
D.
Float
Drogue
Anchor
Cabling
4-16. What type of sonobuoy can be used to detect a target in high ambient noise areas?
A.
B.
C.
D.
Bathythermograph
Directional command activated
Directional frequency analysis and recording
Vertical line array directional frequency and recording
4-17. What type of sonobuoy allows for the control of a wide range of environments?
A.
B.
C.
D.
Bathythermograph
Directional command activated
Directional frequency analysis and recording
Vertical line array directional frequency and recording
4-18. What type of sonobuoy uses a flux gate compass to provide a magnetic direction to a target?
A.
B.
C.
D.
Bathythermograph
Directional command activated
Directional frequency analysis and recording
Vertical line array directional frequency and recording
4-19. What type of sonobuoy is classified as special purpose?
A.
B.
C.
D.
Bathythermograph
Directional command activated
Directional frequency analysis and recording
Vertical line array directional frequency and recording
4-20. A bathythermograph probe descends at what constant speed, in feet per second?
A.
B.
C.
D.
1
3
5
7
4-21. What sonobuoy receiver component contains dual power supplies?
A.
B.
C.
D.
Receiver assembly
Indicator-control unit
Radio frequency status panel
On top position indicator-control unit
4-22. What sonobuoy receiver uses the ARC-143 radio control set for interface?
A.
B.
C.
D.
Receiver assembly
Indicator-control unit
Radio frequency status panel
On top position indicator-control unit
4-23. What sonobuoy receiver component is capable of producing audio outputs used in monitoring?
A.
B.
C.
D.
Receiver assembly
Indicator-control assembly
Radio frequency status panel
On top position indicator-control unit
4-24. What single advanced signal processor component extracts acoustic target information from
received signals?
A.
B.
C.
D.
Power supply
Control-indicator
Spectrum analyzer
Receiver-transmitter
4-25. What single advanced signal processor component protects against the loss of data?
A.
B.
C.
D.
Power supply
Control-indicator
Spectrum analyzer
Receiver-transmitter
4-26. What typical sonar dipping set component provides the output for aural monitoring of signals?
A.
B.
C.
D.
Multiplexer
Sonar receiver
Sonar data computer
Azimuth-range indicator
4-27. What typical sonar dipping set component contains controls to initiates operational tests?
A.
B.
C.
D.
Multiplexer
Sonar receiver
Sonar data computer
Azimuth-range indicator
4-28. What typical sonar dipping set component is the most important?
A.
B.
C.
D.
Dome control
Reeling machine
Sonar transducer
Cable and reel assembly
4-29. What typical sonar dipping set component is used to route signals between the transducer and
the multiplexer?
A.
B.
C.
D.
Dome control
Reeling machine
Sonar transducer
Cable and reel assembly
4-30. What type of metal braid is used to strengthen the cable of a typical sonar dipping set?
A.
B.
C.
D.
Plait
Loop
Armor
Shield
4-31. A typical sonar dipping set cable is between what lengths, in feet?
A.
B.
C.
D.
1,200 to 1,300
1,300 to 1,400
1,400 to 1,500
1,500 to 1,600
4-32. A typical sonar dipping set offers how many modes of operation?
A.
B.
C.
D.
6
7
8
9
4-33. The MH-60R Seahawk helicopter uses what sonar dipping set?
A.
B.
C.
D.
ASQ-20
ASQ-21
ASQ-22
ASQ-23
4-34. What characteristics do modern submarines rely on to accomplish their missions?
A.
B.
C.
D.
Stealth
Speed
Depth
Camouflage
4-35. Other than air, what medium allows magnetic lines of force to pass through, relatively
undisturbed?
A.
B.
C.
D.
Ice
Rock
Water
Earth
4-36. What magnetic angles change in an east to west direction?
A.
B.
C.
D.
Deviation
Variation
Geometric
Aberration
4-37. Other than variation, what natural magnetic characteristic is almost impossible to measure
over short distances?
A.
B.
C.
D.
Dip
Amplitude
Frequency
Wavelength
4-38. What submarine magnetic characteristic determines the intensity of the anomaly?
A.
B.
C.
D.
Profile
Contour
Instant
Moment
4-39. How does the strength of the complex magnetic field vary mathematically with respect to the
distance from the anomaly?
A.
B.
C.
D.
Inverse cube
Constant
Multiple
Percentage
4-40. What Greek letter is used to measure magnetic intensity?
A.
B.
C.
D.
Alpha
Beta
Gamma
Delta
4-41. Other than maneuver noise, what is the other category of magnetic noise sources?
A.
B.
C.
D.
Direct current
Eddy current
Alternating current
Magnetic current
4-42. What rate of aircraft maneuvering reduces the effect of the eddy current field?
A.
B.
C.
D.
