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B767-3S2F ATA 49-00 Page - 1 5/6/13 EFF - ALL

AUXILIARY POWER UNITATA 49


B767-3S2F ATA 49-00 Page - 2 May, 6,2013 EFF - ALL

ATA 49 AUXILIARY POWER TABLE OF CONTENTS

AUXILIARY POWER TABLE OF CONTENTS: ..................................... 2

GRAPHIC .............................................................................................. 3

GENERAL DESCRIPTION......................................................................4

INTRODUCTION ................................................................................... 6

GTCP 331-200ER.................................................................................. 8

ENGINE............................................................................................... 10

APU SYSTEMS AND COMPONENTS................................................ 12

GEARBOX AND ACCESSORIES ....................................................... 14

ELECTRONIC CONTROL UNIT (ECU) INPUTS/OUTPUTS .............. 16

POWERPLANT AIR INTAKE SYSTEM................................................ 18

POWERPLANT AIR INTAKE DOOR AND ACTUATOR ...................... 20

AIR INTAKE DOOR INDICATIONS...................................................... 22

LUBRICATION SYSTEM..................................................................... 24

OIL SUPPLY AND RESERVOIR ......................................................... 26

OIL SYSTEM ....................................................................................... 28

GEARBOX PRESSURIZATION SYSTEM........................................... 32

APU AND GENERATOR OIL SCAVENGE SYSTEM ......................... 34

FUEL SYSTEM.................................................................................... 36

FUEL CONTROL UNIT........................................................................ 40

DRAIN AND VENT ASSEMBLY .......................................................... 42

IGNITION AND STARTING SYSTEM ................................................. 44

IGNITION SYSTEM............................................................................. 46

PNEUMATIC SYSTEM........................................................................ 48

INLET SENSORS................................................................................ 50

INLET GUIDE VANE ACTUATOR....................................................... 52

SURGE BLEED SYSTEM ................................................................... 54

FLOW SENSOR MODULE.................................................................. 56

PROTECTIVE SHUTDOWN................................................................ 58

ELECTRONIC CONTROL UNIT (ECU)............................................... 60

ECU FRONT PANEL/BITE TEST INSTRUCTIONS ........................... 62

MINI-FLAG TEST................................................................................. 64

INDICATION GENERAL DESCRIPTION ............................................. 66

APU INDICATION MONOPOLES (RPM) ............................................. 68

APU INDICATION EGT THERMOCOUPLES....................................... 72



AUXILIARY POWER UNIT



APU - GENERAL DESCRIPTION

General

The APU system contains these subsystems:

- Power plant (49-10)- Engine (49-21)- APU and generator lubrication system (49-27)- Fuel system (49-31)- Ignition/starting system (49-41)- Air system (49-50)- Control system (49-61)- Indicating system (49-70)- Exhaust system (49-81)- Oil indicating system (49-94)

Control System

An APU controller controls APU system functions and is an interface with other airplane systems.

Power Plant

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.

The power plant has these systems and components:

- Auxiliary power unit- APU mounts- APU wire harness- APU air intake- APU drains and vents

EngineThe APU engine has these components:

- Two-stage centrifugal flow compressor- Reverse flow annular combustion chamber- Three-stage axial flow turbine

APU and Generator Lubrication System

The APU and generator lubrication system lubricates and cools these components:

- APU bearings- Gearbox- Electric generator

Oil Indicating System

The APU oil indicating system supplies this data about the APU oil to flight deck displays:

- Temperature- Pressure- Quantity

Engine Fuel System

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.

Ignition/Starting System

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 SystemThe APU exhaust system sends the APU exhaust gases out of the tail cone.



APU GENERAL DESCRIPTION

AUXILIARY POWER UNIT

POWER PLANT

ENGINE

APU AND GENERATOR

ENGINE FUEL

IGNITION/STARTING

AIR

CONTROL

INDICATING

EXHAUSTOIL INDICATING

LUBRICATION

GENERATORAPU

ACCESSORIESGEARBOX AND

SECTIONPOWER

COMPRESSORLOAD



AUXILIARY POWER UNITINTRODUCTION

General

The airborne auxiliary power system supplies electrical and pneumatic power for the airplane. On the ground, this electrical and pneumatic power make the airplane independent of ground support equipment. The APU can be started up to 43,100 feet.

