INTRODUCTION An Allied-Signal RE 220 gas turbine auxiliary

INTRODUCTION An Allied-Signal RE 220 gas turbine auxiliary
Bombardier Global Express - Auxiliary Power Unit
INTRODUCTION
An Allied-Signal RE 220 gas turbine auxiliary power unit (APU) is installed in a fire
resistant enclosure in the tail cone of the airplane behind the rear pressure bulkhead.
The APU is installed outside the main engine rotor burst zone. This enhances airplane
high altitude operation.
The APU provides bleed air for cabin cooling and heating through the Environmental
Control System (ECS), main engine starting, and electrical power on the ground and in
flight.
Under high demand load conditions, the APU electrical load takes priority over
pneumatic load.
The main component of the APU electrical system is the Electronic Control Unit
(FADEC), also known as the Full Authority Digital Engine Control (FADEC). The
acronym FADEC will be used throughout this chapter in lieu of ECU. The APU
FADEC interfaces with EICAS and the Central Aircraft Information Maintenance
System (CAIMS), providing failure detection and isolation of faulty components.
Control of APU speed is automatic and monitoring of APU Exhaust Gas Temperature
(EGT), speed, fuel and oil pressure is through the FADEC. The FADEC also records
operating hours and start cycles.
The engine speed for normal continuous steady state is displayed as 100% rpm.
Overspeed protection is provided. The APU has automatic shutdown for abnormal
ground and in-flight conditions.
APU start and run is initiated by a single switch, located on the APU control panel in
the flight compartment. Operation of the APU electric and bleed system is performed
at the ELECTRICAL and BLEED/AIR CONDITIONING ANTI-ICE panels
respectively.
The APU is capable of operating up to 45,000 feet while supplying electrical power
with operating limitations. The APU starting envelope is up to 37,000 feet. For other
APU operating limitations, refer to AFM, Chapter 2, LIMITATIONS.
Page 1
Bombardier Global Express - Auxiliary Power Unit
DESCRIPTION
APU LOCATION AND ACCESS
APU Access Doors
APU Exhaust
APU Inlet Door
APU Inlet Door
Exhaust Baffle
Inlet Duct
GX_04_001
Exhaust Discharge
APU COMPARTMENT
The APU is mounted in the tail cone by a multi-axis suspension rod system securing it
in all axes.
The APU compartment is completely sealed from the atmosphere with the exception
of the inlet door and exhaust duct. The APU compartment is isolated from the rest of
the airplane for fire protection. The APU is designed for full rotor burst containment.
Cooling of the APU compartment is accomplished by an exhaust eductor system that
draws airflow across the APU engine and the oil cooler. The airflow through the inlet
splits in two sections. One section allows air to flow to the compressor, while the other
section allows the air to flow through the oil cooler to provide cooling for the APU oil.
The air flowing through the oil cooler then passes through the compartment to cool the
APU and its mounted components. This air is then exhausted overboard.
Page 2
Bombardier Global Express - Auxiliary Power Unit
Access to the APU for inspection, maintenance and servicing is provided by two cowl
doors located under the APU. These doors are to be kept closed during normal APU
operation. However, they may be opened for APU inspection while the APU is
running. In such case, to avoid an APU oil overtemperature, limit operation with the
doors opened to a maximum of:
•
•
10 minutes with the APU unloaded (no bleeds, no electrics), and
5 minutes with the APU loaded (bleed air on and a maximum electrical load of
5 kVA)
APU ENGINE
The APU engine consists of the following:
•
•
•
•
•
•
•
Inlet Door - Variable position (0 to 47º). The door opening angle, controlled by the
FADEC, is a function of weight-on-wheels, airplane MACH number and APU
speed
Compressor - Drives a single-stage centrifugal impeller. Delivers approximately
45 psi bleed pressure at normal operating speed
Combustor - Contains 10 fuel nozzles and 2 igniters
Turbine - Two-stage axial flow turbine which drives the gearbox
Gearbox - Provides the sump for the lubrication system and mounting of
component and accessories
Exhaust - The flow across the APU and oil cooler is created by the eductor using
the exhaust discharge velocity
Monitor zones for fire/overheat/smoke events, FIDEEX system health and status
Page 3
Bombardier Global Express - Auxiliary Power Unit
SYSTEM SCHEMATIC
Note: The air system is shown with an APU bleed load.
Aircraft
Skin
Bleed Air
Duct
Load Control
Valve
Surge Valve
Surge Duct
TO AIRCRAFT
BLEED AIR
SYSTEM
FADEC
Inlet
Bleed
Diffuser
FROM/
TO APU
SYSTEMS
OIL OIL
IN OUT
Bleed Air
Check Valve
TO APU
COMPARTMENT
Combustion
FROM/TO
AIRCRAFT
SYSTEMS
AIR/OIL COOLER
EDUCTOR
Turbine
Gearbox
GX_04_002
EXHAUST
Compressor
APU
INLET AIR
COMPRESSED AIR
APU COMPARTMENT
AIRFLOW
ELECTRICAL
CIRCUITS
LUBRICATION SYSTEM
The lubrication system incorporates an integral oil reservoir. The two main areas that
are lubricated are the gearbox and turbine bearings.