Fast
Slow
Rapid
Gentle
4-43. At what distance, in feet, from the aircraft fuselage should magnetometers be installed?
A.
B.
C.
D.
2
4
6
8
4-44. What variable component is used to connect compensation loops in a load center?
A.
B.
C.
D.
Resistor
Inductor
Varactor
Capacitor
4-45. What types of wires are used in newer aircraft to minimize the compensation loop size?
A.
B.
C.
D.
Single
Ground
Twisted
Shielded
End of Book Questions Chapter 5
Indicators
5-1.
What electronic flight display system interface receives signals from the inertial navigation
system and calculates command course information?
A.
B.
C.
D.
5-2.
What electronic flight display system interface incorporates signals from other systems such as
the instrument landing and the marker beacon?
A.
B.
C.
D.
5-3.
True
Relative
Indicated
Electronic
The fixed cardinal marks on the electronic horizontal situation indicator are displayed around
the compass card at intervals of how many degrees?
A.
B.
C.
D.
5-5.
Navigation simulator
Digital data computer
Multi-mode receiver
Tactical air navigation set
The aircraft inertial navigation system provides the electronic flight display system with
magnetic and what other type of heading?
A.
B.
C.
D.
5-4.
Navigation simulator
Digital data computer
Multi-mode receiver
Tactical air navigation set
25
35
45
55
The electronic horizontal situation indicator bearing pointer 1 is selected by which of the
following operators?
A.
B.
C.
D.
Pilot
Copilot
Navigator
Maintainer
5-6.
The electronic flight director crosshair indicator provides a centering cue during what type of
approach?
A.
B.
C.
D.
5-7.
What symbol is used as a reference source for the electronic flight director pitch and roll
indicators?
A.
B.
C.
D.
5-8.
Aircraft
Horizon
Heading
Navigation
The electronic flight director pitch tape provides the position of the pitch tape in reference to
what area of the aircraft?
A.
B.
C.
D.
5-9.
Level
Manual
Localizer
High speed
Tail
Nose
Left wing
Right wing
The electronic flight director heading tape shows the current heading with how many degrees
displayed on each side of the center of the indicator?
A.
B.
C.
D.
5
10
15
20
5-10. When the head-up display attitude switch is placed in AUTO, what type of inertial navigation
data will be used as the primary source?
A.
B.
C.
D.
Raw
Calculated
Unfiltered
Filtered
5-11. How many master modes can be displayed on the head-up display?
A.
B.
C.
D.
Three
Four
Five
Six
5-12. The head-up display air speed box displays what type of air speed?
A.
B.
C.
D.
Indicated
Relative
Calibrated
Unfiltered
5-13. The head-up display vertical velocity section displays the aircraft vertical velocity in what
measurement per minute?
A.
B.
C.
D.
Feet
Miles
Kilometers
Yards
5-14. The head-up display target designator is a square that encompasses how many milliradians?
A.
B.
C.
D.
10
15
20
25
5-15. An “X” displayed through a selected weapon on the head-up display indicates that the master
arm switch is in what position?
A.
B.
C.
D.
Arm
Safe
Auto
Manual
5-16. What cue is displayed on the head-up display when NONE of the fuzing options have been
selected for an air-to-ground weapon?
A.
B.
C.
D.
Dud
Breakaway
Time to impact
Delta time of fall
5-17. What cue is displayed on the head-up display when the selected weapon is a mine,
conventional bomb, or rocket?
A.
B.
C.
D.
Breakaway
Time to impact
Pull up
Delta time of fall
5-18. What type of data signals are received by the multipurpose display group from the mission
computer and radar systems?
A.
B.
C.
D.
Digital
Analog
Raster
Composite
5-19. The digital data indicators receive command signals from the mission computer system via
what type of avionics multiplex bus?
A.
B.
C.
D.
Single
Dual
Composite
Redundant
5-20. The multipurpose color display is the main interface for what system?
A.
B.
C.
D.
Radar
Navigation
Digital map
Communication
End of Book Questions Chapter 6
Infrared
6-1.
What type of infrared radiation sensing uses both active and passive systems?
A.
B.
C.
D.
6-2.
Infrared radiation is a form of what type of energy?
A.
B.
C.
D.
6-3.
Two
Three
Four
Five
Thermal imaging is referenced in which of the following terms?
A.
B.
C.
D.
6-6.
Frequency
Duration
Wavelength
Amplitude
Infrared radiation is divided into how many categories?
A.
B.
C.
D.
6-5.
Kinetic
Electromagnetic
Electrical
Potential
What term is used when discussing the infrared region of radiation?
A.
B.
C.
D.
6-4.
Intermediate
Close
Remote
Far
Reflectivity
Color
Aural
Temperature
Forward Looking Infrared devices use what speed of image framing?
A.
B.
C.
D.
Slow
Medium
Fast
Extreme
6-7.
