TM-11-1520-221-34
TM 11-1520-221-34
TECHNICAL MANUAL
DIRECT SUPPORT AND GENERAL SUPPORT MAINTENANCE MANUAL
ELECTRONIC EQUIPMENT CONFIGURATIONS
ARMY MODELS AH-1G, AH-1Q, AND AH-1S(MOD) HELICOPTERS
This copy is a reprint which includes current pages from
Changes 1 through 3. The title was changed by C 3 to read
as shown above.
HEADQUARTERS, DEPARTMENT OF THE ARMY
SEPTEMBER 1971
*TM 11-1520-221-34
Technical Manual
HEADQUARTERS
DEPARTMENT OF THE ARMY
Washington, D.C., 25 September 1971
No. TM 11-1520-221-34
Direct Support and General Support Maintenance Manual
ELECTRONIC EQUIPMENT CONFIGURATIONS
ARMY MODEL AH-1G AND AH-1Q HELICOPTERS
CHAPTER 1.
2.
Section I.
II.
CHAPTER 3.
Section I.
II.
III.
IV.
CHAPTER 4.
5.
Section I.
II
III.
IV.
CHAPTER 6.
Section I.
II.
APPENDIX A.
GLOSSARY
Section I.
II.
INDEX
INTRODUCTION .............................................................................
INTERUNIT CIRCUIT ANALYSIS AND OPERATION
Introduction to Functioning Discussions .........................................
Analysis and Operation ....................................................................
DIRECT AND GENERAL SUPPORT MAINTENANCE
General Maintenance Techniques ....................................................
Configuration Interunit Troubleshooting ............................................
Electronic Configuration Repairs and Alignment ..............................
Electronic Equipment Unit Troubleshooting and Repair ....................
DIRECT AND GENERAL SUPPORT TESTING PROCEDURES .....
STABILITY AND CONTROL AUGMENTATION SYSTEM (SCAS)
Introduction ......................................................................................
Circuit Analysis ................................................................................
Maintenance Technique....................................................................
Performance Testing and Standards ..............................................
PROXIMITY WARNING SYSTEM
Introduction ....................................................................................
DIRECT SUPPORT MAINTENANCE ...............................................
REFERENCES ................................................................................
.........................................................................................................
Abbreviations ...................................................................................
Definitions of Unusual Terms ............................................................
.........................................................................................................
'This manual supersedes TM 11-1620-221-35, 24 March 1967, including all changes.
Change 2 i
Paragraph
1-1— 1-3
Page
1-1
2-1, 2-2
2-3— 2-14
2-1
2-1
3-1— 3-3
3-4— 3-9
3-10, 3-11
3-12, 3-13
4-1— 4-4
3-1
3-2
3-10
3-11
4-1
5-1, 5-2
5-3— 5-18
5-19— 5-31
5-32— 5-38
5-1
5-2
512
5-38
6-1— 6-3
6-4— 6-7
6-1
6-1
A-1
Glossary-1
Glossary-1
Glossary-1
I-1
TM 11-1520-221-34
Number
2-1
2-2
2-2.1
2-3
2-3.1
3-1
3-2
4-1.
4-2.
5-1
5-2
5-3
5-4
5-5
5-6
5-7
5-8
5-9
5-10
5-11
5-12
5-13
5-14
5-15
5-16
5-17
5-18
FO-1
FO-2
FO-3
FO-4
FO-4.1
FO-5
FO-6
FO-6.1
FO-7
FO-8
FO-8.1
FO-9
FO-10
FO-11
FO-12
FO-12.1
FO-12.2
FO-13
FO-14(1)
FO-14(2)
FO-15
FO-16
FO-17
LIST OF ILLUSTRATIONS
Title
Impedance matching network schematic, configurations A, B, C ...................................................
Impedance matching network schematic, configuration D ............................................................
Impedance matching network schematic, configuration E .............................................................
Impedance matching network circuit board, configurations A, B, C and D......................................
Impedance matching network circuit board, configuration E .........................................................
Adjustment of main inverter .........................................................................................................
Adjustment of standby inverter ....................................................................................................
Transponder Test Set AN/APM-123(V)1 .......................................................................................
Antenna Test hood MX4396/AP-123(V) installation ......................................................................
SCAS control panel, rear view ......................................................................................................
SCAS sensor amplifier unit, front view .........................................................................................
SCAS sensor amplifier unit, rear view ..........................................................................................
Pylon compensation unit, top view ...............................................................................................
Pylon compensation unit, bottom view .........................................................................................
Pitch control channel assembly schematic ....................................................................................
Roll control channel assembly schematic .....................................................................................
Yaw control channel assembly schematic......................................................................................
Valve driver module output waveforms ........................................................................................
Valve driver output test waveforms ..............................................................................................
SCAS control panel test setup connections ..................................................................................
SCAS sensor amplifier unit test setup connections .......................................................................
SCAS control panel and sensor amplifier unit test setup connections ............................................
Three axis gyro assembly .............................................................................................................
Control channel assembly test setup connections .........................................................................
Pylon compensation unit test setup connections ...........................................................................
SCAS control channel assembly module (front) ............................................................................
SCAS control channel assembly module (rear)..............................................................................
MILSTD resistor and capacitor color code markings .....................................................................
Interphone facility schematic, configurations A and B ...................................................................
Interphone facility schematic, configuration C ...............................................................................
Interphone facility schematic, configuration D .............................................................................
Interphone facility schematic, configuration E................................................................................
FM liaison facility schematic..........................................................................................................
Uhf command facility schematic, configuration A, B, C and D .....................................................
Uhf command facility schematic, configuration E .........................................................................
Vhf command facility schematic, configurations A, B, C ................................................................
Vhf command facility schematic, configuration D .........................................................................
Vhf command facility schematic, configuration E ..........................................................................
Adf navigation facility schematic ..................................................................................................
Gyromagnetic compass system schematic ...................................................................................
Transponder facility schematic, configurations A and B
Transponder facility schematic, configurations C and D
Transponder facility schematic, configurations A, B, C and D (when
MWO 55-1520-221-30/13 is accomplished) ...............................................................................
Transponder facility schematic, configuration E.............................................................................
SCAS system block diagram ........................................................................................................
SCAS system schematic (part 1 of 2) ...........................................................................................
SCAS system schematic (part 2 of 2) ...........................................................................................
Ky-28 voice security system provisions schematic, configuration
C, per MWO 55-1520-221-30/36 ...............................................................................................
Ky-28 voice security system provisions schematic, configuration
D, per MWO 55-1520-221-30/36 ...............................................................................................
Proximity warning system..............................................................................................................
Change 2 ii
Page
2-4
2-5
2-6.1
2-7
2-8.1
3-9
3-10
4-4
4-5
5-2
5-3
5-4
5-5
5-6
5-8
5-9
5-10
5-14
5-15
5-19
5-19
5-23
5-27
5-28
5-32
5-37
5-38
TM 11-1520-221-34
WARNING
DANGEROUS VOLTAGES
EXIST IN THESE CONFIGURATIONS
Be careful when working on the 115-volt ac output circuits of the
inverters.
DEATH ON CONTACT
MAY RESULT IF SAFETY PRECAUTIONS ARE NOT OBSERVED
Be careful not to come in contact with or close proximity to high-voltage
connections or any power connections when using this equipment. Turn
off the power and discharge all high-voltage capacitors before making
any connections or doing any work inside the equipment. Voltages as
high as 1,500 volts dc are present in these configurations.
RF BURNS
Do not touch or stand too close to radiating antennas. Serious RF burns
may result. Move away from antenna or transmitting equipment if any
part of the body area feels flushed.
DANGEROUS CHEMICALS ARE USED IN NICKEL-CADMIUM BATTERIES
The electrolyte used in nickel-cadmium batteries contains potassium
hydroxide (KOH), which is a caustic agent. Serious and deep burns of
body tissue will result if the electrolyte comes in contact with the eyes or
any part of the body. Use rubber gloves, rubber apron, and protective
goggles when handling the electrolyte. If accidental contact with the
electrolyte is made, use ONLY clean water and immediately (seconds
count) flush contaminated areas. Continue flushing with large quantities
of clean water for at least 15 minutes. Seek medical attention without
delay.
DO NOT TAKE CHANCES!
Change 2
TM 11-1520-221-34
CHAPTER 1
INTRODUCTION
1-1.
Scope
a. This manual covers direct and general support of
the electronic equipment configuration for Army Model
AH-1G, and AH-1Q Helicopters, Serial Numbers
6615249 through 66-15357, 67-15450 through 6715869, 68-15000 through 68- 15213, 68-17020 through
68-17113, 69-16410 through 69-16447, 70-15936
through 70-16105; and helicopters that have been
retrofitted in accordance with MWO's 55-1520-221-20/5,
55-1520-221-20/7, 55-1520-221-20/9, 55-1520-221-30/1,
55-1520221-30/12, 55-1520-221-30/13, 55-1520-22130/17, 55-1520-221-30/26, and 55-1520-221-30/36. It
includes instructions appropriate to direct support
maintenance personnel for troubleshooting electronic
equipment when the equipment is installed in the
helicopter. This manual lists tools, test equipments, and
materials required by direct support maintenance
personnel to maintain the helicopter electronic
equipment configuration. Also included in this manual
are complete direct and general support instructions with
appropriate lists of tools, test equipments, and materials
required for performing bench or shop maintenance of
certain electronic equipment components.
b. Bench maintenance of many of the electronic
equipment configuration components is covered in other
technical manuals. The pertinent technical manuals for
these electronic equipments are listed in appendix A.
When servicing these electronic equipments, refer to
those manuals for detailed troubleshooting, testing,
aligning, and repair procedures, and for replacing or
repairing maintenance parts.
c. Block diagram analysis of the entire electronic
equipment configuration and the individual facilities that
are contained in the electronic equipment configuration
is covered in TM 11-1520-221-20. Analysis of the
electronic configuration interunit circuits is covered in
paragraphs 2-3 through 2-14 of this manual. Block
diagrams and detailed circuit analyses of electronic
equipment components that do not have separate
manuals are covered in section II, chapter 2, and
chapter 5 of this manual. For electronic equipments
covered by separate technical manuals, refer to
appendix A for pertinent manuals regarding the block
diagrams and detailed circuit analyses.
d. The addition of an asterisk inclosed in
parentheses to the official nomenclature is used to
indicate all models of the equipment discussed in this
manual. TM 11-1520-221-20 lists the equipment to
which this symbol will apply.
e. The reporting of errors, omissions and
recommendations for improving this publication by the
individual user is encouraged. Reports should be
submitted on DA Form 2028 (Recommended Changes
to Publications and Blank Forms) and forwarded to
Commander, US Army Electronics Command, ATTN:
DRSEL-MA-Q, Fort Monmouth, NJ 07703.
NOTE
For applicable forms and records,
see TM 11-1520-221-20.
1-2.
Indexes of Publications
a. DA Pam 310-4. Refer to the latest issue of DA
Pam 3104 to determine whether there are new editions,
changes, or additional publications pertaining to the
equipment.
b. DA Pam 310-7. Refer to the latest issue of DA
Pam 310-7 to determine whether there are modification
work orders (MWO's) pertaining to the equipment.
1-3.
Reference Designations and Equipment
Identification
a. General. The electronic equipment components
illustrated in this manual are grouped by the facility and
the configuration they are associated with, and are
identified by part number or official nomenclature. The
subassemblies and parts of these equipments are
identified by reference designations.
Reference
designations consist of groups of letters and numbers
that identify the subassemblies and parts. Some of the
subassemblies and parts within the electronic
equipments have reference designations assigned to
items according to the unit numbering system, and
some equipments use the block numbering system. For
the reference designation system and the grouping of
items within a particular electronic equipment, refer to
appendix A for the applicable technical manual covering
the equipment.
b. Electronic Configuration. The facilities in the
configuration covered by this manual, and the model
and serial numbers of the helicopters included in the
configuration are in the chart below. For detailed
electronic equipment breakdown of each facility, with its
associated configurations, helicopter models, and serial
numbers, refer to TM 11-1520-221-20.
NOTE
The electronic configuration in the AH-1Q,
designated as configuration F, is the same
as in configurations A, B, C, D, and E except
for location of components, and the main
inverter.
All other components, wire
numbers, etc. are the same. Refer to TM 111520-221-20
for
specific
equipment
relocation.
Change 2 1-1
TM 11-1520-221-34
Facility
Equipment
Facility
Interphone and audio ------------
Control, Intercommunication Set C-1611/AIC
Radio Set AN/ARC-54 or
AN/ARC-131
Radio Set ANIARC-51BX
Ac source (Main inver- ----------ter) (A through E configuration
Ac source (Main inverter) -------(F configuration)
Standby ac source ---------------(standby inverter)---------------
Fm liaison --------------------------Uhf command ---------------------Automatic direction finding (Adf) system----------------Gyromagnetic compass ---------Iff system ---------------------------Vhf command----------------------Stability and control
augmentation system ---------(SCAS) --------------------------Dc source----------------------------
Direction Finder Set
AN/ARN-83
Gyromagnetic Compass
System AN/ASN-43
Transponder Set AN/
APX-44 or ANIAPX-72
Radio Set AN/ARC-134
Configuration ----------------------A ----------------------------------B-----------------------------------C ----------------------------------D -----------------------------------
SCAS, Model 570A
Battery BB-433/A or
BB-649/A
E-----------------------------------F -----------------------------------
Change 2 1-2
Equipment
Motor Generator PU-542
(A)/A or PU-542(*)/A
Inverter, Power 209-075-572
Inverter, Power, Static
PP-6508/U
Helicopter Serial No.
66-15249 - 66-15257
66-15258 - 66-15357
67-15450 - 67-15869
68-15000 - 68-15213
68-17020 - 68-17113
68-16410 - 69-16447
7015936- 70-16105
AH-1Q
TM 11-1520-221-34
CHAPTER 2
INTERUNIT CIRCUIT ANALYSIS AND OPERATION
Section I. INTRODUCTION TO FUNCTIONING DISCUSSIONS
2-1.
Introduction
The purpose, operation, and interoperation of the
various circuits in electronic equipment configuration
and in the individual electronic equipments used in the
electronic equipment configuration are explained in this
chapter and also in the technical manuals covering
certain
electronic equipments of each electronic
equipment configuration. This chapter is divided into
four sections. Section I covers introduction and main
power application. Section II contains detailed circuit
analysis of configuration. Familiarity with the electronic
equipment configurations and the individual electronic
equipments, how they work and why they work that
way, is important in troubleshooting the electronic
equipment configurations and the individual electronic
equipments rapidly and effectively.
2-2.
Main Power Application
Dc power is applied by an engine-driven generator or by
the helicopter battery, or by an externally applied
auxiliary power unit which is connected to the helicopter
through the external power connector. Refer to TM 111520-221-20 for auxiliary power connection.
a During normal in-flight operation, +28 volts dc is
supplied to the dc bus from the engine-driven generator
through a reverse current relay. The generator operates
when the helicopter engine is running. The generator
supplies +28 volts to the dc bus when the GEN control
switch on the instrument pedestal is at ON.
b. The helicopter battery is used for emergency
purposes if the engine-driven generator becomes
inoperative while the helicopter is in flight. The battery
supplies power to the dc bus when the BAT (battery)
switch on the instrument pedestal is at ON.
c. When the helicopter is on the ground, an
external power unit is connected to the helicopter
through the external power connector for use in starting
the helicopter and for testing and troubleshooting of
signal equipment in the helicopter. The BAT(battery)
switch must always be at OFF before connecting an
external power unit to the external power connector.
Section II. ANALYSIS AND OPERATION
2-3.
Primary Power
Low
voltage
for
communication,
navigation,
identification, stability, and interphone facilities is
supplied from an auxiliary power unit, through the
external power receptacle and external power relay, to
the helicopter's +28-volt dc bus in the Instrument panel
or from the helicopter's battery through the BAT switch
and the battery relay to the de bus. High voltage used
in the operation of the radio equipment is supplied by
power components of the radio sets. The radio sets are
connected to the +28-volt de bus through individual
circuit breakers on the instrument panel. Distribution of
primary
power for the interphone facility, communication
facilities, and navigation facilities are covered in a
through i below.
a. Interphone and audio Facility (Control,
Intercommunication, Set C-1611/AIC) Primary Power
(fig. FO-2, FO-3, FO-4 and FO-4.1). Interphone
communication is accomplished through the Control,
Intercommunication Set C-1611(*)/AIC at the pilot's and
gunner's positions. To obtain amplification of the
interphone audio signals, power must be applied to the
amplifier circuits in the C-1611(*)/AIC.
Operating
voltage for the C-1611(*)/AIC is furnished to the power
relay in each C-1611(*) AIC by the helicopter 28-volt dc
bus through the ICS circuit breaker (through pins 37 of
connectors P301A and P301F).
b. Fm Liaison Facility (Radio Set AN/ARC-54)
Primary Power (fig. FO-5). With the FM XCVR-54
circuit breaker button depressed, power for the
Receiver-
Change 1 2-1
TM 11-1520-221-34
Transmitter, Radio RT-348, ARC-54 is applied through
the PTT-RET-HOME switch S101-C on the Control,
Radio Set C-3835/ARC-5-1. When the PTT-RETHOME switch on the C-3835/ARC--54 in the PTT
position, +28 volts dc is applied to receiving and
transmitting circuits of the RT-348/ARC-54 from the de
circuit breaker panel to pins E and C of connector J2107
on the C-3835/ARC-54 through the closed PTT-RETHOME switch to terminals 34 and 36 of connector
J2106 of RT-3481/ARC-54.
c. Uhf Command Facility (Radio Set AN/ARCl5BX) Primary Power (fig. FO-6 and FO-6.1). With the
UHF XCVR circuit breaker button depressed, +28 vdc is
applied to pins A and B of P1403/J1403. The RT742/ARC-51BX receives its primary voltage when the
function selector switch on the C6287/ARC-51 BX is
moved to any position other than OFF.
This is
accomplished by ground being applied from pin A of
J3801 to pin T of J1403 to an internal power relay in the
RT-742/ARC-51BX. A +28 vdc is present on the
contacts of this relay through pins A and B of J1403
whenever the UHF circuit breaker is depressed.
ASN.
g.
lff Facility (Transponder, Set AN/APX-44)
Primary Power (fig. FO-11 and FO-12). With the Iff
circuit breaker depressed, power for the ReceiverTransmitter, Radar RT-494/APX-44 is applied through
the master control switch on the Control, Transponder
Set C-2714/APX-44. With the master control switch in
STBY position, +28 volts dc is applied to receiving and
transmitting circuits of the RT-494/APX-44 through the
master control switch on the C-2714/APX-44 to pin 2 of
J906 to pin 44 of J902.
h. Iff Facility (Transponder- Set AN/APX-72)
Primary Power (fig. FO-11, FO-12, FO-12.1 and FO12.2). With the Iff circuit breaker depressed, power for
the Receiver-Transmitter, Radar RT-859/APX-72 is
applied through the master control switch on the Control,
Transponder Set C-6280/APX-72. With the master
control switch in STBY position, +28 volts dc is applied
to receiving and transmitting circuits of the RT859/APX-72 through the master control switch on the C6280/APX-72 to pin 2 of J906.
d. Vhc Command Facility (Radio Set AN,/ARC134) Primary Power (fig. FO-7, FO-8 and FO-8.1).
With the VHF XCVR circuit breaker depressed, power
for the Receiver-Transmitter, Radio AN/ARC-134 is
applied through the power switch on the Control, Radio
Set C-7197/ARC-134. When the power switch on the C7197/ARC-134 is in the PWR position, power relay
K2001 in the RT-857/ARC-134 is energized, 28 vdc
from the circuit breaker is applied to pins 3 and 4 of
J1904A of the RT-857/ARC-134.
i. Homing Facility (Lead Foil Antenna) Primary
Power (fig. FO-5). With the FM XCVR circuit breaker
on the instrument pedestal depressed, power is applied
to HOME portion of selector switch S101 on Control,
Radio Set C-3835/ARC-54. Power from pin DD of
connector P-2107 on the C-3835/ARC-54 is applied to
the homing module of the Receiver-Transmitter RT348/ARC-54 through pin 16 on P2106. For details on
the AN/ARC-54 homing operation refer to the technical
manual for Radio Set AN/ARC-54.
e. Adf Navigation Facility (Direction Finder Set
AN/ARN-83) Primary Power (fig. FO-9) With the ADF
circuit breaker depressed, power for the Receiver R1391/ARN-83 is applied through the function switch on
the Control, Direction Finder C-6899/ARN-83. With the
function switch in ADF position, +28 volts dc is applied
to receiving circuits of the R-1391/ARN-83 from the dc
circuit breaker panel through 2 pins K and L of J302 on
the C-6899/ARN-83 to pin 26 of J407 on the
R1391/ARN-83.
2-4.
f. Gyromagnetic Compass Facility(Directional Gyro
CN-998/ASN-43). Primary Power (fig. FO-10). With the
GYRO COMP circuit breaker depressed, power for the
compass facility is applied from the ac circuit breaker
panel to pin C of Jill on the CN-998/ASN-43 and pin 7
of P415 on the Amplifier, Electronic Control AM-3209,
Interphone and Audio Signal Distribution
(fig. FO-2, FO-3, FO-4 and FO-4.1)
a. Audio Signals. Audio signals originating at
either pilot's or gunner's Headset-Microphone H-101/U
are
preamplified
in
the
associated
Control,
Intercommunication Sets C-1611(*)/AIC. The position
of the transmit-interphone selector switch on the C1611(*)/AIC will determine the distribution of the audio
signals. In the INT position, the audio signals from the
associated H-101/U are coupled through one C-1611
(*)/AIC to the other C-1611(*)/AIC for interphone
communication. In position 1, the audio signals from
the C-1611(*)/AIC panels are coupled to the transmitter
section of the Receiver/Transmitter RT-348/ARC-54 for
Change 1 2-2
TM 11-1520-221-34
transmission. In position 2, the audio signals from the
C-1611(*)/AIC panels are coupled through the MID-736
discrete signal discriminators to the transmitter section
of the Receiver-Transmitter, Radio RT-742/ARC-51BX
for transmission. In position 3, the audio signals from
the C-1611((*)/AIC panels are coupled through the MID736 discrete signal discriminators to the ReceiverTransmitter RT-857/ARC-134 for transmission. The C1611(*)/AIC panels also contain headset amplifiers for
the amplification of all signals to be received in the H101/U headsets, including the sidetone signals from the
associated H-101/U microphones.
For private
interphone communication, TRANS switch is set to PVT,
and RECEIVERS switch is set to INT (up) position.
Primary power for operation of the interphone facility is
provided by the ICS C-1611 circuit breaker on the
instrument pedestal.
b. Interphone.
(1) Press-to-talk control.
(a) For interphone communication with the
C-1611/AIC, the TRANS selector switch on the C1611/AIC is set to INT. When the pilot's or gunner's
cyclic switch is pushed to ICS (down), the return to
ground is made through pin 14 of J301F or J301A
through interphone relay, which causes the relay to
energize and thus actuate microphone amplifier A4.
(b) When the HOT MIKE switch at one C1611/AIC is actuated to ON (steady) or MC
(momentarily closed), or when ground crew headset
microphone line switch is closed, ground for pins 16 and
17 of J301A or J301F is made to pin 6 of J600 of
impedance matching assembly to complete groundpath.
Completing ground energizes K1 interphone relay in C1611 AIC and keeps all microphones hot.
(2) Transmit-receive
control.
When
the
gunner's footswitch is closed or when cyclic stick switch
is pushed to radio (up), a ground path is completed from
pin H on P91 to pin 5 of J600, out on pin 7 of J600 to pin
15 of P301F. When the pilot's cyclic stick switch is
pressed to radio (up) position, a ground path is
completed from pin H of P34 through pin 4 of J600 and
out on pin 11 of J600 to pin 15 of P301A.
2-5.
Audio Signal Distribution
NOTE
Refer to FO-2 (configurations A and B), FO-3
(configuration C), FO-4 TM 11-1520-221-34
(configuration D) and FO-4.1 (configuration
E).
Audio signals originating at a Headset-Microphone H-
101/U are distributed through the communication
impedance matching network P/N 209-075-235 (fig. 21, 2-2 and 2-2.1) and the Control, Intercommunication
Set C- 161 1(*)/AIC for interphone communication or for
transmission and reception by the Radio Set AN/ARC54 or Radio Set AN/ARC-51 BX or the Radio Set
AN/ARC-134. The mode of operation is controlled by
the transmit-interphone selector switch on the C1611(*)/AIC panel. When in use, the C-1611(*)/AIC may
be operated in any one of four modes, as determined by
the settings of the transmitter-interphone selector switch
and the RECEIVERS switches S1 through S7 in the
control circuits. The three modes of operation used are
two-way
(air-to-air
and
air-to-ground)
radio
communication, radio receiver monitoring, and
intercommunication (interphone and private interphone)
between pilot and gunner.
a. Energizing Circuits. Low voltage (+28 volts
dc) for the pilot's and gunner's distribution panels is
supplied from the ICS C-1611 circuit breaker panel to
pin 37 of J301 of each distribution panel.
b. Pilot's Transmission Circuits. Audio signals
originating at the microphone portion of the pilot's H1O1/U are coupled through terminal board TB22 through
terminals 3 (high) and 22 (low) of the pilot's C1611(*)/AIC.
(1) If the pilot and gunner of the aircraft want to
intercommunicate, they do so by moving the transmitter
phone selector switch to INT or PVT for private
uninterrupted conversation. Through this arrangement
the microphone output signaled by a member's voice is
passed through microphone preamplifier, microphone
amplifier, and control circuits of headset amplifier to the
interphone or private interphone line. The signal portion
applied to headset amplifier is received by the earphone
as sidetone. The amplified signal is applied to the
interphone line and is received by other stations
connected to the same line (PVT).
(2) With the transmit-interphone selector switch
in position 1, audio signals are fed from terminal 24 of
the pilot's C-1611 (*)/AIC, through the impedance
matching assembly and through the C-3835/ARC-54 to
the Receiver-Transmitter, Radio RT-348/ARC-54 for
transmission.
(3) With the transmit-interphone selector switch
on the C-1611(*)/AIC in position 2, audio signals are fed
from terminal 25 of the pilot's C-1611(*)/AIC, through
the communication inpedance matching assembly, to
the
Change 1 2-3
TM 11-1520-221-34
Figure 2-1. Impedance matching network schematic, configurations A, B, and C.
2-4
TM 11-1520-221-34
Figure 2-2. Impedance matching network schematic, configuration D.
2-5
TM 11-1520-221-34
C-6287/ARC-51BX, then to the Receiver-Transmitter,
Radio RT-742/ARC-51BX for transmission.
(4) With the transmit-interphone selector switch
on the C-1611(*)/AIC panel in position 3, audio signals
are fed from terminal 26 of the pilot's C-1611(*)/AIC,
through the communication impedance matching
assembly to AN/ARC-134.
c. Pilot's Receiving Circuits. All audio signals from
the receivers are routed to the headset portion of the H101/U through the C-1611(*)/AIC panel.
(1) Audio signals from the AN/ARC-54 are
routed through J2107 pin N to pin 30 of J301A of the
pilot's C-1611(*)/AIC. The signals are routed through
the transmit-interphone selector switch (position 1) or
RECEIVERS 1 switch to audio output pins 5 and 23 of
J301A of the pilot's C-1611(*)/AIC, through terminal
board TB23 and to the headset portion of the pilot's H101/U.
(2) Audio signals from the AN/ARC-51BX are
routed through J600 pin 31 or J301 of the pilot's C16il(*)/AIC. The audio signals are then routed through
the transmit-interphone selector switch (position 2) or
RECEIVERS 2 switch to audio output pins 5 and 23 of
J301 of the C-1611(*)/AIC, through terminal board TB23
and to the headset portion of the pilot's H-101/U.
(3) Audio from AN,/ARC-134 is routed into pin
32 of J301A of the pilot's C-1611(*')/AIC. The signals
are routed through the transmit-interphone selector
switch (position 3) of RECEIVERS 3 switch to audio
output pins 5 and 23 of J301A of the pilot's C1611(*"),/AIC, through terminal board TB23 and to the
headset portion of the pilot's H-101/U.
d. Gunner's Transmission and Receiving Circuits.