The Garrett GTCP (Gas Turbine Compressor Powered) 331-200ER engine is electronically controlled. The APU control unit or Electronic Control Unit (ECU) supervises all operations of the APU. The ECU is located in the Main Equipment Center - MEC. The E6 rack contains the APU battery, and battery charger. The ECU coordinates the starting sequence, monitors the operation and pneumatic output of the APU and ensures proper shutdown. The ECU features extensive built in test equipment (BITE) that monitors many line replaceable units. It also initiates protective shutdowns to prevent damage to the APU. These shutdowns and failed components are shown on the front face of the ECU.

The airborne auxiliary power system is controlled from the APU control panel located on the P5 panel. This panel features a three-position rotary switch, and fault and run annunciator lights. EICAS shows APU exhaust gas temperature (EGT), RPM. To shut down the APU, turn the control switch off. To shut down the APU during an emergency pull the APU fire handle on the P8 panel, or activate the APU shutdown switch on the APU remote shutdown panel (P40) located on the aft side of the nose gear. When the APU is shut down using the P40 APU shutdown switch, the battery switch in the flight deck must be cycled off and on before the APU can be started.



49-00-977565M

INTRODUCTION



AUXILIARY POWER UNITGTCP 331-200ER

General

The APU, with generator installed, weighs approximately 518 lbs (235 kg). It is capable of supplying 115 volt ac, 3-phase, electrical power up to the airplane service ceiling. Pneumatics are available to an altitude of 19,000 feet. The APU supplies enough pneumatics to start the main engines up to an altitude of 14,000 feet and to maintain a 24 degrees C cabin on a 40 degrees C day at sea level.

Pneumatic Modes and Control

The ECU senses six different pneumatic modes of operation from the airplane pneumatic systems. The ECU positions the IVGs in response to these modes to assure efficient operation and load compressor surge control.

If both electrical and pneumatic demands are present, the ECU reduces the pneumatic output as necessary to prevent exceeding APU EGT limits.

Harness

All electrical wiring to the APU, except APU generator and starter motor connections, are contained in a single wire bundle. The wire bundle is attached to the APU and stays with the APU during removal. It is connected to the airplane with two electrical connectors at the APU firewall.

Air Intake and Exhaust

Air for the APU enters the right side of the fuselage through the APU air intake door located below the vertical stabilizer. Between the intake door and the APU firewall is approximately 10 feet (3 meters) of composite air ducting leading into the air intake plenum. Air flows from the APU air intake plenum into the top of the APU. APU exhaust is ducted overboard through the tail cone of the airplane. The load compressor supplies compressed air to the airplane pneumatic system through the pneumatic system air supply duct.

Access to the APU air intake door actuator is through the service access door in the lower fuselage.

Drains and Vents

Any liquid accumulated in the APU air intake plenum is drained out the right side of the compartment through the APU air intake drain. The APU plenum drain drains any liquid accumulation in the APU intake into the APU compartment. The APU drain mast located in the right APU access door, drains the APU drain assembly overboard.



STABILIZERBLOCK

APU AIR

APUHARNESS

APU AIR

APU

PLENUMDRAIN

APU AIR

APU AIR

ACTUATOR

(CLAM SHELL DOOR)

SERVICE ACCESSDOOR (RH SIDE)

DUCTING

APUFIREWALL

DUCT

DOOR

APU AIR SUPPLYSHUTOFF VALVE

INTAKE D00R

INTAKE DOOR

APU AIRINTAKE

INTAKE PLENUM

SUPPORTMOUNTS

APUEXHAUST

APU DOORS

(RH APU DOOR)APU DRAIN MASTAPU

BAY ACCESS

INTAKEDRAIN(RH SIDE)

CONTROLS

STA STA1843

STA18091728

49-00-977589M

GTCP 331-200ER



AUXILIARY POWER UNIT - ENGINE

General

The APU engine is composed of three distinct modules:

• Power section • Load compressor • Gearbox

Air flows into both the power section and the load compressor. The power section is a single shafted gas turbine engine which converts air and fuel into shaft horsepower. The shaft horsepower generated by the power section is used to drive the load compressor, gearbox and accessories.

Power Section

The power section consists of a two stage centrifugal flow compressor, a reverse flow annular combustor, and a three stage axial flow turbine. The inlet bearing has a labyrinth seal pressurized with Pressure Compressor Discharge (PCD1) or PCD2 buffer air.