What term is used to describe the space between infrared radiation wavelengths?
A.
B.
C.
D.
6-8.
On an emissivity scale of 0 to 1, what number is representative of the perfect emitter?
A.
B.
C.
D.
6-9.
Window
Drawer
Cabinet
Door
0.25
0.50
0.75
1
Infrared optics should be compatible with what type of coating?
A.
B.
C.
D.
Antireflection
Anticorrosive
Anti-jam
Antielectron
6-10. The total energy emitted by an object at all wavelengths is dependent on what characteristic?
A.
B.
C.
D.
Translucency
Capacitance
Temperature
Inductance
6-11. Infrared detectors can either be elemental or what type of optical configuration?
A.
B.
C.
D.
Devising
Carving
Etching
Imaging
6-12. What detector averages the portion of the image to the outside scene into a single signal?
A.
B.
C.
D.
Elemental
Imaging
Geothermal
Magnetic
6-13. Elemental and imaging detectors both use what type of effect?
A.
B.
C.
D.
Photon
Thermal
Magnetic
Cryogenic
6-14. What type of current flows without a radiant input?
A.
B.
C.
D.
Light
Translucent
Dark
Opaque
6-15. The external photo effect is also known as what type of effect?
A.
B.
C.
D.
Photovoltaic
Photoconductive
Photo-reactive
Photo-emissive
6-16. What type of system is used to scan an entire image?
A.
B.
C.
D.
Detector
Detector array
Scene dissection
Single detector
6-17. The Advanced Targeting Forward Looking Infrared system uses what type of thermal and
visual imagery?
A.
B.
C.
D.
Active
Passive
Inactive
Semi-active
6-18. How many different WRAs make up the Advanced Targeting Forward Looking Infrared
system?
A.
B.
C.
D.
10
15
20
25
6-19. What component of the electro-optical sensor unit was designed to eliminate optical errors
associated with maintenance?
A.
B.
C.
D.
Windscreen
Laser spot tracker
Infrared midwave receiver
Optical bench
6-20. What component of the Advanced Targeting Forward Looking Infrared system manages the
flow of aircraft cooling air?
A.
B.
C.
D.
Electro-optical sensor unit
Eurocard module
Environmental control valve
Power interrupt protector
6-21. What unit is the primary interface between the Advanced Targeting Forward Looking Infrared
system, the aircraft, and the laser transceiver unit?
A.
B.
C.
D.
Laser electronics unit
Pod adapter unit
Gimbal mounted telescope
Electro-optical camera
6-22. The laser transceiver unit delivers laser energy at 20 hertz and at what wavelength, in
micrometers?
A.
B.
C.
D.
0.064
1.064
5.056
12.36
6-23. What unit provides the mounting and interface between the Advanced Targeting Forward
Looking Infrared system and the aircraft?
A.
B.
C.
D.
Electro-optical sensor unit
Pod electronics housing
Pod adapter unit
Roll drive motor
6-24. What component provides interface and mounting for the roll drive amplifier and motor?
A.
B.
C.
D.
Environmental control valve
Pod adapter unit
Laser transceiver
Pod electronics housing
6-25. The separated infrared imagery passes through what size of element array before being sent
to the video processor?
A.
B.
C.
D.
250 X 500
350 X 350
640 X 480
800 X 500
6-26. What type of camera is used in the Advanced Targeting Forward Looking Infrared system to
provide visible energy?
A.
B.
C.
D.
Charged coupled device
Photoelectric
Closed-circuit
Infrared
6-27. How many levels of optical field of view are available in the Advanced Targeting Forward
Looking Infrared system?
A.
B.
C.
D.
One
Two
Three
Four
6-28. What subsystem controls air-to-air and air-to-surface autotracking functions?
A.
B.
C.
D.
Laser and Forward Looking Infrared align
Track control
Point control
Advanced Navigation Forward Looking Infrared
6-29. What subsystem of the Advanced Targeting Forward Looking Infrared system is useful for
confirming target designation with ground personnel?
A.
B.
C.
D.
Laser spot tracker
Infrared marker
Laser range
Field of view
6-30. The Advanced Targeting Forward Looking Infrared system has how many built-in test options?
A.
B.
C.
D.
One
Two
Three
Four
End of Book Questions Chapter 7
Weapons Systems
7-1.
What homing-missile guidance, similar to active homing, is completely independent of the
launching aircraft?
A.
B.
C.
D.
7-2.
Other than gas generators and hydraulics, what power source can a homing missile use to
control fins to alter course?
A.
B.
C.
D.
7-3.
Passive only
Semi-active
Active only
Passive and active
What air-to-air missile is a radar-guided weapon that uses a high-explosive warhead?
A.
B.
C.
D.
7-6.