The gearbox sump serves as a reservoir and can be filled through a fill cap. The APU
can also be serviced using the airplane oil replenishment system, simplifying post
flight maintenance actions.
The lubrication system consists of the following components:
•
•
•
•
•
Oil filters - Lube and generator scavenge
Oil temperature sensor - Sends an input to the FADEC for low and high oil
temperature protection. When oil temperature increases to a high predetermined
value for 10 seconds, the APU (on ground only) will shut down
Low Oil Pressure (LOP) switch - When pressure drops below a predetermined
PSIG after the APU has reached on-speed (not less than 99%) for 15 seconds, the
APU (on ground only) will shut down automatically
Oil cooler - Will bypass oil at a predetermined lower than normal operating
temperature, and flow through the cooler when temperatures are greater than the
normal operating range
Magnetic Chip Collector (visual inspection) - Provides a visual indication of metal
particles within the system
Page 4
Bombardier Global Express - Auxiliary Power Unit
OIL PRESSURE
On the prestart BIT check, the LOP switch is monitored by the FADEC. During
operation, if oil pressure decreases below a predetermined PSIG for approximately 15
seconds (on ground), automatic shut down will occur. An “APU OIL LO PRESS”
message will be on for 15 seconds and will be replaced by a cyan “APU
SHUTDOWN” advisory.
A low oil pressure condition in flight will not cause an APU protective shut down.
OIL REPLENISHMENT SYSTEM
The oil replenishment tank volume contains 5.7 liters (6 US quarts). APU oil level is
measured using a sensor which is located in the APU oil tank and provides quantity
information on the EICAS STAT display. Electrical failure of this sensor will be
detected during the BIT check and the indicated quantity will change from numerical
value to amber dashes on EICAS. An “APU OIL LO QTY” advisory message will
occur on EICAS (on ground) when the APU oil level reaches 3.5 U.S. quarts and the
APU has not been operating for 15 minutes.
Page 5
Bombardier Global Express - Auxiliary Power Unit
APU Oil Tank
Honeywell
CKPT (C)
20
19
FWD
AFT
CABIN (C) CABIN (C)
22
22
20
20
OXYGEN
90%
CAB ALT
1300
P
0.00
CAB RATE
LDG ELEV
0
1000
APU/Engine Oil
Replenishment Tank
APU OIL QUANTITY
Indicates APU oil tank
quantity in quarts.
12 . 3
OIL QTY (QTS)
ENG 12.3
APU
5.0
RES
3.2
APU
RPM 100
EGT
650
BRAKE TEMP
03
03
03
GX_04_003
03
An oil replenishment tank is located in the aft equipment bay and contains an electrical
pump and sensor probe for quantity level. The oil replenishment (pressure filling)
system is designed for ground use only and serves both main engines and APU. A
three way electrical valve is incorporated in the replenishment system to allow transfer
of oil to the system being topped up (either engine or APU).
Page 6
Bombardier Global Express - Auxiliary Power Unit
OIL REPLENISHMENT SYSTEM FILLING
The system can be operated using the battery or external electrical power. Oil level
monitoring is required during servicing to verify that the system stops automatically
when the full level is reached.
NOTE
To protect against overfilling due to system component failure,
maintenance instructions must be followed according to the
Airplane Maintenance Manual.
The oil filling system is operated through the oil replenishment panel located behind
the pilot’s seat in the flight compartment.
NOTE
1) A replenishment reservoir TANK LO light remaining on
following panel power-up indicates that the oil replenishment
tank is low. Under this condition refilling is inhibited until the
reservoir is filled.
2) If a low oil replenishment condition occurs during a fill the
system will shut down.
Oil is to be added to the APU when APU OIL LO QTY advisory message is on
EICAS and the LO OIL for APU display is shown on the oil replenishment panel.
The switch legends on the oil replenishment panel can only be displayed when the
SYSTEM ON switch is selected.
The APU may be replenished if:
•
•
•
The APU has been shut down for a minimum of 15 minutes
The APU oil reservoir is not already full
Both engines are shut down and are not currently being replenished
Page 7
Bombardier Global Express - Auxiliary Power Unit
OIL REPLENISHMENT PANEL
LO OIL (APU)
The LO OIL comes on to indicate that the
APU is low in quantity and will remain
on until the APU oil tank is replenished.
SYSTEM ON
Selecting the SYSTEM ON switch does the
Following:
• The SYSTEM ON lamp will come on.
• A three second lamp test will be carried
out on all annunciators.
OIL REPLENISHMENT
POWER
SYSTEM
ON
RESERVOIR
LH ENG
APU
RH ENG
TANK
LO
PUMP
ON
LO
OIL
VLV
OPEN
LO
OIL
VLV
OPEN
LO
OIL
VLV
OPEN
PUMP ON
• The reservoir pump PUMP ON lamp will
come on to indicate operation. The legend
will remain on until the correct level of the
system to be topped up is achieved.