Load Compressor

The load compressor is a centrifugal flow compressor that supplies compressed air for the airplane pneumatic system. It is driven by the power section. Inlet guide vanes regulate the amount of airflow through the compressor. Both load compressor bearings have labyrinth seals pressurized with PCD1 or PCD2 buffer air.

Gearbox

The gearbox is also driven by the power section. It contains gears and drive pads for the various APU accessories including the APU generator.



SEALSLABYRINTH

VANES

GUIDE

INLETSEAL

LABYRINTH

COMPRESSORBLADESCOMPRESSOR

BLADE

COMPRESSOR

LOADGEARBOX POWER SECTION

BLADES

TURBINE_______________

AIR FLOW

CROSS SECTION

AIR INLET

49-00-980562M

ENGINE



AUXILIARY POWER UNITAPU SYSTEMS AND COMPONENTS

Systems

Primary APU systems include:

• Air intake • APU and generator lubrication • Engine fuel • Ignition/Starting • Air system • Control • Indicating

Air Intake System

External ambient air enters the APU through an APU air intake door. This door is located on the upper right side of the fuselage next to the vertical stabilizer. An electrical actuator drives the door open to allow air into the APU air inlet plenum. Air that enters the plenum is used for cooling, supporting combustion and as a pneumatic power source.

APU and Generator Lubrication System

The APU uses a common oil system to cool and lubricate the bearings, gearbox and generator of the APU. The APU generator has a separate, non-bypass oil filter. If the generator should fail, the filter protects the rest of the APU from damage.

Engine Fuel System

The APU engine fuel system regulates and distributes fuel for engine combustion and pneumatic control.

Ignition and Starting System

The APU is started by using a 28 VDC powered electric motor. A single ignitionunit sends a high voltage to the igniter plug that sparks combustion.

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.



AIRPLANE PNEUMATICDEMAND SIGNALS

EGT SENSORS

SHUTTLEVALVE

PRIMARYFUEL

SECONDARY FUEL

INLETTEMPSENSOR

LOADCOMPRESSOR

APU AIR INTAKE DOOR

GUIDE VANEACTUATOR

INLET INLETPRESSURESENSOR

VALVESWITCHING

FLOWSENSOR

LOW OIL PRESS SWITCH

OIL TEMPSENSOR

INLET GUIDE VANES

OIL TEMP SWDE-OIL SOL

GEN OIL FIL

SWITCHDIFF PRESS

STARTER MOTOR

SOLENOIDVALVE

DE-OIL

EICASCOMPUTERS

GEARBOXPRESSREG VLV

APU GEN

VALVE SURGE VALVE

APU EXHAUST

MONOPOLES

POWER SECTION

IGNITER

APU

EXHAUST

COOLINGAIR

UNITIGNITION

FUEL

PNEUMATICS

FLOW DIVIDER

FUEL CONT UNIT

OIL QTY

APU AIR

APU CONTROL UNIT(E6)

w

a

RUN

FAULT

APU CONTROL PANEL (P5)

APU FIRE DETECTION

APU FAULT (C)

APU DOOR (SM)APU OIL QTY (SM)APU BITE (M)

ONSTARTOFF

APU

NOZZLES NOZZLES

EICAS DISPLAY UNITS(P2)

SHUTOFFAPU FUEL

VALVE

49-00-980564M

APU SYSTEMS AND COMPONENTS



APU ENGINEGEARBOX 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.



FRONT VIEW

COOLING FAN

GENERATOR

GENERATOR SCAVENGE PUMP

STARTER MOTOR

OIL PUMP ASSEMBLY

FUEL CONTROL UNIT

49-27-980561M

GEARBOX AND ACCESSORIES



ENGINE CONTROLSELECTRONIC 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.



