B767 ATA 49 Student Book
B767 ATA 49 Student Book
B767 ATA 49 Student Book
ATA 49
B767-3S2F
Page - 1
ATA 49-00
5/6/13
EFF - ALL
TRAINING MANUAL
FOR TRAINING PURPOSES ONLY
B767-3S2F
Page - 2
ATA 49-00
May, 6,2013
EFF - ALL
TRAINING MANUAL
FOR TRAINING PURPOSES ONLY
GRAPHIC .............................................................................................. 3
GENERAL DESCRIPTION......................................................................4
MINI-FLAG TEST................................................................................. 64
INTRODUCTION ................................................................................... 6
GTCP 331-200ER.................................................................................. 8
ENGINE ............................................................................................... 10
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B767-3S2F
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General
The APU and generator lubrication system lubricates and cools these
components:
APU bearings
Gearbox
Electric generator
Temperature
Pressure
Quantity
Power Plant
The APU engine fuel system supplies pressurized and metered fuel to the APU
combustion chamber. It also supplies pressurized fuel to operate the inlet guide
vanes.
The APU is a single shaft gas turbine engine which drives an electric generator
and a load compressor. A gearbox on the front of the APU supplies power to
APU accessories.
Ignition/Starting System
Engine
The APU engine has these components:
- Two-stage centrifugal flow compressor
- Reverse flow annular combustion chamber
- Three-stage axial flow turbine
During engine start, the ignition/starting system turns the APU and supplies
ignition.
Air System
The APU air system supplies pressurized air to the airplane pneumatic system.
Inlet guide vanes control the amount of air supplied to the load compressor. A
surge valve releases excess bleed air overboard. A cooling system cools the
APU compartment and the engine oil.
Indicating System
The APU indicating system supplies APU EGT data for flight deck displays.
Exhaust System
The APU exhaust system sends the APU exhaust gases out of the tail cone.
CONTROL
ENGINE FUEL
IGNITION/STARTING
POWER PLANT
ENGINE
AIR
APU
GENERATOR
GEARBOX AND
ACCESSORIES
LOAD
COMPRESSOR
POWER
SECTION
EXHAUST
OIL INDICATING
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INDICATING
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B767-3S2F
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INTRODUCTION
B767-3S2F
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49-00-977565M
B767-3S2F
Page - 8
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STA
1728
APU AIR
INTAKE D00R
STA
1809
STA
1843
APU AIR
INTAKE PLENUM
APU AIR
INTAKE DOOR
ACTUATOR
APU AIR
INTAKE
DUCTING
APU
EXHAUST
DUCT
APU
SUPPORT
MOUNTS
APU
FIREWALL
APU
HARNESS
APU AIR
INTAKE
DRAIN
(RH SIDE)
STABILIZER
BLOCK
APU DOORS
(CLAM SHELL DOOR)
SERVICE ACCESS
DOOR (RH SIDE)
APU
PLENUM
DRAIN
GTCP 331-200ER
B767-3S2F
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49-00-977589M
B767-3S2F
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GEARBOX
AIR INLET
LOAD
COMPRESSOR
POWER SECTION
AIR FLOW
COMPRESSOR
BLADES
COMPRESSOR
BLADE
LABYRINTH
INLET
SEALS
GUIDE
VANES
LABYRINTH
SEAL
CROSS SECTION
_______________
TURBINE
BLADES
ENGINE
B767-3S2F
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49-00-980562M
B767-3S2F
Page - 12
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Air intake
APU and generator lubrication
Engine fuel
Ignition/Starting
Air system
Control
Indicating
Control System
All operations of the APU are controlled and monitored by the APU Electronic
Control Unit (ECU).
Two APU monopoles supply redundant speed signals to the ECU. The APU
inlet pressure and temperature sensors send signals of inlet air conditions to the
ECU. The ECU uses this information for fuel flow scheduling and surge
protection. APU EGT thermocouples measure exhaust gas temperature.
Indicating System
Operating conditions of the auxiliary power unit are sent to the EICAS
computers for display. EICAS shows APU RPM, EGT, as well as fault
messages.
Oil level information is sent from the oil quantity low level switch directly to
EICAS.
Four EGT thermocouples measure exhaust gas temperature.
APU AIR
INTAKE DOOR
APU FUEL
SHUTOFF
VALVE
OFF
ON
START
RUN w
FAULTa
APU
COOLING
AIR
AIRPLANE PNEUMATIC
DEMAND SIGNALS
APU FIRE DETECTION
IGNITION
UNIT
LOW OIL
PRESS
SWITCH
STARTER
MOTOR
DE-OIL
SOLENOID
VALVE
OIL
TEMP
SENSOR
GEARBOX
PRESS
REG VLV
EICAS
COMPUTERS
INLET
TEMP
SENSOR
IGNITER
INLET GUIDE
VANES
APU GEN
SWITCHING
VALVE
SURGE
VALVE
SHUTTLE
VALVE
MONOPOLES
APU
EXHAUST
FUEL
PNEUMATICS
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SECONDARY
FUEL
NOZZLES
POWER
SECTION
FLOW
SENSOR
APU AIR
VALVE
INLET
PRESSURE
SENSOR
PRIMARY
FUEL
NOZZLES
EXHAUST
LOAD
COMPRESSOR
DE-OIL SOL
OIL TEMP SW
INLET
GUIDE VANE
ACTUATOR
FLOW DIVIDER
TRAINING MANUAL
FOR TRAINING PURPOSES ONLY
49-00-980564M
EGT
SENSORS
OIL QTY
B767-3S2F
Page - 14
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APU ENGINE
GEARBOX AND ACCESSORIES
General
The gearbox contains the various gears and drive pads necessary to drive the
APU generator and accessories. The gearbox is spline shaft driven by the
power section. The various gearbox spur gears convert the power section input
speed into the appropriate accessory speed.
Maintenance TIP
The APU generator seal plate is installed on the APU with a rubber gasket when
it leaves the Garrett factory. This seal plate has porting for the generator
scavenge pump system to allow the APU to be operated without a generator
installed. However the rubber gasket must be removed and the normal
generator aluminum gasket installed prior to APU operation. The rubber gasket
does not allow proper porting, and is for shipping only.
STARTER MOTOR
COOLING FAN
GENERATOR
FRONT VIEW
FUEL CONTROL UNIT
GENERATOR SCAVENGE PUMP
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49-27-980561M
B767-3S2F
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ENGINE CONTROLS
ELECTRONIC CONTROL UNIT (ECU) INPUTS/OUTPUTS
Control
The ECU may be powered by turning the APU control switch to START, or when
this switch is OFF, by activating one of the three toggle switches on the face of
the controller. The controller automatically powers down when the APU control
switch is OFF, APU RPM is below 7 percent, and BITE procedures are
complete.
Input/Output
The ECU receives analog and discrete inputs from the airplane and the APU.
These inputs allow the controller to perform the software tasks that control the
APU engine.
ECU outputs include EGT and RPM signals to EICAS, aircraft discrete signals,
and APU signals, both analog and discrete, for torquemotors and solenoids.
Operation
Normal operation of the APU and ECU is completely automatic, once START is
selected on the APU Control Panel. Once the APU is on-speed (over 95
percent rpm), the operator may draw electrical power, and/or pneumatic power
as desired. System monitoring and protective shutdown functions are
automatically performed by the ECU.
28 V DC
CO NTROL
SW (P5)
ST ART/O N
AI RCRAFT
A NALOG
________
LAST RUN- If Reason is NORMAL STOP SIG, the aircraft
commanded APU stop and all Faulty LRUs detected during last
run can be displayed. If Reason is an automatic shutdown,
displayed Faulty LRUs are only the failed LRUs that could cause
the shutdown.
T
E
S
T
EC S DEM AND
LRU
SUMMARY - Record of all Faulty LRUs detected since the
___________
last Memory Erase.
S ELF
LAMP
ME S
AI R SUP PLY V ALVE
IN LET D OOR
REASON
APU NOT
OPERATING
CONTROL
FAILURE
EGT
OVERTEMP
FIRE
EMERG
STATUS
SPARE
SPARE
INLET
DOOR RLY
#1 SPD
SENSOR
LCIT
SENSOR
#2 SPD
SENSOR
EGT #2
CIRCUIT
AI R/GRO UND
AD P
757/7 67
FAULTY
LRU
IG V POS ITION
EG T 1
EG T 2
RECORD
SELECTED
SP D 1
AP U
ANAL OG
EGT #1
CIRCUIT
FLOW
DIV SOL
P2
SENSOR
CURRENT/
LAST RUN
ECS
CONTROL
ECU
SHUTDOWN
2
UNDER
SPEED
DC PWR
LOSS
O/S TEST
CIRCUIT
NO
DATA
FUEL
SOL
LOP
SWITCH
IGV
ACT
APU
STARTER
FAN
VALVE
SHUTDOWN
3
START
ABORTED
LOW OIL
PRESSURE
HIGH OIL
TEMP
WAIT
PT
SENSOR
FUEL
CONTROL
IGN
UNIT
A/C STRT
CIRCUIT
FILTER
SW(GEN)
SHUTDOWN
4
NO
LIGHTOFF
F R EASON
A
U
L
T LR U
LC IT
PT
TP
R
E
C
O
R
D
S
E
L
E
C
T
APU FAULT
OVER
SPEED
TEST
OK
EP
SENSOR
SURGE
VALVE
DEOIL
SOL
HOT
SENSOR
SEE MNT
MANUAL
LRU
SUMMARY
GEN LOAD
AVAI LABLE
STAR T REL AY (K 197)
DE-O IL SO LENOI D
ERASE
MEMORY
LO P
ST ARTER POWE R
GE N OIL FILT ER
FA N VAL VE
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AP U
AN ALOG
+10V DC R EF
ATA 49-00
AI RCRAF T
DI SCRET E
OI L TEM P
B767-3S2F
RELA Y
GEN
FILTER
SP D 2
P2
APU
D ISCRE TE
E ICAS
STAR T REL AY (K 1)
NORMAL
STOP SIG
REVERSE
FLOW
DOOR
SYSTEM
EC S ENA BLE
SIGN ATURE
PIN
EGT
RPM
FI RE
AIRCRA FT
DISCRE TE
TRAINING MANUAL
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49-60-R18776M
APU
DISC RETE
B767-3S2F
Page - 18
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POWER PLANT
AIR INTAKE SYSTEM
General
The APU Air Intake System supplies the APU with air for pneumatics,
combustion and cooling. The system components include the APU Air Intake
Door and Actuator, APU Air Intake Duct Assembly, and APU Air Intake Plenum.