GX_04_004
TANK LO
The reservoir TANK
LO legend comes
on to indicate that
the reservoir is low
in quantity.
VLV OPEN (APU)
Selecting the switch will illuminate the VLV
OPEN switch legend indicating valve operation.
Oil will be pumped from the reservoir (through
the valve) to the engine until full is achieved.
• The VLV OPEN and LO OIL switch legends
will go out when the correct level is reached.
OPERATION
The following procedure is to be used only as a guide to replenish the APU oil system.
The Airplane Maintenance Manual takes precedence over all servicing procedures.
•
•
•
•
•
•
•
Select the POWER switch (SYSTEM ON) on the oil replenishment panel
Confirm that the LO OIL lamp (APU) on the replenishment panel corresponds to
the condition indicated on EICAS i.e. APU OIL LO QTY advisory message and
quantity in amber on STAT page
Select the switch labeled APU on the replenishment panel
Confirm that the PUMP ON (below RESERVOIR label) and VLV OPEN (below
the APU label) legends are displayed
Monitor the oil level on EICAS for both the APU and reservoir (example: if
approximately one US quart is added to the APU, the oil replenishment tank level
should have reduced by the same amount)
When the APU oil tank is full, confirm that the PUMP ON legend goes out
(indicating pump stoppage). Also confirm that the VLV OPEN legend goes out
(indicating valve closure)
Select the POWER switch, SYSTEM ON legend extinguishes. Record the amount
of oil added and a carry-out a walk around for external leakage (oil overfill)
Page 8
Bombardier Global Express - Auxiliary Power Unit
GRAVITY OIL FILL
The APU oil sump can be filled through the gravity filler. The oil reservoir for the
APU is an integral part of the accessory gearbox assembly and has a capacity of 5.25
US quarts. It is recommended to top up the reservoir when the STAT page indication
shows 4.5 quarts. The gravity fill is designed for a “fill to spill” ease of servicing, and
used only when the oil replenishment system does not function.
FUEL CONTROL AND INDICATION
The fuel system is a fully automatic electronic control system. The fuel control unit
provides metered fuel to 10 fuel injection nozzles regulated by signals received from
the FADEC.
During start the fuel system provides the correct amount of fuel to support combustion
and for smooth acceleration of the engine to full rated speed. Once on speed, fuel flow
is modulated as necessary to meet the demands of varying pneumatic and electrical
loads, while maintaining a constant speed.
AIRFRAME FUEL
Fuel is normally supplied to the APU from the right engine feed line, or from the left
engine feed line by opening the crossfeed shutoff valve. The examples below represent
the APU operation with DC and AC power applications. Please refer to Chapter 11,
FUEL SYSTEM for further information on the airframe fuel system operations.
Page 9
Bombardier Global Express - Auxiliary Power Unit
Crossfeed
Shutoff Valve
Auxiliary Pump
FUEL
384OO LBS
3OOLBS
92OOLBS
146OOLBS
AUX
FUEL USED
P
P
AUX
P
P
22 °C
P
P
22 °C
FUEL USED
3OOLBS
92OOLBS
146OOLBS
AUX
P
P
384OO LBS
146OOLBS
P
P
FUEL
TOTAL FUEL
146OOLBS
P
P
P
P
AUX
P
22 °C
22 °C
P
APU
P
OLBS
32 °C
APU
P
P
32 °C
LO PRESS
Global Express
APU on-speed and no main engines running:
The right PRI pumps feed the APU
through the right engine feed line.
Global 5000
36O5O LBS
FUEL
P
Global 5000
FUEL USED
3OOLBS
61OOLBS
14975LBS
AUX
P
P
P
P
22 °C
TOTAL FUEL
36O5O LBS
22 °C
FUEL
AUX
AUX
P
P
P
P
P
FUEL USED
3OOLBS
61OOLBS
14975LBS
14975LBS
P
32 °C
LO PRESS
Global Express
APU starting and no main engines running:
The right AUX pump supplies the APU through
the right engine feed line.
TOTAL FUEL
OLBS
32 °C
LO PRESS
LO PRESS
P
14975LBS
P
P
P
P
22 °C
22 °C
APU
32 °C
LO PRESS
AUX
P
APU
32 °C
LO PRESS
32 °C
LO PRESS
Page 10
32 °C
LO PRESS
GX_04_005
TOTAL FUEL
Primary Pumps
Bombardier Global Express - Auxiliary Power Unit
IGNITION
The ignition system consists of a dual output ignition unit, two ignition leads and two
igniter plugs. There are two cycles of operation: BURST for starting (at 5%) and
MAINTENANCE for acceleration (duration of the start).
The ignition system is fully automatic and controlled by the FADEC. Ignition occurs
at 5% APU rpm.
During APU ground operation (nonessential mode) ignition is terminated at 50% rpm.
During flight (essential mode) ignition is terminated at 98% rpm.