28V DC

START/O N

ECS DEM AND

FIRE

MES

ECS ENA BLE

AIR SUP PLY V ALVE

INLET D OOR

AIR/GRO UND

EGT 1

EGT 2

LCIT

P2

PT

TP

OIL TEM P

LOP

STARTER POWE R

GEN OIL FILT ER

CONT ROL P ANEL "RUN" LIGH T

EGT

RPM

APU FAULT RELA Y

AIR SUPPL Y REL AY

DE-O IL SO LENOI D

FUEL SOLE NOID

IGNI TION

LVDT EXCI TATIO N

AIRCRAF TDISCRET E

GEN LOADAVAI LABLE

SURG E VAL VE

FLOW DIVI DERSOLE NOID

EICAS

APUDISC RETE

APUANALOG

CONTROLSW (P5)

AIRCRAFTANALOG

AIRCRA FTDISCRE TE

SIGN ATUREPIN

APU

ANAL OG

APUDISCRE TE

FAN VAL VE

TORQ UEMOT OR

ADP

IGV TORQU EMOTO R

SPD 1

SPD 2

IGV POS ITION

M206 APU CONTROL UNIT (ECU)

757/7 67

STAR T REL AY (K 1)

STAR T REL AY (K 197)

APU FUEL C0NT RLY

FUEL CONT TORQ UEMOT OR

+10V DC R EF

DOOR RLYINLET

SPARE

FLOWREVERSE

DOORSYSTEM

NORMALSTOP SIG

#1 SPD SENSOR

EGT #1CIRCUIT

DIV SOLFLOW

SENSORP2

LAST RUNCURRENT/

LCITSENSOR

SPARE

EGTOVERTEMP

EMERGFIRE

#2 SPD SENSOR

EGT #2CIRCUIT

CONTROLECS

ECU

SHUTDOWN2

FAILURECONTROL

SOLFUEL

DATANO

O/S TESTCIRCUIT

SWITCHLOP

IGVACT

STARTERAPU

VALVEFAN

3

UNDER

SENSORPT

WAIT

LOW OILPRESSURE

TEMPHIGH OIL

ABORTEDSTART

CONTROLFUEL

IGNUNIT

CIRCUITA/C STRT

FILTERSW(GEN)

4SHUTDOWN

SENSOREP

OKTEST

SPEEDOVER

FILTERGEN

VALVESURGE

DEOILSOL

HOTSENSOR

SEE MNTMANUAL

SUMMARYLRU

LIGHTOFFNO

SPEED

DC PWRLOSS

RECORDSELECTED

LRUFAULTY

STATUS

OPERATINGAPU NOTREASON

SHUTDOWN

LRU SUMMARY - Record of all Faulty LRUs detected since the

last Memory Erase.

the associated shutdown.Displayed Faulty LRUs are only the failed LRUs that could cause

commanded APU stop and all Faulty LRUs detected during last

displayed Faulty LRUs are only the failed LRUs that could causerun can be displayed. If Reason is an automatic shutdown,

ROTA RY SWITCH OPERATION

___________

_____

________LAST RUN

the shutdown.

SELF

LAMP

SELECT

RD

RECO

LRU

REASON

TEST

FAULT

ERASEMEMORY

2.3.4 - Second, third, and fourth historical fault shutdowns.

- If Reason is NORMAL STOP SIG, the aircraft

49-60-R18776M

ELECTRONIC CONTROL UNIT (ECU) INPUTS OUTPUTS



POWER PLANTAIR 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 COMPRESSORINLET PLENUM

PANELACCESS

ACCESS DOORCONTROLS BAY

AFT APU AIR

INTAKE DUCTFWD APU AIR

INTAKE DUCT

SERVICE

PLENUMINTAKEAPU AIR

PANEL

(REF)SECTION

DOORACCESS

CENTERSTABILIZER

APUFIREWALL

PLENUMAPU

ACCESS

INTAKEDOOR

APU AIR ACTUATORDOORINTAKEAPU AIR

PORTINTAKEAPU AIR

49-16-977595M

AIR INTAKE SYSTEM



POWER PLANTAIR INTAKE DOOR AND ACTUATOR OPERATION

Air Intake Door

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

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.