The gunner's transmission and receiving circuits are
similar to those of the pilot. Audio signals from and to
the gunner's position are distributed through the
gunner's C-1611(*)/AIC in the same manner as
described for the pilot's operation b and c above).
e. Emergency Operation. There is no emergency
operation provision because all transmitted and
received audio signals pass directly through the C1611(*),/AIC panels with controls set for selected
signals.
a. General. Interphone communication between
the pilot and gunner is accomplished through the C1611 ()/AIC. Signals originating at the microphone
portion of a headset microphone are amplified by the
associated C-1611(*)/AIC. Microphone signals from the
pilot are routed through the pilot's C-1611(*)/AIC and
through the gunner's C-1611(*)/AIC to the headset
portions of the H-101/U headsets. Microphone signals
from gunner are routed through the gunner's C1611(*)/AIC and through the pilot's C-1611 (*)/AIC to the
pilot's H-101/U. Audio impedance matching is provided
by the resistor and capacitor network system (fig. 2-1,
2-2 and 2-2.1) mounted on the impedance matching
assembly (fig. 2-3).
b. Interphone Communication. Audio signals for
communication are amplified by the C-1611(*)/AIC
panels. Dc power for operation of the interphone facility
is furnished by the +28V DC bus through the ICS circuit
breaker. The pilot and gunner can carry on interphone
communications by depressing the microphone switch
on the cyclic control grip. One-way communication is
established from the pilot or the gunner when either
operates the transmit-interphone selector switch on his
C-1611(*),/AIC to INT. Microphone signals flow to pin 3
of J301 of distribution panel, through microphone
preamplifier and amplifier and through trans-selector
switch to pin 8 of J301. The amplified signal output
from pilot's C-1611(*)/AIC is connected to the gunner's
H-101/U headset through the gunner's C-1611(*)/AIC.
The amplified signal output from the gunner's C1611(*)/AIC panel is connected to the pilot's H-101/U
through the pilot's C-1611 (*)/AIC.
2-6.
a. General. Radio Set AN/ARC-54 (fig. FO-5)
provides fm communication facilities for liaison
operation. The AN/ARC-54 also provides for homing
facilities by use of the lead foil antenna.
(1) Operating voltage is applied to the receiver
Interphone Communication Operation
NOTE
Refer to FO-2 (configurations A and B), FO-3
(configuration C), FO-4 configuration D) and
FO-4.1 (configuration E).
2-7.
Fm Liaison Communication
(fig. FO-5)
NOTE
Radio Set AN/ARC-131 may be installed in
lieu of Radio Set AN/ARC-54.
In the
following steps, references to Radio Set
AN/ARC-54 also apply to Radio Set AN/ARC131.
Change 1 2-6
TM 11-1520-221-34
Figure 2-2.1 Impedance matching network schematic, configuration E.
Change 1 2-6.1
TM 11-1520-221-34
Figure 2-3. Impedance matching network circuit board. Configuration A. B, C, and D
Change 1 2-7
TM 11-1520-221-34
47A/AIC foot switch actuated, a ground is placed on the
low side of the RF power amplifier; this section activates
the coils in the module of the RT-348/ARC-54 for
transmitter operation.
(b) When the pilot speaks into the
microphone, the audio signals are coupled to pins 3 and
22 of J301A of C-1611(*)/AIC, through microphone
preamplifier and amplifier and through transmitinterphone selector switch to pin 24 of J301A and then
to J2107 of C-3835/ARC-54. From the C-3835/ARC-54
it is applied to pin 6 of P2106 on the RT-348,/ARC-54
and then to the transmit audio module within the lRT348/ARC-54.
The RF power amplifier is now
modulated, and the frequency-modulated- RF signal is
coupled from P2105 to the fm antenna type 437S-1 for
propagation. The gunner may listen to the transmitted
signal from the pilot by operating the RECEIVERS 1
switch on his C-1611 (*)/AIC to the gunner's position.
(3) Transmission circuit.
(a) With the transmit-interphone selector
switch on the gunner's C-1611(*)/AIC operated to
position 1 and the gunner's cyclic control grip
microphone switch pushed to RADIO position, or with
gunner's SA-47A/AIC foot-switch actuated, RT348/ARC-54 operation is set up as described in (2) (a)
above.
(b) When the gunner speaks into the
microphone, the audio signals are coupled to pins 3 and
22 of J301F of C-1611(*)/AIC, through microphone
preamplifier and amplifier, and through transmitinterphone selector switch pin 24 of J301F. The signal
progresses in the same manner as described in (2) (b)
above.
circuits in the Receiver-Transmitter, Radio RT-348/ARC54, through the depressed FM XCVR circuit breaker.
For complete fm set communication operation the ICS
C-1611 circuit breaker must also be depressed. The
RT-348/ARC-54 will be in the receive condition until the
microphone switch on either cyclic control grip is
depressed to RADIO position or until gunner's SA47A/AIC footswitch is depressed. When the pilot or
gunner depresses his microphone switch to position
RADIO or when the gunner actuates his SA-47A/AIC
with C-1611 (*)/AIC TRANS selector switch set to 1, a
full 500 volts dc is applied to the power amplifier tube
plate and 250 volts dc is applied to the screen grids, and
the RT-348/ARC-54 is in the transmit condition.
(2) Signals from the microphone of either the
pilot or gunner station are routed through the C1611(*)/AIC panels to RT-348/ARC-54. Preamplification
of the audio signals occurs in the C-1611(*)/AIC panels.
The output frequency of the transmitter section is
controlled by Control, Radio Set C-3835/ARC-54. The
output of the transmitter section is coupled to the fm
antenna type 437S-1 for propagation.
(3) Signals received by the fm antenna type
437S-1 are coupled to the receiver section of the RT348/ARC-54. The RF signals are demodulated and
amplified in the receiver sections. The resulting audio
output frequency of the receiver section is coupled to
each C-1611(*)/AIC through the C-3835/ARC-54. The
audio output from the pilot's C-1611(*)/AIC is coupled to
the pilot's H-101/U. The audio output from the gunner's
C-1611(*)/AIC is coupled to his H-101/U.
b. Transmission Signal Flow.
(1) General. Positive 28 volts dc is applied to
the AN/ARC-54 fm liaison set (fig. FO-5) through the
FM/ARC-54 circuit breaker, and to the C-1611(*)/AIC
panel through the ICS C-1611 circuit breaker.
Operating power is applied to the C-1611(*)/AIC panels
and to all the circuits in the RT-348/ARC-54 except the
RF power amplifier in the transmitter section. When the
microphone switch on either cyclic control grip is
depressed to position RADIO or when gunner's foot
switch is actuated, voltages are applied to the
transmitter section, enabling the transmitter to operate.
(2) Pilot's transmission circuit.
(a) With the transmit-interphone selector
switch on the pilot's C-1611-(*)/AIC set to 2-8 position 1
and the microphone switch on the pilot's cyclic grip
depressed to RADIO position, or with the gunner's SA-
c. Reception Signal Flow. Incoming RF signals
received by the fm antenna type 437S-1 are amplified
and demodulated in the receiver portion of the RT348/ARC-54. The resulting audio signal is transferred to
C-3835/ARC-54 connector J2107 pin JJ.
It goes
through R101 volume control and departs from J2107
on pin N. It is then transferred to the pilot's and gunner's
C-1611(*) ,AIC control panels, where it is amplified in
the headset amplifiers. From pins 5 and 23 of J301
(Gunners and Pilots distribution panels), it is fed through
TB22 and TB23 to H-101/U headsets (Gunner's and
Pilot's respectively). The AN/ARC-54 uses BHC leadfoil
antenna homing operation.
2-8
TM 11-1520-221-34
Figure 2-3.1 Impedance matching network circuit board, configuration E.
Change 1 2-8.1
TM 11-1520-221-34
a. General. The homing mode of operating is
selected with the mode control switch on the C3835/ARC--54 set to HOME position. This applies the
necessary grounds and voltages to the homing circuits
in the RT-348/ARC-54. Homing mode is available
throughout the entire frequency range of the AN. ARC54.
b. Operation. When homing mode is selected, a
homing switch is energized in the RT-348/ARC-54. The
switch alternately samples left and right inputs from the
homing antenna at a 100-Hz rate. The composite signal
is amplified through the normal RF path in the RT348/ARC-54 and routed to the mechanical chopper
K201. The output of the chopper feeds the homing
indicator needle, causing deflection anytime the aircraft
is not headed toward the transmitting station. The
squelch circuits control the flag arm which in turn
provides a visual indication of signal strength.
b. Audio Distribution.
(1) Audio reception. Audio signals from the
AN/ARC-51BX facility (fig. FO-6 and FO-6.1 are
routed from pin E of J3801 on Control, Radio Set C6287/ARC-51BX through the C-16111(*)/AIC out pin F
of P3801, to pin 27 of J600 of impedance matching
assembly, to pin 22 of P600, to terminal 4 of TB21, to
pin 19 of both C- 1611/AIC panels. The audio signal is
routed through the C-1611(*)/AIC, out on pin 5 of J301F
of the gunner's C-1611/AIC and J301A of the pilot C1611(*)AIC, to J308 and J309 respectively, and to
headsets of the headset-microphones.
(2) Audio transmission. When the pilot or
gunner set their TRANS selector switch on C1611(*)/AIC panel in position 2, and with a cyclic stick
switch pressed to RADIO position or with the gunner's
foot switch depressed, audio signals are fed from
headset-microphone to pins 3 and 22 of J301A on the
C-1611(*)/AIC out pin 24, 25, or 26 of J301 of C1611(*)/AIC to pin 34 of J600 of impedance matching
assembly, out on pin 38, of P600 to pin i on P3802, to
pin i on J3802, to pin E on P1403 of ReceiverTransmitter, Radio RT-472,/ARC-51BX. The signal is
modulated RT-742/ARC-51BX and transmitted through
the AT-1108/ARC antenna.
2-9.
2-10.
2-8.
FM Homing Operation
NOTE
Radio Set AN ARC-131 may be installed in lieu
of Radio Set AN/ARC-54. In the following
steps, references to Radio Set AN ARC--54
also apply to Radio Set AN,/ARC-131.
Uhf Command Operation
(fig. FO-6 and FO-6.1)
a. Power Distribution.
(1) Receiver circuits. With UHF XCVR circuit
breaker depressed and with selector switch on the uhf
control panel set to T/R + G REC, the dc circuit for
power relay coil in uhf receiver-transmitter is completed
to ground. The energized power relay applies primary
operating voltage through closed contacts to receivertransmitter circuits, placing the facility in receive mode.
(2) Transmitter circuits. High voltage dc for
receiver-transmitter is applied through closed contacts
of internal tr relay, placing receiver-transmitter in
transmit mode.
When the Cyclic stick switch
ICS/RADIO is pressed to RADIO position or when the
gunner's footswitch is depressed, dc voltage is applied
to tr relay coil through closed contacts of the power
relay. The dc circuit for tr relay is completed to ground
through the deenergized contacts of disable relay,
through pin P of P1403 of RT-742/ARC-51BX to pin q of
J3802 to pin 34 of C-1611(*)/AIC. Audio disable relay is
energized during tuning cycle and prevents keying of
transmitter during the tuning cycle.
Automatic Direction Finding (Adf) Operation
(fig. FO-9)
a. Power Distribution. Depressing the ADF circuit
breaker on the pilot's ac circuit breaker panel applies 26
volts ac to pin J of Direction Finder Control C6899/ARN-83 and pin 8 of Mounting MIT-3605/ARN-83.
The dc circuit breaker applies 28 volts dc to pin K of the
C-6899/ARN-83. Setting function switch to ADF position
completes a path to pin 26 of P407 on Radio Receiver
R-1391/ARN-83 through pin 36 to ground.
b. Signal Distribution. RF voltage received by the
sense antenna, the loop antenna or both, depending on
mode of operation, are demodulated by the R1391/ARN-83. Audio is fed to the C-6899/ARN-83
through pins 23 and 24 of P407 and pins T and U of
J302. Controlled audio is routed from the control on
pins W and V of J302 to pins 24 and 35 of P600, the
impedance matching assembly. From here, the signal
enters the C-1611(*)/AIC through the NAV RC-VRS
Change 1 2-9
TM 11-1520-221-34
switch is amplified and fed to the headsets. Bearing
data voltages are fed through P407 on pins 19 and 20 to
the indicators.
2-11.
Gyromagnetic Compass System Operation
(fig. FO-10)
a. Power' Distribution.
Depressing the GYRO
COMPS IND circuit breaker applies 115 volts ac, 400
Hz, to the Directional Gyro CN-998/ASN on pins A and
C, and to Amplifier Electronic Control AM-3209/ASN on
pins 7 and 12. Applying 115 volts, 400 Hz, to the AMI3209/ASN activates an inventer circuit that provides 26
volts ac to the Indicator, Radio-Magnetic Compass ID998/ASN for generator excitation.
b. DG Mode. Directional gyro (DG) mode of
operation is selected by setting compass slaving switch,
located on pilot's instrument panel to DG position. In
the DG mode, a stable reference is provided by the
heading and slaving synchros, which are driven by the
gyro motor. The heading synchro rotor and slaving
synchro rotor are mechanically linked through gimbals to
the gyro motor, so that they provide a change in output
for any change in Directional Gyro CN-998/ASN-43
azimuth position. The stator of the heading synchro
provides a three-wire stabilized reference output signal.
The slaving synchro also provides a stabilized reference
output signal to the ID-998/ASN. The heading synchro
stator signals leave the CN-998/ASN-43 on pins G, H,
and J of P411 and are routed to pins 1, 2, and 3 of ID998/ASN.
c. MAG Mode.
Magnetic (MAG) mode of
operations is selected by setting compass slaving
switch, located on pilot's instrument panel, to MAG
position. In MAG mode the CN-998/ASN is slaved to
the earth's magnetic field. The Transmitter, Induction
Compass T-611/ASN is excited by 23.5 volts ac, 400
Hz, from power transformer T1 in the CN-998/ASN-43.
The T-611/ASN senses the direction of the horizontal
component of the earth's magnetic field and produces a
three-wire 800 Hz output reference signal.
Stray
magnetic fields in the aircraft causing an error in the T611/ASN are compensated for by Compensator,
Magnetic Flux CN-405/ASN. The three-wire signal
produced by the CN-998/ASN-43 leave on pins G, H,
and J and enter the ID-998/ASN on pins 1, 2, and 3.
HIGH, or EMER, +28 volts dc is applied to pin 44 of
J902 in Receiver-Transmitter RT-494/APX-44 through
an energized power relay. The ground circuit for the
power relay is completed through pin H of P901 on the
C-2714/APX-44.
b. Audio Distribution. Audio signals from the IFF
transponder facility are routed from pin 35 of J902 on
the RT-494/APX-44 to pin S of J901 on the C2714/APX-44. Audio signals leave C-2714/APX-44 on
pin T and are routed to pin 27 on J301A and J301F
signal distribution panels. Each time pilot's or gunner's
ICS radio switch is pushed to RADIO or gunner's foot
switch is depressed, a ground path is established from
pin H of J34 (or pin H of J91) to pin 4 of J600 (or pin 5
of J600) on impedance matching assembly. The ground
is routed through the deenergized contacts of K8 and
out of J600 on pin 31 to pin 13 of P907, then to pin P of
P901 on the C-2714/APX-44. On the C-2714/APX-44, if
the MIC position on I/P switch is selected each time
RADIO switch is closed, the AN/APX-44 system is
energized for 30 seconds.
2-13.
Iff System Operation (AN/APX-72)
(fig. FO-12, FO-12.1 and FO-12.2)
a. Power Distribution. With IFF XPDR circuit
breaker depressed and master control on the Control,
Transponder C-6280/APX set to STBY, LOW, HIGH, or
EMER, +28 volts dc is applied to pin 2 of J906 on
Receiver-Transmitter RT-859/APX-72 through an
energized power relay. The ground circuit for the power
relay is completed through pin 53 of P907 on the C6280/APX.
b. Audio Distribution. Audio signals from the IFF
transponder facility are routed from pin 51 of J906 on
the RT-859/APX-72 to pin 55 of J907 on the C6280/APX. Audio signals are routed to pin 27 on J301A
and J301F signal distribution panels. Each time the
pilot's or gunner's radio switch is set to RADIO or the
gunner's foot switch is depressed, a ground path is
established between pin H of J34 (or pin H of J91) and
pin 4 of J600 (or pin 5 of J600) or impedance matching
assembly. The ground is routed out of J600 on pin 31 to
pin 9 of P906. On the C-6280/APX, if the MIC position
on I/P switch is selected each time the RADIO switch is
closed, the AN/APX-72 system is energized for 30
seconds.
2-12.
Iff System Operation (AN/APX-44)
(fig. FO-11 and FO-12)
a. Power Distribution. With AN/APX-44 circuit
breaker depressed and master control on the Control,
Transponder Set C-2714/APX-44 set to STBY, LOW,
Change 1 2-10
TM 11-1520-221-34
2-14.
Vhf Command Operation
(fig. FO-7, FO-8 and FO-8.1)
a. Power Distribution.
(1) Receiver circuits.
Depressing the VHF
RCVR circuit breaker on the dc circuit breaker panel
applies +27.5 volts dc to pins 3 and 4 of J190-1A of the
Receiver-Transmitter, Radio RT-857ARC-134 and to pin
a of J1901 of the contact unit. Placing the OFF/PWR
switch on the Control, Radio Set C-7197/ARC-134 to the
PWR position connects a ground to the coil of the power
control relay. The power control relay is energized and
the 27.5 volts dc is connected to the relay contacts to
energize the receiver portion of the RT-857/ARC-134
circuits in the receive mode.
(2) Transmitter circuits. Placing the TRANS
selector switch on the C-1611(*)/AIC in position 3 and
pressing the pilot's or gunner's cyclic stick switch to the
up position or depressing the gunner's foot switch
applies a ground. to the push-to-talk switch in the RT857/ARC-134. This energizes push-to-talk relay which
then applies +27.5 volts dc to the transmitter circuits of
the RT-857/ARC-134. The receiver circuits are disabled
during the transmit mode.
b. Audio Distribution.
(1) Audio reception. Audio signals from the
AN/ARC-134 are routed from pin 35 of J1904B of the
RT-857/ARC-134 to pin 15 of J600 through R26 and out
pin 17 of J600, to pin 12 of J1904A (audio muting
control) and out on pin 11 of J1904A to pin e of J1901 of
the C-7197/ARC-134. Audio signals are routed through
the volume control of the C-7197/ARC-134, out pin d of
J1901, and to pin 32 of C-1611(*)/AIC panels where the
signals are amplified and routed to pin 2 of TB22, TB23,
then to the headset portions of headset-microphones.
(2) Audio Transmission.
With the TRANS
selector switches on the C-1611(*)/AIC in position 3, and
with the pilot's or gunner's cyclic stick switch pressed to
the RADIO position or the gunner's foot switch
depressed, audio signals are transmitted out pin 26 of
J301A or J301F to pin 14 (pin 16 for gunner) of J600,
through R24 (R23 for gunner), through R25 and coupling
condenser C3, out pin 18 of J600 to pin 30 of J1904A at
the RT-857/ARC-134.
Change 1 2-11
TM 11-1520-221-34
CHAPTER 3
DIRECT AND GENERAL SUPPORT MAINTENANCE
Section I. GENERAL MAINTENANCE TECHNIQUES
WARNING
When servicing the electronic equipment configuration in Army model AH-1G and AH-1Q
helicopters be extremely careful because of high voltages present in various electronic
equipment components. Always disconnect power before attempting to make resistance
measurements.
3-1.
General Instructions
a. The direct and general support electronic
equipment configuration maintenance procedures in this
chapter supplement the organizational maintenance
procedures in TM 11-1520-221-20. In addition, these
procedures supplement the procedures given in the
separate technical manuals on the electronic
equipments to provide complete repair and maintenance
instructions for all electronic equipments.
b. The direct and general support electronic
equipment configuration maintenance procedures are
performed in systematic order. Systematic maintenance
begins with functional operation and sectionalization
check that can be performed within the helicopter, and
those checks are followed by procedures for removal
and replacement of units or components. Systematic
maintenance continues with troubleshooting and bench
maintenance of the individual electronic equipment
components which are removed from the helicopter.
Paragraphs 3-4 through 3-9 provide direct and general
support troubleshooting and repair of electronic
equipment configurations within the helicopters as a
supplement to the organizational maintenance
procedures. As a supplement to the separate technical
manuals on the individual electronic equipment,
paragraphs 3-10 through 3-13 provide direct and general
support troubleshooting and repair of electronic
equipment components that have been removed from
the helicopter.
3-2.
Organization of Troubleshooting Procedures
a. General.
Troubleshooting the electronic
equipment configurations in Army model AH-1G and
AH-1Q helicopters is performed in two steps. The first
step, sectionalization, is to trace the fault to a facility
used in a system of the configuration. The second step,
localization, is to trace the trouble to the defective unit
that is part of the faulty facility or associated junction
box, cabling, or wiring.
When performing bench
maintenance on a removed electronic equipment
component, localization includes tracing the trouble to
the defective component responsible for the abnormal
condition. After determining the defective component,
refer to the applicable manual (app. A) for procedures
for isolating the trouble to a defective part.
b. Sectionalization. Listed below is a group of tests
arranged to reduce unnecessary work and to aid in
tracing faults to defective facilities.
(1) Visual inspection.
Visual inspection to
locate faults before operating or testing circuits includes
checking seating of all component connectors, checking
connections to switches and circuit breakers, and
checking connections on terminal boards, connections
to antennas, and other visible details.
(2) Operational tests.
Operational tests
frequently indicate the general location of trouble. In
many instances, the tests will help in determining the
exact nature of the fault. The periodic preventive
maintenance check and service chart (TM 11-1520-22120) may be used for an operational test.
c. Localization. The procedures listed below are
used for localizing facility troubles to the electronic
equipment components or wiring of the Configuration
Refer to TM 11-1520-221-20 for physical location of
junction boxes, control boxes, receivers, and
transmitters.
(1) Configuration
interunit
troubleshooting.
Configuration interunit troubleshooting in paragraphs 3-4
Change 2 3-1
TM 11-1520-221-34
through 3-6 includes a troubleshooting chart for each
facility. These charts are used to localize to a particular
unit or component the cause of a trouble within a
malfunctioning facility.
(2) Voltage measurements.
The voltage
measurement chart (para 3-7) is used when the
applicable facility troubleshooting chart does not correct
a fault or indicates that voltage measurements are
required.
(3) Electronic equipment troubleshooting. The
troubleshooting charts given in paragraph 3-6 will aid in
localizing the cause of a trouble within an electronic
equipment component.
(4) Intermittent troubles.
In all tests, the
possibility of intermittent troubles should not be
Test equipment
Multimeter AN, URM-105
Electronics Equipment Maintenance
Kit MK-7.21/ARC-51X.
Wattmeter AN URM-120
overlooked. If present, this type of trouble often may be
made to appear by tapping or jarring the equipment and
checking wiring and connections to the components.
3-3.
Test Equipment, Tools, and Materials
Required
a. Test Equipment. The following chart lists the
test equipment required for troubleshooting the
complete electronic equipment configurations and
specific electronic equipment components in Army
model AH-1G and AH-1Q helicopters. Also listed is the
associated manual for each item of test equipment.
Technical manual
TM 11-6625-203-12
TM 11-6625-564-12
Use
In-aircraft troubleshooting
In-aircraft troubleshooting
TM 11-6625-446-15
In-aircraft troubleshooting
b. Tools and materials.
(1) Tool Kit, Electronic Repairman TK-100/G.
(2) Tool Kit, Electronic Repairman TK-101/G.
(3) Varnish, Corrosion and Fungus Resistant
MIL-V-173.
Section II. CONFIGURATION INTERUNIT TROUBLESHOOTING
3-4.
Introduction
a. When a malfunction of an electronic equipment
occurs, the first step in correcting the trouble is to
sectionalize the cause to a particular unit in the aircraft
(helicopter). Perform the operational checks in the
periodic preventive maintenance check and service
chart (TM 11-1520-221-20). If the operational checks
and supporting troubleshooting chart are inconclusive as
to which unit or item is causing the trouble, perform the
direct and general support in-aircraft troubleshooting
procedures in this section for the particular defective
facility.
NOTE
Troubleshooting procedures for electronic
equipments that have been removed from
the helicopter are covered in paragraphs 312 and 3-13.
b. The direct and general support in-aircraft
troubleshooting procedures involve the use of special
portable test equipments that are not allocated at the
organizational maintenance level. Since the controls for
the electronic equipments and the other basic
components are remotely located, the troubleshooting
procedures in this section require more than one person.
The organizational maintenance repairman should
remain in the operator's compartment to operate the
controls in accordance with the commands from the
direct or general support maintenance repairman. The
direct support maintenance repairman will then connect
the test equipments (para 3-5) and perform the
procedures outlined in paragraph 3-6.
3-5.
Facility Test Setup AN/ARC-51 BX
a. Radio Set Simulator (Part of Electronics
Equipment Maintenance Kit MK-731/ARC-51X). By
substituting the radio set simulator for the receivertransmitter, the following tests and measurements of the
remaining units or circuits in the aircraft can be made:
(1) Polarity of the aircraft power source.
(2) Magnitude of power source voltage under
simulated load during both transmit and receive.
(3) Receive audio system.
(4) Microphone audio system.
(5) Frequency control selector system.
(6) Transmit/receive T/R) control circuit.
(7) Guard receiver control circuit.
(8) Adf control circuit.
Change 2 3-2
TM 11-1520-221-34
(9)
(10)
(11)
(12)
is provided. Slide the radio set simulator and mounting
tray onto the mounting in the helicopter. Engage the
wingnut fasteners, and tighten to secure the radio set
simulator in place.
c. Cable Connections, Radio Set simulator.
(1) Connect helicopter cable connectors P-1401
and P1403 to radio set simulator jacks J1401 and J1403
respectively.
(2) Connect the helicopter antenna cable to
radio set simulator jack J3.
(3) Plug Headset H-101A/U into the radio set
simulator Headset H-101A/U jack.
d. In-Aircraft Troubleshooting Radio Set AN/ARC51BX. By performing the in-aircraft troubleshooting
procedures as described in this section, a complete
check of the remaining units associated with the
AN/ARC-51BX can be accomplished. The procedures
are listed so that if unsatisfactory indications are
obtained for a particular step, the trouble can be
sectionalized to a particular circuit or unit. If the results
of the troubleshooting procedures are completely
satisfactory, it can be assumed that the cause of trouble
is within the RT-742(*)/51BX.
Antenna and RF circuits.
Shielded ground connections.
SENS control circuit.
Auxiliary audio circuit.
b. Radio Set Simulator Installation.
(1) Turn the radio set control function select
switch to OFF. Turn the main power control switches on
all other equipment associated with the radio set to
OFF.
However, close all aircraft circuit breakers
associated with the radio set.
(2) Disconnect aircraft cable connectors
P1401 and P1403 from the RT-742(*)/51BX jacks J1401
and J1403. Disconnect the antenna cable connector
from reflectometer plug P1405.
(3) Loosen the RT-742(*)/51BX
wingnut
fasteners so they can be disengaged from the mounting,
and slide the RT-742(*) 51BX off the Mounting MIT2653/ARC. Do not remove the reflectometer or external
blower from the RT-742-(*)/51BX.
(4) Remove the radio set simulator from its
storage location within the Electronics Equipment
Maintenance Kit MK-731 ARC-51X carrying case.
Attach the radio set simulator to the mounting tray which
Step
1
1
3
4
5
6
Action
Normal indication
Radio set:
Turn radio set simulator TEST
SELECTOR switch to +27.5
VDC. Set radio set simulator
POWER switch to ON.
Cockpit:
Turn C-6287/ARC-51BX function
select switch to T/R.
Radio set simulator:
Check aircraft intercom system by
talking
into
H-101A/U
microphone.
Radio set simulator multimeter indicates
within green sector. Radio set simulator
+27.5 VDC indicator lamp lights.
Cockpit:
Rotate C-6827/ARC-51BX VOL
control from full clockwise to full
counterclockwise position.
Radio set simulator:
Turn radio set simulator TEST
SELECTOR
switch
to
REMOTE SENS.
Cockpit:
a.
Rotate
C-6287/ARC-51BX
SENS
control
from
full
counterclockwise
to
full
clockwise position.
b. Turn C-6287/ARC-51BX SQ
If abnormal indications
are observed
Helicopter power source is cause of trouble.