Should a flameout occur during operation, ignition sequence will automatically start
through the “Auto Relight” function of the FADEC.
START SYSTEM
Operation of the starter is automatically controlled by the FADEC, through the APU
control switch. Starter operation begins by selecting the START position on the APU
control panel. At sea level, starter cutout occurs at 46%. At altitude, starter cutout may
be as high as 60% to ensure a positive start.
The starter is capable of an immediate restart on roll down when APU rpm is at or
below 7% rpm.
SPEED INDICATION
Two speed sensors provide indicated speed for on-speed control and overspeed APU
protection.
During operation, the FADEC monitors the input and should either sensor fail, there
will be an APU FAULT advisory message displayed on EICAS.
A failure of either sensor will not cause an APU protective shut down to occur.
However, a failure of both sensors will cause an APU protective shutdown both on
ground and in the air.
TEMPERATURE INDICATION
The EGT system consists of a single temperature sensing unit with two probes. The
probes provide redundant signals to the FADEC for fuel schedule trim, turbine
temperature monitoring, and Load Control Valve modulation. The APU is protected
from overtemperature during acceleration by protective features incorporated in the
FADEC.
Loss of one probe will not affect APU operation.
In the nonessential (ground) mode, failure of both probes will cause the FADEC to
shut down the APU and inhibit start.
Page 11
Bombardier Global Express - Auxiliary Power Unit
In the essential (flight) mode, failure of both probes will not cause a shut down.
Instead the FADEC reverts to a preset temperature signal (260ºC) to allow pneumatic
loading and normal operation of electrical power. Because of the loss of EGT control,
the APU should be shutdown unless required for another contingency (refer to QRH).
HOURMETER/CYCLE COUNTER
An hourmeter/cycle counter is powered on at 95% rpm and records the amount of
running hours and start cycles of the APU. It is deactivated when APU shutdown is
initiated.
FADEC COMPONENT CONTROL SCHEMATIC
APU
OFF
RUN
L ENG BLEED
OFF
START
AUTO
ON
FADEC
(ECU)
AUTO
OPEN
OFF
AUTO
ON
APU BLEED
OFF
Load
Control
Valve
AUTO
ON
Surge
Control
Valve
LCV
Speed
Sensor
R ENG BLEED
XBLEED
CLSD
APU Bleed Switch
ThermoCouple
INLET
SCV
GEARBOX
Fuel
Control
Unit
Flow Divider
SECONDARY FUEL
MANIFOLD
GX_04_006
IGNITION
PRIMARY FUEL
MANIFOLD
CONTROL SYSTEM
The APU electrical control system consists of two major sections: FADEC and
electrical accessories. The FADEC is designed to execute precise control of the APU.
Programming within the FADEC controls the APU through all modes and operating
conditions. The FADEC monitors EGT, rpm, oil temperature and pressure, and
provides output signals for information on EICAS. The electrical accessories are used,
in conjunction with the FADEC, to perform the sensing and control functions required
to safely and reliably start and monitor the APU.
Page 12
Bombardier Global Express - Auxiliary Power Unit
PNEUMATIC
The pneumatic bleed load system consists of the Load Control Valve (LCV) connected
to the bleed ducting and normally modulated by the FADEC. The LCV can either be
controlled automatically by the bleed management control system (AUTO selection),
or manually by the APU BLEED switch (ON selection) on the BLEED/AIR COND/
ANTI-ICE panel.
The LCV will not open when manually selected ON if:
•
•
•
Anti-ice is active
The left engine pressure regulating valve is manually opened
The right engine pressure regulating valve and the crossbleed valve are manually
opened
If the left and right PRV and crossbleed valve are in to AUTO position, a manual ON
selection of the APU LCV will result in the BMC reconfiguring all the values to
accommodate pilot selection.
A Surge Control Valve (SCV) works as a “waste gate” to protect the APU compressor
from a potential to Surge (stall). The solenoid valve assembly (which allows
pneumatic air to open the SCV) is energized only when:
•
•
•
The APU generator is providing electrical power and
The APU LCV is CLOSED (i.e APU not supplying any bleed air to the ECS) and
Atmosphere pressure of 7 psia is sensed (at and above 16,375’ during ISA
conditions)
The exhaust of the APU SCV is located on the left side of the fuselage, aft of the left
engine pylon. The operation of the SCV is transparent to the pilot.
Page 13
Bombardier Global Express - Auxiliary Power Unit
APU CONTROL PANEL
RUN
• Initiates the APU prestart BIT.
• On ground, commands the inlet door to full open.
• In flight, commands the inlet door to open to either
10° (0.85 MACH) or 20° (0.40 MACH)
• Activates the flight compartment displays (oil quantity,
speed and RPM).
• Starts the fuel pump.
START
• Spring-loaded to RUN
• Fuel and ignition on at 5%.
• Starter disengage at approximately
50% RPM.
• Ground - ignition off at 50% RPM.
• In-flight - ignition off at 98% RPM.
• Accelerates at 100% RPM.