Air Intake Duct Assembly
The forward and aft air intake ducts connect an intake port to the APU Air Intake
Plenum. The air intake port is a Kevlar/graphite fiberglass composite structure
that houses the APU Air Intake Door and Actuator. The air intake duct is a
two-piece composite structure, forward and aft. The forward duct is a Kevlar/
graphite fiberglass composite structure. The aft duct is a Kevlar/graphite
structure with a fiberglass honeycomb core. Access is through the service
access door in the lower fuselage.
Air Intake Plenum
The APU Air Intake Plenum is an aluminum-stainless steel structure attached to
the aft side APU firewall. An APU plenum access panel is located in the
firewall. Access to the plenum access panel is through the controls bay access
door.
The APU compressor inlet plenum attaches to the APU intake plenum. An
access panel in the compressor inlet plenum allows inspection of the power
section and cooling fan intake screens.
WARNING: STAY OFF THE AFT BODY SERVICE ACCESS DOOR AND
THE CONTROLS BAY ACCESS DOOR. YOUR WEIGHT
CAN CAUSE THE SPRING LOADED LATCHES TO
RELEASE.
APU AIR
INTAKE
DOOR
APU AIR
INTAKE
DOOR
ACTUATOR
APU AIR
INTAKE
PLENUM
APU AIR
INTAKE
PORT
APU
FIREWALL
APU
PLENUM
ACCESS
PANEL
CONTROLS BAY
ACCESS DOOR
ACCESS
PANEL
STABILIZER
CENTER
SECTION
(REF)
SERVICE
ACCESS
DOOR
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49-16-977595M
B767-3S2F
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POWER PLANT
AIR INTAKE DOOR AND ACTUATOR OPERATION
until RPM is less than 15 percent, and also allows the door to remain open in
the air with the main battery switch OFF.
The actuator may be manually operated should the electrical operation fail. An
opening on the inboard side of the actuator container provides access to a
manual drive. The 1/4 inch actuator clutch square drive disengages the electric
motor from the actuator. This also rotates the clutch position flag to reveal the
actuator square drive. A 1/4 inch drive may be inserted in the manual drive to
position the actuator. Thirty turns are required to fully extend the actuator.
The APU Air Intake Door is a one piece cast aluminum door. The door is
located in the unpressurized section of the fuselage, to the right of the leading
edge of the vertical stabilizer. The door is hinged on the aft end to the APU Air
Intake Duct which is located on the upper right side of the fuselage. The APU
Air Intake Door Actuator positions the door in the fully open or fully closed
position. The door opens approximately 22 degrees from the fuselage.
Two seals on the APU Air Intake Duct form an aerodynamic and anti-corrosion
seal to the APU. A removable "P-shaped" seal is bolted to the aft end of the
intake duct port near the intake door hinges. A rectangular seal is bonded to the
forward and side portions of the APU Air Intake Duct.
Air Intake Door Actuator
The APU Air Intake Door Actuator is an electrically operated linear actuator.
A 28 VDC reversible motor drives the actuator. The ten pound (4.5 kg) actuator
extends or retracts in less than 60 seconds. The stroke of the actuator is
approximately 4 inches (11 cm). The actuator is installed in a white actuator
container which is V-band clamped to the APU Air Intake Duct.
Operation
When the APU intake door relay (K176) is relaxed, power is available to the
door closed (retract) contacts of the actuator; and when K176 is energized,
power is available to the door open (extend) actuator contacts. The K176 relay
solenoid is supplied power by either the APU battery bus or the main battery
bus. A ground for the solenoid is supplied by either of two sources.
K176 is initially energized to open the intake door by a ground supplied through
an energized APU fuel control relay (K175), the APU switch in ON or START,
and the main battery switch ON. K175 is energized when no faults or fire
signals exist, the fire switch is NORMAL, and the APU control switch and main
battery switch are both ON. (See APU normal operation) A ground for K176 is
supplied by an electronic switch inside the ECU whenever the speed is 15
percent or greater, to assure that the door remains open during APU shutdown
Maintenance Practices
To remove the APU Air Intake Door, disconnect the actuator by unscrewing the
actuator rod end fitting from the door. The rod end fitting remains attached to
the actuator. Remove the hinge cover plate and remove the bolts from the two
intake door hinges. Installation requires proper positioning of the actuator rod
end fitting into the intake door before fastening the intake door hinges.
To remove the APU Air Intake Door Actuator, disconnect the APU Air Intake
Door from the actuator. Remove and save the actuator rod end fitting from the
rod end of the actuator. The actuator is removed by releasing the V-band clamp
and sliding the actuator out of the APU Air Intake Duct. Installation requires
assembly of the actuator in the container and then attachment of the actuator
rod end fitting. The rod end fitting is then attached to the intake door.
Adjustment of the actuator to close the intake door flush with the fuselage
requires adjustment of the lock nuts at the bottom of the actuator.
CAUTION: DO NOT ATTEMPT ACTUATOR ADJUSTMENT AT ROD END
ATTACHING ACTUATOR TO AIR INTAKE DOOR. DAMAGE TO
THE ACTUATOR WILL RESULT.
POWER
APU AIR
INTAKE DOOR
APU AIR
ACTUATOR
INTAKE
DOOR
AIR INTAKE
DOOR
AIR INTAKE
DOOR SEAL
(BONDED)
ROD END
FITTING
SCREWS (4)
ACTUATOR ROD
END FITTING
ACTUATOR
ROD END
AIR INTAKE
DOOR SEAL
(REMOVABLE)
SERVICE
ACCESS DOOR
HINGE COVER
PLATE
V-BAND
CLAMP
TRANSFER
FLAG
ACTUATOR CLUTCH
SQUARE DRIVE
ACTUATOR
CONTAINER
MAN
MANUAL/ELECTRICAL
SELECTOR SHAFT
ACTUATOR
SQUARE DRIVE
DOOR POSTITION
ADJUSTMENT
FITTING
GROUNDING
STRAP
AIR INTAKE
DUCT
ELEC
MANUAL DRIVE SOCKET
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49-15-977593M
B767-3S2F
Page - 22
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POWER PLANT
AIR INTAKE DOOR INDICATION
Power
Power for operation of the APU Air Intake Door Actuator is supplied by the 28
VDC APU battery bus.
Power for the APU control circuits is supplied by either the main battery bus or
the APU 28 VDC battery bus by a diode circuit.
Air Intake Door Open Switch
The door open switch for the APU Air Intake Door inputs door position to the
APU Control Unit (ECU) and the EICAS computers. The switch is a magnetic
reed switch that provides a ground signal to the ECU and the EICAS computers
when the door is open. The switch is mounted on the intake duct.
The target for the switch is mounted on a flange on the right side of the door.
Door Disagreement Indication
An EICAS status and maintenance message APU DOOR appears whenever a
commanded and actual door position disagreement exists for longer than 60
seconds. The EICAS computer is looking for an open signal. If a ground is
detected in excess of the time delay, the message appears. On the ECU,
DOOR SYSTEM would appear in the REASON APU NOT OPERATING field.
In the FAULTY UNIT field, INLET DOOR RLY or SEE MNT MANUAL would
appear. INLET DOOR RLY appears if it was detected as faulty. SEE MNT
MANUAL appears when no faulty components were detected. The ECU
records a BITE fault when the door does not open within 30 seconds. If the inlet
door eventually opens, the BITE indications are not retained in memory. If there
was a fault, the BITE indications are retained until the next APU start. At the
next start attempt, the BITE indications are erased.
CASE 1: When K176 is first energized, the door full open actuator switch
must be driven to the momentary position within 60 seconds.
CASE 2: When K176 is de-energized on shutdown, the door full closed
actuator switch must be driven to the momentary position within 60
seconds.
28V DC APU
BAT. BUS
"DOOR OPEN"
SIGNAL TO
ECU
C1385
APU INTAKE
DOOR ACTUATOR
28V DC MAIN
BAT. BUS
RETRACT
C1391
APU ALTN CONT CB
EXTEND
R11
28V DC APU
BAT. BUS
FULL OPEN
DOOR FULL OPEN
C1383
APU PRIME CONT CB
R12
C20
APU START
N>15%
60 SEC
START
ON
OFF
ON
START
ON
INTAKE DOOR &
FUEL DRIVER
OFF
S1 APU SW
(P5)
L & R EICAS
COMP
OFF
S2 MAIN
BAT. SW
(P5)
K175 APU
FUEL CONT
RLY (P37)
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APU DOOR
(S,M)
49-70-R187949-70-
B767-3S2F
Page - 24
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APU ENGINE
LUBRICATION SYSTEM
General
The lubrication system consists of oil supply; a pressure system for oiling the
bearings, generator, and starter clutch; a scavenge system for returning oil to
the sump from the bearings, a generator oil scavenge system; a gearbox
pressurization system; and an oil cooler.
Oil Supply
The APU gearbox serves as an oil reservoir. Servicing is by a pour-type fill port
or through the pressure fill connections. Oil quantity is indicated by a sight
glass and an oil quantity signal to EICAS. Magnetic chip detectors are also
installed.
Oil Pressure System
A gear-type oil pump in the gearbox sends pressurized oil through an oil cooler
and filter to the bearings and generator. When the oil is cold, a de-oil solenoid
valve opens allowing the pump to draw air from the gearbox. This unloads the
oil drag, enabling easier starting. A low oil pressure switch and oil temperature
sensor signal the ECU, causing protective shutdowns if limits are exceeded.