Check polarity and continuity of 27.5-volt
dc helicopter wiring.
Radio set simulator T/R indicator lamp lights.
The C-6287/ARC-51BX function selector
switch or aircraft power on-off control
wiring is cause of trouble.
Audio from radio set simulator heard at pilot’s
H-101A/U in cockpit
Trouble may be caused by faulty pilot’s H101A/U. Substitute for H-101A/U to check
this possibility. If R-101A/U is good,
proceed with tests to pinpoint cause of
trouble in helicopter audio system.
Corresponding increase and decrease of
audio level at pilot’s H-101A/U.
The C-6287/ARC-51BX control VOL control
circuit is cause of trouble. Refer to TM 115820-518-35.
Radio set simulator indication varies from 0 to
at least 8 (scale A) as SENS control is
rotated.
The C-6287/ARC-51BX SENS control or
associated aircraft wiring is cause of
trouble. Refer to TM 11-5820-518-35.
Caution: Do not drive multimeter indicator
beyond full scale.
Radio set simulator SQ DIS indicator
3-3
The C-6287/ARC-51BX squelch disable
TM 11-1520-221-34
Step
7
8
Action
DISABLE switch to ON
position.
Cockpit:
Press push-to-talk switch on pilot's
control, and talk into H-101A/U
microphone.
Radio set simulator:
Turn radio set simulator TEST
SELECTOR switch to SHIELD
GROUND.
9
Cockpit:
Turn radio set control function
selector switch to T/R+G.
10
a. Cockpit:
Return
C-6287/ARC-51BX
function selector switch to T/R.
b. Radio set simulator:
Turn radio set simulator TEST
SELECTOR switch to +27.5
VDC.
Operate radio set
simulator XMIT LOAD switch to
ON momentarily.
Radio set simulator:
Turn radio set simulator TEST
SELECTOR switch to VSWR
CAL. Press radio set simulator
PTT switch, and adjust VSWR
CAL control until multimeter
indicates on CAL mark (scale
B). Switch radio set simulator
TEST SELECTOR switch to
VSWR TEST and press PTT
switch.
a. Cockpit:
Turn C-6287, ARC-51BX 10-mc
control through all positions.
b. Radio Set simulator:
Verify radio set simulator
frequency readout.
a. Cockpit:
Turn C-6287/ARC-51BX 1 mc
control through all positions.
b. Radio set simulator:
Verify radio set simulator
frequency readout.
a. Cockpit:
Turn C-6287/ARC-51BX 1-mc
control through all positions.
11
12
13
14
Normal indication
If abnormal indications
are observed
able switch or associated aircraft wiring is
cause of trouble. Refer to TM 11-5820518-35.
Radio set simulator XMIT indicator lights.
Audio from cockpit heard at radio set
simulator H-101A/U headset. Sidetone
audio heard at pilot's H-101A/U headset in
cockpit.
Pilot's push-to-talk control or aircraft T/R
control wiring is cause of trouble. Aircraft
audio system is cause of trouble. Check
for open circuits
or short circuits to ground on head-set and
microphone audio connections.
Radio set simulator multimeter indicates
within the green sector of scale A.
Helicopter interconnecting cable containing
shielded audio conductors is cause of
trouble.
Radio set simulator T R+G indicator lights.
The C-6287/ARC-51BX function selector
switch or helicopter guard receiver control
wiring is cause of trouble. Refer to TM 115820-518-35.
Radio set simulator multimeter indicates
within the green sector and remains there
during XMIT LOAD switch operation.
Radio set simulator XMIT LOAD indicator
lights during test.
Helicopter power source is cause of trouble.
Check for cause of low voltage under
simulated transmit load conditions.
Radio set simulator multimeter indication
does not exceed green sector of scale B
with an SWR of 3:1 or less.
Trouble is caused by either the helicopter
antenna or RF cable between reflectometer
jack J1 and helicopter antenna.
lights.
Radio set simulator frequency read-out
agrees
with
radio
set
control
MEGACYCLES indicator at each position
of 10-mc control.
Radio set simulator frequency read-out
agrees
with
radio
set
control
MEGACYCLES indicator at each position
of 1-mc control.
3-4
The C-6287/ARC-51BX 10-mc control switch
or aircraft wiring associated with 10-mc
frequency control is cause of trouble.
The C-6287/ARC-51BX 1-mc control switch
on aircraft wiring associated with 1-mc
frequency control is cause of trouble.
TM 11-1520-221-34
Step
Action
b. Radio set simulator:
Verify radio set simulator frequency readout.
If abnormal indications
are observed
Normal indication
Radio set simulator frequency readout agrees with radio set control
MEGACYCLES indicator at each
position of .1-mc control.
3-6.Facility Troubleshooting
Direct and general troubleshooting charts for each
facility in each configuration are contained in a through
g below. When using the troubleshooting charts to
determine the cause of malfunction, go directly to the
facility in which the malfunction is reported, start at the
beginning of these procedures, and follow each step in
order. If the indicated checks in the "If abnormal
indications are observed" column fail to locate the
The C-6287, ARC-51BX .1-mc control
switch or aircraft wiring associated
with .1-mc frequency control is
cause of trouble.
trouble, perform the voltage measurements given in
paragraph 3-7. When the trouble is localized to a basic
electronic equipment item, remove the item from the
helicopter and perform the electronic equipment unit
troubleshooting procedures (sec. IV) to determine the
trouble within the malfunctioning electronic equipment
item. Depress all communication and navigation circuit
breakers.
a. Interphone and Audio Facility (fig. FO-2, FO-3, FO-4 and FO-4.1).
Step
1
2
Action
On C-1611(*)/ATC (interphone
panels) turn transmit-receive
selector switch to INT.
Place microphone switch on
cyclic grip to ICS (down)
position. Speak into microphone.
Normal indication
Sidetone heard in H-101/U headsets.
If abnormal indications
are observed
Check that H-101/U headset-microphone jack is properly inserted.
Check for +28 volts dc at pin 37 of
C-1611 (*) AIC.
b. Fm Liaison and Fm Homing Facilities (fig. FO-5).
Step
1
Action
Turn mode control on C-3835/
ARC-54 to PTT.
Normal indication
Radio set is energized
2
On C-3835/ARC-54, turn mode
control to PTT, turn volume
control to increase.
Turn transmit-interphone switch
on C-1611(*)/AIC to number 1.
Minimum background noise heard in
H-101/U.
4
Establish two-way communication with local fm station.
Transmitted signal should be loud and
clear.
5
While keying the RT-348/ARC54 and talking into H-101/U,
set the meter selector switch
on RT-348/ARC-54 to each
of 12 positions.
Set mode control switch to
HOME.
In each position the meter should indicate between 3 and 7 except in position 11 which should not exceed 8.
Position 12 represents OFF.
3
6
Received signal should be loud and
clear.
Vertical pointer flag should disappear
and the vertical pointer should deflect left or right, depending on
bearing to transmitter; indicator
pointer remains centered if aircraft
Change 1 3-5
If abnormal indications
are observed
Probable trouble with FM ARC-54 circuit breaker. Check for 28 volts dc
at FM circuit breaker. Check for
+28 volts dc at pins, 18, 34, and 36
of J2106 on RT-348/ARC-54. Check
for +28 volts dc at pins C, D, and E
of J2107 on C-3835/ARC-54.
Adjust squelch adjustment. Refer to
TM 11-1520-221-20.
Check for correct frequency selection
on C-3835/ARC-54.
Probable faulty antenna cable or connector.
Probable trouble in RT-348/ARC-54.
Probable trouble in fm antenna.
Probable trouble in C-3835/ARC-54.
Improper frequency set in C-3835/
ARC-54.
Probable faulty RT-348/ARC-54.
Probable trouble in fm antenna.
Probable trouble in RT-348/ARC-54.
Probable trouble in RT-348/ARC-54.
Received signal strength inadequate.
Probable defective ID-48(*)/ARN.
TM 11-1520-221-34
Step
Action
c.
Normal indication
is aligned with bearing to transmitter.
If abnormal indications
are observed
Vhf Command Facility (fig. FO-7, FO-8 and FO-8.1).
Step
1
Action
Set OFF PWR switch to PWR.
Normal indication
Indicator dials should glow
2
Turn VOL control clockwise
A rushing noise should be heard in the
headset.
If abnormal indications
are observed
If indicator dials do not glow, replace
Radio Control Set C-7197/ARC-134.
If no noise heard in headset check Receiver-Transmitter RT-857/ARC134. Refer to TM 11-5821-277-25-1.
d. Uhf Command Facility (fig. FO-6 and FO-6.1).
Step
1
2
3
Action
Set function selector switch to
T/R position.
Turn VOL control clockwise
Normal indication
External blower operates
Turn SENS control fully counterclockwise.
No audio heard in headset
Loud noise in headset
If abnormal indications
are observed
Check uhf circuit breaker.
Check fuse F1 in RT unit.
Check VOL control switch.
Check C-6287/ARC-51BX.
Check SENS control.
Check C-6287/ARC-51BX.
e. Adf Direction Finding (fig. FO-9).
Step
1
Action
Set function switch to ADF
Normal indication
Frequency window is illuminated
2
Set BFO-OFF switch to OFF
No cw in headset
3
Rotate loop switch
Rearing indication pointer rotates
f.
If abnormal indications
are observed
Check ADF circuit breaker.
Check ADF function switch.
Check BFO-OFF switch.
Check R-1.391/ARN-83.
Replace control unit.
Gyro-Magnetic Comp)ass Facility (fig. FO-10).
Step
Action
Power on
Normal indication
ID-998 ASN power failure indicator
disappears.
If abnormal indications
are observed
Check GYRO COMP circuit breaker.
Check ID 988/ASN.
g. Iff system Facility (fig. FO-11, FO-12, FO-12.1 and FO-12.2).
Step
1
Action
Set master control switch to
STBY.
Normal indication
Pilot light illuminates
2
Set master control switch to
mode 1.
Appropriate flags appear on transponder test set.
3-7.
Voltage Measurement Chart
Use the voltage chart below when troubleshooting the
electronic equipment configuration in helicopter. When
a trouble develops in a facility and the applicable facility
troubleshooting chart does not correct the fault or
indicates that voltage measurements are necessary,
refer to this chart and make the voltage measurements
shown for the applicable terminals. When a measureTerminal
1
2, 3, and 4
If abnormal indications
are observed
Check for 28 volts dc at circuit
breaker.
Check fuse FO11.
Check pilot light.
Check control unit.
Check RT unit.
Check antenna.
ment does not correlate with the chart, refer to the
electronic equipment configuration schematic wiring
diagram (TAM 11-1520-221-20) and trace the wiring
until the difficulty is found.
Before making
measurements, connect an auxiliary power unit (TM 111520-221-20). Operate the equipment from the pilot's
controls after pressing the pilot's RADIO CONTROL
switch.
Facility
Function
Operation of equipment
Voltage
TB 21 Communication impedance matching assembly
Fm liaison ...............................Power to fm liaison set.........................................Fm liaison facility on .........................................+28 vdc
Interphone ..............................Common ground..................................................Ground ..............................................................Zero
TB 6 Panel lights
Change 1 3-6
TM 11-1520-221-34
Terminal
1, 2
5
1
2
3
4
5
1
2
3
4
5
3-8.
Facility
Function
Operation of equipment
Voltage
Panel lights.............................Power to panel lights............................................Light control fully on...........................................+28 vdc
TB 2 Panel lights
Panel lights.............................Power to panel lights............................................Light control fully on...........................................+28 vdc
TB 22 gunner's headset
lnterphone...............................Gunner's H-101/U earphone audio-.....................Interphone facility turned on...............................Zero
common.
Interphone ..............................Gunner's H-I101/U earphone audio-....................Interphone facility turned on...............................Audio
high.
Interphone ..............................Gunner's H-101/U microphone............................Interphone facility turned on...............................Audio
audio-high.
Interphone ..............................Gunner's H-101/U microphone............................Interphone facility turned on...............................Zero
audio-low.
Interphone ..............................Gunner's H-101/U headset cord and...................Interphone facility turned on...............................Zero
cable shield.
TB 23 Pilot's headset
Interphone ..............................Pilot's H-101/U earphone audio-..........................Interphone facility turned on...............................Zero
common.
Interphone ..............................Pilot's H-101/U earphone audio-..........................Interphone facility turned on...............................Audio
high.
Interphone ..............................Pilot's H-101/U microphone audio- ......................Interphone facility turned on...............................Audio
high.
Interphone ..............................Pilot's H-101/U microphone audio- ......................Interphone facility turned on...............................Zero
low.
Interphone ..............................Pilot's H-101/U headset cord and ........................Interphone facility turned on...............................Zero
cable shield.
Gyromagnetic Facility Alignment
i. Calculate the average of the four deviations.
j. Rotate the T-611/ASN the number of degrees
and in the opposite direction to that of the average
deviation. For example, if the average deviation was
minus 6 degrees, the compass would be rotated 6
degrees positive.
k. Repeat steps g through j to achieve maximum
accuracy. Tighten the T-611/ASN mounting screws and
note the heading measurements for reference.
l. Point the helicopter on a north magnetic
heading.
m. Subtract the south deviation from the north
deviation (determined from notes made in step k) and
divide the result by 2.
n. Adjust the N-S ID-998/ASN screw so that the
indication on the ID-998/ASN moves by the amount and
in the direction calculated in step m. For example, if the
heading was 358 degrees and the calculation in step m
was plus 1.5 degrees, the N-S screw would be adjusted
for a heading of 359.5 degrees.
o. Repeat step n with the helicopter pointing on a
south magnetic heading.
p. Point the helicopter on an east magnetic
heading.
a. Secure all magnetic equipment aboard the
helicopter into normal flight position.
b. Position the helicopter on a compass rose away
from any abnormal magnetic fields such as cars,
buildings, and electrical equipment. No magnetic tools,
jacks, or handling equipment can be used during
alignment, and operators must
not carry any magnetic material, such as watches, keys,
safety shoes, and flashlights.
c. Energize the compass facility and let it warm up
for ten minutes. The slaving switch should be set to the
MAG position.
d. Set flux Compensator, Magnetic Flux CN405/ASN adjusting screws (N-S and E-W) to align their
dots with the dots on the CN-405/ASN case.
e. Loosen the Transmitter Induction Compass T611/ASN mounting screws and align the T-611/ASN with
the helicopter's fore/aft axis.
f. Slowly rotate the helicopter at least one full turn
while watching Radio Magnetic Compass ID-998/ASN.
The ID-998 motion should be smooth and the bearing
should approximate the heading of the helicopter.
g. Point the helicopter on an east magnetic
heading. Note the heading shown on the ID-998/ASN
and determine the deviation.
h. Repeat step g for south, west, and north
magnetic headings.
3-7
TM 11-1520-221-34
q. Subtract the west deviation from the east
deviation (determined from noted made in step k) and
divide the result by 2.
r. Adjust the E-W CN-105r ASN screw so that the
indication on the ID-998/ASN moves by the amount and
in the direction calculates in step q. For example, if the
heading was 90 degrees and the calculation in step q
was plus 0.75 degree, the E-W screw would be adjusted
for a heading of 89.75 degrees.
s. Repeat step r, with the helicopter pointing on a
west magnetic heading.
t. Repeat steps g through s until all deviations are
less than 2 degrees.
u. Make measurements of heading deviation, one
at every 30-degree increment on the compass rose.
Record the deviations on the compass correction card,
along with the T-611/ASN, CN-405/ASN, and ID988/ASN serial numbers.
v. Seal the N-S and E-W screws with lacquer.
3-9. Main and Standby Inverter Adjustment (AH-1 G)
Periodic Check-Inverter Output.
Perform following
procedures to check inverter outputs:
NOTE
Both the main and standby inverter
outputs should be checked in
conjunction with each periodic
inspection.
a. Remove
access
panel
directly
above
ammunition compartment door on left side of helicopter
(helicopters 68-15000 and subsequent for main (250 va)
inverter location, open aft compartment access door).
NOTE
To properly conduct this inverter
check, it will be necessary to apply a
regulated DC ground power source
or ground run the helicopter to
assure an adequate source of DC
power for inverter operation. Under
no circumstances will helicopter
battery power be used.
Engine Oil Pressure
Fuel Pressure
Indicator, Radio-Magnetic Compass ID-998/ASN
Torque Pressure
Transmission Oil Pressure
c. Using the most accurate AC voltmeter available,
check output voltage at terminal(s) B1 and X2 of
transfer relay (K9) located on bulkhead directly above
inverters. If output voltage is found to be within 107 to
115 volts, no adjustment is necessary.
NOTE
(Helicopters
68-15000
and
subsequent)
Connect the AO
voltmeter and a frequency meter to
the 115 vac Bus at the engine
vibration
receptacle
or
other
convenient monitoring point. Check
that the AC bus voltage is 115 ±2.5
vac and the frequency is between
380 and 120 Hz.
d. Should output voltage be above or below the
prescribed range of 107 to 115 volts, proceed as follows.
Turn off DC power to inverter. Dismount inverter from
helicopter structure. Remove cover from end of inverter
that normally faces toward nose of helicopter.
Reconnect bonding jumper to base of inverter. Loosen
hex-head jam nut securing adjustment screw.
e. Close all AC circuit breakers. Actuate all AC
circuits. Turn on inverter power. Connect voltmeter
across terminals B1 and X2 of transfer relay (K9). Note
reading.
Turn inverter output adjustment screw
clockwise to increase, or counterclockwise to decrease
inverter output. Nominal setting of 111 volts at full
output load should produce an output frequency within
limits of 380 to 420 Hz. See figure 3-1 for directional
references.
NOTE
(Helicopters
68-15000
and
Subsequent)
The voltage (VOLT)
and frequency (FREQ) adjustment
screws are located on the end of the
inverter (Main) adjacent to the power
receptacle.
b. Turn on main inverter. Close all AC circuit
breakers. Actuate the following AC circuits to produce
maximum demand on main inverter:
AC 115 Volt
AC Failure Relay
Attitude Indicator
Fuel Quantity
AN, ASN-43
SAS Power
Transformer (25 volt)
Weapon Power
Inverter Balance
AC 26 Volt
Indicator, Course ID-250. ARN
Attitude Indicator (Gunner)
Change 2 3-8
NOTE
If frequency measuring equipment is
available, it is highly recommended a
frequency check be accomplished in
conjunction with voltage check. If
frequency check reveals frequency is
not within the high low limit (380 or
420), voltage should be adjusted
upward or downward to bring
frequency within range.
TM 11-1520-221-34
Figure 3-1. Adjustment of main inverter (PU-542(A)/A or PU-543(*)/A).
f. Check and adjustment procedure is essentially the same for the static inverter (located adjacent to main inverter)
with the exception that inverter need not be removed from the aircraft or disassembled to gain access to adjustment
screws. Connect voltmeter test lead to terminals B3 and X2 of transfer relay K9.
g. Voltage adjustment screw is located at upper right corner of inverter. Adjustment is accomplished by inserting a
small insulated screw driver through perforated cover of inverter, engaging slots in adjustment screw. Turn counter
clockwise to increase voltage or clockwise to decrease voltage. See figure 3-2 for directional references.
NOTE
Frequency output of the static inverter is electronically controlled and is not a function of RPM
as is the case with the rotary inverter; however, if frequency check equipment is available, it is
highly recommended that a frequency check be accomplished in conjunction with the voltage
check. Should it become necessary to readjust frequency output of the static inverter,
adjustment screw is located at lower right corner of inverter.
3-9
TM 11-1520-221-34
Figure 3-2. Adjustment of standby inverter (PP-6508B/U)
Adjustment is accomplished by inserting an
insulated screw driver through perforated cover,
engaging slots in adjustment screw. Turn screw
counterclockwise to increase frequency output
or clockwise to decrease output frequency.
h. Should readjustment of the static inverter
become necessary, adjust to 115 volts 400 Hz with full
AC load applied.
3-9.1. Main and Standby Inverter Periodic Output
Check (AH-1Q)
a. Place NON ESS BUS switch (S4) to NORMAL.
Close MAIN INV, STBY INV, CAUTION LTS, and AC
FAIL RLY circuit breakers. Check that INST INVERTER
caution light illuminates.
b. Place INV selector switch (S3), located on pilot's
electrical control panel, to MAIN position. Check that
main inverter is energized.
Check that INST
INVERTER caution light is extinguished.
c. Connect an ac voltmeter and a frequency meter
to the essential 115-volt ac bus at engine vibration
receptacle or other convenient monitoring point. Set
essential bus voltage to 28 ±0.5 volts. Check that ac
bus voltage is 115 +3.5, -6.5 volts and that frequency is
400 ±10 Hz.
d. Switch TOW system on. Check for 115 +3.5, 6.5 volts ac between each of the two active circuits on
TOW PWR circuit breaker (CB76) and ground. Check
that essential ac bus remains energized and that INST
INVERTER caution light remains extinguished.
e. Switch TOW system off. Check for no voltage
on the active circuits on the TOW PWR circuit breaker.
Check that essential bus is energized and INST
INVERTER caution light is extinguished.
f. Open MAIN INV circuit breaker. Check that
main inverter is deenergized and that INST INVERTER
caution light is illuminated.
g. There is no external adjustment controls,
therefore, all adjustments must be conducted by a
higher level of maintenance. Remove and replace
inverter if inspection requirements are not met.
Change 2 3-10
NOTE
Refer to paragraph 3-9 for checking
and adjusting the standby inverter.
TM 11-1520-221-34
Section III. ELECTRONIC CONFIGURATION REPAIRS AND ALIGNMENT
3-10. General
The repair and alignment procedures that can be
performed in the helicopter by direct support
maintenance personnel are covered in section IV.
These procedures supplement the organizational
maintenance repairs and alignment in TM 11-1520-22120 to provide complete repair and alignment procedures
for the electronic equipment configurations. For repair
and alignment procedures on electronic equipments
that have been removed from the helicopter, refer to
paragraphs 3-12 and 3-13.
3-11. Removal and Replacement of Components
Removal and replacement of all electronic equipments,
including those parts within the impedance matching
box, are covered in the helicopter organizational manual
TM 11-1520-221-20.
Section IV. ELECTRONIC EQUIPMENT UNIT TROUBLESHOOTING AND REPAIR
3-12. General
Direct and general support troubleshooting and repair of
electronic equipment components that have been
removed from helicopters, except impedance matching
assemblies, are covered in the separate technical
manuals for the individual equipments (app. A).
3-13.
Troubleshooting and Repair of Impedance
Matching Network Assemblies (P/N 209-75235)
(fig. 2-1.2-2, 2-2.1,2-3 and 2-3.1)
a. Types of Troubles. Three types of troubles are
encountered in the impedance matching network:
defective components, defective conductors, or
defective printed circuit boards P/N 209-075-246.
Replace broken, cracked, or blistered boards.
(1) Removal of protective coating. If repairs are
extensive, soak the board in trichloroethylene to soften
the protective coating. Wipe the area clean with a lint
free cloth. If repairs are minor, carefully scrape the
protective coating from the area to be repaired; use a
knife or similar sharp tool.
(2) Application of protective coating. If the
entire protective coating was removed during repair,
replace the coating by spraying two coats of varnish,
moisture and fungus resistant, MIL V-173, on both sides
of the board. If the repairs were minor in nature, brushapply two coats of varnish to the affected area.
c. Replacing Defective Parts. Replace defective
parts as follows:
NOTE
Resistor and capacitor color code
diagrams (fig. FO-1) are provided to
air
maintenance
personnel
in
determining the value, voltage rating,
and tolerance of capacitors and
resistors.
CAUTION
Use only pencil-type soldering irons
with a maximum rating of 25 watts
when repairing impedance matching
network.
b. Coating. The impedance matching network
assemblies on the printed circuit boards are coated with
protective coating MIL-V-173.
Remove protective
coating from the immediate area before making repairs.
When repairs are completed, apply new protective
coating. Removal and application procedures for the
protective coating are given below:
WARNING
Trichloroethylene is toxic.
Avoid
breathing the fumes.
Perform
cleaning in a well ventilated area,
using a clean, lint free cloth. If
solvent comes in contact with the
skin, wash the skin thoroughly with
soap and water immediately.
(1) Remove the defective part by cutting its
leads near mounting holes on the part-bearing side of
the board.
(2) Remove protective coating as directed in
b(1) above.
CAUTION
Do not apply heat longer than
necessary; prolonged heating can
damage the board.
(3) Apply heat at the mounting holes until the
solder is melted, and remove remaining pieces of the
part's wire leads.
Change 2 3-11
TM 11-1520-221-34
(4) Heat the solder in the mounting holes and
remove it with a stiff bristle brush.
(5) Bend the leads of the replacement part to
fit the mounting holes.
(6) Insert the leads in the mounting holes, and
press the part firmly against the board.
(8) Bend and press the leads against the
printed circuit conductor.
(9) Using a heat sink, solder the replacement
part to the printed circuit conductor.
(10) Coat the new part and the repaired area
with protective coating as directed in b(2) above.
(7) Cut the leads approximately one-eighth
inch from the wiring side of the board.
Change 2 3-12
TM 11-1520-221-34
CHAPTER 4
DIRECT AND GENERAL SUPPORT TESTING PROCEDURES
4-1.
General
a. Testing procedures are prepared for use by
maintenance
shops
and
supporting
service
organizations responsible for performing direct and
general support maintenance on avionic equipments to
determine the acceptability of repaired equipments.
These procedures set forth specific requirements that a
repaired electronic equipment must meet before it is
returned to the using organization.
b. All electronic equipment testing procedures,
except those for the impedance matching network for all
configurations, are covered in Separate technical
manuals for the individual equipments (app.
A).
Paragraphs 4-2 through 4-4 cover the direct and general
support testing procedures for the impedance matching
network. Comply with the instructions preceding the
body of each chart in this chapter before performing the
procedures. When fully repaired impedance matching
network assemblies are being tested, perform each test
for the particular unit or component in the sequence
given in paragraphs 4-3, and 4-4.
c. When an equipment has had minor repairs
performed on it by general support maintenance teams
operating within a depot (or operating under depot
supervision) and is to be returned to the user instead of
the Army supply stocks,
deviations from the testing procedures may occur if(1) The deviation does not result in a lower
performance standard.
(2) The specific deviations are approved by the
quality assurance officer of the applicable depot.
d. The performance standards listed in the
assume that all pertinent modification work orders
been performed. Check the current issue of DA
310-7 to find the latest listing of modification
orders of the equipment under test.
tests
have
Pam
work
4-2.
Test Equipment, Tools and Materials
Required
All test equipment, tools, and materials required to
perform the testing procedures in this chapter are listed
below.
a. Test Equipment and Materials.
Multimeter
AN/URM-105 and Varnish Corrosion and Fungus
Resistant MIL-V-173 are the only test equipment and
materials required.
b. Tools. All tools required are contained in Tool
Kit, Radio Repair TK-100/G.
4-3.
Physical Tests and Inspection
a. Test Equipment and Materials. None.
b. Test Connections and Conditions. Impedance
matching network removed from impedance matching
support P/N 209-075-236. Refer to TM 11-1520-221-20.
c. Procedure (fig. 2-3 and 2-3.1).
Step No. Test ProcedurePerformance Standard
1
2
a. Inspect board for cracks and damage .................
b. Inspect protective coating for chips and cracks ....
c. Inspect printed circuitry for damage ....................
a. Inspect resistors, capacitors, and diodes for.........
faulty solder connections and damage. ..............
b. Inspect relays for secure mounting and evi- .........
dence of broken leads and damage....................
Change 1 4-1
a. No damage is evident.
b. Protective coating covers all components; no
damage is evident.
c. No damage is evident.
a. All solder connections appear secure and no
damage is evident.
b. All mountings secure and no evidence of broken
leads or damage.
TM 11-1520-221-34
4-4.
Impedance Matching Network (P/N 209-075235), Component Tests
a. Test Equipment and Materials.
(1) Multimeter AN/URM-105.
(2) Varnish, Corrosion and Fungus Resistant
MIL-VN-173.
b. Test
Connection
(
fig
2-3
and
2-3.1).
Connect Multimeter AN/URM-105 leads to the leads on
the components.
NOTE
To permit good electrical contact
prior to checking each individual
resistor, capacitor, or diode, scrape
off varnish coating where test leads
are to be connected. After checking
the components, brush-apply two
coats of varnish on the area in which
varnish was removed.