APU
RUN
START
GX_04_007
OFF
OFF (APU enters a 60 second unloaded, i.e. bleed and AC loads removed, cooldown period).
• RPM decreases to 70% RPM for 60 seconds (below 20,000 ft.) or remains at 100% above
(20,000 ft.).
• After 60 seconds the RPM will continue to decrease and fuel will stop at this time.
• Below 25% RPM the inlet door closes.
• Below 5% RPM the EICAS displays and indications are removed.
START SEQUENCE
The APU requires 28 VDC to start. APU start is automatic following switch selections
of RUN and START on the APU control panel.
The start sequence is initiated by selecting the APU control switch to RUN:
•
•
•
•
•
APU IN BITE (on ground only) advisory message comes on
APU rpm and EGT indications appear on the EICAS STAT page
APU inlet door opens (on ground)
APU fuel SOV is commanded open and right DC auxiliary fuel pump is energized
APU IN BITE (on ground) advisory message goes out (approximately 10
seconds)
Select the APU control switch to START position (spring-loaded from START to
RUN) for greater than one second and note the following:
•
•
•
•
•
In flight, the APU IN BITE message would now annunciate momentarily
At approximately 5 percent rpm, fuel and ignition occur
Between 46 and 60 percent the starter disengages, and
RPM accelerates to 100 percent
For ground starts, ignition is deactivated at 50 percent. In flight, ignition is
deactivated at 98 percent
Page 14
Bombardier Global Express - Auxiliary Power Unit
NOTE
At 99% rpm plus 2 seconds, the APU is ready to load electrically.
At 99% rpm plus 60 seconds on ground, the APU is ready to load
pneumatically, if the prestart EGT < 149°C. At 99% rpm plus 2
seconds on ground, the APU is ready to load pneumatically, if
the prestart EGT ≥ 149°C. At 99% rpm plus 2 seconds in flight,
the APU is ready to load pneumatically.
APU DOOR POSITIONING
The APU door is positioned as a function of WOW, Mach number, and APU speed.
When RUN is selected on the APU control panel and the airplane is on ground, the
APU door is commanded to the full open position (47°).
DOOR OPERATION
The APU inlet door is located on the upper right fuselage area. It is electrically
actuated and is scheduled opened by the FADEC. The door will be commanded to full
open for start and on-speed condition for ground operation. In flight prior to start, the
inlet door will be positioned according to Mach number until the APU reaches 20%
speed and then will begin to gradually open until the door has reached the full open
position.
The inlet door will be commanded to the closed position by the FADEC when the
speed drops below 25% on shut down.
A fully opened door will cause profile drag and affect performance (refer to AFM
Chapter 6, PERFORMANCE).
EICAS DISPLAY
DOOR INDICATION
The APU door position is normally NOT displayed on the EICAS STAT page. It is
only indicated when there is a door fault and will appear in conjunction with an
APU DOOR FAIL caution message. When a door fault is sensed by the FADEC an
amber numerical readout in degrees will be displayed.
Page 15
Bombardier Global Express - Auxiliary Power Unit
Honeywell
CKPT (C)
20
19
FWD
AFT
CABIN (C) CABIN (C)
22
22
20
20
OXYGEN
90%
CAB ALT
1300
P
0.00
CAB RATE
LDG ELEV
0
1000
APU DOOR
INDICATION
Indicates that a door
fault exists.
APU DOOR
12 . 3
OIL QTY (QTS)
ENG 12.3
APU
5.0
RES
3.2
APU DOOR
RPM 100
13.2
EGT
650
BRAKE TEMP
03
03
03
APU EGT
INDICATION
Indicates that RUN
position is selected on
the APU control panel.
03
GX_04_008
APU RPM
INDICATION
Indicates that RUN
position is selected on
the APU control panel.
APU FIRE PROTECTION
When the APU DISCH fire handle is pulled, the FADEC initiates an immediate APU
shut down (with no cooldown period) and sends a signal to display the APU
SHUTDOWN advisory message. When the pulled APU fire handle is then turned, the
first fire extinguishing bottle is discharged. If necessary, the second fire bottle can be
discharged by displacing the APU bottle unlock pin, and turning the fire handle in the
opposite direction (this is a two-handed operation).
APU Bottle
Unlock Pin
Disch Handle
DISCH
1
2
L
A
P
U
PULL
DISCH
1
2
R
PULL
PULL
Page 16
GX_04_009
DISCH
1
2
Bombardier Global Express - Auxiliary Power Unit
Although there are protective shutdown features for the APU (see “Protective
Shutdowns” on page 6-20), there is no automatic discharging of the fire agent in the
event of a fire. The APU must not be left unattended for ground operation. Refer to
FIRE PROTECTION chapter 9 in this manual for information on APU fire protection
system.
WARNING
THE APU MUST NOT BE LEFT UNATTENDED DURING
GROUND OPERATIONS.
APU LOADING
The FADEC controls the ready to load signals, one for electrical loading and one for
pneumatic loading. Electrical loading is activated 2 seconds after the APU speed
reaches 99%. If the APU drops below 95%, electrical loading is no longer available
(on ground and in flight).