Oil Cooling
An air-type oil cooler is located between the oil pressure pump and bearings.
An oil cooler bypass valve sends cold oil around the oil cooler. This valve also
allows bypass of an obstructed cooler.
Oil Scavenge System
Three scavenge pumps return oil to the reservoir. The compressor bearing
scavenge pump and generator scavenge pump are positive-displacement
gear-type. The turbine bearing scavenge pump is a gerotor type.
Scavenge oil from the generator flows through a non-bypass filter to protect the
APU from oil contamination if the generator fails. A generator oil filter
differential pressure switch signals the ECU if the generator oil filter becomes
obstructed. This initiates a protective shutdown.
Protective shutdowns occur for low oil pressure , high oil temperature , and for a
blocked generator oil filter GEN FILTER.
The faulty LRUs stored in the ECU memory include LOP SWITCH, DEOIL SOL,
HOT SENSOR, and FILTER SW(GEN).
GEARBOX
PRESSURE
DEOIL
REGULATING
COOLING SOLENOID
VALVE
OIL
FAN (REF) VALVE
COOLER
SHUTTLE
VALVE
FAN ISOLATION
VALVE (REF)
TO SURGE
VALVE
OIL COOLER
BYPASS VALVE
APU
GENERATOR
DRIVE PAD
AND SEAL
PLATE (REF)
PCD 1
LOP
SWITCH
PCD 2
HOT
SENSOR
OIL FILL
PORT
GENERATOR
SCAVENGE
OIL PUMP
OIL PUMP
AND FILTER
ASSY
LOW OIL
LEVEL SWITCH
GEARBOX SHUTOFF
VALVE
FWD
GEN OIL
FILTER DP
GEN OIL
SWITCH
FILTER
LOW OIL
LEVEL SWITCH
STATUS
FAULTY
LRU
NORMAL
STOP SIG
CONTROL
FAILURE
UNDER
SPEED
REVERSE
FLOW
EGT
OVERTEMP
DC PWR
LOSS
LOW OIL
PRESSURE
GEN
FILTER
DOOR
SYSTEM
FIRE
EMERG
O/S TEST
CIRCUIT
HIGH OIL
TEMP
OVER
SPEED
SPARE
SPARE
NO
DATA
WAIT
TEST
OK
LCIT
SENSOR
FUEL
SOL
PT
SENSOR
EP
SENSOR
#1 SPD
SENSOR
#2 SPD
SENSOR
FUEL
CONTROL
SURGE
VALVE
EGT #1
CIRCUIT
EGT #2
CIRCUIT
LOP
SWITCH
IGV
ACT
IGN
UNIT
DEOIL
SOL
FLOW
DIV SOL
ECS
CONTROL
APU
STARTER
A/C STRT
CIRCUIT
P2
SENSOR
RECORD
SELECTED
START
NO
ABORTED LIGHTOFF
INLET
DOOR RLY
CURRENT/
LAST RUN
ECU
SHUTDOWN
2
FAN
VALVE
FILTER
SW (GEN)
SHUTDOWN SHUTDOWN
3
4
APU GENERATOR
MAGNETIC CHIP
DETECTOR PORT
DE-OIL
SOLENOID
VALVE LOW
TEMP SWITCH
FRONT VIEW
REASON
APU NOT
OPERATING
DE-OIL SOLENOID
LOW TEMP SWITCH
LOW OIL
LEVEL SWITCH
UP
HOT
SENSOR
SEE MNT
MANUAL
LRU
SUMMARY
M206 ECU
LUBRICATION SYSTEM
B767-3S2F
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49-27-R78294
B767-3S2F
Page - 26
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APU ENGINE
OIL SUPPLY AND RESERVOIR
Oil Reservoir
Oil reservoir capacity is 6.2 quarts (5.9 liters). Service the APU by pouring oil
through the fill port until it almost overflows into the scupper drain. Pressure fill
connections are adjacent to the sight glass. A drain plug with a magnetic chip
indicator is located on the bottom of the gearbox.
Oil Quantity Indication
An oil level sight glass is located near the fill port. Oil level information is sent to
the EICAS computers by a low oil level switch.
DE-OIL
SOLENOID
VALVE
LOW TEMP
SWITCH
OIL
LEVEL
SIGHT
GLASS
PRESSURE
FILL
PROVISIONS
FRONT VIEW
SIDE VIEW
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49-27-980555M
B767-3S2F
Page - 28
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HOT Sensor
General
Operation of the APU oil system is automatic. Pressure regulation, cooling,
de-oiling, and protective monitoring all occur without external control or
indication.
The ECU tests the oil temperature sensor during pre-start, monitor and self-test
BITE. If the sensor is detected as failed, the ECU uses 60oF (16oC) for the first
three minutes of operation and 120oF (49oC) for the remainder of operation.
The de-oil solenoid valve is deactivated at start and the APU runs without high
oil temperature protection.
Gen Filter
Protective Shutdowns occur for low oil pressure, high oil temperature or
generator filter blockage. The APU FAULT light and APU FAULT advisory
EICAS message appear until the APU control switch is turned OFF. All three
switches are LRUs. Further LOP start attempts are inhibited until the fault
memory is erased.
A blockage of the generator filter opens the generator filter differential pressure
switch, causing a GEN FILTER protective shutdown. To prevent nuisance
shutdowns, this protective shutdown is inhibited if the oil temperature is less
than 46oC.
POWER
POWER
HARDWARE
SOFTWARE
PWR
SUPPLY
+28V
5 SEC
TO EICAS
K175
APU FUEL
CONT RLY
28V DC
95% SPEED
LOP
LOGIC
LOW OIL
PRESS S/D
APU FAULT
RELAY
SIG
COND
OIL
TEMP
SENSING
SPEED > 7%
START/ON SIGNAL
START RLY ENERGIZED
T >46C
MD&T
A A
(L1) APUFAULT
T <6.7 6.6C
10 SEC
T >154C
95% SPEED
VENT
OIL
TEMPERATURE
SENSOR
GEARBOX
PRESSURE
REGULATING
VALVE
P
LOW OIL
PRESSURE
SWITCH
GEN
28V DC
(STARTER)
GEARBOX
SWITCHING
VALVE
FAN
BUFFER
AIR
AIR/OIL SEPARATOR
SEAL
BUFFER
AIR
STARTER
CLUTCH
COOLING
FAN BRG
DE-OIL
SOLENOID
VALVE
TO
SURGE
VALVE
2ND
STAGE
< -4C
DE-OIL SOL
TEMP SW
EXHAUST
TURBINE
BRG SCAVENGE
PUMP
PRESSURE
FILTER
TEST
PORT
GEN OIL
FILTER DIFF
PRESS SW
GEN OIL
FILTER ASSY
2
AIR/OIL
COOLER
THERMAL
T BYPASS
VALVE
APU FAUL
T (C)
SCAVENGE
PUMP
EICAS COMPUTE
RS
PRESS PUMP
OIL QTY
GEARBOX
GEARBOX DRAIN
PLUG MAG CHIP
DETECTOR
SHUTTLE VALVE
MAG CHIP DET
OIL SYSTEM
B767-3S2F
Page - 29
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STATUS ECS/MSG
2
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APU BIT
E (M)
APU OILQTY (S,
M)
B767-3S2F
Page - 30
ATA 49-20
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STRT CIRCUIT is erroneously stored as a faulty LRU in the ECU memory, since
this signal is also used to detect starter feedback voltage. The temperature
switch remains closed until oil temperature rises above 4oC. It remains open
until oil temperature falls below -4oC. The switch is an LRU.
Failure Modes, BITE, and Troubleshooting
The de-oil solenoid is tested for opens, shorts, and overcurrent during prestart
and self-test BITE. Failure causes DE-OIL SOL to be stored in the ECU
memory. During cold temperatures with a failed closed valve, or electrically
open solenoid, a START ABORTED protective shutdown may result due to
excessive oil drag. A failed open valve causes continuous air addition to the
pressure oil, leading to a LOP protective shutdown. An electrically shorted
solenoid causes the ECU driver to turn off, causing the same conditions as for
an electrical open. If the ECU driver fails high, the solenoid does not
de-energize at starter cutout. This causes a LOW OIL PRESSURE protective
shutdown. ECU is stored as a faulty unit.
Oil Cooler and Thermal Bypass Valve
Oil is cooled by inlet air wich is moved by gearbox driven cooling fan. An oil
cooler bypass valve allows cold oil to bypass the oil cooler for faster warm-ups.
This bypass valve also provides pressure relief for a blocked cooler.
Oil Cooler
The cooler is an air/oil exchanger, designed to maintain the oil temperature at
approximately 66oC above ambient, and below 152oC nominal. The oil cooler
and thermal bypass valve are an LRU as an assembly.
Oil Cooler Bypass Valve
The bypass valve consists of a poppet and thermal expansion element
containing a temperature sensitive compound. As oil temperature increases,
the expansion element closes the poppet, rerouting the oil through the cooler.
The valve is fully open below 60 degrees C and fully closed at 77oC. If the
differential pressure across an obstructed cooler reaches 50 psid, the poppet
opens against the spring to allow bypass. The valve is not an LRU, except by
replacing the oil cooler assembly.