Step No. Test ProcedurePerformance Standard
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
Check R9 .................................................................
Check R10................................................................
Check R11................................................................
Check R12................................................................
Check R13................................................................
Check R14................................................................
Check R15................................................................
Check R16................................................................
Check R17................................................................
Check R18 ...............................................................
Check R19 ...............................................................
Check R20 ...............................................................
Check R21 ...............................................................
Check R22 ...............................................................
Check R23 ...............................................................
Check R24 ...............................................................
Check R25 ...............................................................
Check R26 (A, B, and C) .........................................
Check R26 (D) .........................................................
Check R27 (A, B, and C) .........................................
Check R27 (D) .........................................................
a. Check C5 ............................................................
b.
a.
b.
a.
b.
a.
b.
a.
b.
a.
b.
a.
b.
a.
b.
a.
g.
a.
b.
a.
b.
a.
b.
a.
b.
Reverse polarity and observe deflection again......
Check CR5 .........................................................
Reverse leads to CR5 .........................................
Check CR6 .........................................................
Reverse leads on CR6 ........................................ .
Check CR7 .........................................................
Reverse leads on CR7 ........................................
Check CR8 ......................................................... .
Reverse leads on CR8 ........................................ .
Check CR9 .........................................................
Reverse leads on CR9 .........................................
Check CR10 . ......................................................
Reverse leads on CR10 ......................................
Check CR11. .......................................................
Reverse leads on CR11 .......................................
Check CR12 .......................................................
Reverse leads on CR12 .......................................
Check CR13 ....................................................... .
Reverse leads on CR13 ......................................
Check CR14 ....................................................... .
Reverse leads on CR14 ......................................
Check CR15 ....................................................... .
Reverse leads on CR15 ......................................
Check CR16 .......................................................
Reverse leads on CR16 ...................................... .
Change 1 4-2
73 to 86 ohms
95 to 105 ohms
95 to 105 ohms
95 to 105 ohms
142 to 158 ohms
65 to 71 ohms
95 to 105 ohms
95 to 105 ohms
95 to 105 ohms
171 to 189 ohms
371 to 409 ohms
142 to 158 ohms
142 to 158 ohms
37 to 41 ohms
114 to 126 ohms
114 to 126 ohms
78 to 86 ohms
314 to 347 ohms
285 to 315 ohms
209 to 231 ohms
285 to 315 ohms
a. Quick pointer deflection to near zero scale,
then gradual (4 seconds) return to infinity.
b. Same as a.
a. Forward resistance 100 ohms
b. Reverse resistance 3 megohms
a. Same as 21a
b. Same as 21b
a. Same as 21a
b. Same as 21b
a. Same as 21a
b. Same as 21b
a. Same as 21a
b. Same as 21b
a. Same as 21a
b. Same as 21b
a. Same as 21a
b. Same as 21b
a. Same as 21a
b. Same as 21b
a. Same as 21a
b. Same as 21b
a. Same as 21a
b. Same as 21b
a. Same as 21a
b. Same as 21b
a. Same as 21a
b. Same as 21b
TM 11-1520-221-34
4-5.
(2) Set the controls on the control unit C6280A(P)/APX as follows:
Testing Procedures, IFF SystemAN/APX-72.
a. Purpose of External Test Equipment for IFF Set.
The AN/APM-123(V)1 transponder test set (figure 4-1) is
used to provide a coded radio frequency (rf)
interrogation signal to check the transponder set
receiver and decoder and, in addition, check the
transponder set transmitter and coder by evaluating the
coded rf replies. The test set can be directly coupled to
the transponder antenna system utilizing the antenna
test hood MX-4396/APM-123(V) in conjunction with the
55db attenuator. (See figure 4-2.)
CAUTION
Failure to use the 55db attenuator
will seriously damage the AN/APM123(V)1l transponder test set.
b. Preliminary Test Setup.
(1) Visually inspect the IFF set installation for
defects or damage.
(2) Install antenna test hood MX-4396/APM123(V) over AT-884( )/APX antenna in accordance with
TM 11-6625-667-12.
(3) After the couple to the antenna is made,
connect the AN/APM-1 23(V)1 to either a 28V DC or 11
5V AC power source.
(4) Connect external power 27V DC to external
power receptacle of helicopter.
(5) Close
appropriate
circuit
breakers;
energize the AN/APX-72 by setting MASTER switch to
STBY and the AN/APM-123(V)l by setting the 28V DCOFF-115V AC switch to the selected power. Allow
approximately 10 minutes for the equipment to warm
up. Perform the following tests.
c.
Testing - Mode 1 Checks.
(1) Set the controls on the AN/APM-123(V)1 as
follows:
FUNCTION switch
MODE
CODE dials
ISLS
SYSTEM
1
0000
OFF
MASTER switch
then NORM
IDENT switch
M-1 switch
M-2, M-3/A and M-C
switches
MODE 1 code dials
MODE 2 code dials
(on transponder)
MODE 3 code dials
MODE 4 ON-OUT switch
AUDIO-OUT-LIGHT switch
CODE selector (Mode 4)
STBY (for 3 minutes)
OUT
ON
OUT
00
0000
0000
OUT
OUT
ZERO
(3) Press the PUSH TO TEST switch on the
AN/APM-123(V)1 test set. The ACCEPT light should
illuminate.
(4) Change CODE dials on both AN/APM123(V)1 and C-6280A(P)/APX to 73.
(5) Press the PUSH TO TEST switch on the
AN/APM-123(V)I. The accept light should illuminate.
d. Testing - Modes 2, 3/A and TEST Checks.
Repeat above steps c (1) through c (5) for modes 2 and
3/A and TEST using 0000 and 7777 codes for each
mode. Mode 2 codes are selected on the code dials on
the RT unit. When checking the TEST mode, hold RAD
TEST-OUT-MON switch in the RAD TEST position.
NOTE
On the transponder set control, the
two code selector MODE 1 wheels
correspond to codes A and B on the
test set and the four code selector
wheels for modes 2 and 3/A
correspond to codes A, B, C and D
on the test set.
e. Testing - Mode C Checks (When AltimeterEncoder AA U-21/A is Installed).
(1) Place the C-6280A(P)/APX M-C switch to
ON and the other mode switches to OUT.
(2) Place the AN/APM-123(V)1 MODE switch
to C.
(3) Set 29.92 inches of Hg. in the barometric
pressure (in Hg) window on the front of AAU-21/A
Altimeter-Encoder by turning the barometric zero setting
knob.
Change 1 4-3
TM 11-1520-221-34
EL 1520-221-34-TM-61
Figure 4-1. Transponder Test Set AN/APM-123(V)1.
Change 1 4-4
TM 11-1520-221-34
Figure 4-2. Antenna Test Hood MX-4396/APM-123(V) Installation
(4) Observe the Altimeter-Encoder pointer
indication and set the corresponding reply code into the
AN/APM-123(V) as shown in the following chart:
Altimeter-Encoder,
Reply code to be set
AAU-2 1/A Pointer
Indication (feet)
-200
-100
000
100
200
300
400
500
600
700
800
900
into
AN/APM- 123(V) 1
0640
0660
0620
0630
0610
0210
0230
0220
0260
0240
0340
0360
If the pointer indication is 100 feet, then the proper code
for the test should be 0630.
NOTE
If the indicated altitude is between two
of those listed above, use the nearest
altitude and corresponding code.
Because
the
altimeter-encoder
tolerance is plus or minus 40 feet, it
may be necessary to use the other
altitude and corresponding code.
(5) Depress the AN/APN-123(V)1 PRESS TO
TEST switch. The ACCEPT light should illuminate.
Change 1 4-5
TM 11-1520-221-34
f.
Testing - Emergency Checks.
(3) On the C-6280A(P)/APX, momentarily set
the INDENT-OUT-MIC switch to IDENT. The ACCEPT
light should illuminate for a period of 15 to 30 seconds.
(4) Repeat step (3) for AN/APM-123(V)1 MODE
switch settings of 2 and 3/A.
(5) Release PUSH TO TEST switch on
AN/APM-1 23(V)1.
NOTE
Confine the EMERGENCY position
and codes 7600 or 7700 in either
modes 2 or 3/A to closed
loop
testing.
Code 7600 signifies a
communi-cations failure and code
7700 signified an aircraft in distress.
NOTE
The MIC position of the IDENT
switch is disabled; therefore, not
checks are required in the MIC
position of the IDENT switch.
(1) Set the controls on the C-6280A(P)/APX as
follows:
M-1, M-2, M-3/A
MODE 1 code dials
MODE 2 code dials
(on transponder)
MODE 3A code dials
MASTER switch
Optional
00
h. Testing - Mode 4 Checks.
(1) Connect Interrogator
Computer KIR-I
A/TSEC to test set MODE 4 connector using cable CX12216/APM-123(V). ZEROIZE light on the test set
should light.
0000
Optional
EMER
(2) On
the
AN/APM-123(V)1,
set
the
FUNCTION switch to EMER and press the PUSH TO
TEST switch. The ACCEPT light should illuminate with
the AN/APM-123(V)1 MODE switch in position 1 and
2 when the AN/APM-123(V)1 CODE dials match those
of the C-6280A(P)/APX.
(2) Using Code Changer Key KIK-18/TSEC, key
the KIR-1A and close the access door. XEROIZE
light on the test set should go out.
(3) Install
Computer
KIT-IA/TSEC
in
the
aircraft.
(3) Repeat step (2) with the AN/APM-123(V)1
MODE switch set to 3/A and the CODE dials set to
7700. The ACCEPT light shall illuminate regardless of
the setting of the C-6280A(P)/APX CODE dials.
(4) Connect
headset
to
aircraft
intercom
system.
(5) Set the controls on the C-6280A(P)/APX as
follows:
g. Testing - IDENT Checks.
(1) Set the controls on the C-6280A(P)/APX as
follows:
M-1, M-2, and M-3/A
MODE 1 code dials
MODE 2 code (on
transponder)
MODE 3/A code dials
MASTER switch
ON
00
0000
0000
NORM
(2) Set the controls on the AN/APM-123(V) as
follows:
FUNCTION switch
MODE switch
PUSH TO TEST
switch
CODE dials
I/P
1
LOCK
Control
MASTER
TEST M-1/OUT
TEST M-2/OUT
TEST M-3/OUT
TEST MC/OUT
AUDIO/OUT/LIGHT
CODE
MODE 4 ON/OUT
Position
NORM
OUT
OUT
OUT
OUT
AUDIO
A
OUT
(6) On the AN/APM-123(V)1 test set, place the
FUNCTION Switch to SYSTEM, the MODE 4 DIR/RAD
Switch to DIR, the MODE Switch to 4, the MODE 4
Code A/B Switch to A and the PUSH TO TEST switch to
the lock position, and when operating test set observe
the following:
(a) On the test set, the REJECT light
0000
should light.
Change 1 4-6
TM 11-1520-221-34
(b) Audio tone should be heard in headset.
(16) On 4-6280A(P)/APX, place CODE switch to
HOLD, then return to A.
(c) IFF CAUTION light should light.
(7) Using KIK-18/TSEC, key the KIT-18/TSEC
and close access door. Observe same indications listed
in (6) above. Release PUSH TO TEST Switch.
(8) On C-6280A(P)/APX, place the MODE 4
switch to ON.
(9) On the AN/APM-123(V)1 test set, briefly
depress the PUSH TO TEST Switch to observe the
following:
(17) Wait at least 15 seconds and then on the
C-6280A(P)/APX turn MASTER switch to OFF.
(18) Wait at least 15 seconds and then on the
C-6280A(P)/APX turn MASTER switch to STBY for a
warmup of about 30 seconds, then turn MASTER Switch
to PUSH
(19) On the test set, briefly depress PUSH TO
TEST switch. ACCEPT light should light.
(a) On the test set, the ACCEPT light
should light.
(20) On the C-6280A(P)/APX pull out CODE
switch and turn to ZERO, and place AUDIO/LIGHT
switch to AUDIO position.
(b) On the C-6280A(P)/APX, the REPLY
light should light.
(21) On the test set, place PUSH TO TEST
switch to LOCK position, and observe the following:
(c) Audio tone should be heard in headset.
(a) On
the test set the REJECT
light
should light.
(d) Aircraft IFF CAUTION light should be
OFF.
(b) Audio
tone
should
be
heard
to
headset.
(10) On the C-6280A(P)/APX place the
AUDIO/LIGHT switch to the LIGHT position, and repeat
the above test. Audio tone should not be heard, but
REPLY light should light.
(11) On the test set, place the MODE 4 CODE
A/B switch to B and briefly depress the PUSH TO TEST
switch. The REJECT light should light. Return MODE 4
CODE A/B Switch to A.
(12) On the test set, place the MODE 4 VER
BIT 1 switch to 1 and briefly depress the PUGH TO
TEST switch. The REJECT light should light. Return
MODE 4 VER BIT I switch to OFF.
(13) On the test set, place the MODE 4 VER
BIT 2 switch to 2 and briefly depress the PUSH TO
TEST switch. The REJECT light should light. Return
MODE 4 VER BIT 2 switch to OFF.
(14) On the test set, place the ISLS switch to
ON and briefly depress PUSH TO TEST switch. The
REJECT light should light. Return ISLS switch to OFF.
(15) Set IFF CODE HOLD switch located on
aircraft instrument panel to ON. IFF CODE HOLD light
located on aircraft instrument panel should light.
(c) IFF CAUTION light should light.
i.
Test Procedure Using the TS-1843/APX.
(1) Set the controls on the C-6280A(P)/APX as
follows:
MASTER switch
IDENT
MODES 1, 2, 3/A & C
MODE 1 CODE
MODE 2 CODE (on transponder)
MODE 3/A CODE
RAD TEST-OUT-MON
NORM
OUT
ON
Any code
Any code
Any code
OUT
(2) Place M-1 switch on the C-6280A(P)/APX in
the TEST position.
(3) The
green TEST light on the C6280A(P)/APX should illuminate, indicating the following
conditions exist:
(a) The
TS-1843 has
interrogation of power MODE 1 signals.
initiated
an
(b) The RT-859/APX-72 has recognized the
interrogation and transmitted reply.
Change 1 4-7
TM 11-1520-221-34
(c) The TS-1843 has evaluated the reply
and is satisfied that the frequency (1090 plus or minus
3.0 MHz), the power (20 to 28 DBW), the bracket pulse
spacing (20.3 plus or minus 0.15 µsec.) and the antenna
VSWR (8 plus or minus 2.5 db or less) are within
specified limits.
(4) Repeat steps (a), (b), and (c) above for
MODES 2, 3/A and C.
(5) Place FUNCTION selector ill SYSTEM
position.
(6) Place RAD TEST-OUT-MON switch in MON
position, repeat Mode 1 checks in above steps c (1)
through c (5), and observe that the test light glows
whenever the ACCEPT indicator remains illuminated on
the AN/APM-123-V. Place the RAD TEST-OUT-MON
switch in RAD TEST position and note that the TEST
light does not illuminate. This demonstrates that the
TEST light on the C-6280A(P)/APX will not illuminate
when being interrogated in the TEST mode if the RAD
TEST-OUT-MON switch is in RAD TEST position.
NOTE
The TEST light may blink out momentarily at a
slow steady rate while in MON. This
is normal and does not indicate a
failure.
No light or a random
flickering light shall indicate a
failure. When not conducting a MON
check for an extended period of time
return RAD TEST-OUT-MON switch
to OUT Position.
(7) Remove electrical power from the IFF Set.
Change 1 4-8
TM 11-1520-221-34
CHAPTER 5
STABILITY AND CONTROL AUGMENTATION SYSTEM (SCAS)
Section I. INTRODUCTION
5-1.
dicators.
Scope
Output:
Engage ...............................
Power..................................
a. The following information is required for
maintenance of the Model 570A Stability and Control
Augmentation System (SCAS) installed in the Army
Model AH-1G Helicopter. It includes appropriate
instructions for testing and troubleshooting the electronic
components SCAS Control Panel P/N 570-074-060 and
Sensor Amplifier Unit P/N 570-074-010 when the
equipment is installed in the helicopter. It lists tools, test
equipment, and materials required by maintenance
personnel to maintain, test, align, and adjust the stability
augmentation system. Also included are instructions
required for performing troubleshooting and bench or
shop testing and maintenance of the SCAS Control
Panel Sensor Amplifier Unit, and Pylon Compensation
Unit P/N 570-074-131.
d. Sensor Amplifier Unit
Voltage requirements ..............
...............................................
transducers).
Input signals ...........................
Output signals .......................
Voltage requirement................
Output signal ..........................
Voltage requirement................
Output signal ..........................
f.
Input signal.............................
Torque motor:
Coil .....................................
Current................................
Output signal ..........................
a. SCAS Voltage Requirements.
4.5 amps at 27.5 +2 volts
c.
35 VA at 115 volts ac, single
phase.
Indicators:
NO GO lights ......................
26 volts ac, 380 to 420 Hz
(from sensor amplifier
unit).
Control error signal.
2000 ±200 ohms.
±5 ma maximum.
Actuator position.
+27.5 ±2 volts dc.
h. Pylon Compensation Unit.
Current ...................................
0.5 gpm maximum at 1500
Output signal ..........................
SCAS Control Panel, BHC
Voltage requirements ..............
20 volts dc (from sensor
amplifier unit).
Control position, to sensor
amplifier unit.
20 volts dc (from pylon compensation unit).
Pylon position to pylon compensation unit.
g. Solenoid Valve.
Voltage requirement................
b. SCAS Hydraulic Power. Requirements.
Each servo actuator ................
psi.
Servo actuator position feedback, aircraft rates.
Aircraft control positions.
To servo actuators.
Servo Actuator.
Voltage requirement................
Technical Characteristics of the SCAS
Augmentation System
Direct current .........................
dc.
Alternating current ..................
27.5±2 volts dc (regulated to
20 volts de for control transducers).
115 volts ac tll.5, 380 to 420
Hz (stepped down to 26
volts
internally
for
e. Control Motion Transducer
b. A detailed description of the SCAS is contained
in TM 11-1520-221-20.
c. Analysis of the SCAS circuits is covered in
section II. Detailed circuit analysis of the Control Panel
and the Sensor Amplifier Unit are also covered in
section II.
d. Operational checks, troubleshooting charts, and
procedures are included in section III. The charts
include functional checks, normal reactions, and
procedures to aid maintenance personnel to properly
repair and service the SCAS electronic equipment.
e. Section IV contains specific bench tests and
performance criteria for new or repaired SCAS
electronic equipment.
5-2.
To solenoid valves.
Ac and de power to system.
27.5 volts dc ±2.
115 volts ac ±11.5, 380 to
420 Hz.
0.25 amps.
27.5 ±2 vdc.
Compensation pylon motion
signal
(to
sensor
amplifier
unit.
System disability warning in-
5-1
TM 11-1520-221-34
Section II. CIRCUIT ANALYSIS
Figure 5-1. SCAS control panel, rear view.
is connected through pin U of the control panel
connector 2J1 to one side of the SAS POWER switch
S1, then through S1 to terminal E2 in the control panel,
where it is distributed to pins S, C, E, and N of 2J1, and
to DS1, DS2, and DS3 NO GO indicator lights. From
pins S, E, and C of 2J1 dc power is applied to the pitch,
roll, and yaw solenoid valves respectively through pins
A
of connectors J703/P703, J702/P702, and
J701/P701. Dc power is applied to the S2 (PITCH), S3
(ROLL), and S4 (YAW) engage switch holding coils
through pin h of the sensor amplifier unit connector 1J1,
through the protective fuse F1, through pin 5 of 1J6,
and then through the contacts of the ac innerlock relay
K1 through pin 2 of 1J6 and pin g of 1J1 and pin MI of
2J1 to pin 4 on S2, S3, and S4 from pin N of 2J1.
5-3.
Introduction to Functioning Discussions
The purpose, operation, and interoperation of the
various circuits used in the system are explained in this
section. Familiarity with the system (fig. FO-13 and
FO-14) and the individual electronic components (how
they work and why they work that way) is important in
troubleshooting and maintaining the system and the
individual electronic components. For parts location
refer to figures 5-1 through 5-5.
5-4.
Power Circuits
(fig. FO-14)
a. Dc Power Circuits. The Model 570 SCAS
receives 28 volts dc from the pilots dc circuit breaker
panel through the 5-ampere SAS CONT circuit breaker.
With dc power on the circuit breaker closed, 28 volts dc
5-2
TM 11-1520-221-34
Figure 5-2. SCAS Sensor amplifier unit, front view.
The S2, S3, and S4 holding coil ground is provided from
pin 5 of S2, S3, and S4 to ground terminal E1 through
pin P of 2J1, pin U of J34, through the normally closed
contacts of emergency disengage switch S41 (pilot's
cyclic stick grip), through pin V of J34, through pin U of
J91, through the normally closed contacts of emergency
disengage switch S44 (gunner's cyclic stick grip),
through pin V of J91, and through pin H of 2J1. F1 also
distributes 28 volts dc to R1 and to pins D of connectors
1J4, 1J3, and 1J2. From pin D of the above connectors,
dc power is furnished to pins 2 and 9 of the Built-In Test
Equipment (B.I.T.E.) module, pin 9 of the sensor
amplifier unit, front view. VALVE DRIVE module, and
the positive side of C3. Dc power is supplied from pin D
of 1J4 to the inductor L1 for filtering. The filtered dc is
then distributed to pins S of 1J4, 1J3 and 1J2 from pins
3, 2, and 1 of L1 respectively. Filtered dc is supplied
from pins S of 1P4, lP3, and 1P2, to the positive side of
C1, R17, R6, and pin 5 of valve driver module.
b. Ac Power Circuits. The SCAS receives 115
volts ac through the 1-ampere SCAS PWR circuit
breaker. With ac power on and the circuit breaker
closed, 115 volts ac is connected through pin T of
connector 2J1 to the control panel POWER switch S1.
Ac power is applied through S1
Change 1 5-3
TM 11-1520-221-34
Figure 5-3. SCAS Sensor amplifier unit, rear view.
and pin V of 2J1 connector to pin R of 1J1 connector.
From pin R of 1J1, ac power is applied to pin 3 of the
AC power module A1 and to the 115v pin of the pulse
generator module A2. The 26-volt ac two-phase power
output of Al is applied to each rate gyro spin motor; pins
1 and 5 of MP1 (Pitch), MP2 (Roll), and MP3 (Yaw)
through pins S and N (Pitch), L and H (Roll), and M and
J (Yaw) of 1J5 from pins 7, 6, 2, and 4 of A1. In-phase
26 volts ac is supplied from pin 4 of A1 to the anode of
CR2 and pin 2 of S2. In-phase 26 volts ac power is
applied to pin A of the control tube assemblies Z2, Z3,
and Z4 through pins B, C, and Y respectively of
connector 1J1 for excitation of the feedback transducers
located in the actuators.
c. Regulated Dc Circuits. A regulated 20 volts dc
is furnished by CR1 and is applied to B+ of the pulse
generator module A2. The 20 volts dc is also applied to
pitch (MT1), roll (MT2), and yaw (MT3) control motion
transducers through pins a, r, and t of 1J1, and through
pin C of connector J704 and J706 for pitch and yaw and
through pin A of J705 and J706 for roll and yaw.
5-5.
Pilot's Control Signal Circuit
The maximum swing of the control signal is 20 volts dc,
and this magnitude can be reduced if necessary to
achieve the desired gains by increasing the value of R2.
The pilot's control signals from each individual channel
are inserted into the sensor amplifier unit at pins p, c,
and N of 1J1 through pin B of connectors J704, J705,
and J706. From pins p, c, and n of 1J1 the control
signal for each individual axis is distributed to pin M of
1J4, 1P3, and 1J2 for the corresponding channel. From
pin
5-4
TM 11-1520-221-34
Figure 5-4. Pylon compensation unit, top view.
M, the control signal is shaped for each transfer function
which is required in pitch, roll, and yaw. Each transfer
function is obtained by R12, C4, R15, R16, C5, C6, and
R20 (fig. 5-4 and 5-5). Resistor-capacitor combination
R12 and C4 form a pilot's signal lag circuit. Resistors
R15 and R16, in addition to providing a summing circuit
for the pilot's signal and the rate gyro signal, are used in
parallel to form a signal lag circuit with capacitor C5.
Transformer T1 and R17, C5, CR3, CR4, CR5, and CR6
serve as a demodulation circuit for the rate gyro signal
and do not materially affect the pilot's signal except for
an enlarging effect on C5. The control signal is then
applied to the base of emitter follower stage Q1.
Collector bias is furnished to Q1 by CR1 in the form of
5-5
TM 11-1520-221-34
Figure 5-5. Pylon compensation unit, bottom view.
20 volt regulated dc. R19 is the emitter resistor for Q1.
Upon leaving the emitter of Q1, the control signal
passes through a lead circuit in the form of C6 and R20,
which is referred to as the washout circuit. R20, in
addition to being a part of the washout circuit, is the
signal mixing resistor which applies the control signal to
the input of the valve driver amplifier at pin 6. The gain
of each channel is set by the choice of R20. In pitch
and roll only, a small amount of pilot lead is also
obtained by resistor-capacitor combination R14, C2.
The control signal is now amplified through the valve
driver module A2 and is applied to the actuators Z2, Z3,
and Z1 from pins 1 and 10 of the valve driver modules
A2 through pins E and T of connector 1J2, 1J3, and 1J4;
through pins f and q, b and e and L and 5I of 1J1, and
finally through pins E and F of P707, P708, and P709
for pitch, roll, and yaw respectively.
5-6
TM 11-1520-221-34
5-6.
Ac Interlock Circuit
The function of this circuit is to provide automatic
disengagement for the SCAS in case the 115 volts ac
fails. Control panel switches S2, S3, and S4 open
automatically when 28 volts dc is removed from their
coils. Therefore, by energizing the relay coil of K1 with
rectified dc from the 115-volt ac source, the main 28
volts dc through the closed contacts of K1 to S2, S3,
and S4 can be interrupted and the system will disengage
in case of ac power failure. This auxiliary dc supply for
the coil of K1 is derived from the ac supply through the
one-half wave rectifier CR2, dropping resistor R2, and
filter capacitor C1.
5-9.
Pulse Generator Module Circuit
(fig. FO-14)
One pulse generator module A2 is required for each
SCAS. A2 receives 20 volts dc from CR1 on pin
designated B+, 115 volts ac on pin designated 115V,
and ground on pin designated GRD. A2 furnishes two
separate pulse outputs, one positive going and the other
negative going.
One output, the positive pulse
appearing at pins pp is applied through pin H of
connector 1J2, 1J3, and 1J4 to pin 3 of the valve driver
module for gating of the input. The other output of the
pulse generator module A2, the negative pulse, appears
at pin NP and is applied to pin 4 of the transformer T1
through pin F of connector 1J2, 1J3, and 1J4 to
synchronize the demodulator in the compensating circuit
to 400 Hz. The negative pulse is also applied through
pin F of connectors 1J2, 1J3, and 1J4 to pin 2 of the
valve driver module A2 to gate this module in
synchronism with 400 Hz.
5-7.
Solenoid Valve Control Circuit
The solenoid-operated hydraulic valve in each channel
is normally closed and opens only when 28 volts dc is
applied between pins A and B of connectors J701, J702,
and J703. These valves are used to furnish hydraulic
pressure to the hydraulic actuators Z2, Z3, and Z4. The
28 volts dc is supplied to pins A of P701, P702, and
P703 through pins S, E, and C of 2J1 from S1. Pins B
of the solenoid valves are connected to ground by S2,
S3, and S4 through pins q, b, and c of 2J1 of the control
head.
5-10.
Valve Driver Module Circuit
(fig. FO-14)
Valve driver module A2 furnishes current for the servo
coil in the hydraulic actuators. One valve driver module
A2 is required for each channel of the SCAS. This
module is essentially a gated dc amplifier with two
outputs; one output is the reference voltage, and the
other varies in accordance with the various inputs to the
valve driver module A2 from the rate gyro, pilot's control
circuits, pylon compensator (roll channel only) and
actuator position feedback. For zero signal input, the
reference level of the output at pin 10 of the valve driver
module A2 is set by the amount of regulated 20 volts dc
received through RT1 from CR1, which is applied at pin
4 after being attenuated by R3 and R4. A combination
of all the signals applied at pin 6 also appears at pin 10
of A2 in the form of a 0.0002-sec pulse with a repetition
rate of 400 Hz. The level of this pulse, for zero signal
on the input, is set at the same level as the reference
output valve by the amount of 20 volts dc received
through RT1 from CR1, which is applied at pin 4 of A2
after being attenuated by R5, R11, R18, and R19. R5
allows the pulse and the reference outputs at pin 10 of
A2 to be balanced for minor production and aging
tolerances. The other output of the valve driver module
A2, pin 1, follows the level of the 0.0002-sec pulse.