Target detector
Receiver
Warhead
Rocket motor
What type of guidance system does the AIM-120 Advanced Medium-Range Air-to-Air Missile
use until it approaches a target?
A.
B.
C.
D.
7-5.
Electrical
Mechanical
Thermodynamic
Fluid
What component of a semi-active homing missile computes target information and sends
electronic commands to the control section?
A.
B.
C.
D.
7-4.
Active
Semi-active only
Passive only
Semi-active and passive
AIM-9M Sidewinder
AIM-9X Sidewinder
AIM-120 Advanced Medium-Range Air-to-Air Missile
AIM-7 Sparrow
What air-to-ground missile is used to detect and destroy enemy air defense systems?
A.
B.
C.
D.
AGM-65 Maverick
AGM-84 Harpoon
AGM-88 High-Speed Anti-Radiation Missile
AGM-114 Hellfire
7-7.
What air-to-surface tactical missile can use infrared or laser guidance?
A.
B.
C.
D.
7-8.
What air-to-ground missile can be guided to a target by laser energy either inside or outside
the aircraft?
A.
B.
C.
D.
7-9.
AGM-65 Maverick
AGM-84 Harpoon
AGM-88 High-Speed Anti-Radiation Missile
AGM-114 Hellfire
AGM-65 Maverick
AGM-84 Harpoon
AGM-88 High-Speed Anti-Radiation Missile
AGM-114 Hellfire
What torpedo uses existing hardware and software from other torpedo programs?
A.
B.
C.
D.
MK 46
MK 48
MK 50
MK 54
7-10. How many variants of the F/A-18 series are currently being used tactically by the Navy?
A.
B.
C.
D.
Four
Five
Six
Seven
7-11. What type of path does the F/A-18E/F armament safety override switch provide for master arm
power when engaged?
A.
B.
C.
D.
Ground
Series only
Parallel only
Series and parallel
7-12. How many volts direct current are directed from the F/A-18E/F main landing gear weight-offwheels relay to the master arm circuit breaker when the landing gear is in the UP position?
A.
B.
C.
D.
10
15
22
28
7-13. What F/A-18E/F computer system contains the weapons insertion panel?
A.
B.
C.
D.
Armament
Mission
Air data
Flight control
7-14. What digital data display form shows the type, number, and status of weapons loaded on the
F/A-18E/F?
A.
B.
C.
D.
Weapon
Wing
Configuration
Bomb
7-15. What display is touch sensitive and provides the keypad, option select, scratchpad, and option
displays?
A.
B.
C.
D.
Head-up
Digital data
Weapon insertion
Up-front control
7-16. What F/A-18E/F switch controls the flow of coolant/high-pressure pure air to the AIM-9M
seeker head?
A.
B.
C.
D.
AIR-TO-AIR WEAPONS SELECT
CAGE/UNCAGE
INFRARED COOL
WEAPON VOLUME CONTROL
7-17. What F/A-18E/F air-to-ground system switch initiates the functions of the AGM-88 missile?
A.
B.
C.
D.
AIR-TO-GROUND WEAPON SELECT
CAGE/UNCAGE
THROTTLE DESIGNATOR CONTROL
DESIGNATOR CONTROL
7-18. When other jettison modes have failed, what F/A-18E/F jettison mode uses gravity to jettison
stores/weapons from selected pylon stations?
A.
B.
C.
D.
Emergency
Selective
Auxiliary
Starboard
7-19. The F/A-18E/F M61 gun system has how many firing modes?
A.
B.
C.
D.
One
Two
Three
Four
7-20. What light on the P-3 armament control panel indicates the weapon/store is prepared for
release?
A.
B.
C.
D.
ARM HAZARD
MASTER ARM
KILL READY
JETTISON
7-21. What P-3 interconnection box contains four subassemblies that provide control circuitry?
A.
B.
C.
D.
Port
Starboard
Forward
Aft
7-22. What P-3 component is the heart of the Maverick missile control system?
A.
B.
C.
D.
Missile/Infrared detection set status panel
Missile armament panel
Missile interface box
Missile controllers
7-23. After jettison is initiated, how many seconds does it take for the kill stores to jettison from the
P-3?
A.
B.
C.
D.
10
20
30
40
7-24. What MH-60R armament system provides for the interface, processing, and display of all
avionics and weapons systems?
A.
B.
C.
D.
Primary mission/flight computer
Processing interface units
Stores management
Data handling unit
7-25. What switch on the MH-60R hand control unit enables the release of torpedoes?
A.
B.
C.
D.
RELEASE CONSENT
TORPEDO RELEASE
MASTER ARM
ARMAMENT OVERRIDE
7-26. What valve does the sonobuoy stepper motor drive to the selected sonobuoy tube?
A.
B.
C.
D.
Lock
Distribution
Manual dump
Rotary
7-27. When the MH-60R gimbal switch is placed in the disable position, what happens to the
forward-looking infrared turret?