POWER
POWER
HARDWARE
SOFTWARE
PWR
SUPPLY
+28V
5 SEC
TO EICAS
K175
APU FUEL
CONT RLY
28V DC
95% SPEED
LOP
LOGIC
LOW OIL
PRESS S/D
APU FAULT
RELAY
SIG
COND
OIL
TEMP
SENSING
SPEED > 7%
START/ON SIGNAL
START RLY ENERGIZED
T >46C
MD&T
A A
(L1) APUFAULT
T <6.7 6.6C
10 SEC
T >154C
95% SPEED
VENT
OIL
TEMPERATURE
SENSOR
GEARBOX
PRESSURE
REGULATING
VALVE
P
LOW OIL
PRESSURE
SWITCH
GEN
28V DC
(STARTER)
GEARBOX
SWITCHING
VALVE
FAN
BUFFER
AIR
AIR/OIL SEPARATOR
SEAL
BUFFER
AIR
STARTER
CLUTCH
COOLING
FAN BRG
DE-OIL
SOLENOID
VALVE
TO
SURGE
VALVE
2ND
STAGE
< -4C
DE-OIL SOL
TEMP SW
EXHAUST
TURBINE
BRG SCAVENGE
PUMP
PRESSURE
FILTER
TEST
PORT
GEN OIL
FILTER DIFF
PRESS SW
GEN OIL
FILTER ASSY
2
AIR/OIL
COOLER
THERMAL
T BYPASS
VALVE
APU FAUL
T (C)
SCAVENGE
PUMP
EICAS COMPUTE
RS
PRESS PUMP
OIL QTY
GEARBOX
GEARBOX DRAIN
PLUG MAG CHIP
DETECTOR
STATUS ECS/MSG
2
1
2
SHUTTLE VALVE
MAG CHIP DET
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APU BIT
E (M)
APU OILQTY (S,
M)
49-27-R54281M
B767-3S2F
Page - 32
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APU ENGINE
GEARBOX PRESSURIZATION SYSTEM
General
The gearbox pressurization system maintains gearbox pressure at four psi
above ambient. This pressure prevents oil foaming which leads to low oil
pressure shutdowns. The system is also used for compressor and cooling fan
seal buffer air.
Operation
When PCD2 pressure is greater than 52 psi, at lower altitudes, the gearbox
shutoff valve closes. Afterward, PCD1air moves the shuttle valve. Then, PCD1
air is used for cooling fan and compressor seal buffer air. The gearbox pressure
regulating valve is open, venting the gearbox to atmosphere.
When PCD2 pressure is less than 52 psi, (at higher altitudes), the gearbox
shutoff valve opens. Afterward, PCD2 moves the shuttle valve. Then, PCD2 is
used for cooling fan buffer air and compressor seal buffer air. PCD2 air also
balances the gearbox pressure regulating valve against gearbox pressure.
Gearbox pressure increases from air leakage past internal seals. The gearbox
pressure regulating valve modulates to maintain gearbox pressure at four psi
above ambient.
ACTUATOR
PCD 2
GEARBOX
PRESSURE
PCD 2
TO TAILPIPE
AIR/OIL
SEPERATOR
SLEEVE
DISCHARGE
TO
TAILPIPE
VENT
POPPET
GEARBOX
PRESSURE
SEAT
AMBIENT
VENTED
TO SURGE
VALVE
SEAL
BUFFER
AIR
DISCHARGE
TO
TAILPIPE
VENT
GEARBOX
PRESSURE
PRESSURIZED
NO REGULATION
VENT
SHUTTLE VLV
GEARBOX
SHUTOFF
VALVE
COOLING
FAN
BUFFER
AIR
PCD 1
GEARBOX
PRESSURE
PRESSURIZED
REGULATED
GEARBOX PRESSURE
REGULATING VALVE
GEARBOX
PRESSURIZATION
AIR
FAN SEAL
BUFFER AIR
SHUTTLE
VALVE
VENT TO
TAILPIPE
BEARING
SEAL
BUFFER
AIR
TO PCD 2
PORT
GEARBOX
SHUTOFF VALVE
ATA 49-20
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49-27-980544M
TO SURGE
VALVE
PCD 2
B767-3S2F
Page - 34
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APU ENGINE
APU AND GENERATOR OIL SCAVENGE SYSTEM
General
The oil scavenge system returns oil to the reservoir after it has been utilized for
lubrication and cooling. There are three scavenge oil pumps. Two pumps are
gear box driven; one for the compressor bearings and one for the generator.
The third pump is driven by the main rotating shaft. It scavenges the turbine
bearing area.
Compressor Bearings Scavenge Pump
This pump is a gear-type pump and is contained within the oil pump assembly.
The oil pump assembly is an LRU. (See the oil pump assembly graphic for
details.)
Turbine Bearing Scavenge Pump
This pump is a gerotor type. The pump is press fit onto the main shaft of the
power section. It returns oil from this cavity to the gearbox through an external
hard line. The pump is not an LRU.
Generator Oil Scavenge System
The oil pumped through the generator flows into a sump cavity between the
generator and gearbox. The generator scavenge pump draws the oil from the
cavity and sends it to the gearbox reservoir.
The generator scavenge pump is a gear pump of 7.5 gpm capacity. It is an
LRU, located in the generator sump cavity. The generator must be removed for
access. If the pump fails, or if the filter becomes obstructed, oil accumulates in
the generator sump cavity until a LOW OIL PRESSURE protective shutdown
occurs. (See the oil supply system) The generator scavenge oil filter prevents
contaminants from a failed generator from re-entering the APU oil gearbox and
damaging the APU.
It is thus a non-bypass type, and uses the same type filter element as the oil
pressure system filter. Indication of a plugged filter is by a pop-out indicator and
a differential pressure switch.
The differential pressure switch is normally closed. It opens when the filter
DELTA-P reaches 35 psid. The ECU initiates a protective shutdown if the
switch opens and oil temperature exceeds 46OC. A failed open or disconnected
switch is faulted in Prestart and Self-Test BITE. The ECU stores FILTER
SW(GEN) as the faulty LRU. If the switch is detected open during Prestart
BITE, the APU then operates without protection from a blocked filter. The
switch is an LRU.
GENERATOR OIL
FILTER DIFFERENTIAL
PRESSURE SWITCH
GENERATOR
DRIVE PAD
GENERATOR
SCAVENGE PUMP
DIFFERENTIAL
PRESSURE
INDICATOR
(POP-OUT)
GENERATOR OIL
FILTER ASSEMBLY
GENERATOR
GENERATOR OIL
FILTER ASSEMBLY
TURBINE
BEARING
SCAVENGE
PUMP
POWER
35 PSID
GEN FILTER
PROTECTIVE
SHUTDOWN
OIL TEMP >46C
(HOT SENSOR)
SOFTWARE
M206 ECU (E-6)
GEN OIL
FILTER DIFF
PRESS SW
GEN OIL
FILTER ASSY
SCAVENGE
PUMP
OIL PUMP ASSY
GEARBOX
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49-27-R18972M
B767-3S2F
Page - 36
ATA 49-30
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start, over 100 PSI offsets a check valve in the flow divider for initial start ad
acceleration. The fuel flow divider also has an electric solenoid valve. The valve
opens during the normal run sequence, above 95% to supply secondary fuel to
the APU at a lower pressure setting of 35 PSI. The valve is controlled by the
ECU.
Fuel Manifold/Nozzles
Two separate fuel manifolds encircle the APU combustion chamber. Each
manifold has six, permanently attached, fuel nozzles. The nozzles and
manifolds are replaced as a single unit and are an LRU.
ECU BITE
The Electronic Control Unit (ECU) controls APU operation automatically. The
ECU regulates fuel flow by controlling an excitation current to a torquemotor.
The torquemotor is located on the fuel control unit. The ECU receives air inlet
pressure from the (P2) sensor and inlet air temperature from the load
compressor inlet temperature (LCIT) sensor. The ECU uses these signals to
adjust fuel flow for starting and normal operation. There are two fuel schedules
used for APU operation. The acceleration schedule is used below 95% RPM
while the speed schedule is used above 95% RPM.
The ECU receives EGT from two thermocouple circuits. This signal is used to
adjust fuel flow to prevent an OVERTEMP protective shutdown.
Fuel Control Unit
The fuel control unit filters, pressurizes, and meters fuel. It has two electrical
connections. One electrical connection is for the torquemotor. The torquemotor
meters fuel based on ECU excitation signals. The other connection is for the
fuel shutoff solenoid valve. This valve controls the flow of metered fuel to the
fuel flow divider. The fuel shutoff solenoid valve is an LRU. The torquemotor is
not an LRU.
The fuel control unit is mounted to the oil pump assembly.
Fuel Flow Divider
The fuel flow divider separates fuel flow into the primary and secondary fuel
manifolds. The primary manifold is used all the time. The secondary fuel
manifold is used when higher fuel flows are required. Fuel pressure during
The following REASON APU NOT OPERATING lamps are associated with the
APU fuel system and are shown on the REASON APU NOT OPERATING lamp
field:
UNDER SPEED
START ABORTED
EGT OVERTEMP
OVER SPEED
The following FAULTY LRU lamps are associated with the APU fuel system and
are shown on the FAULTY LRU lamp field: ECU: FUEL CONTROL, FLOW DIV
SOL, FUEL SOL.
FUEL CONTROL
APU INLET
PRESS SENSOR
(P2)
APU INLET
TEMP SENSOR
(LCIT)
FUEL
CONTROL
FUEL
MANIFOLD
MONOPOLE
(REF)
FUEL FILTER
FUEL FILTER
IGVA
FRONT
TORQUE MOTOR
LEFT SIDE
FUEL SHUTOFF
SOLENOID VALVE
POP-OUT INDICATOR
FAULTY
LRU
RECORD
SELECTED
NORMAL
STOP SIG
REVERSE
FLOW
DOOR
SYSTEM
CONTROL
FAILURE
EGT
OVERTEMP
FIRE
EMERG
SPARE
SPARE
INLET
DOOR RLY
#1 SPD
SENSOR
EGT #1
CIRCUIT
FLOW
DIV SOL
P2
SENSOR
CURRENT/
LAST RUN
LCIT
SENSOR
#2 SPD
SENSOR
EGT #2
CIRCUIT
ECS
CONTROL
ECU
SHUTDOWN
2
UNDER
SPEED
DC PWR
LOSS
O/S TEST
CIRCUIT
NO
DATA
FUEL
SOL
LOP
SWITCH
IGV
ACT
APU
STARTER
FAN
VALVE
SHUTDOWN
3
START
ABORTED
LOW OIL
PRESSURE
HIGH OIL
TEMP
WAIT
PT
SENSOR
FUEL
CONTROL
IGN
UNIT
A/C STRT
CIRCUIT
FILTER
SW(GEN)
SHUTDOWN
4
NO
LIGHTOFF
GEN
FILTER
OVER
SPEED
TEST
OK
KP
SENSOR
SURGE
VALVE
DEOIL
SOL
HOT
SENSOR
SEE MNT
MANUAL
LRU
SUMMARY
SOLENOID
VALVE
INFLOW
PRIMARY
OUTFLOW
SECONDARY
OUTFLOW
FLOW DIVIDER
FUEL MANIFOLDS
FUEL SYSTEM
B767-3S2F
Page - 37
SURGE
CONTROL
VALVE
(REF)
ATA 49-30
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49-31-R18975M
B767-3S2F
Page - 38
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Acceleration Scheduling
Operation
The APU is in the acceleration mode when the APU control switch is on,
Prestart BITE is complete, speed is below 95 percent, and no software
protective shutdowns are present. The acceleration schedule is also monitored
to maintain RPM, EGT and acceleration limits. If the APU fails to meet the RPM
time schedule targets, a START ABORTED protective shutdown occurs.