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



SERVICEACCESS DOOR

APU AIR INTAKEDOOR

ACTUATORINTAKE DOORAPU AIR

DUCT

DOOR FLANGEAPU AIR INTAKE

DOOR ACTUATORAPU AIR INTAKE

CLAMPV-BAND

SQUARE DRIVEACTUATOR CLUTCH

CONTAINERACTUATOR

SQUARE DRIVEACTUATOR

DOOR POSTITIONADJUSTMENTFITTING

(SHOWN IN MANUAL DRIVE POSN)

CLUTCH POSITION FLAG

GROUNDINGSTRAP

AIR INTAKE DUCT)(ATTACHED TO APUDOOR OPEN SWITCHS506 APU INTAKE

AIR INTAKE

TO DOOR)TARGET (ATTACHEDOPEN SW MAGNETICAPU INTAKE DOOR

(REMOVABLE)DOOR SEALAIR INTAKE

PLATEHINGE COVER

ACTUATOR RODEND FITTING

SCREWS (4)FITTINGROD END

ROD ENDACTUATOR

(BONDED)DOOR SEALAIR INTAKE

DOORAIR INTAKE

TRANSFER

SELECTOR SHAFTMANUAL/ELECTRICAL

FLAG

SOCKETDRIVEMANUAL

ELEC

MAN

49-15-977593M

AIR INTAKE DOOR AND ACTUATOR OPERATION



POWER PLANTAIR 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.

• CASE 3: The actuator position is also compared to the door position as sensed by the door open switch (S506) and the door open relay (K547). If a ground is available longer than 60 seconds the EICAS message APU DOOR appears.

If S506 fails closed (door open signal) the ECU starts the APU before the door is fully open.



EICAS DISPLAY UNITS

L & R EICASCOMP

60 SEC

DOOR OPEN RLY (P49)

K547 APU INTAKE

DOOR OPEN SWS506 APU INTAKE

"DOOR OPEN"SIGNAL TOECU

DOOR ACTUATOR M406 APU INTAKE

ON

OFF

START

K175 APU

OFF

ENERGIZED - NO FAULTS - NO FIRE - FIRE SW "NORMAL" - APU SW "ON" - MAIN BAT. SW "ON"

FUEL CONTRLY (P37)

M206 ECU (E6-1)

R11

R12

DOOR ACTUATOR

APU INTAKE

C1385

APU ALTN CONT CB

C1391

APU START

C20

APU PRIME CONT CB

C1383

28V DC APUBAT. BUS

P11 CIRCUIT BREAKER PNL

BAT. BUS28V DC MAIN

INTAKE DOORK176 APU

AFT EQUIP CENTER (E6)

28V DC APUBAT. BUS

STARTOFFON

N>15%

M

DOOR FULL CLOSED

RETRACT

EXTEND

DOOR FULL OPEN

E6 AFT EQUIP CTR

RLY (P49)

ON

S2 MAINBAT. SW(P5)

S1 APU SW(P5)

FUEL DRIVER

APU DOOR(S,M)

INTAKE DOOR &

FULL OPEN

49-70-R187949-70-

AIR INTAKE DOOR INDICATION



APU ENGINELUBRICATION 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.

Gearbox Pressurization System

At higher altitudes (approximately 18,000 ft), the low ambient air pressure could cause oil foaming. The gearbox pressurization system prevents this by pressurizing the gearbox with 2nd stage compressor air (PCD2). Components include a gearbox shutoff valve, a shuttle valve, and a gearbox pressure regulating valve. Operation is automatic and controlled pneumatically. This system also increases bearing seal buffering air pressure at high altitudes.

ECU Bite

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).



GENERATOR

GENERATOR

FRONT VIEW

DRIVE PAD

APU

AND SEAL

COOLINGFAN (REF)

GEARBOXPRESSUREREGULATINGVALVE

DEOILSOLENOIDVALVE

GEN OILFILTER DPSWITCH

OIL PUMPAND FILTERASSY

OILCOOLER

OIL FILLPORT

PLATE (REF)