A.
B.
C.
D.
Turret defaults to stow.
Turret slew is set to high speed.
Turret slew is inhibited.
Turret slew is set to low speed.
7-28. How many 32-round countermeasures dispenser magazines are located on the tail pylon of
the MH-60R?
A.
B.
C.
D.
One
Two
Three
Four
End of Book Questions Chapter 8
Computers
8-1.
What internal characteristic of a computer determines the processing speed and power?
A.
B.
C.
D.
8-2.
What hardware component is the key part of a computer?
A.
B.
C.
D.
8-3.
Memory
Input device
Mass storage device
Central processing unit
Java is an example of what type of programming language?
A.
B.
C.
D.
8-6.
Memory
Input device
Mass storage device
Central processing unit
What hardware component is used by an operator to manually enter data?
A.
B.
C.
D.
8-5.
Memory
Input device
Mass storage device
Central processing unit
What hardware component is used to permanently store large amounts of data?
A.
B.
C.
D.
8-4.
Size
Power
Scope
Components
Localized
Specialized
Generalized
Randomized
What type of software enables a developer to alter computer hardware architecture?
A.
B.
C.
D.
Compiler
Assembler
Application
Operating system
8-7.
What type of software is used to translate the source code of one computer language into
another computer language?
A.
B.
C.
D.
8-8.
What type of software is used to run computer applications?
A.
B.
C.
D.
8-9.
Compiler
Assembler
Application
Operating system
Compiler
Assembler
Application
Operating system
A computer can use what methods to gather data?
A.
B.
C.
D.
Automatic only
Manual and automatic
Manual and semi-automatic
Automatic and semi-automatic
8-10. What computer function uses memory or external storage devices?
A.
B.
C.
D.
Store
Display
Process
Disseminate
8-11. What computer function routes data to peripheral devices?
A.
B.
C.
D.
Store
Display
Process
Disseminate
8-12. What computer function allows an operator to view processed data?
A.
B.
C.
D.
Store
Display
Process
Disseminate
8-13. What computer function involves the calculation and manipulation of data?
A.
B.
C.
D.
Store
Display
Process
Disseminate
8-14. Accounting and payroll are examples of what application of a computer?
A.
B.
C.
D.
Business
Database
Simulation
Process control
8-15. What application of a computer involves an operator entering a keyword and viewing specific
information?
A.
B.
C.
D.
Business
Database
Simulation
Process control
8-16. What application of a computer uses real-time data to initiate immediate corrective action?
A.
B.
C.
D.
Business
Database
Simulation
Process control
8-17. Analog computers must be able to convert analog data into what type of data?
A.
B.
C.
D.
Digital
Electrical
Electronic
Mechanical
8-18. What type of digital computer is designed to follow a specific set of instructions?
A.
B.
C.
D.
All-purpose
Multi-purpose
Special-purpose
General-purpose
8-19. A 0 and 1 in binary code represent what two signals in a computer respectively?
A.
B.
C.
D.
ON and OFF
OFF and ON
ON and ON
OFF and OFF
8-20. What is the term used to describe any device that is connected to a computer for input, output,
and communication?
A.
B.
C.
D.
Internal
Dependent
Peripheral
Independent
8-21. Binary code in a computer is adjusted by voltage and what other value?
A.
B.
C.
D.
Time
Current
Quotient
Numerical operator
8-22. Peripheral devices NOT under direct control of a computer are described as being what?
A.
B.
C.
D.
Inline
Online
Offline
Outline
8-23. Other than electrical, what type of cable can be used to carry data and signals?
A.
B.
C.
D.
Virtual
Optical
Mechanical
Environmental
8-24. What type of data transmission channel requires a signal return path to control information?
A.
B.
C.
D.
Simplex
Multiplex
Full-duplex
Half-duplex
8-25. What type of data transmission is capable of transmitting and receiving information, but only in
one direction at a time?
A.
B.
C.
D.
Simplex
Multiplex
Full-duplex
Half-duplex
8-26. What type of data transmission can simultaneously transmit and receive data?
A.
B.
C.
D.
Simplex
Multiplex
Full-duplex
Half-duplex
8-27. What method of digital data transmission uses photons to transmit and receive information?
A.
B.
C.
D.
Serial
Parallel
Fiber optic
Series-parallel
8-28. What method of digital data transmission uses a single wire to transmit and receive
information?
A.
B.
C.
D.
Serial
Parallel
Fiber optic
Series-parallel
8-29. A typical fiber optic system incorporates transmitting and receiving capabilities into one unit
called what?
A.
B.
C.
D.
Oscillator
Modulator
Transceiver
Transformer
8-30. Aircraft fiber optic cables are normally a maximum of how many feet?
A.
B.
C.
D.