On the ground, pneumatic loading is available 60 seconds after the APU reaches 99%
if the APU pre-start EGT was < 149°C. If the APU prestart EGT was ≥ 149°C,
pneumatic loading is available on the ground 2 seconds after the APU reaches 99%.
In flight, pneumatic loading is available 2 seconds after the APU reaches 99%,
regardless of the pre-start EGT. Bleed air extraction is limited to 30,000 feet.
The APU LCV is opened upon receiving a bleed air request from the airplane bleed
management control system or if the APU BLEED switch on the BLEED/AIR COND/
ANTI-ICE panel is selected. Open and closed positions of the control valve are
determined by the status of weight-on-wheels, main engine starting, and
environmental control system signals. The bleed and load management systems are
responsible to ensure that the bleed air request is activated only when another source
of bleed air is not commanded. Example: L engine bleed valve open and/or the R
engine bleed valve open and crossfeed valve open, the LCV will remain closed to
prevent damage to the APU.
The normal position for the APU Bleed switch is AUTO. The AUTO position
automatically integrates control of the APU LCV. The manual ON position will
command the LCV to open as selected, but only if allowed by the FADEC (to
guarantee APU self-preservation). The manual OFF position will command the LCV
to close as selected.
APU SHUTDOWN
When the “OFF” position on the APU control panel is selected, the FADEC controls
the shut down sequence. The ready-to-load signals are cancelled, commanding the
LCV closed and the generator is tripped off line. During cooldown, the APU speed is
gradually lowered to 70 percent rpm over 60 seconds below 20,000 feet or remains at
100 percent rpm for 60 seconds above 20,000 feet.
Page 17
Bombardier Global Express - Auxiliary Power Unit
NOTE
If the APU RUN switch is selected to RUN prior to completion of
the 60 second cooldown period, the APU returns to 100 percent
and continues normal operation.
After cooldown is completed, the APU FADEC shuts down the APU. When the speed
drops below 25 percent the inlet door is closed, APU operating hours and fault
information are stored in the FADEC. APU indications are removed from EICAS
when the rpm drops below 5 percent.
If the BATT MASTER switch is selected OFF with no AC power on (i.e. APU GEN,
VFGs, Ext AC) or if either the APU shutoff switches (External Services Panel or APU
compartment) are selected the APU FADEC will cancel the cooldown period and
initiates an immediate shutdown.
APU RPM AND EGT INDICATIONS
For normal operations, two APU parameters (rpm and EGT) are displayed on the
status page when the RUN position is selected on the APU control panel. With the
APU switch selected to OFF the display remains active until APU speed drops below
5 percent, and the APU door is closed. The numerical readouts change to red when
their limit values are exceeded (AFM, Chapter 2, LIMITATIONS).
EMERGENCY SHUTDOWN
The following methods are considered non-normal shutdown procedures, but may be
used in an emergency situation. Actioning any or all of these procedures will result in
shutdown.
NOTE
Carrying out any of the following shutdown procedures will
cancel the “cooldown” mode and shutdown will occur
immediately.
•
•
•
•
BATT MASTER switch selected to OFF with no AC power on
APU DISCH handle pulled
APU SHUTOFF button on the external services panel pushed in momentarily and
released, or
APU compartment SHUT DOWN button, located inside the APU compartment
(on the forward bulkhead) pushed in momentarily and released
Page 18
Bombardier Global Express - Auxiliary Power Unit
EXTERNAL SERVICES PANEL
APU Compartment
Forward Bulkhead
EXT AC
AVAIL
IN USE
GROUND
SERVICE
ON
EXT DC
BATTERY
MASTER
AVAIL
IN USE
BATT
ON
MIC
HDPH
LAMP
TEST
APU
SHUT-OFF
GX_04_010
APU Compartment
Shutdown Button
APU Emergency
Shutoff Button
RESTART AFTER EMERGENCY SHUTDOWN
In order to restart the APU following an emergency shutdown procedure, two
conditions have to be met:
•
•
The BATT MASTER switch has to be in the ON position
The switch on the APU control panel must be placed to the OFF position before
moving it to the momentary START position (to reset the FADEC start logic)
Page 19
Bombardier Global Express - Auxiliary Power Unit
PROTECTIVE SHUTDOWNS
The FADEC will automatically shut down the APU when any of the following are
detected:
SHUTDOWN CONDITIONS
GROUND
FLIGHT
FADEC Failure: Internal failure.
x
x
Inlet Door: Not in commanded position.
x
x
Loss Of Overspeed Protection: Loss of any combination of speed sensors,
FADEC overspeed circuitry or fuel solenoid that results in a loss of both overspeed
systems.
x
x
Overspeed: APU speed greater than 106 percent.
x
x
Loss Of Speed: Loss of both APU speed signals.
x
x
Fire: Fire signal received by APU FADEC.
x
DC Loss: Loss of DC power to the FADEC.
x
x
Slow Start: No crank, slow start, no acceleration, no flame or fall back (starter
cutout and subsequent drop below 25 percent)
x
x
High Oil temperature: Oil temperature limit exceeded.
x
Low Oil Pressure: Low oil pressure condition detected.
x
LOP Switch Fail: Low oil pressure switch failed.
x
Loss Of Both EGT Sensors: Failure of both EGT thermocouples.
x
Reverse Flow: APU inlet temperature exceeded.
x
Underspeed: APU drops below 80 percent.
x
Overtemperature: EGT exceeds scheduled limits.
x
NOTE: An X in one or both columns indicate when shutdown can or will occur.