If the APU fails to meet EGT minimums a NO LIGHTOFF protective shutdown
occurs.
To increase high altitude starting capability, a modified acceleration schedule is
used above 30,000 feet. This schedule meters fuel to match less dense air.
On-Speed Scheduling
At 95 percent speed the ECU switches from acceleration to on speed
scheduling. The APU operates at either 100 percent, or 101 percent RPM, as a
function of the pneumatic modes. The lower RPM is used except when Main
Engine Start (MES) or Inflight (INFLT) pneumatic modes are active.
Torquemotor current is a function of actual speed vs the reference speed.
Maximum and minimum fuel schedules are provided for flameout and surge
protection. The minimum fuel schedule prevents flameout. The maximum fuel
schedule prevents power section compressor surge.
The flow divider operation is hydraulic and automatic. The drain valves are
spring loaded to port the manifolds to the drain mast, to prevent nozzle coking
when the APU is not operating. As metered fuel from the FCU enters the
divider, the drain valves are pushed open by fuel pressure, closing the drain port
and allowing flow to the manifolds. The sequence valves delay secondary fuel
flow until the APU requires the higher flow rates for operation.
Since the fuel pump is gearbox driven, output is low when APU rpm is low. To
provide proper atomization at low rpm, such as during the start cycle, a primary
nozzle with a small orifice is used. As pump output increases with rpm, the
small opening restricts flow, increasing pressure. At 100 psi, a start sequence
valve opens, allowing flow to the secondary manifold. This manifold has large
nozzle orifices to support proper atomization at higher fuel flows. The flow
divider solenoid is energized at 95% to allow flow to the secondary manifold
through the run sequence valve. Thus, above 95%, proper atomization is
maintained even if system pressure drops below the 100 psi.
INLET GUIDE
VANE ACTUATOR
AIR INLET
PLENUM
FUEL
METERING
ASSEMBLY
FUEL
PUMP
OIL PUMP
ASSEMBLY
SEAL
DRAIN
FUEL
FUEL
INLET
INLET
FILTER
FLOW
DIVIDER
SOLENOID
VALVE
FWD
START SEQ
VALVE 100 PSIG
RUN SEQ
VALVE 35 PSIG
SECONDARY
DRAIN
VALVE
FUEL FLOW
DIVIDER
DRAIN
TANK
TO ECU
SPRING
COMBUSTOR
SECONDARY
FUEL NOZZLES
PRIMARY
FUEL NOZZLES
GEARBOX
DRAIN
MAST
(OPTION)
SCREEN
OVERBOARD
DRAIN PORT
FUEL INLET
SECONDARY NOZZLE
PORT
FUEL FLOW
DIVIDER SOLENOID
VALVE
FLOW DIVIDER
______________
(LOCATED BEHIND AND UNDER SURGE VALVE)
FUEL SYSTEM
B767-3S2F
Page - 39
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49-31-R18976M
B767-3S2F
Page - 40
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Fuel Pump
The fuel pump is a gear pump that provides up to 1980 lbs/hr (898 KG/HR) of
fuel. It is spline driven from the oil pump assembly.
The actuator pressure regulator provides pressurized fuel to the Inlet Guide
Vane Actuator (IGVA). It regulates the fuel pressure supplied to the IGVA to 250
+/- 25 psig.
The fuel shutoff solenoid valve controls the supply of fuel from the control unit.
It is a spring-loaded-closed valve that, when closed, bypasses fuel back to the
fuel pump inlet. The valve is energized to open by 28 volt dc supplied from the
ECU. The valve is an LRU.
Maintenance TIP
A witness drain plug is located on the bottom of the FCU. Fuel or oil seepage
from this plug indicates seal leakage. The FCU should be replaced.
QUICK ATTACH
DETACH CLAMP
ACTUATOR
RETURN PORT
FUEL FILTER ELEMENT
FUEL CONTROL
TORQUE MOTOR
IGV ACTUATOR
INLET FILTER
DIFFERENTIAL
PRESSURE INDICATOR
(POP-OUT)
FUEL HIGH
PRESSURE
FILTER
HIGH PRESS
RELIEF VALVE
DIFF
PRESS REG
FUEL
HIGH
PRESS
FILTER
FUEL INLET
PORT
PRESSURIZING
VALVE
APU FUEL
FEED SYSTEM
METERING
PORT
METERED
FUEL OUT
METERING
VALVE
FUEL
PUMP
FUEL
FILTER ELEMENT
CLEVIS
VALVE
TEST PORT
TORQUE MOTOR
______________
METERING
VALVE
________________
TM
TO ECU
LEGEND
LOW PRESS FUEL
METERED FUEL
REGULATED HIGH PRESS FUEL
FUEL CONTROL
TORQUE MOTOR
TO ECU
FUEL SHUTOFF
SOLENOID VALVE
(DE-ENERGIZED)
FUEL SHUTOFF
SOLENOID VALVE
(ENERGIZED)
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49-31-R20888M
B767-3S2F
Page - 42
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POWER PLANT
DRAIN AND VENT ASSEMBLY
Description
The drain and vent assembly consists of four drain lines that exhaust fluids
overboard through the APU drain mast. The four drain lines are:
The fuel pump-oil pump and inlet guide vane actuator drain line, which
drain any mechanical seal leakage from these units.
The bearing seal cavity vent line vents the APU bearing seals. Oil leakage
from this line indicates bearing seal wear or a gearbox pressurization
problem.
The turbine plenum drain line drains fuel from wet starts from the turbine
area. A spring loaded open pressure valve is installed in this line which
allows drainage only when low pressures are present in the turbine area.
The flow divider and heat shield drain line drains fuel from the fuel nozzles
and manifolds upon APU shutdown and liquids accumulated around the
combustor.
Tell tale drains are installed in each of the three bearing seal cavity lines and the
fuel pump-oil pump and inlet guide vane actuator drain lines.
IGV
ACTUATOR
TURBINE
PLENUM
DRAIN
MID - BEARING
OIL SEAL
GEARBOX
FWD
LAB SEAL
LAB SEAL
FORWARD
BEARING
OIL SEAL
FUEL CONT
UNIT
FLOW DIVIDER
& HEAT SHIELD
DRAIN
BEARING SEAL
CAVITY VENT
FUEL-OIL PUMPS
& INLET GUIDE
VANE ACTUATOR
DRAIN MAST
(RIGHT APU
APU DRAINS
_____________
ACCESS DOOR)
(BOTTOM VIEW)
MID BEARING
SEAL CAVITY
OIL
PUMP
IGV
ACTUATOR
TELL TALE
DRAINS
FUEL CONTROL UNIT/OIL
PUMP - TELL TALE DRAIN
APU INLET
PLENUM DRAIN
ATA 49-30
5/6/13
FORWARD BEARING
SEAL CAVITY
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49-15-977600M
B767-3S2F
Page - 44
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IGNITION/STARTING SYSTEM
B767-3S2F
Page - 45
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49-41-977630M
B767-3S2F
Page - 46
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RIGHT REAR
MOUNT
CERAMIC
INSULATOR
IGNITER
PLUG
FWD
IGNITION UNIT
IGNITION
LEAD
INPUT
POWER
RIGHT
SIDE
__________
+28V
IGNITE
HASTELLOY X
TUNGSTEN
ALLOY
IGNITER PLUG
_____________
COOLING
AIR HOLES
SOFTWARE HARDWARE
TRIGGER
AND
DISCHARGE
CIRCUITS
IGN
GND
ECU
IGNITER
PLUG
IGNITION UNIT
IGNITION SYSTEM
B767-3S2F
Page - 47
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49-41-B07657M
B767-3S2F
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Cooling Air
Air from the plenum is drawn by the gearbox-driven fan to the oil cooler, and into
the APU compartment.
ECU BITE
The ECU stores REVERSE FLOW and DOOR SYSTEM failures in the
REASON APU NOT OPERATING field. The LCIT SENSOR, ECS CONTROL,
IGV ACT, FAN VALVE, PT SENSOR, DELTA-P SENSOR, SURGE VALVE, and
INLET DOOR RLY can be stored in the FAULTY LRU field.