Thus, current will flow in one direction or the other when
the servo coil of the actuator is connected between pins
1 and 10 of A2, flow direction depending upon the
displacement of the pulse above or below the reference.
The percent of available feedback information which is
received by the
5-8.
Built-In Test Equipment (B.I.T.E.) Module
Circuit
One B.I.T.E. module is used in each channel of
the SCAS to energize the NO GO lights. If the
ac pulse at terminal 10 of the valve driver
module A2 exceeds 6 ±2 volts higher or lower
than the valve driver module bias level at pin 10
because of a malfunction or warmup time, the
NO GO lights come on. If the pulse level at pin
10 of the valve driver module A2 exceeds its
specified limits, the pulse being fed through R7
and R8 to pin 1 of the B.I.T.E. module will
cause A1 to present 28 volts dc at pin 8 to
energize the NO GO light for that channel. The
NO GO lights DS1, DS2, DS3 in the sensor
amplifier unit receive 28 volts from pin 8 of the
B.I.T.E. module through pins C of connectors
1J2, 1J3, and 1J4. The NO GO lights on the
control panel receive power applied to pin 2
from pin 8 of B.I.T.E. module through pins C of
connectors 1J2, 1J3, and 1J4 through pins n, d,
and P of 1J1; through pins R, D, and F of 2J1.
The B.I.T.E. module receives 28 volts dc on
pin 9. Pin 6 is ground for this module.
5-7
TM 11-1520-221-34
Figure 5-6. Pitch control channel assembly schematic
valve driver module A2 is determined by the attenuating
network, R13 and R21. The feedback gain of the valve
driver module is set by R9. RT1 and R10 are included
to insure thermal stability of the valve driver A2 outputs.
Actuator servo coil current drift is the chief area of
stabilization affected by temperature variations. When
28 volts dc is applied to pin 9 of A2 with pin 8 of A2
being ground, filtered 28 volts dc from the ac power
module Al is applied at pin 5 of A2. The positive and
negative outputs of the pulse generator A1 are applied
to pins 3 and 2 of A2 respectively for gating. The
reference output from the valve driver module A2 at pin
10 is applied to pin E of Z2, Z3, and pin FZ4 control
tube assemblies through R7; through pin T of 1J2, 1J3,
and 1J4; and through pins f, b, and L of 1J1.
5-8
TM 11-1520-221-34
Figure 5-7. Roll control channel assembly schematic.
The reference output is also applied to pin 1 and 10 of
the B.I.T.E. module J1 through R7 and R8 to activate
the NO GO lights when the 0.0002-sec pulse limits
exceed a certain value.
C3, which is connected
between 28 volts dc and pin 10 of valve driver module
A2 through R7 is present for RF filtering. The output of
the valve driver A2 at pin 1 of A2 is applied to pin E of
Z2, and Z3, pin F of Z4 through R1; through pin E of
1J2, 1J3, and 1J4; and through pins q, e, and M of 1J1.
5-11. Rate Gyro Circuit
One rate gyro is required for each channel (pitch, roll,
and yaw) to sense the various rates encountered by the
helicopter in each axis. The spin motors of the gyros
(MP1 pitch, MP2 roll, and MP3 yaw) require 26 volts ac
two-phase for operation.
In addition, the output
elements
5-9
TM 11-1520-221-34
Figure 5-8. Yaw control channel assembly schematic
of the gyros are excited on pin 7 by a 5.2-volt 318degree, 400-Hz signal from pin 5 of the ac power
module Al through the GYRO TEST switch S1 in the
sensor amplifier unit and through pins K, D, and E of
1J5. The output of each individual gyro (MP1 pitch,
MP2 roll, and AIP3 yaw) to the appropriate control
channel assembly (A4 pitch, A5 roll, and A6 yaw) is
through V and X, T and P, and R and U of 1J5. The
gyro signals are inserted into each control channel
assembly (fig. 5-6, 5-7, and 5-8) through pins L and P
of 1J2, 1J3, and 1J4. One side of the gyro output
winding (pin L) is applied to R16, R12, and C4, which is
essentially at ground to 400 Hz since the impedance of
C4 is relatively small at that frequency. From pin P, the
gyro signal is shaped for each transfer function required
for pitch, roll, and yaw. Each channel transfer function
is obtained by R14, R15, R16, C2, C4,
5-10
TM 11-1520-221-34
gunner is achieved by interrupting the ground circuit for
the holding coil of the S2, S3, and S4 engage switches.
The engage switches control dc power to the three
hydraulic solenoid valves K32, K33, and K34. When dc
power is removed, the solenoid valves close, removing
hydraulic pressure from the three control actuators Z2,
Z3, Z4. When there is no hydraulic pressure applied to
the actuators, the actuators assume their neutral
positions and lock, providing a mechanically rigid link in
the helicopter control system. Ground for the holding
coils of the engage switches in the control panel is
present at pin 5 of S2, S3, and S4; through pin P of 2J1
through pin U of J34, through the emergency disengage
switch on the pilot's cyclic stick grip, through pin V of
J34, through pin U of J91, through the emergency
disengage switch on the gunner's cyclic stick grip,
through pin V of J91, and through pin H of 2J1.
C5, C6, and R20. In addition to forming an attenuation
network, resistors R15 and R16 are used in parallel with
C5 to form a lag circuit for the gyro signal after it has
been demodulated by the sampling circuit R17, C5,
CR3, CR4, CR5, CR6, and T1. This sampling circuit,
besides being a demodulating circuit, has an enlarging
effect on C5. The rate gyro signal is then applied to the
base of emitter follower stage Q1 and summed with any
control signal which may be present.
A 20-volt
regulated dc collector bias is furnished to Q1 by CR1.
R19 is the emitter resistor for Q1, and R6 is the series
dropping resistor for CR1. Upon leaving the emitter Q1,
the gyro signal passes through a lead circuit in the form
of C6 and R20 which is referred to as the wash out
circuit. R20, in addition to being a part of the washout
circuit, is the signal mixing resistor which applies the
rate gyro signal to the input of the valve driver amplifier
at pin 6 of A2. The gain of each channel is set by the
choice of R20. Additional lead is obtained by applying
the gyro signal from pin P of 1J5 through C2 and R14 to
pin 6 of the valve driver module A2.
5-14. Control Motion Transducer
The pilot's control movements are detected by BIT1
(pitch), MIT2 (roll), and MT3 (yaw) transducers. The
transducers are 1K linear motion potentiometers which
have 20 volts dc applied to pin C of connector J704 for
pitch and to pin A of connectors J705 and J706 for roll
and yaw. The pitch transducer seeks ground through
pin A of connector J704; through pin K of 1J1; through J
of 1J2 and through R2 to ground. The roll and yaw
transducers seek ground through pin C of J705 and
J706; through pins S and MI of 1J1; through pin J of 1J3
and 1J4; and through R2 to ground. Signals induced by
the pilot, relative to helicopter control displacements,
from the transducers are supplied through pin B of
connectors J704, J705, and J706.
5-12.
Control Panel
(fig. 5-1)
The control panel (unit 2) contains the system POWER
switch S1, three channel engage switches (S2, S3, and
S4) which furnish power to the hydraulic solenoid valves
(K32, K33, and K34), and the NO GO indicator lights for
the pilot's checkout operation. Also contained in the
control panel are two edgelights (DS4 and DS5) which
are energized from the pilot's instrument panel light
dimmer through pin B of 2J1 and through pin J of J8.
The system POWER switch for the SCAS is a positive
action switch which controls both the 28 volts dc and the
115 volts ac. The PITCH, ROLL and YAW switches are
solenoid hold-in type switches which require 28 volts dc
to the holding coils to remain in engaged, position.
These switches are capable of being turned off or
disengaged either manually or electrically. Loss of 28
volt dc or 115 volt ac or pressing of either the pilot's or
gunner's emergency disengage switch (S41 or S44)
located in the cyclic stick grips, will cause the engage
switches to be turned off. Each time power is reapplied,
the engage switches must be manually reengaged since
these switches are solenoid hold-in type only.
5-15.
Hydraulic Actuators and Pylon
Compensation Unit
a. Hydraulic Actuators. Three hydraulic actuators
are required for each SCAS. Each channel (pitch, roll,
and yaw) has one actuator linked in series in the control
system of the helicopter. Each actuator (pitch Z2, roll
Z3, and yaw Z4) has a total travel of 0.9 inch. Each
actuator contains a servo coil which is connected
between pins E and F of connectors J707, J708, and
J709. With pin E as a reference, this servo coil requires
current of up to ± 5 ma for operation. The velocity and
direction of the actuators is determined from the
magnitude and polarity of the servo coil current. This
coil current is supplied by the valve
5-13.
Pilot's Emergency Disengage
(fig. FO-14)
The emergency disengage function by either the pilot or
5-11
TM 11-1520-221-34
transducer. The transducer seeks ground through pin c,
J918 to pin F, J917. The signal from the transducer is
inserted into the pylon compensation unit through pin B,
J918 through pin C, J917 to resistor R2.
driver modules A2 located in the Control Channel
Assembly (A4, A5 and A6) for each channel. The
actuators also contain a linear variable differential
transformer (LN7DT) to provide position feedback
information. The LVDT produces an in-phase 400 cycle
signal for an extending actuator, the magnitude of which
is linearly proportional to the displacement of the
actuator from its neutral position. For a retracting
actuator, an out-of-phase signal is produced by the
feedback transducer (LVDT). The primary excitation of
the feedback transducer (LVDT) is an in-phase 26-volt,
400-Hz signal from the ac power module Al in the
sensor amplifier unit which is applied to Pin A of J707,
J708, and J709, with pin B of J707, J708, and J709
being grounded. From this excitation, the (LVDT) output
is developed at pin D of J707, J708, and J709, with pin
C of J707, J708, and J709 being grounded. The
hydraulic actuators also contain a disengage feature that
automatically returns the actuator to its mechanical
center position and locks the actuator in its center
position if hydraulic pressure is turned off or lost to the
actuator. This feature assures no loss of pilot control
through the mechanical controls of the helicopter.
b. Resistors R1 and R2 serve as a summing point
for the transducer signals. The parallel combination of
R1 and R-, C1, and R3 in parallel with R4 provide a lead
term circuit for the pylon signals. Q1 and R5 serve as
an emitter follower isolation stage in the network. C2,
C3, C4, R6, R7, and RS form a twin-T network which
filters out 10.8 Hz. Q2, R9 and R10 form a stage of
isolation and amplification. Additional lead is obtained
from C5 and R22 (located in sensor-amplifier unit on
570-074-037-15 roll channel assembly).
c. The compensated signal from the pylon
compensation unit is inserted through pin K, J917,
through pin K, 1J1, to pin N, 1J3 in the sensor-amplifier
unit. R22 serves as a mixing resistor to insert the
compensated signal into the input Cf the valve driver
module.
5-18. Gyro and actuator Test Switches
a. Gyro Test Switch. The GYRO TEST switch,
mounted on the sensor amplifier, serves to enable
testing of the rate gyro. Depressing the GYRO TEST
switch removes all excitation to gyro rate output
transducer. If a high null exists, indicating an unbalance
in the system (causing NO GO light to illuminate)
pressing test switch will eliminate this problem (causing
NO GO light to extinguish) thus indicating a faulty rate
gyro.
b. Pylon Compensation Unit. The 570-074-131-1
pylon compensation unit receives 28-volts dc At pin D of
J917 from pin N of P700. R11 serves as a dropping
resistor for CR1 which furnishes a regulated 20-volts dc
for bias on Q1 and Q2 and excitation to each pylon
motion transducer.
5-16. Two-Transducer Installation
The excitation voltage is distributed through pin G, J917
to pin C, J916 to the aft transducer; through pin H, J917
to pin A, J915 to the forward transducer.
The
transducers seek ground through pins C, J915, and A,
J916 to pins E and F, J917. The signal from the forward
pylon motion transducer is inserted into the pylon
compensation unit through Pin B, J915 to pin C, J917 to
resistor R2. The signal from the aft transducer is
inserted through Pin 5, J916 through pin B, J917 to
resistor R1.
b. Actuator Test Switch. The ACTR TEST switch,
mounted on the sensor amplifier, serves to enable
testing of the servo actuator. Depressing ACTR TEST
switch removes all excitation to the actuator feedback
transducer. If a high null
exists, indicating an unbalance in the system (causing
NO GO light to illuminate) pressing test switch will
eliminate this problem (causing NO GO light to
extinguish) thus indicating a faulty servo actuator.
5-17. Single Transducer Installation
a. The excitation voltage is distributed through pin
H, J917 through pin A, J918 to the pylon motion
Section III. MAINTENANCE TECHNIQUES
be performed in the helicopter and they continue with
the bench testing and maintenance of the individual
electronic components.
5-19. General Instructions
The systematic maintenance procedures begin with the
functional operation and sectionalization checks that can
5-12
TM 11-1520-221-34
5-20.
Organization of Troubleshooting
Procedures
a. General.
Troubleshooting the stability and
control augmentation system (SCAS) in AH-1G and AHQ helicopters is performed in three steps.
The first step, sectionalization, is to trace the fault to a
component used in the system. The second step,
localization, is to trace the trouble to the defective unit
that is part of the faulty system and/or associated
cabling or wiring. When performing bench maintenance
on a removed electronic component, localization
includes tracing the fault to a defective subassembly or
module with the component. The third step, isolation, is
to isolate the trouble within the component to a
defective part.
b. Sectionalization. Listed below is a group of tests
arranged to reduce unnecessary work and to aid in
tracing troubles to the defective component.
(1) Visual inspection. Visual inspection is used
to locate faults prior to operation or testing the circuits.
Observe seating of all component connectors,
connections to switches and circuit breakers,
connections on terminals, wiring, etc.,
and sectionalize the fault to a particular component if
possible.
(2) Operational tests.
Operational tests
frequently indicate the general location of trouble. In
many instances, the tests will help in determining the
exact nature of the fault. Operation tests are to be
found in paragraph 5-9.
c. Localization. The procedures listed below are
used for localizing troubles within the system to the
electronic equipment components or system helicopter
wiring.
(1) Stability and control augmentation system
performance testing. Testing the complete stability and
control augmentation system performance for normal
operation often reveals the defective components.
(2) Voltage and resistance measurements. Use
the system voltage and resistance chart (para 5-31) to
find the normal readings, and compare them to the
actual readings taken.
(3) Intermittent troubles.
In all tests, the
possibility of intermittent troubles should not be
overlooked. If present, this type of trouble often may be
made to appear by tapping or jarring the equipment and
checking wiring and connections.
(4) Signal substitution.
Signal substitution
procedures enable the repairman to localize a
component trouble quickly to a subassembly or part.
d. Isolation. After the trouble has been localized,
the methods in (1) through (4) below will aid in isolating
the trouble to a defective circuit element within a
component.
(1) Waveform analysis (fig.
5-9).
The
waveform at the output of the valve driver module can
be used to analyze failures in the circuit. Waveforms
must be taken and compared with waveforms provided
in figure 5-10. Resistance measurements ((3) below)
then must be taken to isolate the trouble.
(2) Voltage measurements This equipment is
transistorized. When measuring voltages, use tape or
sleeving (spaghetti) to insulate the entire test prod,
except for the extreme tip. A momentary short circuit
can ruin a transistor. Use the same or equivalent
voltmeter specified on the voltage and resistance chart.
(3) Resistance
measurements.
Make
resistance measurements in this equipment only as
directed on voltage and resistance diagrams or charts.
When using the voltmeter, set it to the resistance range
specified on these charts; otherwise, the indications
obtained will be inaccurate.
(4) Intermittent troubles. In all the tests, the
possibility of intermittent troubles should not be
overlooked. If present, this type of trouble often may be
made to appear by tapping or jarring the equipment.
Perform a visual inspection of the wiring and
connections to the modules on the component. Minute
cracks in a printed circuit board can cause intermittent
operation. A magnifying glass is often helpful in locating
defects in the printed circuit boards.
Continuity
measurements of printed conductors may be made by
using the same technique ordinarily used on hidden
conventional wiring; observe the voltmeter resistance
measurement precautions discussed in (3) above.
5-21. Test Equipment Required
All test equipment and other equipment required to
perform the tests in this chapter is listed below. (Refer
to appendix A for list of manuals covering the test
equipment.)
a. Electronic Voltmeter ME-30E/U (Voltmeter).
b. Multimeter AN/USM-223 (Multimeter).
c. Oscilloscope AN/USM-281 (Oscilloscope).
d. Signal Generator SG-298/U (Signal Generator).
Change 2 5-13
TM 11-1520-221-34
Figure 5-9. Valve driver module output waveforms.
e. Dc power source; 27.5 + 2.0 volts, 5 amps.
f.
5-22.
On-Ship Operational Checks and
Troubleshooting
Ac power source; 115 V, 400 Hz, 50 va.
g. Test Set
(SCAS test set).
Electronic
System
a. When a malfunction of the Stability and Control
Augmentation System (SCAS) occurs, the first step in
correcting the malfunction is to sectionalize the cause to
a particular unit in the
AN/ASM-338
h. Tool Kit, Electronic Equipment TK-101/G.
5-14
TM 11-1520-221-34
remotely located, the troubleshooting procedures in this
section may require more than one person. One man
will be required to operate the controls and another to
observe the results.
5-23. Test Setup
a. The operational tests in paragraph 5-24 are
performed with the system installed in the AH-1G and
AH-1Q helicopters.
Electrical and hydraulic power is required. The POWER
switch on the control panel should be OFF and the SAS
PWR circuit breakers should be open.
b.
The following equipment is required for
operational tests in paragraph 5-24:
(1) Extender Module MX-8096, ASM-338
(extender board).
(2) Multimeter AN/USM-223.
Figure 5-10. Valve driver output test waveforms.
system. Perform the on-ship operational checks and
troubleshooting procedures in paragraph 5-24.
b. Since the controls for the basic components are
5-24.
Step
1
On-Ship Operational Check and Troubleshooting Chart
Action
Engage SAS CONT and SAS
PWR circuit breakers. Set
POWER switch on control
panel to ON.
Normal indication
NO GO lights, PITCH, ROLL, and
YAW, shall come on for less than
60 seconds- and then go out.
If abnormal indications
are observed
a. If no lights come on(1) Check bulbs by pressing to
test.
(2) Observe NO GO lights in sensor amplifier unit. If these
come on and NO GO lights on
the control panel do not, malfunction is in control panel.
Substitute control panel known
to be good.
(3) Check 28-volt dc fuse F1
in the sensor amplifier unit.
(4) Check for 28 volts dc to
ground with volt-ohmmeter at
pin D and pin S on the extender board in any channel
(fig. 5-6, 5-7, and 5-8). If
there is 28 volts dc at only
one of these test points, change
the sensor amplifier unit. If
28 volts dc is not present at
either terminal, check 28-volt
dc wiring.
(5) With the controls centered,
check the voltage between
ground and pin M on the extender board of any channel.
If the voltage is not from 6
to 15 volts dc, replace the sensor amplifier unit.
(6) With hydraulic power off and
electrical power on, engage
switches should remain up
(engaged); if not, check from
pin J of the gyro connector
(1J5, 1P5) to ground for 26
volts ac. If 26 volts ac is not
Change 2 5-15
TM 11-1520-221-34
Step
Action
Normal indication
5-16
If abnormal indications
are observed
present, check 115-volt ac wiring. If the 115-volt ac circuit
is operative, change the sensor
amplifier unit.
(7) Substitute the pulse generator
module A2.
(8) If the above checks do not
isolate the malfunction, check
each channel as in b below.
b. If one or two NO GO indicator
lights fail to illuminate.
(1) Check bulbs.
(2) Substitute B.I.T.E. module
known to be good.
(3) Substitute valve driver module known to be good.
(4) Substitute control channel assembly known to be good.
(5) If fault is not corrected by
above procedure, substitute
sensor amplifier unit known
to be good.
Note. By use of extender
board, any control channel assembly may be used in any
other channel of the sensor
amplifier unit.
(6) If fault is not corrected by
the above procedure, substitute a control panel known to
be good.
c. If all NO GO lamps are lighted
initially but one or more lamps
fail to go out in less than 60
seconds:
(1) Press GYRO TEST switch on
sensor amplifier unit. If NO
GO light goes out, trouble is
in gyro. Replace gyro assembly A3.
(2) Press ACTR TEST switch. If
NO GO light goes out, trouble
is in actuator circuit.
(3) Balance control channel assembly.
(a) Remove control channel
assembly.
(b) Insert extender board into
sensor amplifier unit in
place of control channel
assembly.
(c) Plug control channel assembly into the extender
board.
(d) Turn POWER switch on
and allow 30 to 60 seconds
for circuit to reach operating conditions.
(e) Connect VOM between pin
T and pin E of extender
board, set the voltmeter to
10OV scale. Reverse meter
polarity if meter reading
is negative.
TM 11-1520-221-34
Step
Action
Normal indication
2
Engage Pitch switch .......................................... Engage switch remains in up position.
3
Move cyclic stick forward................................... Pitch actuator should retract
4
Engage Roll Switch ........................................... Engage switch remains in up position.
5
Move cyclic stick lef ........................................... Roll actuator should retract
6
Engage Yaw switch ........................................... Engage switch remains in up position.
7
Rotate sensor amplifier unit in ........................... Yaw actuator should retract
a left yaw direction.
5-17
If abnormal indications
are observed
(f) Adjust R5 on the control
channel assembly until
VOM reads 0+0.1 volt.
(g) Turn POWER off, remove extender board, and
replace control channel
assembly in sensor amplifier unit.
(4) Substitute control channel assembly known to be good.
d. If the Roll NO GO light fails to
go out:
(1) Substitute pylon compensation
unit known to be good.
(2) If fault is not corrected by
above procedure, perform test
outlines in c(l), (2), and (3)
above.
a. Substitute control panel.
b. Check emergency disengage circuit. Check continuity from pin
H to pin P of P700. If open,
check switches on pilot and gunner cyclic sticks.
c. Substitute sensor amplifier unit
known to be good.
d. Check helicopter wiring.
a. Substitute control channel assembly known to be good.
b. Check pitch control motion transducer (para 5-14).
c. If both tests fail, check actuator
circuit (para 5-15).
a. Substitute control panel.
b. Check emergency disengage circuit. Check continuity from pin
H to pin P of P700. If open,
check switches on pilot and gunner cyclic sticks.
c. Substitute sensor amplifier unit
known to be good.
d. Check helicopter wiring.
a. Substitute control channel assembly known to be good.
b. Check roll control transducer
(para 5-14).
c. If both tests fail, check actuator
circuit (para 5-15).
a. Substitute control panel.
b. Check emergency disengage circuit. Check continuity from pin
H to pin P of P700. If open,
check switches on pilot and gunner cyclic sticks.
c. Substitute sensor amplifier unit
known to be good.
d. Check helicopter wiring.
a, Substitute control channel assembly known to be good.
b. Substitute gyro assembly known
to be good.
c. Replace sensor amplifier unit.
TM 11-1520-221-34
Step
8
9
Action
Normal indication
Reinstall sensor amplifier unit.
Press emergency disengage ............................. PITCH, ROLL, and, YAW engage
switch on pilot's cyclic stick
switches immediately move to OFF
grip.
position.
5-25.
Bench Operational Check and Troubleshooting Chart, Control Panel
a. Connecting SCAS Control Panel and SCAS
Test Set (fig. 5-11).
(1) Position test set controls as follows:
(a) PWR switches to OFF.
(b) CHANNEL switch to PITCH.
If abnormal indications
are observed
a. Substitute control panel known to
be good.
b. Check continuity from 2P1 pin p
(control panel connector) to terminal E1 (ground); should be
open.
c. Measure resistance from pin H to
pin P of J700. Should be 0 ohms.
Press emergency disengage
switch on pilot's and on gunner's
cyclic stick. Should be open circuit when switch is depressed.
(c) MODE switch to CP.
(2) Set POWER switch on control panel to
OFF.
(3) As shown in figure 5-11, connect control
panel to the SCAS test set and the external power
supply source with special purpose Electrical Cable
Assemblies CX-10853/U and CX-10854/U, respectively.
b. Procedures.
Step
1
2
3
4
5
Action
Set EXT POWER switches on
test set to ON positions.
Set POWER switch on control panel to POWER.
Depress momentarily all NO
GO lights on control panel.
Press NO GO TEST switch on
test set.
Set PITCH, ROLL, and YAW
engage switches on the control panel to up position.
6
Set CHANNEL selector on the
test set to ROLL.
7
Set CHANNEL selector on test
set to YAW.
in up position, and ENGAGED
light on test set remains lighted.
Depress EMER DISENGAGE
switch on test set.
8
9
10
Set CHANNEL selector on test
set to ROLL.
Set CHANNEL selector on test
set to PITCH.
If abnormal indications
Normal indication
are observed
Edgelit panel is lighted........................................... DS4, DS5, or associated wiring defective (para 5-12).
AC and DC lights on test set are
Faulty POWER switch S1 or associlighted.
ated wiring (para 5-5).
Lights will come on when depressed
Defective bulb, defective wiring, or
defective engage switch.
All NO GO lights on control panel
Check control panel wiring.
will come on.
a. Engage switches remain in up poDefective switch or wiring in hold-in
sition.
coil circuitry (para 5-5). (This step
b. ENGAGED light on test set is
checks PITCH switch.)
lighted.
PITCH, ROLL, and YAW engage
Defective switch or wiring in hold-in
switches on control panel remain
coil circuitry (para 5-5). (This step
in up position, and ENGAGED
checks ROLL switch.)
light on test set remains lighted.
PITCH, ROLL, and YAW engage
Defective switch or wiring in hold-in
switches on control panel remain
coil circuitry (para 5-5). (This step
checks YAW switch.)
a. PITCH, ROLL, and YAW
switches move to OFF.
b. ENGAGED light on test set is
not lighted.
ENGAGED light on test set goes out
ENGAGED light on test set goes out
5-18
Defective switch or wiring in hold-in
coil circuitry (para 5-5).
Defective switch or wiring on hold-in
coil circuitry (para 5-5).
Defective switch or wiring in hold-in
coil circuitry (para 5-5).
TM 11-1520-221-34
Figure 5-12. SCAS sensor amplifier unit test setup
connection
Figure 5-11. SCAS Control Panel Test setup
connections.
5-26.
(a) DC POWER switch to OFF.
(b) AC POWER switch to OFF.
(c) FEEDBACK knob to 0.
(d) CHANNEL selector switch to PITCH.
(e) MODE selector switch to SAU.
(2) Connect voltmeter positive lead to
Bench Operational Check and
Troubleshooting Chart, Sensor
Amplifier Unit
(fig. 5-12)
a. Connecting Sensor Amplifier Unit and SCAS
Test Set.
(1) Position SCAS test set controls as follows:
5-19
TM 11-1520-221-34
SCAS test set TP1 and negative lead to TP2, and set
to 10V dc (not shown in fig. 5-12).
(3) Connect multimeter between SCAS set
TP5 and GRD and set to 3V scale (not shown in fig.
5-12).
sensor amplifier unit to the SCAS test set and
test external power source with Special
Purpose Cable Assemblies CX-10851/U and
CX-10854/U, respectively.
(4) As shown in figure 5-12, connect the
b. Procedures.
Step
1
Action
Set AC and DC POWER
switches on test set to ON.
Adjust FEEDBACK for
NULL reading on Multimeter.
Normal indication
a. AC and DC indicator lights on the
test set come on.
b. NO GO lights shall come on for
less than 60 seconds and then go
off.
5-20
If abnormal indications
are observed
Check ac and dc power circuitry.
a. No NO GO lights come on in any
channel upon first application of
power.