SCAVENGEOIL PUMP

OIL COOLERBYPASS VALVE

GEN OILFILTER

LEVEL SWITCHLOW OIL

SW (GEN)FILTER

LOP

DEOIL

GEN

HOT

DOOR RLYINLET

SPARE

FLOWREVERSE

DOORSYSTEM

NORMALSTOP SIG

#1 SPD SENSOR

EGT #1CIRCUIT

DIV SOLFLOW

SENSORP2

LCITSENSOR

SPARE

EGTOVERTEMP

EMERGFIRE

#2 SPD SENSOR

EGT #2CIRCUIT

CONTROLECS

ECU

FAILURECONTROL

SOLFUEL

DATANO

O/S TESTCIRCUIT

SWITCH

IGVACT

STARTERAPU

VALVEFAN

UNDER

SENSORPT

WAIT

LOW OILPRESSURE

TEMPHIGH OIL

ABORTEDSTART

CONTROLFUEL

IGNUNIT

CIRCUITA/C STRT

SENSOREP

OKTEST

SPEEDOVER

FILTER

VALVESURGE

SOL

SENSOR

SEE MNT

MANUAL

LIGHTOFFNO

SPEED

DC PWRLOSS

SHUTDOWNLAST RUNCURRENT/ SHUTDOWN

2 3 4

SHUTDOWNSUMMARYLRURECORD

SELECTED

LRUFAULTY

STATUS


TEMP SWITCHVALVE LOWSOLENOIDDE-OIL

DETECTOR PORTMAGNETIC CHIPAPU GENERATOR

UP

VALVETO SURGE

FWD

M206 ECU

SHUTTLEVALVE

PCD 1

VALVESHUTOFFGEARBOX

VALVE (REF)

LOW TEMP SWITCHDE-OIL SOLENOID

SENSORHOT

SWITCHLOP

FAN ISOLATION

PCD 2

LEVEL SWITCHLOW OILLEVEL SWITCH

LOW OIL

49-27-R78294

LUBRICATION SYSTEM



APU ENGINEOIL 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.



PRESSURE FILL

PROVISIONS

FRONT VIEW SIDE VIEW

DE-OILSOLENOID

SWITCH FILL PORT AND SCUPPER DRAIN

OIL LEVEL TO EICAS

VALVELOW TEMP OIL

LEVELSIGHTGLASS

OIL RESERVOIR DRAIN PLUGAND MAGNETIC CHIP DETECTOR

49-27-980555M

OIL SUPPLY AND RESEVOIR



APU ENGINE - OIL SYSTEM

General

Operation of the APU oil system is automatic. Pressure regulation, cooling, de-oiling, and protective monitoring all occur without external control or indication.

Oil System Protective Shutdowns

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.

Low Oil Pressure (LOP)

The LOP switch is normally open, and is closed by pressure. An oil pressure of less than 31 psig for 15.5 seconds causes a LOW OIL PRESSURE protective shutdown. If a LOW OIL PRESSURE protective shutdown occurs during a start attempt the time limit for oil pressure to reach 31 psig decreases from 15 seconds to 1 second on the second start attempt. If the second start fails to meet the new oil pressure requirements, all further starts are inhibited. This start inhibit is indicated during an APU BITE procedure by a flashing LOW OIL PRESSURE lamp. To remove the start inhibit, erase the ECU's memory.

LOP SWITCH

The low oil pressure switch is tested by the ECU during pre-start and self-test BITE. If the switch fails in the closed (ground) position, the ECU records LOP SWITCH as a faulty unit. APU start is inhibited. If the switch fails in the open position, this fault remains undetected by the ECU until an APU start is attempted. With no signal of oil pressure, the ECU initiates the false LOW OIL PRESSURE protective shutdown.

High Oil Temperature (HOT)

A protective shutdown is initiated at a sensed oil temperature greater than 154o C.

HOT Sensor

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

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.

Gen Filter Switch

The switch is normally closed. If it is found open during the Prestart BITE, FILTER SW(GEN) is stored as a faulty LRU. The APU starts and operates normally but does not have blocked generator filter protective shutdown capability. If it opens while the APU is running, a protective shutdown occurs.

Scavenge Pump

The scavenge pump is a gear pump that scavenges oil from the APU compressor bearings. The pump is driven by the gearbox and provides about 4 gpm of scavenge oil flow.

Oil Pump Assembly

The oil pump assembly is bolted to the gearbox case. The pump assembly is an LRU but requires removal of the fuel control unit for access. The assembly consists of the pressure pump, scavenge pump, pump relief valve, oil filter with a differential pressure pop-out indicator, and the pressure regulator valve. The pressure pump is a gear-type pump that supplies 12 gpm of oil flow to the lubrication system. The gearbox drives the pump through a spline shaft. The pump relief valve prevents oil system over pressurization. The valve is a spring loaded piston and sleeve unit. The valve opens at 200 +/- 5 psid. It is an LRU. The oil filter is a pleated fiberglass 10 micron nominal disposable filter element. It is housed in a screw-on cap and requires maintenance every 500 hours. There is no filter bypass.