COOLING
FAN
OIL
COOLING
AIR DUCT
SURGE
VALVE
INLET GUIDE
VANE (IGV) ACTUATOR
APU GEN MOUNT
(REF)
REASON
APU NOT
OPERATING
FWD
STATUS
FAULTY
LRU
FLOW
SENSOR
RECORD
SELECTED
UNDER
SPEED
START
ABORTED
REVERSE
FLOW
DC PWR
LOSS
LOW OIL
PRESSURE
GEN
FILTER
DOOR
SYSTEM
FIRE
EMERG
O/S TEST
CIRCUIT
HIGH OIL
TEMP
OVER
SPEED
SPARE
SPARE
NO
DATA
WAIT
INLET
DOOR RLY
LCIT
SENSOR
FUEL
SOL
PT
SENSOR
EP
SENSOR
#1 SPD
SENSOR
#2 SPD
SENSOR
LOP
SWITCH
FUEL
CONTROL
SURGE
VALVE
EGT #1
CIRCUIT
EGT #2
CIRCUIT
IGN
UNIT
DEOIL
SOL
FLOW
DIV SOL
ECS
CONTROL
A/C STRT
CIRCUIT
HOT
SENSOR
P2
SENSOR
ECU
CURRENT/
LAST RUN
SHUTDOWN
2
PNEUMATIC SYSTEM
B767-3S2F
Page - 49
ATA 49-50
5/6/13
EFF - ALL
TRAINING MANUAL
FOR TRAINING PURPOSES ONLY
NO
LIGHTOFF
CONTROL
FAILURE
EGT
OVERTEMP
NORMAL
STOP SIG
49-52-R18797M
IGV
ACT
APU
STARTER
FAN
VALVE
SHUTDOWN
3
FILTER
SW(GEN)
SHUTDOWN
4
TEST
OK
SEE MNT
MANUAL
LRU
SUMMARY
B767-3S2F
Page - 50
ATA 49-50
5/6/13
EFF - ALL
TRAINING MANUAL
FOR TRAINING PURPOSES ONLY
If the load compressor stalls (surges), the LCIT sensor reports the higher
compressed air temperatures to the ECU. The ECU then performs a
REVERSE FLOW protective shutdown.
The APU inlet pressure sensor supplies pressure altitude input to the ECU. The
input is used to modify the fuel schedule for increased efficiency and also adjust
the surge margin for the load compressor. It consists of a tube, open to the
inside of the plenum, connected to a piezoresistive solid-state transducer. It is
an LRU mounted on the left side of the intake plenum duct.
The LCIT sensor is tested during prestart, monitor, and self test BITE. Each test
ensures that the LCIT resistance range is between -100F to 450F (-73.3C to
232.2C). If the LCIT sensor is detected open or out of range LCIT SENSOR is
stored as a faulty LRU.
Detection for the reverse flow protective shutdown is no longer possible with a
failed LCIT SENSOR . An alternate program value, based on P2, is utilized by
the ECU to maintain APU operation, but load compressor surge protection is not
available. The LCIT (T2) value based on P2 is a function of ISA numbers
(International Standard Atmosphere) for altitude versus temperature.
BA SE D ON P
AL TE RN AT E VA LU E
SL . IS A
60
40
4. 4
20
-6 .7
T F
2
LOAD COMPRESSOR
INLET TEMPERATURE
SENSOR (LCIT)
-1 7. 8
0
35,000 ISA
-20
-40
0
10
P PSIA
2
INLET SENSORS
B767-3S2F
Page - 51
ATA 49-50
5/6/13
EFF - ALL
15 .6
T C
2
INLET PRESSURE
SENSOR P2
TRAINING MANUAL
FOR TRAINING PURPOSES ONLY
49-52-980581M
-2 8. 9
-4 0
15
B767-3S2F
Page - 52
ATA 49-50
5/6/13
EFF - ALL
TRAINING MANUAL
FOR TRAINING PURPOSES ONLY
SINGLE
INLET
TORQUE
MOTOR
COMMAND
SIGNAL
FROM
ECU
SPRING
SERVO VALVE
ygmm-49-52-0003 (mod)
RETURN
CONNECTING
ROD (TO IGVS)
EXCITATION
FROM ECU
ELECTRICAL
CONNECTOR
BUSHING
(2 EA)
VANES
CLOSED
OPEN
ACTUATOR
PISTON
FEEDBACK
TO ECU
CLOSE
BLOCK
ASSEMBLY
BELLCRANK
TO FUEL
CONTROL
UNIT
LVDT
ATA 49-50
5/6/13
EFF - ALL
TRAINING MANUAL
FOR TRAINING PURPOSES ONLY
49-52-980589MM
B767-3S2F
Page - 54
ATA 49-50
5/6/13
EFF - ALL
TRAINING MANUAL
FOR TRAINING PURPOSES ONLY
Operation
Surge protection is maintained by modulating the surge valve to assure that
load compressor output is matched to IGV position. As the IGVs open, the air
mass flow must increase in proportion. For each IGV angle, there is a target
mass flow that maintains an adequate surge margin. As the airplane pneumatic
demand changes, the surge valve modulates to keep the flow on target valve.
The surge valve is positioned by a torquemotor input from the ECU. The valve
is spring loaded open and modulates closed with increasing current.
Target mass flow (values on the control line) is calculated by a schedule, based
on IGV position, in ECU software. This mass flow schedule is adjusted to
varying ambient conditions using inputs from the P2 and T2 sensors.
The actual mass flow is calculated using the Delta-P and PT transducers. The
target and actual mass flows are then compared. If actual mass flow is less
than the target, a signal is sent to the surge valve torquemotor to modulate the
surge valve open. The surge valve remains open when PCD2 is less than 7.5
PSIA. If the DELTA-P or PT sensor signal fails, the torquemotor signal is
removed, causing the surge valve to open. This results in a large reduction in
pneumatic output to the airplane. If there is a rapid rise in LCIT, the torquemotor
signal is removed and a protective shutdown occurs. The surge valve is always
open below 95 percent RPM.
ATA 49-50
5/6/13
EFF - ALL
TRAINING MANUAL
FOR TRAINING PURPOSES ONLY
49-53-B07649M
B767-3S2F
Page - 56
ATA 49-50
5/6/13
EFF - ALL
TRAINING MANUAL
FOR TRAINING PURPOSES ONLY
VARIABLE VOLUME
CHAMBER
TOTAL PRESSURE
TRANSDUCER
FLEX LINES
TO AIRPLANE
TO SURGE VALVE
PS
DIRECTIONAL
FLOW CONTROL
DIFFERENTIAL
PRESSURE
TRANSDUCER
VOLUME
CHAMBER
PT-PS
ECU
DIRECTIONAL
FLOW CONTROL VALVE
SOFTWARE
PT PROBE
PS PROBE
PT
SURGE
VALVE
FILTERS
ORIFICE
PT
FROM
APU
TOTAL PRESS
TRANSDUCER
ATA 49-50
5/6/13
EFF - ALL
TRAINING MANUAL
FOR TRAINING PURPOSES ONLY
49-53-980587M
B767-3S2F
Page - 58
ATA 49-60
5/6/13
EFF - ALL
TRAINING MANUAL
FOR TRAINING PURPOSES ONLY
ENGINE CONTROLS
PROTECTIVE SHUTDOWN
General
There are two separate APU protective shutdown logic systems in the ECU,
analog (hardware) protective shutdown logic and digital (software) protective
shutdown logic.
Shutdown Annunciation
The ECU sends a signal to the EICAS computer, and illuminates the FAULT
light on the APU control panel whenever a protective shutdown occurs. The
ECU stores the reason for the protective shutdown in nonvolatile memory for
later recall on the REASON APU NOT OPERATING light array on the face of
the ECU.
Restart After Fault Shutdowns
Turning the APU control switch OFF after a protective shutdown turns off the
FAULT light and causes the EICAS APU FAULT advisory message to
disappear. A restart may then be attempted, except for an O/S TEST CIRCUIT
shutdown and certain LRU faults. If the fault is still present, a new protective
shutdown is initiated.
O/S Test Circuit
This shutdown trips an internal breaker in the ECU. The ECU must be replaced.
LRU Faults
Some LRUs are tested in prestart BITE, and terminate the start if detected as
faulty.
LATCH
107%
1
MONOPOLE NO. 1
HIGHEST
WINS
MONOPOLE NO. 2
>95%
ANALOG
PROTECTIVE
SHUTDOWNS
621C
EICAS
COMPUTERS
APU FUEL
SOLENOID VALVE
LATCH
EGT #1 CIRCUIT
HIGHEST
WINS
EGT #2 CIRCUIT
IGNITION UNIT
109%
STARTER MOTOR
OVERSPEED
OVERTEMP
AIR VALVE
DIGITAL
HOT
95%
899C
LOP
95%
GENERATOR
649C
DC PWR LOSS
APU FAULT
RELAY
EGT
DOOR SYSTEM
40%
100%
FIRE EMER
START ABORTED
UNDER SPEED
NO LIGHTOFF
REVERSE FLOW
RPM
NORMAL
STOP SIG
REASON
APU NOT
OPERATING
STATUS
REVERSE
FLOW
DO OR
SYSTEM
SPARE
INLET
DOOR RLY
FAULTY
LRU
CONTROL
FAILURE
EGT
OVERTEMP
FIRE
EMERG
SPARE
LCIT
SENSOR
UNDER
START
NO
SPEED
ABORTED
LIGHTOFF
DC PWR
LOW OIL
LO SS
PRESSURE
FUEL
SOL
LOP
TEMP
WAIT
GEN
F ILTER
OVER
SPEED
TEST
OK
PT
VP
SENSOR
SENSOR
#1 SPD
SENSOR
#2 SPD
SENSOR
FUEL
SURGE
EGT #1
CIRCUIT
EGT #2
IGV
IGN
DEOIL
CIRCUIT
ACT
UNIT
SOL
SWITCH
CONTROL
S
E
L
E
C
T
R
E
C
O
R
D
DIGITAL
PROTECTIVE
SHUTDOWNS
VALVE
FLOW
APU
A/C STRT
ECS
HOT
DIV SOL CONTROL STARTER
CIRCUIT
SENSOR
FAN
FILTER SEE MNT
P2
ECU
MANUAL
VALVE
SW(GEN)
SENSOR
RECORD CURRENT/ SHUTDOWN SHUTDOWN SHUTDOWN
LRU
SELECTED LAST RUN
2
3
4
SUMMARY
FREASON
A
U
L
T LRU
"FAULT" LIGHT
DC PUMP
FUEL S/O VLV
CONTROL FAILURE
GEN OIL FILTER P
OIL TEMP >46C
ANALOG OVERSPEED SHUTDOWN
CIRCUIT FAILURE
(O/S TEST CIRCUIT)
ERASE
MEMORY
BREAKER
M206 ECU
PROTECTIVE SHUTDOWN
B767-3S2F
Page - 59
ATA 49-60
5/6/13
EFF - ALL
TRAINING MANUAL
FOR TRAINING PURPOSES ONLY
49-61-R20207M
FUEL CONTROL
TORQUE MOTOR
INJECTED OVERSPEED
SIGNAL 107% FOR
NORMAL SHUTDOWN
B767-3S2F
Page - 60
ATA 49-60
5/6/13
EFF - ALL
TRAINING MANUAL
FOR TRAINING PURPOSES ONLY
ENGINE CONTROLS
ELECTRONIC CONTROL UNIT (ECU)
General
The APU control unit (ECU) is the central element of the APU control system. It
is a digital microprocessor located in the aft equipment center (E6). It weighs
approximately 38 lbs (17.4 kg) and is mounted on the top shelf of the E6 rack
using standard rack type connectors.