Page 20
x
Bombardier Global Express - Auxiliary Power Unit
SYSTEM OVERVIEW SCHEMATIC
BLEED AIR/ANTI-ICE SYNOPTIC PAGE
BLEED / ANTI-ICE
AIR
COND
R
L
LP
LP
HP
Load
Control
Valve
40
40
PSI
PSI
HP
APU
APU BLEED
OFF
AUTO
ON
GENERATOR
CONTROL
APU BLEED
SELECTOR
EGT
RPM
APU
ELECTRONIC
CONTROL
UNIT
APU GEN
ON
OFF
GENERATOR OUTPUT
TO BUS DISTRIBUTION
Page 21
FAIL
OFF
PUSH
OFF/RESET
GX_04_011
GENERATOR
CONTROL
UNIT
Bombardier Global Express - Auxiliary Power Unit
ELECTRICAL POWER AND DISTRIBUTION
The electrical control of the APU consists of electrical sensing, starting and ignition,
and the electronic control system through the FADEC.
APU electrical power may be used in flight or on ground. Electrical power is extracted
from the APU in the form of horsepower that drives the APU generator, and may be
used to feed the airplane electrical power system.
Under high electrical load demands, the APU’s electrical load takes priority over
pneumatic load demands.
The APU generator load limit is 40 kVA.
For operations above 37,000 feet, if the APU is powering a bus, the associated
hydraulic pump must be selected off (due to the heavy load of the pump).
The FADEC is mounted remotely from the APU in a compact enclosure located in the
aft equipment bay.
The FADEC is powered up when the BATT MASTER switch is selected ON. The
BATT MASTER switch powers the airplane BATTERY BUS, which provides
electrical power to the FADEC.
The FADEC uses the APU acceleration rate to calculate when to de-energize the
starter motor and the ignition exciter. The values shown (START CONTROL
SCHEMATIC below) are the maximum speeds at which the starter motor and the
ignition exciter are permitted to operate.
START CONTROL SCHEMATIC
0% RPM
ENERGIZED
APU STARTER
MOTOR
46% - 60% RPM
DE-ENERGIZED
ELECTRONIC
CONTROL
UNIT
28 VOLT
DC
APU IGNITION
EXCITER
5% RPM
ENERGIZED
50% (GROUND)
98% (AIR)
DE-ENERGIZED
APU
RUN
START
DATA ACQUISITION
UNIT (DAU) #3
Page 22
APU EGT AND
RPM INDICATIONS
ON EICAS STATUS
PAGE
GX_04_012
OFF
Bombardier Global Express - Auxiliary Power Unit
The FADEC control outputs include fuel metering, arming and regulation of the LCV
and control of the SCV. It also performs protective shutdowns when the APU is not
within allowable operating limits.
A BITE capability of the FADEC tests components for serviceability and initiates the
start sequence. It also enables reliable fault isolation within the system.
FADEC INPUTS AND OUTPUTS
The following are input signals received by the FADEC:
•
•
•
•
•
•
28 VDC power, supplied by the DC BATTERY BUS (the AVIONICS BATTERY
DIRECT BUS is used as a backup)
Environmental Control System, fuel and engine start
Inlet door position
Feedback of all applicable parameters during start, acceleration, run and shut down
Fuel, bleed/air conditioning, anti-icing, engine start and electrical control panels
APU FIRE DISCH handle, APU SHUTOFF (external services panel and APU
bay), and WOW status
The following are outputs generated by the FADEC:
•
•
•
•
•
APU start and fuel feed shutoff
Door opening and closing operations
On speed loading of pneumatics and electrics
ARINC 429 Communication signals to EICAS
Interface with CAIMS
Page 23
Bombardier Global Express - Auxiliary Power Unit
FADEC SCHEMATIC
INPUTS
OUTPUTS
INLET DOOR
APU START
FUEL SOV
ECS
FUEL
ENGINE START
DOOR
OPENED/CLOSED
COMMANDS
-FEED BACK PARAMETERSSTART
ACCELERATION
RUN
SHUTDOWN
L ENG BLEED
OFF
AUTO
AUTO
CLSD
E
L
E
C
T
R
O
N
I
C
R ENG BLEED
XBLEED
ON
OFF
OPEN
AUTO
ON
APU BLEED
AUTO
OFF
ON
RUN
BATT MASTER
START
ELECTRICAL
OFF
O
EMS
EXT AC
EXT DC
AVAIL
AVAIL
ON
ON
GEN 1
GEN 2
GEN 3
GEN 4
FAIL
FAIL
FAIL
FAIL
OFF
OFF
OFF
OFF
APU GEN
FAIL
OFF
429 COMMUNICATION
EICAS STATUS
DISPLAYS
DOOR
RPM
EGT
RAT GEN
ON
OFF
PUSH
OFF/RESET
APU
LOAD
CONTROL
VALVE
WARNING
AND
CAUTION
MESSAGES
U
N
I
T
ON
PUSH OFF/RESET
INPUT
OUTPUT
C
O
N
T
R
O
L
APU
OFF
ON SPEED
PNEU/ELECTRICAL
LOADING
AVAILABLE
DISCH
1
2
A
P
U
CAIMS
PULL
COMPARTMENT
SHUTDOWN BUTTON
GX_04_013
APU BAY
EXTERNAL
SERVICES PANEL
WOW
SHUTDOWN BUTTON
Page 24
BITE CODES
OPERATING HOURS
Bombardier Global Express - Auxiliary Power Unit
EICAS MESSAGES
APU FIRE
Indicates that an
APU fire has
occured.