200
300
400
500
8-31. What type of military specification connectors are used in aircraft fiber optic systems?
A.
B.
C.
D.
MIL-DTL-38899
MIL-DTL-38989
MIL-DTL-39899
MIL-DTL-38999
8-32. Fire control components represent what category of peripheral avionics systems?
A.
B.
C.
D.
Radar
Data link
Weapons
Navigation
8-33. Aircraft instrument landing components represent what category of peripheral avionics
systems?
A.
B.
C.
D.
Radar
Data link
Weapons
Navigation
8-34. Global positioning components represent what category of peripheral avionics systems?
A.
B.
C.
D.
Radar
Data link
Weapons
Navigation
8-35. A typical F/A-18 series aircraft mission computer system uses how many mux bus impedance
matching networks?
A.
B.
C.
D.
Two
Three
Four
Five
8-36. What designator is used to identify the primary mux bus for all avionics mux channels?
A.
B.
C.
D.
V
W
X
Y
8-37. Each module in the processor section of the digital data computer is divided into how many
sections?
A.
B.
C.
D.
Four
Five
Six
Seven
8-38. What component of a typical F/A-18 mission computer system uses a fixed software program
and a central processing unit?
A.
B.
C.
D.
Control-convertor
Digital data computer
Electronic equipment control
Mission computer/hydraulic isolation assembly
8-39. A typical F/A-18 mission computer system uses how many avionics mux channels to receive
and transmit data?
A.
B.
C.
D.
Four
Five
Six
Seven
8-40. What avionics mux channel is used to interface with the mission data loader system?
A.
B.
C.
D.
1
2
3
4
End of Book Questions Chapter 9
Automatic Carrier Landing System/Instrument Landing System
9-1.
What characteristic of an airfoil and its relationship to the airstream is important?
A.
B.
C.
D.
9-2.
What is the term used to describe the rear surface of an airfoil?
A.
B.
C.
D.
9-3.
Camber
Chord line
Angle of attack
Relative wind
What is the term used to describe the straight line from the leading edge to the trailing edge of
an airfoil?
A.
B.
C.
D.
9-6.
Camber
Chord line
Angle of attack
Relative wind
What is the term used to describe the departure from a straight line from the leading edge to
the trailing edge of an airfoil?
A.
B.
C.
D.
9-5.
Camber
Chord line
Trailing edge
Leading edge
What is the term used to describe the direction of the airstream in relation to the airfoil?
A.
B.
C.
D.
9-4.
Width
Length
Weight
Shape
Camber
Chord line
Angle of attack
Relative wind
What force counteracts the effects of weight?
A.
B.
C.
D.
Lift
Drag
Mass
Thrust
9-7.
What force resists motion, as it acts in parallel and in the opposite direction in relation to the
relative wind?
A.
B.
C.
D.
9-8.
What force must be greater than or equal to the effects of drag for flight to begin or to be
sustained?
A.
B.
C.
D.
9-9.
Lift
Drag
Mass
Thrust
Lift
Drag
Mass
Thrust
What rotational axis is parallel to the primary direction of the aircraft?
A.
B.
C.
D.
Lateral
Vertical
Diagonal
Longitudinal
9-10. What rotational axis is perpendicular to and intersects the roll axis?
A.
B.
C.
D.
Lateral
Vertical
Diagonal
Longitudinal
9-11. Other than azimuth information, what information is transmitted by the SPN-41 instrument
carrier landing system?
A.
B.
C.
D.
Speed
Direction
Elevation
Angle of attack
9-12. What instrument landing system component detects and amplifies the microwave signals from
the instrument carrier landing system?
A.
B.
C.
D.
Radio receiver
Pulse-decoder
Ku band antenna
Ku band waveguide assembly
9-13. What instrument landing system component routes the elevation and azimuth error signals to
the aircraft displays?
A.
B.
C.
D.
Radio receiver
Pulse-decoder
Ku band antenna
Ku band waveguide assembly
9-14. What instrument landing system component provides the path for signal routing?
A.
B.
C.
D.
Radio receiver
Pulse-decoder
Ku band antenna
Ku band waveguide assembly
9-15. The standby attitude reference indicator uses a gimbal-mounted sphere capable of rotating
how many degrees?
A.
B.
C.
D.
180
270
360
450
9-16. What automatic flight control system interlock is required to couple and process data link
signals to the pitch and bank channels?
A.
B.
C.
D.
Safety
Failsafe
Electrical
Acquisition
9-17. A typical automatic flight control system provides synchronization in how many axes?
A.
B.
C.
D.
Three
Four
Five
Six
9-18. What radar beacon component produces the X-band reply signals?
A.
B.
C.
D.
Receiver
Receiver-transmitter
Ka band coaxial cable
Ka band waveguide assembly
9-19. The radar beacon receiver produces what type of modulated signal envelope, called spin
error?