Major Software Tasks
The ECU maintains full authority over all APU operations through signals to
torquemotors and solenoids; and by interrogating various APU and airplane
sensors and signals. These tasks include:
1
OFF
ON
START
S351T020-19 AND ON
FLIGHT DECK
2
APU RPM%
UNDER
NORMAL
CONTROL
SPEED
STOP SIG FAILURE
REASON
EGT
REVERSE
DC PWR
APU NOT
OVERTEMP
FLOW
LOSS
OPERATING
FIRE
DOOR
O/S TEST
EMERG
SYSTEM
CIRCUIT
NO
SPARE
SPARE
STATUS
DATA
FUEL
INLET
LCIT
SOL
DOOR RLY SENSOR
LOP
#1 SPD
#2 SPD
SENSOR
SENSOR
SWITCH
FAULTY
EGT #2
EGT #1
IGV
LRU
CIRCUIT CIRCUIT
ACT
APU
ECS
FLOW
DIV SOL CONTROL STARTER
P2
FAN
ECU
SENSOR
VALVE
CURRENT/ SHUTDOWN SHUTDOWN
RECORD
2
3
SELECTED LAST RUN
E.C.U.
4
E.C.U.
5
E.C.U.
E.C.U.
7
ERASE
MEMORY
SELF
TEST
E.C.U.
REASON
LRU
R
E
C
O
R
D
S
E
L
E
C
T
START
NO
ABORTED LIGHTOFF
LOW OIL
GEN
PRESSURE FILTER
HIGH OIL
OVER
TEMP
SPEED
TEST
WAIT
OK
PT
P
SENSOR
SENSOR
FUEL
SURGE
CONTROL
VALVE
DEOIL
IGN
SOL
UNIT
A/C STRT
HOT
CIRCUIT
SENSOR
SEE MNT
FILTER
MANUAL
SW(GEN)
SHUTDOWN
LRU
4
SUMMARY
ERASE
MEMORY
E.C.U.
10
F
A
U
L
T
E.C.U.
8
LAMP
___________
LRU
SUMMARY - Record of all Faulty LRUs detected since the
last Memory Erase.
EICAS MAINT
PAGE
FLIGHT DECK
LAMP
TEST
SELF
T
E
S
T
ATA 49-60
5/6/13
EFF - ALL
TRAINING MANUAL
FOR TRAINING PURPOSES ONLY
49-61-R18774M
B767-3S2F
Page - 62
ATA 49-60
5/6/13
EFF - ALL
TRAINING MANUAL
FOR TRAINING PURPOSES ONLY
ENGINE CONTROLS
ECU FRONT PANEL/BITE TEST INSTRUCTIONS (-19 ECU)
Record Selected
General
This lamp field identifies the RECORD SELECT switch position. It is illuminated
when the ECU is powered, except during the mini-flag test.
Test Switch
Pre-start
Monitor
Self-test
Pre-start BITE is a automatic system self test. It is the first step in the start
sequence. It begins when the APU Start Switch is moved to the START/ON
position.
Monitor BITE is a system monitoring test that works during APU operation. It
begins when the pre-start bite test is completed.
Self test BITE is a system test. It is an operator initiated test. Self test BITE is
initiated without the APU running.
A placard, located on the E6 aft equipment center access door, contains
instructions for doing an ECU BITE procedure. To further clarify ECU BITE, a
description of ECU lamp fields, and switches follows.
The TEST switch is a two position, center off switch. The SELF and LAMP
position do not function with the APU running. Moving the switch to the SELF
position initiates a system test. This test is identical to the pre-start test.
Moving the TEST switch to the LAMP position initiates a test of the lights in
each lamp segment. (i.e. OVERSPEED, LOP SWITCH etc.) There are two
lights behind each lamp segment. The lights are not LRUs. They can only be
replaced in a repair/overhaul facility. BITE is not inhibited when both lights,
behind one lamp segment, fail. However, accurate troubleshooting cannot be
assured.
After all lamp segments are tested, the ECU automatically initiates a mini-flag
test. The mini-flag test, designed primarily for bench troubleshooting, identifies
internal ECU faults as well as external faults. The external faults are associated
with the LRUs that appear in the FAULTY LRU field. Holding the TEST switch in
the LAMP position for greater than 10 seconds also initiates the mini-flag test.
Record Select/Fault Switches
The RECORD SELECT switch controls what is displayed on the lamp fields.
The FAULT switch selects which lamp field, REASON APU NOT OPERATING
or FAULTY UNIT, illuminates lamp segments. Both switches are used in
conjunction with one another for proper fault identification. The switches may
be used when the APU is running or when it is shutdown.
The following table shows switch position with the corresponding lamp
indication.
Erase Memory Switch
The ERASE MEMORY switch is a momentary, two position switch that is
located behind a metal guard. Moving the ERASE MEMORY switch up erases
the ECU's memory. The memory cannot be erased while the APU is running.
1
OFF
ON
START
S351T020-19 AND ON
FLIGHT DECK
2
APU RPM%
UNDER
NORMAL
CONTROL
SPEED
STOP SIG FAILURE
REASON
EGT
REVERSE
DC PWR
APU NOT
OVERTEMP
FLOW
LOSS
OPERATING
FIRE
DOOR
O/S TEST
EMERG
SYSTEM
CIRCUIT
NO
SPARE
SPARE
STATUS
DATA
FUEL
INLET
LCIT
SOL
DOOR RLY SENSOR
LOP
#1 SPD
#2 SPD
SENSOR
SENSOR
SWITCH
FAULTY
EGT #2
EGT #1
IGV
LRU
CIRCUIT CIRCUIT
ACT
APU
ECS
FLOW
DIV SOL CONTROL STARTER
P2
FAN
ECU
SENSOR
VALVE
CURRENT/ SHUTDOWN SHUTDOWN
RECORD
2
3
SELECTED LAST RUN
E.C.U.
4
E.C.U.
5
E.C.U.
E.C.U.
7
ERASE
MEMORY
SELF
TEST
E.C.U.
REASON
LRU
R
E
C
O
R
D
S
E
L
E
C
T
START
NO
ABORTED LIGHTOFF
LOW OIL
GEN
PRESSURE FILTER
HIGH OIL
OVER
TEMP
SPEED
TEST
WAIT
OK
PT
P
SENSOR
SENSOR
FUEL
SURGE
CONTROL
VALVE
DEOIL
IGN
SOL
UNIT
A/C STRT
HOT
CIRCUIT
SENSOR
SEE MNT
FILTER
MANUAL
SW(GEN)
SHUTDOWN
LRU
4
SUMMARY
ERASE
MEMORY
E.C.U.
10
F
A
U
L
T
E.C.U.
8
LAMP
___________
LRU
SUMMARY - Record of all Faulty LRUs detected since the
last Memory Erase.
EICAS MAINT
PAGE
FLIGHT DECK
LAMP
TEST
SELF
T
E
S
T
ATA 49-60
5/6/13
EFF - ALL
TRAINING MANUAL
FOR TRAINING PURPOSES ONLY
49-61-R19065
B767-3S2F
Page - 64
ATA 49-60
5/6/13
EFF - ALL
TRAINING MANUAL
FOR TRAINING PURPOSES ONLY
ENGINE CONTROLS
MINI-FLAG TEST
General
The mini-flag test, designed primarily for bench troubleshooting, identifies
internal ECU faults as well as external faults. The external faults are associated
with the LRUs that appear in the FAULTY LRU field.
Starting the Mini-Flag Test
The mini-flag test may be conducted with or without the APU running.
With the APU shutdown, moving and holding the TEST switch in the LAMP
position for 10 seconds begins the mini-flag test. The mini-flag test also begins
automatically after the LAMP test is completed.
With the APU running, moving the TEST switch to the LAMP position causes a
mini-flag test to begin immediately.
Interpreting the Mini-Flag Test
To proper view fault codes, tilt your head to the right, at a 90 degree position,
relative to the front face of the ECU. The left edge of the ECU face should now
appear as the bottom of the mini-flag fault code display.
The mini-flag fault codes are displayed as numbers from 1 to 199. Use the
maintenance manual to associate a fault code with a failed component.
If no mini-flag fault codes are stored, he letters O K appear.