1 . 55
APU OIL LO PRESS
Indicates that a low
pressure condition
exists.
APU EGT SENSORS
Indicates both
thermocouples have
failed.
APU FIRE
APU OVERTEMP
APU OVERSPEED
APU BLEED SYS FAIL
APU OIL LO PRESS
APU OIL HI TEMP
APU EGT SENSORS
APU DOOR FAIL
APU REVERSE FLOW
APU FUEL SOV
APU BLEED SYS FAIL
Indicates that the APU
LCV does not match
command position.
APU OIL HI TEMP
Indicates that a high oil
temperature condition
exists.
APU DOOR FAIL
Indicates that the APU
door position does not
match command
position.
APU FUEL SOV
Indicates that the APU
fuel shutoff valve has
failed open.
789
GX_04_014
APU REVERSE FLOW
Indicates that a reverse
flow from the engine
bleed(s) to the APU
exists.
APU OVERTEMP
Indicates that an EGT
overtemperature
exists.
APU OVERSPEED
Indicates that an APU
overspeed protective
shutdown has
occurred.
Page 25
Bombardier Global Express - Auxiliary Power Unit
EICAS MESSAGES (Cont)
APU OIL LO QTY
Indicates that the APU
oil level has reached
3.5 quarts (2 quarts
low).
APU BLEED DISABLED
Indicates that the LCV
command has been
received, and either:
• The inlet pressure is less
than 3.3 psia (35,000 ft).
• The 60 second warm-up
period (on ground only)
is in progress.
Note:
The Airplane Flight Manual
limits the use of APU bleed
extraction to 30,000 ft.
APU FAULT
Indicates a failure in
one of the following:
•single speed sensor,
•EGT thermocouple,
•fuel solenoid (failed to
Close),
•fuel/oil filters in
impending bypass,
•low oil pressure switch
has failed (in flight).
APU FADEC FAIL
Indicates that no data
is received by the DAU.
1 . 55
APU NOT AVAILABLE
Indicates that when
START or RUN is
selected,checks/
testing is in
progress.
APU FADEC FAIL
APU OIL LO QTY
APU NOT AVAILABLE
APU BLEED DISABLED
APU SHUTDOWN
APU FAULT
APU IN BITE
APU BLEED ON
APU BLEED OFF
APU SOVS CLSD
APU FUEL SOV CLSD
APU
SHUTDOWN
Indicates that an APU
protective shut down
has occurred, other
than an overspeed or
overtemperature.
APU IN BITE
Indicates that RUN is
selected and the
prestart BITE is in
progress.
APU BLEED ON
Indicates that the APU
BLEED switch is in the
ON position, and the
load control valve is
open.
APU SOVS CLSD
Indicates that both
fuel and bleed air
shutoff valves are
closed.
789
GX_04_015
APU BLEED OFF
Indicates that the APU
BLEED switch is in the
OFF position, and the
load control valve is
closed.
APU FUEL SOV CLSD
Indicates that the APU fuel
shutoff valve is closed.
Page 26
Bombardier Global Express - Auxiliary Power Unit
EMS CIRCUIT PROTECTION
CIRCUIT BREAKER - SYSTEM
1/2
AFCS
DOOR
AIR COND/PRESS
ELEC
APU
ENGINE
BLEED
FIRE
CAIMS
FLT CONTROLS
COMM
FUEL
M
BRT
STAT
SYS
SYSTEM
BUS
PREV
PAGE
NEXT
PAGE
CNTL
CB - APU SYSTEM
BUS
EMER
CONT
TEST
1/1
APU DOOR
APU BATT ASCA IN
APU FADEC PWR 1
BATT
APU FADEC PWR 2
AV BATT
APU OIL HEAT
AC 4
IN
APU START
BATT
IN
IN
DCPC IN
APU START CONTACT APU BATT ASCA IN
M
Page 27
GX_04_016
CIRCUIT BREAKER
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