(1) Observe DC indicator light on
test set. If it is off:
(a) Check 28-volt fuse F1
(b) Check 28-volt power circuitry. If it is on: Check
28 volts dc to ground in
any channel with voltmeter at pin D (28 volts
dc) and pin S (filtered 28
volts dc) on the extender
board to ground. If there
is 28 volts dc at only one
test point or if 28 volts
dc does not appear at
these test points, check
28-volt dc power circuitry.
(2) Observe the AC indicator light
on the test set. If off, check
the 115-volt ac power circuitry,
especially the ac interlock.
(3) Check the voltage between
ground and pin M (control
signal) on the extender
board of any channel. The
voltage should be 6 to 15
volts dc; if not, check the
+ 20-volt zener and associated
circuitry.
b. NO GO lights in one or two channels
do not come on when power
switches are turned on.
(1) Check bulbs.
(2) Substitute B. I. T. E. module
known to be good in the
faulty channel.
(3) Substitute valve driver module known to be good in the
faulty channel.
(4) Substitute control channel assembly known to be good.
(5) Check NO GO circuitry.
c. NO GO lights stay on after warmup
period.
(1) If all NO GO lights stay on,
press GYRO TEST button on
sensor amplifier unit, and replace the gyro assembly if the
lights go out when button is
depressed.
TM 11-1520-221-34
Step
Action
Normal indication
2
Reverse DC meter polarity if
meter reading is negative.
Voltmeter should read 0±.1 volt
3
Slowly lift rear of sensor amplifier unit to an angle of approximately 30 degrees momentarily and then return to
original position.
Voltmeter will indicate + voltage
when unit is lifted and returned to
original position.
4
Rotate FEEDBACK knob
clockwise until multimeter
indicates 1 volt.
DC voltmeter indicates 3.1±9 volts
for pitch, 3.1±1 volts for roll,
6.4±.3 volts for yaw.
5
Rotate FEEDBACK knob
counterclockwise until multimeter indicates 0.5 volt.
DC voltmeter indicates 3.1±9 volts
for pitch, 3.1±1 volts for roll,
6.4±3 volts for yaw.
6
Set FEEDBACK knob to 0,
rotate FEEDBACK knob
counterclockwise until NO
GO light illuminates.
Set FEEDBACK knob to 0,
rotate FEEDBACK knob
clockwise until NO GO light
comes on.
Momentarily depress ACTR
TEST switch on the sensor
amplifier unit.
Adjust FEEDBACK knob to
obtain null indication on multimeter.
Connect signal generator to None.
TP3 and TP4 on the test set.
Caution: Do not ground TP3
or TP4. Dc bias is present on
TP4.
Set oscilloscope controls as follows:
a. VERTICAL SENSITIVITY: 2 volt cm.
b. AMPLIFIER INPUT
switches: DC
c. HORIZONTAL SWEEP:
.1 millisecond/cm.
d. TRIGGER SOURCE:
EXT-115 vac 400 Hz
NO GO light illuminates at 6±2 volts
7
8
9
10
11
If abnormal indications
are observed
(2) Substitute pulse generator module known to be good if all
lights stay on.
(3) If one or two lights stay on
after warmup, balance the
control channel assembly
(para 5-28).
(4) Substitute valve driver module
known to be good in defective
channel.
(5) Substitute control channel assembly known to be good.
a. Adjust balance by turning R5 until
meter reading is 0+.1 volt.
b. If balance cannot be adjusted, substitute control channel assembly
known to be good.
a. If no deflection, substitute gyro assembly known to be good.
b Substitute PITCH control channel
assembly.
c. Check sensor amplifier unit power
circuits (para 5-5).
a. Substitute valve driver module if
gain is low.
b. Check control channel assembly
(para 5-28).
c. Check feedback circuitry.
a. Substitute valve driver module if
gain is low.
b. Check control channel assembly
(para 5-28).
c. Check feedback circuitry.
a. Substitute B.I.T.E. module.
b. Check control channel assembly
(para 5-28).
NO GO light comes on at 6±2 volts.
NO GO light goes out when switch is
depressed.
5-21
Check S2.
TM 11-1520-221-34
Step
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
Action
Note. Use oscilloscope to adjust signal generator output
for 10 volts peak to peak sine
wave signal.
Connect oscilloscope vertical
lead to TP1 on the test set.
Adjust signal generator to frequency A as shown in table
5-1.
Adjust signal generator to frequency B as shown in table
5-1.
Adjust signal generator to frequency C as shown in table
5-1.
Remove signal generator
Reverse Voltmeter polarity
(+ DC).
Set CHANNEL selector on the
test set to ROLL.
Slowly raise left side (when
viewed from front) of sensor
amplifier unit to produce an
angular motion.
Normal indication
None.
Observe peak-to-peak voltage indication as shown in table 5-1.
Same as 13 above.
None.
None.
None.
Voltmeter indicates positive voltage
during motion.
Lower left side of sensor amplifier unit to original position.
Repeat 4 through 17 above
to test roll channel.
Set CHANNEL selector on the
test set to YAW.
Slowly rotate the sensor amplifier unit counterclockwise.
None.
Rotate the sensor amplifier unit
clockwise to original position.
Repeat 4 through 17 above to
test yaw channel.
Connect positive lead of voltmeter to pin M of TJ2, on
the test set. Connect negative
lead of voltmeter to GND.
Set AC Power switch to OFF.
None.
.03............................
.1..............................
.5..............................
Refer to paragraph 5-28 to troubleshoot
each control channel assembly.
Same as 13 above.
a. If no deflection, substitute gyro assembly.
b. Substitute PITCH control channel
assembly.
c. Check sensor amplifier unit power
circuits (para 5-5).
Same as 4 through 17 above.
None.
Voltmeter indicates positive voltage
during motion.
a. If no deflection, substitute gyro assembly.
b. Substitute PITCH control channel
assembly.
c. Check sensor amplifier unit power
circuits (para 5-5).
Same as 4 through 17 above.
Voltmeter should read 27.5 ± 2.0 vdc
Voltmeter indicates 0 volts
Frequency (His) Pitch Output Vp-p Roll Output Vp-p
A.
B.
C.
If abnormal indications
are observed
a. If no voltage, substitute relay known
to be good.
b. Check associated relay energizing
circuitry.
a. If voltage remains, substitute relay
known to be good.
b. Check associated relay energizing
circuitry.
Table 5-1
Yaw Output Vp-p
2.4±0.8 ..................................................
3.3±1.0 ..................................................
1.8±0.6 ..................................................
5.0±1.5 ..............................................................
8.5±2.5 ..............................................................
3.0±1.0 ..............................................................
5-22
5.0±1.5
8.5±2.5
3.0±1.0
TM 11-1520-221-34
5-27.
Control Panel and Sensor Amplifier Unit
Operational Check and Troubleshooting
Chart
a. Connect control panel, sensor amplifier unit and
the external power source to the SCAS test set as
shown in figure 5-13 as follows:
(1) Position test set controls as follows:
(a) POWER switches OFF.
(b) CHANNEL switch to PITCH.
(c) MODE switch to CP/SAU.
(d) FEEDBACK knob to 0.
(2) Connect voltmeter positive lead to SCAS
test set TP1 and negative lead to TP2,
and set to 10 vdc scale (not shown in fig.
5-13).
(3) Connect multimeter between SCAS test
set TP5 and GRD and set to 3V scale (not
shown in fig. 5-13).
(4) Connect the SCAS test set to the control
panel, sensor amplifier unit, and external
power source using Special Purpose
Cable Assemblies CX-10853/U, CX10851/U and CX10854/U, respectively.
(5) Position POWER switch on control panel
to OFF.
(6) Open access cover on front of
sensoramplifier unit.
Figure 5-13. SCAS control panel and sensor amplifier unit test setup connections.
5-23
TM 11-1520-221-34
b.
Procedures.
Step
1
2
Action
Normal Indication
Set ac and de POWER switches Control panel edge lights come on_
on test set to ac and dc.
(para 5-12).
Set POWER switch on the
PITCH, ROLL and YAW NO GO
control panel to POWER.
lights and the NO GO light on the
test set come on for less than 60
seconds and then go out. AC and
DC lights on the test set come on.
5-24
If abnormal indications
are observed
DS4, DS5, or associated wiring bad
Check AC and DC circuitry according
to paragraph 5-12.
a. No NO GO lights illuminate in any
channel upon first application of
power.
(1) Observe 28-volt indicator light on
test box.
If off(a) Check 28-volt fuse.
(b) Check 28-volt power circuitry.
If on(2) Check 28 volts dc to ground in
any channel with a voltmeter at
pin D (28 volts) and pin S (filtered
28 volts) on the extender board to
ground.
If there is 28 volts at
only one pin or if no 28 volts
appears at these points, check
28-volt
power circuitry.
(3) Observe the 115-volt ac indicator
light on the test box. If
off,
check
the
115-volt
power
circuitry.
(4) Check the voltage between
ground and pin M (control signal
of any channel). The
voltage
should be 6 to 15 volts
dc; if
not, check the +20-volt zener and
associated circuitry.
b.
NO GO lights in one or two channels
do not come on when power
switches are turned on.
(1) Check bulbs.
(2) Substitute B. I. T. E. module
known to be good in faulty
channel.
(3) Substitute valve driver module
known to be good in faulty
channel.
(4) Substitute control channel
assembly known to be good.
Repair (para 5-28).
(5) Check NO GO circuitry by 570078-016.
c.
NO GO lights stay on after warmup
period.
(1) If all NO GO lights stay on, press
GYRO TEST button on sensor
amplifier unit, and replace the
gyro assembly (fig. 5-10) if lights
go out when button is depressed.
(2) Substitute
pulse
generator
module known to be good if all
lights stay on.
(3) If one or two lights stay on after
warmup, balance the control
channel assembly (para. 5-28).
TM 11-1520-221-34
Step
Action
If abnormal indications
are observed
(4) Substitute valve driver module known
to be good in defective channel.
(5) Substitute control channel assembly
known to be good.
Repair (para 528).
The AC and DC indicator
d.
Bad S1 or
Normal Indication
Note.
associated wiring (para 5-5)
lights on the test set stay on except as
specifically stated in this test.
None.
None.
3
4
Set multimeter to .1-volt scale
Adjust FEEDBACK knob on
the test set to obtain null indication on the multimeter.
5
Adjust R5 potentiometer in the
None.
PITCH channel assembly of
the sensor amplifier unit to
obtain 0 indication on the
voltmeter.
6
Set CHANNEL selector on the
None.
test set to ROLL.
7
Repeat 5 above -------------None.
8
Set CHANNEL selector on the
None.
test set to YAW.
9
Repeat 5 above.
10
Set PITCH, ROLL, and YAW
ENGAGED light on the test set illumengage switches on the coninates.
circuitry (para 5-5).
(This step
trol panel to up (engaged)
engage switches remain engaged.
position.
11
Set CHANNEL selector on the
PITCH, ROLL, and YAW engage
test set to ROLL.
switch on control panel remain enNote. When the CHANNEL
gaged. ENGAGED light on the test
selector on the test set is roset remains illuminated.
tated to a new position, the NO
GO light on the test set may
come on for a few seconds and
then go out.
If any of the engage switches on the control
panel are not engaged, the appropriate NO GO light may
illuminate.
12
Set CHANNEL selector on the
PITCH, ROLL, and YAW engage
test set to PITCH.
switches on the control panel remain engaged.
the test set stays on.
13
Depress momentarily the
PITCH, ROLL, and YAW engage
EMER DISENGAGE switch
switches immediately move to OFF.
on the test set.
ENGAGED light on the test set
goes out.
14
Set PITCH, ROLL, and YAW
Engage switches hold in engaged
switches on the control panel
position.
to engaged position.
test set comes on.
15
Set AC switch on the test set
PITCH, ROLL, and YAW switches on
to OFF.
the control panel immediately move
to OFF.
16
17
Set AC switch on the test set
to AC.
Set PITCH, ROLL, and YAW
engage switches on the control panel to engaged position.
on the test set go out.
AC light on the test set comes on -__
PITCH, ROLL, and YAW engage
switches hold in engaged position.
ENGAGED light on the test set
comes on.
5-25
Bad switch or wiring in hold-in coil
PITCH, ROLL, and YAW
coil
checks yaw switch.)
Bad switch or wiring in hold-in coil
circuitry (para 5-5).
(This step
checks roll switch.)
Bad switch or wiring in hold-in coil
circuitry (para 5-5). (This step
ENGAGED light on checks pitch switch.)
Bad switch or wiring in hold-in coil
circuitry (para 5-5).
ENGAGED light on the
Bad AC interlock relay. Bad rectifying
diode. Bad filter capacitor.
ENGAGED and AC lights Bad AC wiring
(para 5-5).
Bad coil circuitry.
Faulty S1 or associated wiring.
TM 11-1520-221-34
Step
Action
If abnormal indications
are observed
Normal Indication
18
Set POWER switch on control
panel to OFF.
19
Set POWER switch on the control panel to engaged position.
20
Adjust FEEDBACK knob on
the test set to obtain 0 indication on the voltmeter.
Slowly raise the aft side of
Voltmeter indicates positive voltage
the sensor amplifier unit to
produce an angular position.
21
22
23
Return sensor amplifier unit to
original position.
Turn FEEDBACK knob clockwise until multimeter indicates 0.5 volt.
PITCH, ROLL, and YAW engage
switches immediately move to OFF.
ENGAGED, AC, and DC lights on
the test set go out.
NO GO lights on the control panel and
test set come on for approximately
60 seconds or less, and then go out.
AC and DC indicators on the test
set come on.
None.
DC voltmeter should indicate3.1+0.9 volts for pitch, `
4.0±1.2 volts for roll,
7.0±2.1 volts for yaw.(para 5-28).
Rotate FEEDBACK knob to 0
then clockwise until
Voltmeter indication is 6 +2 volts __
25
26
Return FEEDBACK knob to 0 _
Reverse voltmeter polarity
(+dc).
Turn FEEDBACK knob counterclockwise until multimeter
indicates 0.5 volt.
None.
28
Rotate FEEDBACK knob to 0,
then counterclockwise until
NO GO lights come on.
Voltmeter indication is 6 ±2 volts
29
Remove voltmeter from test
None.
set.
Depress and hold ACTR TEST
NO GO lights go out
switch on the set.
Release ACTR TEST switch _
NO GO lights come on.
Adjust FEEDBACK knob to
None.
obtain null indication on the
voltmeter.
Connect signal generator to
None.
TP3 and TP4 on the test set.
Caution: Do not ground TP3
or TP4. DC bias is present on
TP4.
Set oscilloscope switches as
None.
follows:
VERTICAL SENSITIVITY:
2 VOLT/CM AMPLIFIER
INPUT switches: DC
HORIZONTAL SWEEP:
.1 MILLISECOND/CM
30
31
32
33
34
Same as step 2.
a. If no deflection, substitute gyro assembly (fig.
5-15).
b. Substitute pitch control channel assembly.
c. Check sensor amplifier unit power
circuits (para 5-5).
Voltmeter indicates 0.
24
27
Bad switch or wiring in hold-in coil
circuitry.
DC voltmeter should indicate3.1±0.9 volts for pitch
4.0± 1.2 volts for roll,
7.0±2.1 volts for yaw.
5-26
a. Substitute valve driver if gain is
low.
b. Check control channel assembly
c. Check feedback circuitry.
a. Substitute B.I.T.E. module assembly
(para 5-8).
b. Check control channel assembly
(para 5-28).
a. Substitute valve driver if gain is
low.
b. Check control channel assembly
(para 5-28).
c. Check feedback circuitry.
a. Substitute B.I.T.E. module 570-074048-1.
b. Check control channel assembly
(para 5-28).
Check switch.
TM 11-1520-221-34
Step
35
36
37
38
39
40
41
Action
TRIGGER SOURCE:
EXT 115 vac, 400 Hz.
Note. Use oscilloscope to adjust signal generator output
for 10-volt peak-to-peak sine
wave signal.
Connect oscilloscope vertical
lead to TP1 on the test set.
Adjust signal generator to frequency A as shown in table
5-1.
Adjust signal generator to frequency B as shown in table
5-1.
Adjust signal generator to fre
quency C as shown in table
5-1.
Remove signal generator
Connect voltmeter positive to
TP1 and negative lead to
TP2.
Set CHANNEL selector on the
test set to ROLL.
Normal Indication
If abnormal indications
are observed
None.
Observe peak-to-peak voltage indication on the oscilloscope. Acceptable
performance standard is listed in
table 5-1.
Same as 36 above.
Same as 36 above.
None.
None.
Set at 10 vdc and +DC.
None.
Figure 5-14. Three axis gyro assembly.
Change 1 5-27
Refer to paragraph 5-28 to troubleshoot
each control channel assembly.
TM 11-1520-221-34
Step
Action
If abnormal indications
are observed
Normal Indication
42
Slowly raise left side (when
viewed from front) of sensor amplifier unit to produce an angular motion of
the sensor amplifier unit,
Voltmeter indicates positive voltage
during motion.
43
Lower left side of sensor amplifier unit to original position.
Repeat 23 through 40 to test
roll channel.
Set CHANNEL selector on the
test set to YAW.
Slowly rotate the sensor amplifier unit counterclockwise.
None.
Return the sensor amplifier
unit to original position.
Repeat 23 through 40 to test
yaw channel.
None.
44
45
46
47
48
a. If no deflection, substitute gyro assembly.
b. Substitute pitch control channel
assembly.
c. Check sensor amplifier unit power
circuits (para 5-5).
Same as 23 through 40 above.
None.
Voltmeter indicates positive voltage
during motion.
a. If no deflection, substitute gyro assembly.
b. Substitute pitch control channel assembly.
c. Check sensor amplifier unit power
circuits (para 5-5).
Same as 23 through 40 above.
5-28.
Bench
Operational
Check
and
Troubleshooting Chart, Control Channel
Assembly
a. Connecting Control Channel Assembly to SCAS
Test Set (fig. 5-15).
(1) Position test set controls as follows:
(a) DC POWER switch to OFF.
(b) AC POWER switch to OFF.
(c) MODE switch to AIOD.
(d) FEEDBACK knob to 0.
(2) Connect voltmeter positive lead to TP1 and
negative lead to TP2 on the SCAS test set (not
shown on fig. 5-15).
(3) Connect multimeter between TP5 and GRD on
the SCAS test set and set multimeter to 3-volt
scale (not shown on fig. 5-15).
(4) Connect the SCAS test set to the external power
source using cable assembly CX-10854/U.
(5) Insert control channel assembly 570074-037-7, ,15, or -11 into TJ4 of the test set.
Figure 5-15. Control channel assembly test setup
connections.
5-28
TM 11-1520-221-34
Step
1
2
3
4
5
Action
Set AC and DC POWER
switches to AC and DC.
Adjust FEEDBACK knob for
null indication on VTVM.
Adjust R5 on control channel
assembly to obtain 0+1.V indication on VOM.
Set AC and DC POWER
switches to OFF.
Set POWER switches on test
set to AC and DC
If abnormal indications
are observed
Normal Indication
a. NO GO light on the test set comes
on and goes off in less than 60
seconds.
a.
b.
c.
d.
e.
f.
g.
h.
b. NO GO light comes on but does not
go off in less than 60 seconds.
a.
b.
c.
d.
6
Turn FEEDBACK knob clockwise until multimeter indicates 0.5 volt.
7
Turn FEEDBACK knob to 0,
then clockwise until NO GO
light comes on.
VOM indicates3.1+0.9 volts for pitch,
4.0+1.2 volts for roll,
7.0+2.1 volts for yaw.
VOM indicates 6.0+2.0 volts
e.
f.
a.
b.
c.
d.
a.
b.
c.
d.
e.
8
9
10
Return FEEDBACK knob to 0
Reverse voltmeter polarity _
Turn FEEDBACK knob counterclockwise until multimeter
indicates 0.5 volt.
11
Turn FEEDBACK knob to 0,
then counterclockwise until
NO GO light comes on.
Remove voltmeter from test
set.
Adjust FEEDBACK for null
on multimeter.
Connect signal generator to
TP3 and TP4.
12
13
14
None.
None ---------------------------------------Voltmeter indicates3.1+0.9 volts for pitch,
4.0+1.2 volts for roll,
7.0+ 2.1 volts for yaw.
Voltmeter indicates 6.0+2.0 volts
None.
5-29
Substitute B.I.T.E. module.
Substitute valve driver module.
Check R8.
Check R7.
Defective 28-volt dc circuitry on
board (both pins D and S) (para
5-5).
Defective NO GO circuitry (para
5-5).
Check ground circuitry (pin 6 of
B.I.T.E. to ground through pin)
and check all of the ground circuitry on control channel assembly.
Defective pulse generator circuitry
from pulse generator through the
entire control channel assembly
(para 5-9).
Defective B.I.T.E. module.
Defective valve driver module.
Check power and ground circuitry
(para 5-5).
Check R4, R3, R18, Rll, R5, RT1,
R6, CR1, R10, R9, and R21.
Check C6, R20, C2, and R14.
Check R22 (Roll only).
Substitute valve driver module.
Check R7 and R1.
Check R13, R21 and R9.
Check R6 and CR1.
Check B.I.T.E.
module.
Check valve driver module.
Check pulse circuitry on control
channel assembly (para 5-9).
Check CR1 for 20 vdc.
Check R3 and R4.
Same as 6 above.
Same as 7 above.
TM 11-1520-221-34
Step
15
16
17
18
19
20
21
22
23
Action
Caution: Do not ground TP3
or TP4. Dc bias is present on
TP4.
Set oscilloscope VERTICAL
SENSITIVITY to 2 volt cm.
Set oscilloscope AMPLIFIER
INPUT switches to DC.
Set oscilloscope HORIZONTAL
sweep to .1 MILLISECOND/
CM.
Set oscilloscope TRIGGER
SOURCE to EXT-115 vac,
400 Hz.
Use oscilloscope to adjust signal generator output for 10volt peak-to-peak sine wave
signal.
Connect oscilloscope vertical
lead to TP1.
Adjust signal generator to frequency A as shown in table
5-1.
peak-to-peak voltage indication on oscilloscope.
Adjust signal generator to frequency B in table 5-1.
serve and record peak-topeak voltage indication on
oscilloscope.
Adjust signal generator to frequency C in table 6-1.
serve and record oscilloscope
peak-to-peak indication.
ceptable values are shown in
table 5-1.
If abnormal indications
are observed
Normal Indication
Observe peak-to-peak voltage indication on the oscilloscope.
Observe and record
Normal indication is listed in table 5-1.
Same as 21 above.
Ob-
Same as 21 above
ObAc-
5-30
a. Check valve driver.
b. Check R1.
c. Set the signal generator for 20 volts
peak-to-peak sine wave signal at
.1 Hz, and check + side of C4 for
approximately .6 volt for PITCH,
.6 volt for ROLL, and .7 volt for
YAW peak-to-peak summed with
approximately 10 volts de.
d. Check pin 2 of T1 for approximately
.55 volt for PITCH, .6 volt for
ROLL, and .7 volt for YAW,
peak-to-peak.
e. Check + side of C5 for approximately .4 volt for PITCH, .6 volt
for ROLL, and .4 volt for YAW,
peak-to-peak at .1 Hz summed
with approximately 10 volts dc.
If
there is no voltage, check CR3,
CR4, CR5, CR6, and C5.
f. Check the collector of Q1 for 20±1
volts de. If there is no voltage
present, check R6 and CR1.
g. Check the emitter of Q1 for approximately .35 volt for PITCH,
.5 volt for ROLL, and .4 volt for
YAW, peak-to-peak at .1 Hz summed with approximately 10 volts
dc
h. Check between C6 and R20 for approximately .3 volt for PITCH, .5
volt for ROLL, and .3 volt for
YAW at .1 Hz. If there is no
TM 11-1520-221-34
Step
Action
Normal Indication
Position AC and DC power
switches to OFF.
Remove assembly under test
from TJ4.
Insert 570-091-011-1 extender
card into TJ4.
Set oscilloscope switches as follows:
VERTICAL SENSITIVITY
0.1 volt/cm AMPLIFIER
INPUT switches: DC HORIZONTAL SWEEP: 5 msec/
cm TRIGGER SOURCE:
EXT-115 vac, 400 Hz.
Connect oscilloscope input
leads to pins P and L on
extender card.
Position AC and DC power
switches to AC and DC.
Adjust amplitude of signal
generator to obtain 0.2 volts
peak-to-peak modulation envelope.
Position AC and DC power
switches to OFF.
Remove extender card and in
sert control assembly in TJ4.
Set oscilloscope switches as
follows:
VERTICAL SENSITIVITY:
2 volt/cm.
AMPLIFIER INPUT
switches: DC
HORIZONTAL SWEEP:
0.1 msec/cm.
TRIGGER SOURCE:
EXT-115 vac, 400 Hz.
Connect oscilloscope vertical in
put to TP1.
switches to AC and DC.
Adjust frequency of signal
generator to frequency A in
table 5-2.
None.
If abnormal indications
are observed
voltage present, check C6 and R20.
24
25
26
27
28
26
30
31
32
33
34
35
None.
None.
None.
None.
None.
Oscilloscope should indicate 0.2 volts
peak-to-peak.
None.
None.
None.
None.
Position AC DC
Observe peak-to-peak indication on oscilloscope. Performance standard is
listed in table 5-2.
5-31
a. Substitute valve driver module
known to be good.
b. Check R1 and R7.
c. Check pin 2 of T1 for approximately
.25 volt for pitch, .3 volt for roll,
and 1.2 volts for yaw.
d. Check + side of C5 for approximately .25 volt for Pitch, .3 volt
for roll, and 1.2 volt for yaw,
peak-to-peak at .1 Hz summed
with approximately 10 volts dc. If
there is no voltage, check CR3,
CR4, CR5, CR6, and C5.
e. Check the collector Q1 for 20 vdc.
If there is no voltage present,
check R6 and CR1.
f. Check the emitter of Q1 for approximately .25 volt for pitch, .2 volt
for roll, and 1.2 volts for yaw,
TM 11-1520-221-34
Step
Action
36
37
Normal Indication
Adjust frequency of signal
generator to frequency B in
table 5-2.
Adjust frequency of signal generator to frequency C in table 5-2.
Frequency (Hz)
A
B
C
If abnormal indications
are observed
Observe peak-to-)kPak indication on
osc.
in table 5.-2.
Observe peak-to-peak indication on
osc.
in table 5-2.
Pitch Output Vp-p
.03 ........................
.1 ..........................
.5 ..........................
Table 5-2
Roll Output Vp-p
2.5 +.6 .........................
3.5 +1 ..........................
2.0 +.6 .........................
peak-to-peak at .1 Hz summed
with approximately 10 vdc.
g. Check between C6 and R20 for approximately .15 volts for pitch,
.2 volt for roll, and 1 volt yaw, at
.1 Hz.
If there is no voltage present, check C6 and R20.
h. Check the waveform at pin 10 of the
valve driver module (para 5-30).
Same as 35.
Performance standard is listed
Same as 35.
Performance standard is listed
Yaw Output Vp-p
1.9 +.6 ............................ 1.8 +.6
2.6 +.9 ............................ 2.6 +.9
1.5 +.5 ............................ 1.5 +.5
5-29.
Pylon Compensation Unit Operational
Check and Troubleshooting Chart
a. Connecting Pylon Compensation Unit to SCAS
Test set (fig. 5-16).
(1) Position test set controls as follows:
(a) POWER switches OFF.
(b) The position of the other controls is not
applicable to this test. They may be set in any position.
(2) Connect the pylon compensation unit to the
external power source and the SCAS test set using
cable assemblies CX-10854/U and CX-10852/U,
respectively.
(3) Connect voltmeter positive lead to TP8 and
negative lead to GRD on the SCAS test set (not shown
in fig.5-16). Set voltmeter to 50 vdc scale.
EL1520221-35-TM-9
Figure 5-16. Pylon compensation unit test setup
connections.
b.
Procedure.
Step
1
2
Action
Turn on external power source
Position dc power switch to
DC.
If abnormal indications
are observed
Normal Indication
None.
Voltmeter indicates 10 + 1 vdc
5-32
a. Check R11.
b. Check CR1.
c. Check continuity from pin G, J1 to
E2.
TM 11-1520-221-34
Step
Action
If abnormal indications
are observed
Normal Indication
3
Connect voltmeter positive lead
to TP10.