OIL SYSTEM

MAG CHIP DET

SCREEN

OIL JETROLLER BEARINGBALL BEARING

VENTPRESSURINGAIR LINESCAVENGESUPPLYPRESSURE

SHUTTLE VALVEMAG CHIP DET2

1

RELAYAPU FAULT

VALVESURGETO

AIRBUFFERFAN

1

SWITCHPRESSURELOW OIL

SENSORTEMPERATURE

OIL

T

APU OIL QTY (S,M)APU BITE (M)

K175

< -4C

OIL QTY

GEARBOX DRAIN

GEARBOX

APU FAULT (C)

(STARTER)28V DC

TEMP SWDE-OIL SOL

GEN

FILTER ASSYPRESS SWFILTER DIFF

POWER

95% SPEED

1ST STGAIR

SEAL BUFFER

VENT

PUMPBRG SCAVENGETURBINE

EXHAUST

DETECTORPLUG MAG CHIP

PUMPSCAVENGE

CLUTCHSTARTER

FAN BRGCOOLING

P

AIRBUFFER

AIR/OIL SEPARATOR

PORTTEST

FILTERPRESSURE

OIL PUMP ASSEMBLY

VALVESOLENOIDDE-OIL

GEN OILGEN OIL

PRESS PUMP

VALVEREGPRESS

PUMP RELIEF VLV

COOLERAIR/OIL

VALVEBYPASSTHERMAL

A

(L1) APU FAULT

A

CONT RLYAPU FUEL

28V DC

SOFTWARE

HARDWARE+28VSUPPLYPWR

10 SEC

OIL TEMP S/D

SPEED > 7%

SPEED < 95%

PRESS S/DLOW OIL

GEN FILTER S/D

POWER

START/ON SIGNAL

START RLY ENERGIZED

SENSINGTEMP

OIL T >46C

T <6.7 6.6C

T >154C

2NDSTAGE

GEARBOXSWITCH-INGVALVESEAL


95% SPEEDLOGICLOP

CONDSIG

M206 APU CONTROL UNIT (ECU) (E6)

M1 APU CONT PNL (P5)

5 SEC

EICAS COMPUTERS

MD&T

STATUS ECS/MSG

2

2

TO EICAS



APU ENGINE - OIL SYSTEM (CONT.)

Oil Pump (Cont.)

The oil filter differential pressure indicator is a standard pop-out type indicator. It activates at 20 +/- 5 psid across the pressure filter. The indicator is mechanically locked when the oil temperature is below approximately 46 degrees C. This prevents viscous cold oil from activating the indicator. It is an LRU. The pressure regulator valve regulates the output pressure from the oil pump assembly to 65 +/- 5 psid. It is a spring-loaded piston and sleeve valve. It is an LRU, but is not line adjustable.

Pump De-Oiling System

Cold, viscous oil causes a high drag on the APU during starts, possibly leading to START ABORTED protective shutdowns. Adding air to the oil unloads the system. The de-oil solenoid valve, when energized, ports gearbox air to the inlet of the pressure pump. The pump de-oils during normal shutdowns and during starts when APU oil is cold.

Operation

To prepare the APU for the next start, the ECU energizes the de-oil valve solenoid during the normal shutdown cycle. When the APU control switch is in the OFF position and APU RPM is less than 95%, the ECU energizes the solenoid. When APU RPM drops below 7% the ECU de-energizes the solenoid, terminating de-oiling. The solenoid is an LRU.

Two temperature sensors, wired in parallel, are also used to energize the de-oil valve solenoid. The HOT temperature sensor senses oil temperature in the oil

manifold. If the temperature is less than -6.7 +/- 6.6oC and a start is requested, the ECU energizes the solenoid. When an APU start is attempted after an aircraft descent from extended cold soak conditions, the manifold temperatures might recover more rapidly than other parts of the oil system. To allow the de-oil solenoid to energize during these conditions, a dedicated de-oil low temperature switch energizes the solenoid.

The de-oil solenoid low temperature switch is mounted in the generator scavenge cavity. When 28 volts dc is available at the starter terminal, and the cavity oil temperature is less than approximately minus 4 degrees C, the de-oil solenoid energizes. An in-line fuse protects the wiring. If the fuse is open, A/C

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.