A.
B.
C.
D.
Amplitude
Frequency
Alternating
Wavelength
9-20. How many components make up the radar beacon system?
A.
B.
C.
D.
Three
Four
Five
Six
9-21. What automatic carrier landing system mode is a fully automatic approach from entry point to
touchdown?
A.
B.
C.
D.
I
II
III
IV
9-22. What automatic carrier landing system mode uses talkdown guidance from a shipboard
controller?
A.
B.
C.
D.
I
II
III
IV
9-23. Apart from descent, what is the other phase of the aircraft carrier landing sequence?
A.
B.
C.
D.
Marshal
Approach
Transition
Conversion
9-24. What channel is assigned to the aircrew when the aircraft has been cleared to approach the
aircraft carrier?
A.
B.
C.
D.
Radar
Data link
Detector
Communication
9-25. The instrument carrier landing system freezes compensation messages to the aircraft at
approximately how many seconds before touchdown?
A.
B.
C.
D.
1.5
2.5
3.5
4.5
End of Book Questions Chapter 10
Electrostatic Discharge
10-1. Atmospheric static is the most critical at what frequency?
A.
B.
C.
D.
500 kilohertz
25 megahertz
50 megahertz
500 megahertz
10-2. What is the large electrical breakdown between two clouds or the ground?
A.
B.
C.
D.
Corona discharge
Precipitation static
Lightning
Electrical noise
10-3. What audio output results from atmospheric static?
A.
B.
C.
D.
Low humming
High-pitched squeal
Solid tone
Irregular popping
10-4. Precipitation static is a severe problem at what frequency band(s)?
A.
B.
C.
D.
Low and medium
Low only
Ultra high
Medium only
10-5. Broadband random noises consist of what characteristics?
A.
B.
C.
D.
Constant in voltage and duration only
Irregular in shape and duration
Constant in voltage, duration, shape, and recurrence rate
Regular in shape and duration
10-6. What type(s) of broadband interference are characterized by a buzzing in an audio output
device?
A.
B.
C.
D.
Impulse only
Random noise
Pulse only
Pulse and impulse
10-7. What type of interference could result in the complete blocking of received signals?
A.
B.
C.
D.
Narrow band
Broadband
Atmospheric
Precipitation
10-8. What type of interference is created when a brush moves from one commutator bar to
another?
A.
B.
C.
D.
Static charge
Sliding contact
Audio- frequency hum
Commutation
10-9. Which of the following has little influence on the interference-generating capability of a direct
current motor?
A.
B.
C.
D.
Speed
Voltage
Size
Field windings
10-10. What type of sine wave is the ideal output of an alternating current generator?
A.
B.
C.
D.
Square
Pure
Narrow
Basic
10-11. What circuit is the likely cause of radio interference from an operating radar system?
A.
B.
C.
D.
Indicator
Modulator
Receiver
Synchronizer
10-12. What switch acts as an electromagnetically operated remote control?
A.
B.
C.
D.
Relay
Power
Electronic
Pulse
10-13. Propeller control equipment generates what maximum number of clicks and transients per
second?
A.
B.
C.
D.
10
20
30
40
10-14. What signal is mixed with another radio frequency to create an intermediate frequency?
A.
B.
C.
D.
Harmonic
Sinusoidal
Local oscillator
Noise
10-15. What strength of signal can cause a nonlinear element to act like a detector or mixer?
A.
B.
C.
D.
Mixed
Strong
Weak
Interfering
10-16. Typical aircraft single- and three-phase power systems operate in what nominal frequency?
A.
B.
C.
D.
200 hertz
400 hertz
800 hertz
1,200 hertz
10-17. High order harmonics become a problem in what frequency band?
A.
B.
C.
D.
Low
High
Very high
Ultra high
10-18. Which of the following actions will reduce inductive magnetic coupling in aircraft wiring?
A.
B.
C.
D.
Decreasing the spacing between wires
Reducing the bend angle of the wires
Increasing the spacing between wires
Replacing all wires with shielded wiring
10-19. What type of shielding material has little to no effect upon a magnetic field?
A.
B.
C.
D.
Magnetic
Nonferrous
Ferrous
Composite
10-20. What characteristic of a battery lowers the effect of coupled interference?
A.
B.
C.
D.
Low impedance
Low operation frequency
High impedance
High operation frequency
10-21. At certain frequencies, almost all of the wiring in an aircraft can act like what type of
equipment?
A.
B.
C.
D.
Relay
Oscillator
Antenna
Beacon
10-22. At which of the following points in the tuning band(s) of a receiver can oscillator leakage be the
greatest?
A.
B.
C.
D.
High and low end
Low end only
Middle range
High end only
10-23. What coupling problem may require the use of multiple solutions to solve?
A.
B.
C.
D.