Voltmeter indicates 10+1 vdc-
4
5
Disconnect voltmeter
Set osc as follows:
VERTICAL SENSITIVITY: 1 volt/cm;
AMPLIFIER INPUT
SWITCHES: DC;
HORIZONTAL
SWEEP: 0.1 msec/cm;
TRIGGER SOURCE:
EXT 115 vac, 400 Hz.
Using osc, adjust signal generator to a 1.0 Hz sinewave
output with a peak-to-peak
amplitude of 3.0 volts.
Connect generator output to
TP8 and TP9 of test set.
Caution: DC bias is present
on TP8, do not ground.
Set vertical sensitivity on osc
to 10 millivolts, 'cm.
Connect vertical input of osc
to TP7 of the test set.
Set vertical sensitivity on osc
to 20m/volts/'cm.
Adjust signal generator to 2.5
Hz.
Set vertical sensitivity on osc
to 50m/volts/cm.
Adjust signal generator to 4.0
Hz.
Adjust signal generator to 8.0
Hz.
None.
None.
Set vertical sensitivity on osc
to 10m/volts/cm.
Adjust signal generator output
frequency to obtain a null
on the osc.
Set vertical sensitivity on osc
to 0.1 volt/'cm.
Adjust signal generator to 20.0
Hz.
Set vertical sensitivity on osc
to 0.2 volts/cm.
Adjust signal generator to 40.0
Hz.
None.
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
a Check R11.
b. Check CR1.
c. Check continuity from pin H, J1 E2.
None.
None.
None.
Osc should indicate 40+15m/volts
peak-to-peak.
None.
a. Check R1, R2, R3, R4, R5, and C1.
b. Check R9, R10, and C5.
Osc should indicate 130+20m/volts
peak-to-peak.
None.
Same as 9.
Osc should indicate 200+30m/volts
peak-to-peak.
Osc should indicate 180+50m/volts
peak-to-peak.
Same as 9.
Null frequency should be 11+1 Hz
a. Check R1, R2, R3, R4, R5, and C1.
b. Check R9, R10, and C5.
c. Check R6, R7 R8, C2, C3, and C4.
Check R6, R7, R8, C2, C3, and C4.
None.
Osc should indicate 650+90m/volts
peak-to-peak.
None.
Same as 14.
Osc should indicate 1.5+0.2 volts
peak-to-peak.
Same as 14.
b. Negative pulse from pin NP is applied to pin 4
of the 324-5D transformer through pin F of connectors
1J2, 1J3, 1J4 to synchronize the demodulator in the
compensating circuit to 400 Hz. The negative pulse is
also applied through pin F of connector 1J2, 1J3, and
1J4 to pin 2 of the valve driver module to gate this
module in synchronism with 400 Hz (fig. 5-9, view B).
5-30.
Sample Waveforms
The waveforms illustrated in (fig. 5-9) are provided for
comparison with the waveforms taken by the repairman.
a. Positive pulse from pin pp of pulse generator
module is applied through pin H of connectors 1J2, 1J3,
and 1J4 to pin 3 of the valve driver module for gating of
the input (fig. 5-9, view A).
5-33
TM 11-1520-221-34
e. For output of pin 10 of the valve driver as a
result of the control channel assembly being unbalanced
in the negative direction or a negative signal being
applied at the input terminal pin 6, see figure 5-9, view
E.
f. For the valve driver in a saturated condition as
a result of warmup, large positive signal on the input, or
a malfunction, see figure 5-9, view F.
g. For the valve driver in a saturated condition as
a result of a large negative signal on the input or a
malfunction, see figure 5-9, view G.
h. For waveform at pin 6 of the valve driver
module, see figure 5-9, view H.
c. For zero signal input, the reference level of the
output at pin 10 of the valve driver is set by the amount
of regulated 20 volts dc received through RT1 from CR1
which is applied at pin 4 after being attenuated by R3
and R4.A combination of all signals that are applied at
pin 6 also appears at pin 10 in the form of a 200-usec
pulse with a repetition of 400 Hz. The level of this pulse
for zero signal on the input is set at the same level as
the reference output value by the amount of 20 volts dc
received through RT1 from CR1 which is applied at pin
4 after being attenuated by R5, R11, R18, and R10. R5
allows the pulse and the reference outputs at pin 10 to
be balanced for minor production and aging tolerances.
The correct balanced output appears at pill 10 of the
valve driver module for zero signal input (fig. 5-9, view
C).
d. For output at pin 10 of the valve driver as a
result of the control channel assembly being unbalanced
in the positive direction o0' a positive signal being
applied at the input terminal pin 6, see figure 5-9, view
D.
Neg. lead from
5-31.
Voltage and Resistance Measurements
Chart
The following chart of system voltages and resistances
is furnished as an aid to troubleshooting and repair of
the stability and control augmentation system.
NOTE
All resistance measurements must be
taken with power off.
Point of measurement positive lead
Voltage
Grd
Grd
Grd
With A2, K1, A4, A5, A6 removed and 1P5 unplugged.
Pin 5 of 1J6 ......................................
Normal indication
Voltage-off
resistance
28 V DC ........
E4.....................................................
DA6, DA5, DA4, IN of L1 ...................
Pin GRD of A2 .................................
28 V DC ........
28 V DC ........
Pin 2 of A1 ........................................
Pin 3 of A1 ........................................
Pin 4 of A1 ........................................
Pin 5 of A1 ........................................
.....................
.....................
.....................
.....................
Grd
Pin 6 of A1 .......................................
Pin 7 of A1 ........................................
Pin 3 of A1 .......................................
Grd
Pins A, B, and F of 1J5 ....................
Grd
Pins D, E, and K of 1J5 ....................
.....................
.....................
115V ac 400..
Hz.................
0 volts ...........
.....................
26V ac 400....
Hz.................
Isolating procedure
Infinity.............. If low, check CR1, L1, C2, and
shorts in wiring (fig. 5-17 and
5-18).
Infinity
Infinity
0
Check A. If high, check continuity
pin 1 of Al to ground.
Check
Grd of A2 to pin 3 of A1.
Infinity
Infinity ............. Replace A1.
Infinity.............. Replace Al.
ApproxiIf shorted, check wiring and Al.
mately
If open, check Al and conti2.6Ω
nuity.
Check gyro test
switch
if open.
Infinity.............. Grd of A2 to pin 3 of A1.
Infinity.............. Grd of A2 to 3A1.
Check continuity from pin 3 of
A1 to pin R of iJ1.
Check continuity from pins A, B,
and F to grd.
Check continuity from pins D, E,
and K to pin 5 of A1.
Check
continuity between pins 1 and
2 of gyro test switch.
If no
volt-
Grd
Pin L of 1J5 ......................................
26V ac 400....
Hz.................
5-34
age at pin 5 of A1 with pin 5
open, replace A1.
Check continuity from pin L of
1J5 to pin 7 of Al.If zero ohms
but no voltage, replace Al.
TM 11-1520-221-34
Neg. lead from
Point of measurement positive lead
Grd
Pin M of 1J5 .....................................
Pin 5 Al
E5 ....................................................
Grd
E5.....................................................
IN of L1
S of A4 and 1 of L1 ..........................
IN of L1
S of A5 and 2 of L1 ..........................
IN of L1
Grd
S of A6 and 3 of L1 ...........................
Power on, all control channel as
semblies, signal generator
module removed and
1P5 removed.
Pin S of 1J5 .....................................
Grd
Pins H, J, and N of 1J5 .....................
Normal indication
Voltage-off
Isolating procedure
Voltage
resistance
26V ac 400....
........................
Check continuity from pin M of
Hz.
1J5 to pin 6 of Al.
.....................
1.8Ω ................ If shorted, check wiring and Al.
If open, check Al and continuity. Check gyro test switch if
open.
.....................
.8Ω ................. If shorted, check wiring and Al.
If open, check Al and continuity. Check gyro test switch if
open.
.....................
ApproxiCheck continuity from 5 to termately
minal 1, L1 bad if shorted or
43Ω.
open.
.....................
ApproxiCheck continuity from 5 to termately
minal 1. L1 bad if shorted or
430Ω.
open.
.....................
Approximately
43Ω.
26V dc 400 ...
Hz.
26V ac 400....
Hz.
........................ Check continuity from pin S of
1J5 to pin 2 of Al.
........................ Check continuity from pins H, J,
and N of 1J5 to pin 4 of Al.
zero ohms but no voltage, replace A1.
........................ Check continuity from pin S of
A4 to pin 1 of L1. Check voltage at IN of L1. This should
If
Grd
Pin S of A4 .......................................
28V dc ..........
Grd
Pin S of A5........................................
28V dc ..........
.
Grd
Pin S of A6 .......................................
28V dc ..........
Grd
Grd
With K1 removed from socket.
Pin 7 of 1J6 ......................................
Pin 3 of 1J6 ......................................
be
28V dc.
........................ Check continuity from pin S of
A5 to pin 2 of L1. Check voltage at IN of L1. This should
be 28V dc.
........................ Check continuity from pin S of
A6 to pin 3 of L1. Check voltage at IN of L1. This should
be
28V de.
Pulse generator removed.
Pin NP of 1J7....................................
Pin PP .............................................
Grd
Pin 115 of 1J7 (pulse module) ...........
Grd
Pin B+ of 1J7 ...................................
Complete SAU operation, test ..........
box and extender card.
Control channel connector Pin:
.....................
Approximately
38v dc.
Zero Ω ............. Check continuity to grd. bus.
Check C1, R2, and CPR2.
.....................
........................ Check wiring.
Continuity to pin H of A4, A5,
Check wiring.
and A6.
115V ac 400..
........................ Check continuity from pin 115 of
Hz.................
1J7 to pin R of lJ1. Check resistance of pin 3 to pin 1 of
A1. Resistance should be 7.6
(power off).
+20V dc .......
........................ Check R1 (36 ohms). Check continuity E4 to pin h of 1J1.
Check CR1.
.....................
........................ Refer to paragraph 6-6 for
troubleshooting.
5-35
TM 11-1520221-34
Neg. lead from
Point of measurement positive lead
A
B
C
D
E
....................................................
....................................................
....................................................
....................................................
....................................................
F ....................................................
H ....................................................
J
....................................................
K ....................................................
L ....................................................
....................................................
....................................................
M ....................................................
N ....................................................
P ....................................................
....................................................
R ....................................................
....................................................
....................................................
....................................................
S ....................................................
T ....................................................
U ....................................................
V ....................................................
Normal indication
Voltage-off
Voltage
resistance
Isolating procedure
Open.
Grd.
+28V when NO GO light is on.
+ 28V.
See figure 5-10, view A, for 11Valve driver output at pin 1.
16V dc when CC assembly is
balanced.
Negative pulse (para 5-30b) .......... Pulse generator and associated
circuitry.
Positive pulse (para 5-30b)............ Pulse generator and associated
circuitry.
Ground on roll and yaw, 3-4V
dc on pitch.
Grd.
Approximately 10V de and outControl or gyro circuitry control.
put of gyro (200 mv peak/
deg !see).
Approximately 11V dc.
Open.
10V dc and output of gyro (200
Control or gyro circuitry.
mv peak /deg/!sec).
In-phase for clockwise motion on
Feedback information.
feedback knob. Out of phase
for counterclockwise motion on
feedback knob.
28V dc.
See figure 5-10, view B ------Valve driver output.
Open.
Open.
5-36
TM 11-1520-221-34
NOTE:
R16 NOT INSTALLED ON
PITCH CONTROL ASSEMBLY
EL 1520-221-35-TM-26
Figure 5-17. SCAS control channel assembly module (front).
Change 1 5-37
TM 11-1520-221-34
Figure 5-18. SCAS control channel assembly module (rear).
Section IV.
PERFORMANCE TESTING AND STANDARDS
5-32. General
a.
The testing procedures in this section are
prepared for use by maintenance shops and supporting
organizations responsible for performing maintenance of
the stability augmentation system. These procedures
set forth specific requirements that the repaired SCAS
control panel, sensor amplifier unit and control channel
assemblies must meet before they are returned to the
using organization.
5-38
TM 11-1520-221-34
and verify the results against the data given in the
Performance standard column.
b. Comply with the instructions preceding the body
of each chart before performing the procedures in the
chart.When new or fully repaired components are being
tested, perform each test for the particular component in
the sequence given. Do not vary the sequence. For
each step, perform all the actions in the Control settings
column, then perform each specific test procedure,
5-33.
Test Equipment
Test equipment and other equipment required to
perform the testing procedures in this chapter are listed
in paragraph 5-21.
5-39
TM 11-1520-221-34
5-34.
Control Panel Bench Testa. Test Equipment and Materials.(Refer to paragraph 5-21.)
b. Test Connections. Connect the equipment as shown in figure 5-11.
c. Procedures.
Step
No.
1
Control Settings
Test Equipment
Equipment Under Test
DC POWER switch:
OFF.
AC POWER switch:
OFF.
MODE selector: CP.
CHANNEL selector:
PITCH.
POWER switch (2S1):
OFF.
Test Procedure
a. Set AC and DC POWER switches of the
test set to AC and DC position.
b.
Set 2S1-POWER switch on the control
panel to POWER.
c. Depress momentarily each NO GO indicator light on the control panel.
d. Depress NO GO TEST pushbutton switch
on the test set.
e. Set PITCH engage switch 2S2 to up position comes on.
f. Set CHANNEL selector to ROLL
g. Set ROLL engage switch 2S3 to up (engaged) position.
h. Set CHANNEL selector to YAW
I.
j.
Set YAW engage switch S24 to up (engaged) position.
Depress momentarily the EMER DISENGAGE switch on the test set.
Performance Standard
a. Edgelit panel lights come on. All control
panel markings are clearly visible and
uniformly lighted, no visible light leakage at panel junctions, and no visible
light leakage because of panel flaws on
surfaces or edges.
b. AC and DC indicator lights on the test set
come on and will stay on throughout the
test except as specifically stated in this
test.
c. All NO GO indicator lights on the control
panel come on.
d. All NO GO lights on control panel and NO
GO light on test set come on and stay
as long as the NO GO TEST switch is
depressed.
e. ENGAGED indicator light on the test set
f.
ENGAGED light goes out. PITCH engage
switch 2S2 stay up (engaged).
g. ENGAGED light on the test set comes on.
h. ENGAGED light goes out. PITCH 2S2
and ROLL 2S3 remain engaged.
i. ENGAGED light on the test set comes on.
j.
PITCH 2S2, -ROLL 2S3 and YAW 2S4 engage switches immediately move to OFF.
The ENGAGED light on the test set goes
out.
5-35.
Sensor Amplifier Unit Bench Test
a. Test Equipment and Materials.(Refer to paragraph 5-21.)
b. Test Connections. Connect the equipment as shown in figure 5-13 and open sensor amplifier unit access door to expose control channel assemblies.
c. Procedure.
Step
No.
1
Control Settings
Test Equipment
Equipment Under Test
DC POWER switch:
OFF
Test Procedure
a. Connect voltmeter to the test set as follows:
Change 1 5-40
Performance Standard
a. None.
TM 11-1520-221-34
AC POWER switch:
OFF.
MODE selector: SAU
CHANNEL selector:
PITCH.
b.
c.
d.
e.
f.
g.
h.
i.
j.
k.
l.
m.
n.
o.
p.
q.
r.
s.
t.
u.
Positive lead (Red) to TPI.
Ground lead (Black) to TP2.
Set voltmeter to 10V scale
Connect multimeter to the test set as follows:
Positive lead (Red) to TP5.
Ground lead (Black) to GRD.
Set multimeter to .1 scale
Set AC and DC switches on the test set
to AC and DC.
Adjust FEEDBACK knob to obtain null
indication on the multimeter.
Remove multimeter,
Adjust R5 potentiometer in the PITCH
control channel assembly (BHC 570074-037-7) to obtain 0 indication on
the voltmeter.
Set CHANNEL selector on the test set to
ROLL.
Adjust R-5 potentiometer in the ROLL
control channel assembly (BHC 570974-037-15) to obtain a 0 indication on
the voltmeter.
Set CHANNEL selector on the test set to
YAW.
Adjust R5 potentiometer in the YAW control channel assembly (BHC 570-074037-11) to obtain 0 indication on the
voltmeter.
Set CHANNEL selector on the test set to7
PITCH.
Connect voltmeter same as a and b above
Slowly raise rear of sensor amplifier unit
to produce an angular motion of the
sensor amplifier unit.
Lower rear of sensor amplifier unit to
original position.
Rotate FEEDBACK knob clockwise until
multimeter indicates 0.5 volt.
Set FEEDBACK knob to 0, then rotate
knob clockwise until NO GO light lights.
Reverse voltmeter polarity
Rotate FEEDBACK knob counterclockwise
until multimeter indicates 0.5 volt.
Set FEEDBACK knob to 0, then rotate
knob counterclockwise until NO GO
light lights.
5-41
b. None.
c. None.
d. None.
e. AC and DC indicator lights on the test set
come on. NO GO amplifier unit and on
the test set come on and then go out
within one minute.
f. None.
g. None.
h. None.
i.
None.
j.
None.
k. None.
l.
None.
m. None.
n. None.
o. Voltmeter indicates positive voltage during
motion.
p. None.
q. Voltmeter indicates 3.1+0.9 volts for pitch,
4.0+1.2 volts for roll, 7.0+2.1 volts for yaw.
r. Voltmeter indicates 6.0+2 volts.s. None.
t. Voltmeter indicates 3.1+ 0.9 volts for pitch,
4.0+1.2 volts for roll, 7.0±2.1 for yaw.9
u. Voltmeter indicates 6.0+2 volts.
TM 11-1520-221-34
Step
No.
Control Settings
Test Equipment
Equipment Under Test
Test Procedure
v. Depress and hold ACTR TEST switch 1S2
on, on sensor amplifier unit.
w. Release ACTR TEST switch 1S2.
x. Adjust FEEDBACK knob to obtain 0 indication on voltmeter.
y. Remove voltmeter
z. Connect signal generator to TP3 and TP4
on the test set.
Caution: Do no ground TP3 or TP4. DC
bias is present on TP4.
aa. Set oscilloscope controls as follows
VERTICAL SENSITIVITY: 1 Volt cm.
AMPLIFIER INPUT switches: DC.
HORIZONTAL SWEEP: .1 millisecond/cm.
TRIGGER SOURCE: LINE.
Note. Use oscilloscope to adjust signal generator output for 10 volts peak-to-peak sine
wave signal.
ab. Connect oscilloscope vertical lead to TP1
on the test set.
ac. Adjust signal generator to frequency A
as shown in table 5-1.
ad. Adjust signal generator to frequency B
as shown in table 5-1.
ae. Adjust signal generator to frequency C
as shown in table 5-1.
af. Remove signal generator
ag. Connect voltmeter as in a and b
ah. Set CHANNEL selector on the test set
to ROLL.
ai. Slowly raise left side (when viewed
from front) of sensor amplifier unit to
produce an angular motion of the.
sensor amplifier unit.
aj. Lower left side of sensor amplifier unit
to original position.
ak. Repeat q through ag above to test roll
channel.
al. Set CHANNEL selector on the test set
to YAW.
am. Slowly rotate this sensor amplifier unit
counterclockwise.
5-42
Performance Standard
v.
NO GO light on test and NO GO indicator
light in sensor amplifier unit go out.
w. NO GO light on test set and NO GO indi-in
cator light in sensor amplifier unit come
on.
x. None.
y. None.
z. None.
aa. None.
ab. None.
ac. Observe' peak-to-peak voltage indication
on the oscilloscope. Acceptable performance standard is listed in table
5-1.
ad. Same as aa above.
ae. Same as aa above.
af. None.
ag. None.
ah. None.
ai. Voltmeter indicates positive voltage during motion.
aj. None.
ak. Same as q through ag.
ad. None.
am. Voltmeter indicates positive voltage during motion.
TM 11-1520-221-34
an. Rotate the sensor amplifier unit clockwise to original position.
ao. Repeat q through ag above to test yaw
channel.
ap. Connect positive lead of VOM to pin M
of TJ2 on Test Set; connect negative
lead of VOM to ground.
an. None.
aq.Set AC POWER switch to OFF
aq.VOM indicates 0 volts.
ao. Same as q through ag.
ap. VOM should indicate 27.5+2.0 volts.
5-36.
Control Panel and Sensor Amplifier Unit Bench Test
a. Test Equipment and Materials.(Refer to paragraph
5-21.)
b. Test Connections. Connect the equipment as shown in figure 5-13.
c. Procedures.
Step
No.
1
Control Settings
Test Equipment
Equipment Under Test
DC POWER switch:
Control panel POWER
OFF.
(2S1) switch: OFF
AC POWER switch:
OFF.
MODE selector:
CP/SAU .the test set to AC and DC.
CHANNEL selector:
PITCH.
Test Procedure
Performance Standard
a. Connect Voltmeter to test set as follows:
Positive lead (Red) to TP1.
Ground lead (Black) to TP2.
b. Set voltmeter to 100V scale
c. Set AC to DC EXT POWER switches on
a. None.
d. Set POWER switch on the control head
to POWER.
d. PITCH, ROLL, and YAW NO GO lights
on the control panel and the NO GO light
on the test set come on for approximately
60 seconds and then go out. AC and DC
indicator lights on the test set come on.
Note. The AC and DC indicator lights on the
test set will stay on except as specifically
stated in this test.
e. None.
e. Connect multimeter to the test set as fol
lows:
Positive lead (Red): TP5.
Negative lead (Black): GRD.
f. Set multimeter to .1 volt scale
g. Adjust FEEDBACK knob on the test set
to obtain null indication on the multimeter.
h. Adjust R5 potentiometer in the PITCH
control channel assembly of sensor amplifier unit to obtain 0 indication on the
voltmeter.
i. Set CHANNEL selector on the test set to
ROLL.
j. Repeat h above
k. Set CHANNEL selector on the test set to
YAW.
l. Repeat h above
5-43
b. None.
c. Control panel edge lights come on.
f. None.
g. None.
h. None.
i.
None.
j. None.
k. None.
l.
None
TM 11-1520-221-34
Step
No.
Control Settings
Test Equipment
Equipment Under Test
Test Procedure
m. Set PITCH, ROLL, and YAW engage
switches on the control panel to up (engaged) position.
n. Set CHANNEL selector on the test set to
ROLL.
Note. When the CHANNEL selector on the
test set is rotated to a new position, the NO
GO light on the test set may come on for a
few seconds and then go out. If any of the
engage switches on the control panel are not
engaged the appropriate NO GO light may
illuminate.
o. Set CHANNEL selector on the test set to
PITCH
p. Depress momentarily the EMER DISEN
GAGE switch on the test set.
q. Set PITCH, ROLL, and YAW switches on
the control panel to engaged position.
r.
Set AC switch on the test set to OFF
s. Set AC switch on the test set to AC
t. Set PITCH, ROLL, and YAW engage
switches on the control panel to engaged
position.
u. Set POWER switch on control panel to
OFF.
v. Set POWER switch on the control panelv.
to engaged position.
w. Adjust FEEDBACK knob on the test set
to obtain 0 indication on the voltmeter.
x. Slowly raise the aft side of the sensor amplifier unit to produce an angular motion.
y. Return sensor amplifier unit to original
position.
z. Rotate FEEDBACK knob clockwise until
VTVM indicates 0.5 volt.
5-44
Performance Standard
m. ENGAGED light on the test set comes on.
PITCH, ROLL, and YAW engage
switches remain engaged.
n. PITCH, ROLL, and YAW engage switches
on control panel remain engaged. ENGAGED light on the test set stays on.
o. PITCH, ROLL, and YAW engage switches
on the control panel remain engaged. ENGAGED light on the test set stays on.
-p. PITCH, ROLL, and YAW engage switches
immediately move to OFF. ENGAGED
light on the test set goes out.
q. Engage switches hold in engaged position.
ENGAGED light on the test set comes
on.
r. PITCH, ROLL, and YAW engage switches
on the control panel immediately move to
OFF. ENGAGED and AC lights on the.
test set go out.
s. AC light on the test set comes on.
t. PITCH, ROLL, and YAW engage switches
hold in engaged position. ENGAGED
light on the test set comes on.
u. PITCH, ROLL, and YAW engage switches
immediately move to OFF. ENGAGED
AC and DC lights on the test set go out.
NO GO lights on the control panel and test
set come on for approximately 60 seconds
or less, and then go out. AC and DC indicators on the test set come on.
w. None.
x. Voltmeter indicates positive voltage.
y. None.
z. Voltmeter indicates 3.1-2.9 volts for pitch,
4.0+1.2 volts for roll, 7.0+2.1 volts for
yaw.
TM 11-1520-221-34
aa. Set FEEDBACK knob to 0, then rotate
knob clockwise until NO GO light
lights.
ab. Set FEEDBACK knob to 0
ac. Reverse voltmeter polarity
ad. Rotate FEEDBACK knob counterclockwise until multimeter indicates 0.5
volt.
ae. Set FEEDBACK knob to 0, then rotate
knob counterclockwise until NO GO
light lights.
af. Depress and hold ACTR TEST switch
on the test set.
ag. Release ACTR TEST switch
ah. Adjust FEEDBACK knob to obtain null
indication on the voltmeter.
ai. Remove voltmeter
aj. Connect signal generator to TP3 and
TP4 on the test set.
Caution: Do not ground TP3 or TP4. DC
bias is present on TP4.
ak. Set oscilloscope switches as follows:
VERTICAL SENSITIVITY: 1
VOLT/CM.
AMPLIFIER INPUT switches: DC.
HORIZONTAL SWEEP: .1 MILLISECOND/CM.
TRIGGER SOURCE: LINE EXT
115 vac, 400 Hz.
Note. Use oscilloscope to adjust signal generator output for 10 volts peak-to-peak sine
wave signal.
al. Connect oscilloscope vertical lead to TP1
on the test set.
am.Adjust signal generator to frequency A
as shown in table 5-1.
an. Adjust signal generator to frequency B
as shown in table 5-1.
ao. Adjust signal generator to frequency C
as shown in table 5-1.
ap. Remove signal generator
aq. Connect voltmeter as in a and b above.
Reverse voltmeter polarity (+dc).
ar. Set CHANNEL selector on the test set
to ROLL.
as. Slowly raise left side (when viewed
from front) of sensor amplifier unit
5-45
aa. Voltmeter indicates 6.0+2 volts.
ab. None.
ac. None.
ad. Voltmeter indicates 3.1+0.9 volts for
pitch, 5.0+1.5 volts for roll, 7.0+2.1
volts for yaw.
ae. Voltmeter indicates 6.0+2 volts.
af. NO GO lights go out.
ag. NO GO lights illuminate.
ah. None.
ai. None.
aj. None.
ak. None.
al. None.
am.Observe peak-to-peak voltage indication
on the oscilloscope. Acceptable performance standard is listed in table 5-1.
an. Same as aj above.
ao. Same as aj above.ap. None.
aq. None.
ar. None.
as. Voltmeter indicates positive voltage dur- ing motion.
TM 11-1520-221-34
Step
No.
Control Settings
Test Equipment
Equipment Under Test
Test Procedure
to produce an angular motion of the
sensor amplifier unit.
at. Lower left side of sensor amplifier unit
to original position.
au. Repeat z through oq to test roll channel
av. Set CHANNEL selector on the test set
to YAW.X
aw.Slowly rotate the sensor amplifier unit
counterclockwise.
ax. Return the sensor amplifier unit to original position.
ay. Repeat z through aq to test yaw channel.
Performance Standard
at. None.
au. Same as z through aq above.
av. None.
aw. Voltmeter indicates positive voltage during motion.
az. None.
ay. Same as z through aq above.
5-37.
Control Channel Assembly Bench Test
a. Test Equipment and Materials.(Refer to paragraph 5-21.)
b. Test Connections. Connect the equipment as shown in figure 5-15 and insert control channel assembly to be tested in TV, on the test set.
c. Procedures.
Step
No.
1
Control Settings
Test Equipment
Equipment Under Test
DC POWER switch:
N/A OFF.
AC POWER switch:
OFF.
MODE selector: MOD.
CHANNEL selector
PITCH.
Test Procedure
a. Connect multimeter to test set as follows
Positive lead (Red) to TP5.
Ground lead (Black) to GRD.
b. Set multimeter to 3V scale
c. Connect voltmeter to the test set as follows:
Positive lead (Red) to TP1.