Note:
F
A
U
L
T
REASON
Page - 65
LRU
R
E
C
O
R
D
S
E
L
E
C
T
B767-3S2F
5/6/13
MEMORY
ERASE
ATA 49-60
EFF - ALL
EGT
SENSOR
CODE 34
TRAINING MANUAL
MINI-FLAG TEST
49-61-R19125
LAST RUN
LRU
REASON
CURRENT/
RECORD
SELECTED
SENSOR
R
E
C
O
R
D
SHUTDOWN
ECU
SHUTDOWN
VALVE
FAN
STARTER
CONTROL
DIV SOL
P2
APU
IGV
ACT
SWITCH
ECS
SENSOR
EGT #2
CIRCUIT
SENSOR
FLOW
LOP
#2 SPD
#1 SPD
EGT #1
SOL
CIRCUIT
FUEL
DATA
LCIT
SENSOR
INLET
DOOR RLY
NO
IGN
UNIT
SHUTDOWN
SW(GEN)
FILTER
CIRCUIT
A/C STRT
MEMORY
ERASE
SUMMARY
LRU
MANUAL
SEE MNT
SENSOR
HOT
SOL
DEOIL
VALVE
SURGE
FUEL
CONTROL
EP
SENSOR
PT
OK
TEST
SPEED
OVER
FILTER
GEN
LIGHTOFF
MEMORY
ERASE
SUMMARY
LRU
MANUAL
SEE MNT
SENSOR
SENSOR
WAIT
TEMP
HIGH OIL
CIRCUIT
NO
O/S TEST
FIRE
SPARE
EMERG
DOOR
SPARE
SYSTEM
PRESSURE
LOSS
LRU
S
E
L
E
C
T
START
EGT
LOW OIL
ABORTED
UNDER
SPEED
DC PWR
FAILURE
OVERTEMP
CONTROL
FLOW
NORMAL
REVERSE
SHUTDOWN
STOP SIG
SHUTDOWN
SW(GEN)
FILTER
CIRCUIT
HOT
VALVE
FAN
FAULTY
STATUS
OPERATING
APU NOT
REASON
LRU
SUMMARY - Record of all Faulty LRUs detected since the
___________
Displayed Faulty LRUs are only the failed LRUs that could cause
2.3.4
_____ - Second, third, and fourth historical fault shutdowns.
the shutdown.
R
E
C
O
R
D
SHUTDOWN
displayed Faulty LRUs are only the failed LRUs that could cause
commanded APU stop and all Faulty LRUs detected during last
________
LAST
RUN - If Reason is NORMAL STOP SIG, the aircraft
REASON
LAST RUN
CURRENT/
RECORD
SELECTED
ECU
DEOIL
VALVE
SOL
IGN
CONTROL
EP
SURGE
FUEL
OK
TEST
SENSOR
PT
A/C STRT
APU
STARTER
ECS
CONTROL
SENSOR
OVER
SPEED
UNIT
FLOW
P2
NO
FILTER
GEN
LIGHTOFF
SENSOR
WAIT
TEMP
HIGH OIL
PRESSURE
ACT
IGV
SWITCH
LOP
SOL
FUEL
DATA
NO
CIRCUIT
DIV SOL
CIRCUIT
EGT #2
SENSOR
EGT #1
#2 SPD
#1 SPD
CIRCUIT
LCIT
SENSOR
INLET
SPARE
SPARE
DOOR RLY
FIRE
EMERG
DOOR
SYSTEM
LRU
START
SPEED
LOW OIL
ABORTED
UNDER
DC PWR
O/S TEST
FAILURE
LOSS
CONTROL
OVERTEMP
REVERSE
FLOW
NORMAL
STOP SIG
FAULTY
STATUS
OPERATING
APU NOT
REASON
LRU
SUMMARY - Record of all Faulty LRUs detected since the
___________
Displayed Faulty LRUs are only the failed LRUs that could cause
S
E
L
E
C
T
START
NO
NORMAL CONTROL UNDER
REASON STOP SIG FAILURE SPEED ABORTED LIGHTOFF
EGT
GEN
DC PWR LOW OIL
APU NOT REVERSE
PRESSURE FILTER
FLOW OVERTEMP LOSS
OPERATING
FIRE
DOOR
O/S TESTHIGH OIL OVER
EMERG CIRCUIT TEMP
SYSTEM
SPEED
NO
TEST
WAIT
SPARE
STATUS
SPARE
DATA
OK
PT
EP
FUEL
LCIT
INLET
SENSOR SENSOR
SOL
DOOR RLY SENSOR
FUEL
LOP
#1 SPD #2 SPD
SURGE
SENSOR SENSOR SWITCH CONTROL VALVE
FAULTY
DEOIL
IGN
IGV
EGT #1 EGT #2
LRU
SOL
ACT
UNIT
CIRCUIT CIRCUIT
ECS
A/C STRT HOT
APU
FLOW
DIV SOL CONTROL STARTER CIRCUIT SENSOR
FAN
P2
FILTER SEE MNT
ECU
VALVE SW(GEN) MANUAL
SENSOR
RECORD CURRENT/ SHUTDOWNSHUTDOWNSHUTDOWN LRU
2
3
4
SELECTED LAST RUN
SUMMARY
E
LAMP
SELF
LAMP
SELF
___________
LRU
SUMMARY - Record of all Faulty LRUs detected since the
2.3.4
_____ - Second, third, and fourth historical fault shutdowns.
Displayed Faulty LRUs are only the failed LRUs that could cause
the shutdown.
displayed Faulty LRUs are only the failed LRUs that could cause
displayed Faulty LRUs are only the failed LRUs that could cause
the shutdown.
commanded APU stop and all Faulty LRUs detected during last
commanded APU stop and all Faulty LRUs detected during last
LAST
RUN - If Reason is NORMAL STOP SIG, the aircraft
________
PROPER
MINI-FLAG TEST VIEWING ANGLE
___________________________________
________
LAST
RUN - If Reason is NORMAL STOP SIG, the aircraft
T
E
S
T
SELF
LAMP
OK
NO MINI-FLAG FAULTS
B767-3S2F
Page - 68
ATA 49-70
5/6/13
EFF - ALL
TRAINING MANUAL
FOR TRAINING PURPOSES ONLY
APU INDICATION
INDICATION GENERAL DESCRIPTION
General
The APU control unit (ECU) sends analog signals to the EICAS computers for
display of RPM, exhaust gas temperature (EGT), and EICAS messages.
Indications
APU speed in percent RPM and EGT in degrees Celsius are displayed on the
EICAS PERF/APU page. EGT is also displayed on the STATUS page. The
display of APU RPM is on the status page.
The EICAS advisory message APU FAULT appears and the FAULT light
illuminates to annunciate an APU protective shutdown. The FAULT light also
shows transit of the APU fuel shutoff valve. APU BITE appears on the ECS/
MSG page to indicate that a non-critical LRU fault is stored in the ECU.
However, under almost all conditions, if a failed LRU causes a protective
shutdown or causes a loss of pneumatic power, no APU BITE message will
appear.
The white RUN light on the APU control panel comes on when the APU is
operating above 95 percent speed. The RUN light also blinks two times during
starting. This indicates that the pre-start BITE has been completed.
An APU hour meter shows total APU operating hours when the APU is
operating above 95%.
An APU cycle meter shows the total number of APU starts. The cycle meter
indicates another start each time the APU control switch is placed in the start
position when the APU RPM is less than 95 percent.
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If both monopoles fail during operation (APU SPEED > 50%), the APU shuts
down due to UNDERSPEED or START ABORTED and identifies #1 SPD
SENSOR and #2 SPD SENSOR as the faulty LRU's.
Note:
The monopoles are not tested during Prestart BITE. If they are
faulty, APU start is not inhibited. During start, the starter motor will
rotate the APU. However, since no speed signal is sensed, the
ECU initiates a START ABORTED protective shutdown. The APU
STARTER is identified as the faulty LRU. The monopoles are not
stored as faulty because the ECU logic assumes that the starter
motor did not crank the APU.
Maintenance TIP
Attempting to use pliers or a similar gripping tool on the knurled section to
remove the monopole deforms the housing. This action possibly fractures the
potting material inside which makes the monopole unusable.
APU DR IVE
SHAFT
MONOPOLE
WRENCH
MO UN TI NG
TH RE AD S
FERROMAGNETIC
NUT (P OWER
SECTION BR G.
RETAINING NU T)
KNUR LE D
SECT IO N
MO NO PO LE (2 P LACES)
#1 S PD S ENS OR
#2 S PD S ENS OR
FWD
RE MO VA L SL OT
(2 PLACES)
EL EC TR IC AL
CO NN EC TO R
#2 SP D SE NS OR
(MONOPOLE)
SC RE W TH RE AD S
FO R IN ST AL LA TI ON
PULS E SE NS OR
MAGNET & CO IL
TIP
TRANSFORMER
SE AL S
MONOPOLES (RPM)
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APU INDICATION
EGT THERMOCOUPLES
General
APU exhaust gas temperature (EGT) is measured by 4 individual
chromel-alumel thermocouple assemblies. Each assembly consists of two
thermocouple probes enclosed in an inconel support tube. The support tube is
attached to a common stainless steel header. The thermocouple assemblies
are mounted in the APU tailpipe. The two assemblies on the left side are wired
together to form EGT CIRCUIT #1. The two assemblies on the right side are
wired together to form EGT CIRCUIT #2. These circuits supply two redundant
EGT signals to the ECU. The ECU uses the highest EGT signal for operation.
The EGT thermocouple assemblies are LRUs.
Sensing and Failure Modes
The ECU tests both EGT circuits during prestart, monitor and self-test BITE for
an output signal greater than -100 degrees F (-88 degrees C).If both EGT circuit
fail pre-start BITE or if they both fail during the start cycle, a START ABORTED
protective shutdown occurs. EGT #1 CIRCUIT and EGT #2 CIRCUIT are
stored as faulty LRUs.
When APU speed is greater than 95%, the two circuits cannot disagree more
than 150OF (66OC). The rake reporting the lower temperature is considered
failed and the ECU records EGT #1 CIRCUIT or EGT #2 CIRCUIT as a faulty
unit.
If both circuits fail, with APU speed above 95%, the inlet guide vanes close and
the surge control valve opens. The APU continues to operate.
APU EGT
THERMOCOUPLES
EGT #2
CIRCUIT
EGT #1
CIRCUIT
THERMOCOUPLE
PROBE TIPS
(2 PLACES)
REINFORCING
WELDS
(2 PLACES)
INCONEL
SUPPORT
TUBE
STAINLESS
STEEL HEADER
THERMOCOUPLE
EGT THERMOCOUPLES
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