Simple
Inductive-magnetic
Inductive-capacitive
Complex
10-24. What discrete component is used to short-circuit radio interference across the source?
A.
B.
C.
D.
Resistor
Capacitor
Inductor
Transistor
10-25. At what frequency is the value of a capacitor as a bypass lost?
A.
B.
C.
D.
Above resonant only
Below resonant only
Above and below resonant
Resonant
10-26. What is the crossover frequency of a typical 4-microfarad capacitor with 3-inch leads?
A.
B.
C.
D.
0.25 megahertz
0.30 megahertz
0.34 megahertz
0.47 megahertz
10-27. How many times greater than the voltage of the circuit being filtered should the capacitor
voltage be?
A.
B.
C.
D.
Two
Three
Five
Ten
10-28. What type of energy can be created when a capacitor discharges at a high rate?
A.
B.
C.
D.
Kinetic
Potential
Chemical
Transient
10-29. To ensure maximum absorption of transients, a resistive-capacitive filter should have what
characteristics?
A.
B.
C.
D.
Resistance should be high and capacitance low.
Resistance should be low and capacitance high.
Resistance and capacitance should be equal.
Resistance and capacitance should be high.
10-30. The ideal low-pass filter has no insertion loss at which of the following frequency levels?
A.
B.
C.
D.
At cutoff
Above cutoff only
Above and below cutoff
Below cutoff only
10-31. A high-pass filter is very effective at keeping which of the following items from reaching an
antenna and being radiated?
A.
B.
C.
D.
Peak voltage
Undesired harmonics
Low amperage
Sine waves
10-32. What type of filter is used to reject or block a band of frequencies from being passed?
A.
B.
C.
D.
High-pass
Bandpass
Band-stop
Resistive-capacitive
10-33. What type of aircraft bonding is defined as the process of obtaining conductivity between metal
parts?
A.
B.
C.
D.
Hydrostatic
Mechanical
Wavelength
Electrical
10-34. Which of the following bonding methods is considered ideal for all radio frequencies?
A.
B.
C.
D.
Direct
Indirect
Simplex
Multiple
10-35. What process protects personnel and aircraft from the hazards associated with lightning
discharges?
A.
B.
C.
D.
Cementing
Fixing
Binding
Bonding
10-36. What characteristic of a conductor increases directly with frequency?
A.
B.
C.
D.
Inductive capacitance
Inductive reactance
Inductive impedance
Inductive voltage
10-37. What length should a bonding jumper never exceed?
A.
B.
C.
D.
1 1/2 inches
3 inches
4 inches
6 inches
10-38. What minimum voltage can result in a device being damaged or destroyed by electrostatic
discharge?
A.
B.
C.
D.
20 volts
50 volts
75 volts
100 volts
10-39. Which of the following terms describes the generation of static electricity?
A.
B.
C.
D.
Dielectric effect
Prime charge
Electrostatic charge
Triboelectric effect
10-40. In which of the following conditions is generated static electricity decreased?
A.
B.
C.
D.
Humid air
Hot air
Dry air
Cold air
10-41. Which of the following substances will retain a positive charge when rubbed against
aluminum?
A.
B.
C.
D.
Paper
Fur
Saran
Rubber
10-42. What maximum number of electrostatic volts can be generated when a person walks across a
carpet on a low humidity day?
A.
B.
C.
D.
1,200
1,500
20,000
35,000
10-43. Which of the following testing methods should be used to verify that equipment was damaged
by electrostatic discharge?
A.
B.
C.
D.
Visually inspect
Use equipment built-in test
Verify output voltages
Check for reverse current leakage
10-44. What is the minimum resistance of personnel ground straps?
A.
B.
C.
D.
25,000 ohms
150,000 ohms
250,000 ohms
500,000 ohms
10-45. What type of electrostatic discharge protective material normally consists of metal and metalcoated materials?
A.
B.
C.
D.
Conductive
Reactive
Antistatic
Inductive
10-46. What type of electrostatic discharge protective material is pink tinted?
A.
B.
C.
D.
Reactive
Conductive
Inductive
Antistatic
10-47. What type of clothing material should be worn when electrostatic discharge protective smocks
are unavailable?
A.
B.
C.
D.
Polyester
Cotton
Linen
Wool
10-48. What electrostatic discharge protective material protects equipment from both static and
conduction?
A.
B.
C.
D.
Antistatic
Conductive
Hybrid
Inductive
10-49. What type of periodic check should be conducted on personnel ground straps?
A.
B.
C.
D.
Voltage
Continuity
Temperature
Capacitance
10-50. Which of the following publications provides guidance on packaging electrostatic discharge
sensitive materials?
A.
B.
C.
D.
NAVSEA OP 3565
OPNAVINST 3750.6R
MIL-HDBK-773
NAVSUP 723
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