Ground lead (Black) to TP2.
d. Set voltmeter to 10V scale
e. Set AC and DC switches on test set to AC
and DC
less than 60 seconds.
f. Adjust FEEDBACK knob to obtain null
indication on the multimeter.
g. Adjust R5 potentiometer on the control
channel assembly to obtain o + .1 volt
indication on the voltmeter.
h. Rotate FEEDBACK knob clockwise until
multimeter indicates 0.5 volt.
i.
j.
Set FEEDBACK knob to 0, then rotate
knob clockwise until NO GO light lights.
Set FEEDBACK knob to 0
Change 2 5-46
Performance Standard
a. None.
b. None.
c. None.
d. None.
e. AC and DC indicator lights on the test set
come on. The NO GO light goes out in
f.
None.
g. None.
h. Voltmeter indicates 3.1+0.9 volts for pitch,
4.0-+1.2 volts for roll, 7.0+2.1 volts for
3 yaw.
i Voltmeter indicates 6.0:+2 volts.
j.
None.
TM 11-1520-221-34
k. Reverse voltmeter polarity
I. Rotate FEEDBACK knob counterclockwise until multimeter indicates 0.5 volt.
m. Set FEEDBACK knob to 0, then rotate
knob counterclockwise until NO GO
light lights.
n. Adjust FEEDBACK knob to obtain null
indication on the multimeter.
o. Remove voltmeter
p. Connect signal generator to TP3 and TP4
on the test set.
Caution: Do not ground TP3 or TP4.
bias is present on TP4.
q. Set oscilloscope switches as follows
VERTICAL SENSITIVITY: 1 VOLT/
CM.
AMPLIFIER INPUT switches: DC.
HORIZONTAL SWEEP: .1 MILLISECOND/CM.
TRIGGER SOURCE: LINE EXT 115
vac, 400 Hz.
Note. Use oscilloscope to adjust signal generator output for 10 volts peak-to-peak sine
wave signal.
r. Connect oscilloscope vertical lead to TP1
on the test set.
s. Adjust signal generator to frequency A as
shown in table 5-1.
t.
u.
v.
w.
x.
y.
z.
aa.
Adjust signal generator to frequency B
as shown in table 5-1.
Adjust signal generator to frequency C
as shown in table 5-1.
Remove signal generator
Connect signal generator to TP6 and GRD
on the test set.
Position AC and DC power switches to
OFF.
Remove assembly under test from TJ4
Insert 570-091-011-1 extender card into
TJ4.
Set osc switches as follows:
VERTICAL SENSITIVITY: 0.1
volts/cm.
AMPLIFIER INPUT SWITCHES:
DC.
HORIZONTAL SWEEP: 5msec/cm.
TRIGGER SOURCE: EXT 115 vac
5-47
k. None.
l. Voltmeter indicates 3.1+0.9 volts for pitch,
4.0+1.2 volt for roll, 7.0±2.1 volts for
yaw.
m. Voltmeter indicates 6.0±.2 volts.
n. None.
o. None.
p. None.
Dc
q. None.
r.
None.
s. Observe peak-to-peak voltage indication on
the oscilloscope. Acceptable performance
standard is listed in table 5-1.
t. Same as s above.
u. Same as s above.
v. None.
w. None.
x. None.
y. None.
z. None.
aa. None.
TM 11-1520-221-34
Step
No.
Control Settings
Test Equipment
Equipment Under Test
ab.
ac.
ad.
ae.
af.
ag.
ah.
ai.
aj.
Test Procedure
400 Hz.
Connect Osc input leads to pins P and
L on extender card.
Position AC and DC power switches to
AC and DC.
Adjust amplitude of signal generator to
obtain 0.2 volts peak-to-peak modulation envelope.
Position AC and DC power switches to
OFF.
Remove extender card and insert control
assembly in TJ4.
Set osc switches as follows:
VERTICAL SENSITIVITY. 0.2
volt/cm.
AMPLIFIER INPUT SWITCHES:
DC.
HORIZONTAL SWEEP: 0.1 m/sec/
cm.
TRIGGER SOURCE: EXT 115 vac,
400 Hz.
Connect osc vertical to TP1
Position AC and DC switches to AC and
DC.
Adjust frequency of signal generator to
frequency A in table 5-2.
ak. Adjust frequency of signal generator to
frequency B in table 5-2.
al.Adjusts frequency of signal generator
C to table 5-2.
Performance Standard
ab. None.
ac. None.
ad. Osc should indicate 0.2 volts peak-topeak.
ae. None.
af. None.
ag. None.
ah. None.
ai. None.
aj. Observe peak-to-peak indication on osc.
Performance standard is listed in table
5-2.
ak. Observe peak-to-peak indication on osc.
Performance standard is listed in table
5-2.
al. Observe peak-to-peak indication on osc.
Performance standard is listed in table
5-2.
5-38.
Pylon Compensation Unit Bench Test
a. Test Equipment and Materials.(Refer to paragraph 5-21.)
b. Test connections. Connect the equipment as shown in figure 5-6.
c. Procedures.
Step
No.
1
Control Settings
Test Equipment
Equipment Under Test
DC POWER switch:
OFF.
AC POWER switch:
OFF.
Test Procedure
a. Connect voltmeter positive lead to TP8
and negative lead to GRD on test set.
Set voltmeter on 50 VDC scale.
b. Energize external power source
5-48
Performance Standard
a. None.
b. None.
TM 11-1520-221-34
Note.
Position of
other controls may be
anywhere for this test.
c.
d.
Position DC power switch to DC
Connect voltmeter positive lead to TP10
on test set.
e. Disconnect voltmeter.
f.
Set osc as follows:
VERTICAL SENSITIVITY: 1 volt/
cm.
AMPLIFIER INPUT SWITCHES:
DC.
HORIZONTAL SWEEP: 0.1 m/sec/
cm.
TRIGGER SOURCE: EXT 115 vac,
Hz.
g. Using osc adjust signal generator to a 1.0
Hz sine wave output with a peak-to-peak
amplitude of 3.0 volts.
h. Connect generator output to TP8 and TP9
of test set.
Caution: Do not ground TP8 or TP9. DC
bias is present on TP8.
i.
Set vertical sensitivity on osc to 10 millivolts/cm.
j.
Connect vertical input of osc to TP7 of
the test set.
Note.
Potentiometer R5 should be set to the
full clockwise position.
k. Set vertical sensitivity on osc to 20 millivolts/cm.
l.
Adjust signal generator to 2.5 Hz
c
d.
Voltmeter indicates 10+1 volts.
Voltmeter indicates 10+1 volts.
e.
f.
None.
None.
g.
None.
h.
None.
i.
j.
None.
Osc should indicate 40+15 millivolts peakto-peak.
k.
None.
l.
m.
m.
n.
Set vertical sensitivity on osc to 50 millivolts/cm.
Adjust signal generator to 4.0 Hz
Osc should indicate 130-20 millivolts peakto-peak.
None.
o.
Adjust signal generator to 8.0 Hz
o.
p.
Set vertical sensitivity on osc to 5 millivolts/cm.
Adjust signal generator output frequency
to obtain a null on the osc.
Set vertical sensitivity on osc to 0.1 volts/
cm.
Adjust generator to 20 Hz
p.
Osc should indicate 200+30 millivolts peakto peak.
Osc should indicate 180+50 millivolts peakto-peak.
None.
q.
Null frequency should be 11+1 Hz.
r.
None.
s.
Set vertical sensitivity on osc to 0.2 volts/
cm.
Adjust generator to 40.0 Hz
t.
Osc. should indicate 650±90 millivolts peakto-peak.
None.
u.
Osc should indicate 1.5±0.2 volts peak-to-peak.
q.
r.
s
t.
u.
5-49
n.
TM 11-1520-221-34
CHAPTER 6
PROXIMITY WARNING FACILITY
SECTION I.
INTRODUCTION
6-1. Scope
a. This chapter covers direct and general support
and depot maintenance of the Proximity Warning
Facility YG-1054 for use with Model AH1G and TH-1G
helicopters Serial Numbers 6615249 through 66-15357,
67-15450 through 6715869, 68-15000 through 6815213, 68-17020 through 68-17113, 68-16410 through
69-16447 and 70-15936 through 70-16105. This chapter
includes instructions appropriate to direct support
maintenance personnel for performance of periodic
inspections and for troubleshooting the proximity
warning facility when installed in the helicopter.
b. Bench maintenance of the proximity warning
facility is covered in a separate technical manual.
c. Block diagram analysis is contained in TM 111520-221-20. Analysis of the electronic configuration
interunit circuits is covered in paragraph 6-3 of this
chapter. For detailed circuit analysis and block diagram
of the proximity warning facility refer to the
operating/service manual.
6-2. Electronic Configuration The proximity warning
facility can be used with configuration A through D
starting with aircraft serial number 66-15249 after MWO
55-1520-22130-49.
6-3.
PROXIMITY WARNING FACILITY YG-1054
CONFIGURATIONS A, B. C AND D.
(fig. FO-15)
a. Power Distribution. Primary power (+28volt dc)
for the proximity warning facility, YG1054 ReceiverTransponder is supplied through circuit breaker PROX.
WARN. With PROX. WARN. circuit breaker depressed,
+28-volts dc is applied to pin A of J8010 at ReceiverTransponder YG-1054.
Panel
lighting
for
the
Receiver-Transponder (+28-volt dc) is routed from
terminal 3 of terminal board TB6 to pin C of J8010 at
the Receiver-Transponder.
b. Audio Distribution.
Audio signals from the
proximity warning facility are routed to the
intercommunications system as follows: Audio signals
from the proximity warning facility are coupled through
pin F of J8010 and P8010 to F.S. 115. At F.S. 115 cut
wires, SX803B22 and SX803C22, and attach wire
PWD3A22 to wire SX803C22 through a 16, 000 ohm
resistor.
Also,
attach wire PWD-4A22 to wire
SX803B22 through a second 16, 000 ohm resistor. The
16, 000 ohm resistors serve as isolation resistor
between the AN/APX-72 audio and the proximity
warning facility audio. No change is made in the
AN/APX72 audio wiring.
SECTION II. DIRECT SUPPORT MAINTENANCE
6-4. General Instructions.
The direct support maintenance procedures in this
chapter supplement the organizational maintenance
procedures in TM 11-1520-221-20. These procedures
also supplement the operating and service instructions.
The proximity warning
facility maintenance procedures begin with the
functional operation and sectionalization checks which
can be performed by organizational and direct support
maintenance personnel within the helicopter and are
extended to removal and replacement of units or
components from the helicopter. When the components
are removed
Change 2 6-1
TM 11-1520-221-34
from the helicopter, the systematic maintenance
procedures continue with the bench maintenance of the
individual electronic equipment components. Paragraph
6-7 of this chapter provides direct support
troubleshooting and repair of the proximity warning
facility installation within the helicopter and supplement
the organizational maintenance procedures.
6-5. Troubleshooting Procedures.
a. General. Troubleshooting the proximity warning
facility in Army Model AH-1G and TH1G helicopters is
performed to localize the trouble to the defective unit
that is part of the system and/or associated junction box,
terminal boards, cabling or wiring.
b. Sectionalization. Listed below is a group of tests
arranged to reduce unnecessary work and to aid in
tracing troubles to the defective facility.
(2) Troubleshooting
Chart.
The
troubleshooting chart will aid in localizing the trouble. If
the corrective measures indicated do not restore normal
equipment operation, troubleshooting the cabling circuits
may be necessary. When the trouble is isolated to an
installed item, remove the item from the helicopter and
replace it with an installation item known to be in
working order. When the trouble is isolated to the
proximity warning facility receiver-transponder, remove
the receiver-transponder for bench testing and replace it
with one known to be in good working order.
Note on the repair tag how the equipment performed
and what corrective measures were taken.
(3) Intermittent Troubles. In all tests, the
possibility of intermittent troubles should not be
overlooked.If present, this type of trouble often may be
made to appear by tapping or jarring the equipment and
checking wiring and connections to the components.
(1) Visual Inspection. Visual inspection is
used to locate faults before operating or testing circuits.
The seating of all component connectors, bent pins,
connections to switches and circuit breakers,
connections on terminal boards,
connections to
antennae, chafing, etc., should be observed and an
attempt made to locate the fault.
d. Isolation. After the trouble has been localized
(c) above, the methods described in the proximity
warning facility operation and service manual will aid in
isolating the trouble to a defective circuit element within
a component.
(2) Operational Tests. Operational tests as
outlined in TM 11-1520-221-20 will help , in determining
the exact nature of the fault.
The test equipment and tools required for
troubleshooting the proximity warning facility as installed
in AH-1G and TH-1G Model Helicopters are listed in TM
11-1520-221-20.
c. Localization.
The procedures listed below are
used for localizing troubles within the proximity warning
facility to the faulty component or unit.
(1) Performance Tests.
The
periodic
preventive maintenance checks and services chart test
(TM 11-1520-221-20) are used on conjunction with the
troubleshooting charts to locate faulty items.
Symptom
Control panel lamps do
not light when helicopter
primary power switch is
set to ON.
6-6. Test Equipment and Tools Required.
6-7. Troubleshooting Proximity Warning Facility
YG-1054 (Configuration A through D).
a. Facility Performance Test. Refer to TM 111520221-20 for performance test.
b. Proximity
Warning
Facility
YG-1054
Troubleshooting Chart (Configuration A, B, C, and D).
Probable
Trouble
Corrective
Measures
Panel lamps loose in sockets
or burned out.
Change 2 6-2
Check panel lamps for proper
seating and replace if
necessary.
TM 11-1520-221-34
Symptom
Probable
Trouble
Corrective
Measures
PROX WARN circuit breaker
opens with receiver-transponder is
turned on.
Primary power is shorted in
wiring from circuit breaker
or receiver-transponder.
Disconnect receivertransponder, depress breaker.
If breaker does not trip, replace
receiver-transponder.
If breaker trips, check out
primary wiring.
Receiver-transponder
ABOVE,
EQUAL and BELOW lamps do not
light when CONFIDENCE TEST
switch is ON.
a. Panel lamps defective.
a. Replace panel lamps.
b. Receiver-transponder
defective.
b. Replace receiver-transponder.
Receiver-transponder
ABOVE,
EQUAL and BELOW lamp cycle
when CONFIDENCE TEST switch
is ON but audio alarm is not heard
in headset.
a. Audio line from
receiver-transponder
open or shorted.
a. Check audio lines from
receiver-transponder.
b. Receiver-transponder
defective.
b. Replace receiver-transponder.
Replace receiver-transponder.
Continuous alarm or no alarm.
Defective receiver-transponder
(digital/display module).
Change 2 6-3
TM 11-1520-221-34
APPENDIX A
REFERENCES
Following is a list of references applicable and available to direct and general support and depot maintenance personnel
for the Army Model AH-1G and AH-1Q tactical helicopters.
DA Pam 310-4
DA Pam 310-7
TB SIG 291
TM 55-1500-323-25
TM 11-1520-221-20
TM 11-1520-221-34P
TM 11-5820-518-35
TM 11-5821-244-34
TM 11-5826-225-35
TM 11-5895-217-35
TM 11-5965-215-15
TM 11-5965-240-15
TM 11-6605-202-3
TM 11-6625-446-15
TM 11-6625-1704-1
Parts
TM 11-6625-203-12
TM 11-6625-320-12
TM 9-6625-2362-12
TM 11-6625-1703-15
TM 11-6625-399-12
Index of Technical Manuals, Technical Bulletins, Supply Manuals (types
7, 8, and 9), Supply Bulletins, and Lubrication Orders.
US Army E(quipment Index of Modification Work Orders.
Safety Mleasures to be Observed When Installing and Using lW'hip Antennas, Field Type MIasts, Towers, Antennas and 'Metal Poles That are
Used With Communication, Radar, and Direction Finder Equipment.
Organizational, DS, GS, and Depot Maintenance Manual: Installation
Practices for Aircraft Electric and Electronic Wiring.
Organizational Maintenance Manual: Electronic Equipment Configuration Army, Model
AH-1G and AH-1Q Helicopters.
Direct Support and General Support Maintenance Repair Parts
and Special Tools Lists (Including Depot Maintenance Repair
Parts and Special Tools): Helicopter, Attack, AH-1G (Bell).
DS, GS, and Depot Maintenance Manual: Radio Sets AN, ARC-51X and
AN, , /ARC-51BX.
Direct Support and General Support Maintenance Manual: Radio
Set AN/ARC-54 (NSN 5821-00-082-3598).
DS, GS, and Depot Maintenance Manual: Direction Finder Set AN/
ARN-83.
DS, GS, and Depot Maintenance Manual Including Repair Parts
List: Transponder Sets AN/APX-44 and AN/APX-44B.
Operator, Organizational. Field and Depot Maintenance Manual: HeadsetMicrophone H-101A/U.
Operator, Organizational, Field and Depot Maintenance Manual: Adapter,
Headset-Microphone MX-1646 'AIC.
DS, GS, and Depot Maintenance Manual: Gyromagnetic Compass Set
AN/ASN 43.
Operator's, Organizational, DS, GS, and Depot Maintenance Manual: Wattmeter AN/URM-120.
Operator, Organizational, DS, GS and Depot Maintenance Manual Including Repair
and Special Tool Lists: Test Set Electronic System
AN/'ASN-338.
Operator and Organizational Maintenance Manual: Multimeters
AN/URM-105 and AN/URM-105C Including Multimeters ME-77/U
and ME-77C/U.
Operator and Organizational Maintenance Manual: Voltmeter, Meter ME30A/U and Voltmeters, Electronic MIE-30B/'U, ME-30C, 'U, and ME30E/U.
Operator's Manual: Oscilloscope AN, USM-281.
Operator, Organizational, DS, GS, and Depot Maintenance Manual Including Repair
Parts and Special Tool Lists: Oscilloscope AN, USM-281A.
Operator and Organizational Maintenance Manual: Generator, Signal SG298/U.
Change 2 A-1
TM 11-1520-221-34
GLOSSARY
Section I.
ABBREVIATIONS
att ........................................................................................... Attitude
bat ........................................................................................... Battery
int............................................................................................. Interphone
invtr ......................................................................................... Inverter
max.......................................................................................... Maximum
nav .......................................................................................... Navigation
noness ..................................................................................... Nonessential
osc ........................................................................................... Oscilloscope
squel ........................................................................................ Squelch
vol............................................................................................ Volume
xmit/rec.................................................................................... Transmit-receive
xmtr ......................................................................................... Transmitter
B.I.T.E. .................................................................................... Built-in test equipment
Section II.
DEFINITIONS OF UNUSUAL TERMS
Basic signal electronic equipment---Equipment for which the US Army Electronics Command has logistic and
maintenance responsibility and for which there are DA Publications covering troubleshooting, testing, aligning, and
repairing of the equipment through replacing maintenance parts and repairing specific maintenance parts. These
equipments are used without modification in more than one aircraft, and are Government-furnished to the aircraft
manufacturer for installation.
Configuration---An all-inclusive term that encompasses all the electronic equipments that are installed in the aircraft
regardless of their function or use.
Facility---A major subdivision of a system that groups component equipments that are interrelated to perform a unit
function or service, such as interphone and audio, uhf command, fm liaison, and others.
Hot mike---Microphone always on (no push-to-talk function).
Sidetone---Part of a signal originating from the transmitter portion of a headset-microphone that is returned to the
receiver portion of the same headset-microphone for monitoring communications.
System---A major subdivision of a configuration that groups like facilities, for instance, communication, navigation,
instrumentation, and others.
Glossary-1
TM 11-1520-221-34
INDEX
Ac interlock circuit......................................................................................................................
Audio signal distribution .............................................................................................................
Automatic Direction Finding (Adf) Operation ..............................................................................
Bench operational check and troubleshooting chart, control channel assembly...........................
Bench operational check and troubleshooting chart, control panel .............................................
Bench operational check and troubleshooting chart, sensor amplifier unit ..................................
Built-In Test Equipment (BITE) module circuit............................................................................
Circuit analysis:
AC interlock circuit.........................................................................................................
Built-In Test Equipment (BITE) module circuit .............................................................
Control panel .................................................................................................................
Control motion transducer..............................................................................................
Gyro and actuator test switches .....................................................................................
Hydraulic actuators and pylon compensation unit ..........................................................
Introduction to functioning Discussions ..........................................................................
Pilot's emergency disengage .........................................................................................
Pilot's control signal circuit.............................................................................................
Power circuits- ...............................................................................................................
Pulse generator module circuit.......................................................................................
Rate gyro circuit ............................................................................................................
Single transducer installation .......................................................................................
Solenoid Valve control circuit.........................................................................................
Two-transducer installation ............................................................................................
Valve drive module circuit .............................................................................................
Compass facility alignment ........................................................................................................
Configuration interunit troubleshooting:
Facility test setup AN, /ARC-51BX .................................................................................
Facility troubleshooting ..................................................................................................
Introduction....................................................................................................................
Voltage measurement chart...........................................................................................
Control Channel Assembly bench test ........................................................................................
Control motion transducer ..........................................................................................................
Control panel- ............................................................................................................................
Control panel and Sensor Amplifier unit bench test ....................................................................
Control panel and Sensor Amplifier unit operational check and troubleshooting chart.................
Control Panel bench test ............................................................................................................
FM Homing Operation................................................................................................................
General instructions ...................................................................................................................
Gyro and actuator test switches .................................................................................................
Gyromagnetic Compass Set AN/ASN-43....................................................................................
Hydraulic actuators and pylon compensation unit .......................................................................
Impedance Matching Network (P/N 209-075-235), component tests ...........................................
lff system operation (AN/APX-44)...............................................................................................
Iff system operation (AN/APX-72)...............................................................................................
Iff system, Testing procedures (AN/APX-72) ..............................................................................
Indexes of publications...............................................................................................................
Inspection standards ..................................................................................................................
Interphone and audio signal distribution ....................................................................................
Interunit circuit analysis and operation:
Audio signal distribution ................................................................................................
Automatic Direction Finding (Adf) Operation .................................................................
FM liaison communications operations ..........................................................................
FM homing operation.....................................................................................................
Gyromagnetic Compass System Operation ...................................................................
Change 1 Index-1
Paragraph
5-6
2-5
2-10
5-28
5-25
5-26
5-8
Page
5-7
2-3
2-9
5-28
5-18
5-19
5-7
5-6
5-8
5-12
5-14
5-18
5-15
5-3
5-13
5-5
5-12
5-9
5-11
5-17
5-7
5-16
5-10
3-8
5-7
5-7
5-11
5-11
5-12
5-11
5-2
5-11
5-4
5-11
5-7
5-9
5-12
5-7
5-12
5-7
3-7
3-5
3-6
3-4
3-7
5-37
5-14
5-12
5-36
5-27
5-34
2-8
3-1
5-18
2-11
5-15
4-4
2-12
2-13
4-5
1-2
5-2
2-4
3-2
3-5
3-2
3-6
5-46
5-11
5-11
5-43
5-23
5-40
2-9
3-1
5-12
2-10
5-11
4-2
2-10
2-10
4--3
1-1
5-1
2-2
2-5
2-10
2-7
2-8
2-11
2-3
2-9
2-6
2-9
2-10
TM 11-1520-221-34
Iff system operation (AN/APX-44) ..................................................................................
Iff system operation (AN/APX-72) ..................................................................................
Interphone and audio signal distribution .........................................................................
Interphone communications operations..........................................................................
Introduction....................................................................................................................
Main power operation ....................................................................................................
Primary power ...............................................................................................................
UHF Command Operation .............................................................................................
VHF Command Operation .............................................................................................
Interphone communication operation..........................................................................................
Introduction:
Indexes of publications ..................................................................................................
Paragraph
212
2-13
2-4
2-6
2-1
2-2
2-3
2-9
2-14
2-6
Page
2-10
2-10
2-2
2-6
2-1
2-1
2-1
2-9
2-11
2-6
1-2
1-1
Organization of troubleshooting procedures ............................................................................... 3-2
3-1
Performance testing and standards:
Control Channel Assembly bench test............................................................................
Control Panel and Sensor Amplifier unit bench test .......................................................
Control Panel bench test................................................................................................
General .........................................................................................................................
Sensor Amplifier unit bench test ....................................................................................
Test Equipment .............................................................................................................
Physical tests and inspection......................................................................................................
Pilot's emergency disengage......................................................................................................
Pilot's control signal circuit .........................................................................................................
Power circuits.............................................................................................................................
Primary power............................................................................................................................
Pulse generator module circuit ...................................................................................................
Pylon compensation unit operational check and troubleshooting chart........................................
Rate gyro circuit .........................................................................................................................
Reference designations and equipment identification .................................................................
Removal and replacement of components .................................................................................
5-37
5-36
5-34
5-32
5-35
5-33
4-3
5-13
5-5
5-4
2-3
5-9
5-29
5-11
1-3
3-11
5-46
5-43
5-40
5-38
5-40
5-39
4-1
5-11
5-4
5-2
2-1
5-7
5-32
5-9
1-1
3-10
5-30
1-1
5-35
5-17
5-7
5-33
1-1
5-40
5-12
5-7
5-16
5-10
5-2
3-3
4-2
5-21
5-23
3-13
5-12
5-7
5-1
3-2
4-1
5-13
5-15
3-11
Sample waveforms ....................................................................................................................
Scope ......................................................................................................................................
Sensor Amplifier unit bench test.................................................................................................
Single transducer installation......................................................................................................
Solenoid valve control circuit .....................................................................................................
Stability and Control Augmentation System (SCAS):
Two-transducer installation ............................................................................................
Valve drive module circuit .............................................................................................
SCAS technical characteristics ......................................................................................
Test Equipment..........................................................................................................................
Test equipment, tools and materials required .............................................................................
Test equipment required (SCAS)................................................................................................
Test setup ..................................................................................................................................
Troubleshooting and repair of Impedance Matching Network Assemblies (P/N 209-075-235) ....
UHF Command Operation.......................................................................................................... 2-9
2-9
Voltage and resistance measurements (SCAS) .......................................................................... 5-31
Voltage measurement chart ....................................................................................................... 3-7
Vhf Command Operation ........................................................................................................... 2-14
5-34
3-6
2-11
Index-2
TM 11-1520-221-34
By Order of the Secretary of the Army:
Official:
VERNE L.. BOWERS
'Major General, United States Army,
The Adjutant General.
W. C. WESTMORELAND,
General, United States Army,
Chief of Staff.
Distribution:
To be distributed in accordance with DA Form 12-31 (qty rqr block No. 265) direct and general support
maintenance requirements for the AH-1G aircraft.
*U.S. GOVERNMENT PRINTING OFFICE : 1990 - 261-872 (20954)
Figure FO-1. Mil STD resistor and capacitor color code markings
Figure FO-2. Interphone facility schematic, configurations A and B
Figure FO-3. Interphone facility schematic, configuration C
Figure FO-4. Interphone facility schematic, configuration D.
Figure FO-4.1. Interphone facility, schematic diagram, configuration E.
Change 1
Figure FO-5. Fm liaison facility schematic
Figure FO-6. Uhf command facility schematic.
Figure FO-6.1. UHF command facility, schematic diagram, configuration.
Change 1
Figure FO-7. Vhf command facility schematic, configurations A, B, and C..
Figure FO-8. Vhf command facility schematic, configuration D.
Figure FO-8.1. VHF command facility, schematic diagram, configuration.
Change 1
Figure FO-9. Adf navigation facility schematic.
Figure FO-10. Gyromagnetic compass system schematic
Figure FO-11. Transponder facility schematic, configurations A and B.
Figure FO-12. Transponder facility schematic, configurations C and D.
Figure FO-12.1. Transponder facility, schematic diagram, configuration A, B, C, and D (when MWO 55-1520-221-30/13 is accomplished).
Change 1
Figure FO-12.2. Transponder facility, schematic diagram, configuration E.
Change 1
Figure FO-13. SCAS block diagram.
TM 11-1520-221-34
Figure FO-14 (1). SCAS schematic diagram (part 1 of 2).
TM 11-1520-221-34
Figure FO-14 (2). SCAS schematic diagram (part 2 of 2).
Change 3
TM 11-1520-221-34
Figure FO-15. KY-28 voice security system provisions, schematic diagram, configuration C, per MWO 55-1520-221-30/36.
Change 1
TM 11-1520-221-34
Figure FO-16. KY-28 voice security provisions, schematic diagram, configuration D, per MWO 55-1520-221-30/37.
Change 1
TM 11-1520-221-34
Figure FO-17. Proximity warning system.
Change 2
PIN: 028845-000
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