MAG CHIP DET

SCREEN

OIL JETROLLER BEARINGBALL BEARING

VENTPRESSURINGAIR LINESCAVENGESUPPLYPRESSURE

SHUTTLE VALVEMAG CHIP DET2

1

RELAYAPU FAULT

VALVESURGETO

AIRBUFFERFAN

1

SWITCHPRESSURELOW OIL

SENSORTEMPERATURE

OIL

T

APU OIL QTY (S,M)APU BITE (M)

K175

< -4C

OIL QTY

GEARBOX DRAIN

GEARBOX

APU FAULT (C)

(STARTER)28V DC

TEMP SWDE-OIL SOL

GEN

FILTER ASSYPRESS SWFILTER DIFF

POWER

95% SPEED

1ST STGAIR

SEAL BUFFER

VENT

PUMPBRG SCAVENGETURBINE

EXHAUST

DETECTORPLUG MAG CHIP

PUMPSCAVENGE

CLUTCHSTARTER

FAN BRGCOOLING

P

AIRBUFFER

AIR/OIL SEPARATOR

PORTTEST

FILTERPRESSURE

OIL PUMP ASSEMBLY

VALVESOLENOIDDE-OIL

GEN OILGEN OIL

PRESS PUMP

VALVEREGPRESS

PUMP RELIEF VLV

COOLERAIR/OIL

VALVEBYPASSTHERMAL

A

(L1) APU FAULT

A

CONT RLYAPU FUEL

28V DC

SOFTWARE

HARDWARE+28VSUPPLYPWR

10 SEC

OIL TEMP S/D

SPEED > 7%

SPEED < 95%

PRESS S/DLOW OIL

GEN FILTER S/D

POWER

START/ON SIGNAL

START RLY ENERGIZED

SENSINGTEMP

OIL T >46C

T <6.7 6.6C

T >154C

2NDSTAGE

GEARBOXSWITCH-INGVALVESEAL


95% SPEEDLOGICLOP

CONDSIG

M206 APU CONTROL UNIT (ECU) (E6)

M1 APU CONT PNL (P5)

5 SEC

EICAS COMPUTERS

MD&T

STATUS ECS/MSG

2

2

TO EICAS

49-27-R54281M

OIL SYSTEM (CONT)



APU ENGINEGEARBOX 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.



SHUTOFF VALVEGEARBOX

GEARBOXPRESSUREACTUATOR

DISCHARGE

SEAT

PRESSURE

NO REGULATION

AMBIENTVENTED

PCD 2

GEARBOXPRESSURE

GEARBOXPRESSURE

PCD 2

DISCHARGE

GEARBOX

TO TAILPIPEVENT

TOTAILPIPEVENT

PRESSURIZEDPRESSURIZEDREGULATED

GEARBOXPRESSURIZATIONAIR

PCD 2

TO SURGEVALVE

SHUTTLEVALVE

TO SURGEVALVE

VENT TOTAILPIPE

TO PCD 2PORT

SLEEVE

POPPET

SHUTOFFGEARBOX

VALVE

BUFFERAIR

SEAL

PCD 1

TO TAILPIPE SHUTTLE VLV

GEARBOX PRESSURE

VENT

AIR/OILSEPERATOR

BUFFER AIRFAN SEAL

COOLINGFAN

BUFFERAIR

BEARINGSEALBUFFERAIR

REGULATING VALVE

49-27-980544M

GEARBOX PRESSURIZATION SYSTEM



APU ENGINEAPU 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 delta pressure (pop-out) indicator activates at 20 psid. A mechanical lock-out prevents activation from DELTA-P when the oil temperature is less than

46OC.

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.



M206 ECU (E-6)

CAVITYGEN SUMP

DRIVE PADGENERATOR

FILTER DIFFERENTIALPRESSURE SWITCH

GENERATOR OIL

PRESS SW

TURBINE SCAVENGE PUMP

POWER

35 PSID

(POP-OUT)INDICATOR

OIL TEMP >46C

FILTER ASSEMBLYGENERATOR OIL

SCAVENGE PUMPGENERATOR

FILTER ASSEMBLYGENERATOR OIL

PRESSUREDIFFERENTIAL

PUMPSCAVENGEBEARINGTURBINE

SOFTWARE

(HOT SENSOR)

PUMP

GEARBOX

SCAVENGE

FILTER DIFF

FILTER ASSYGEN OIL

GEN OIL

GENERATOR

OIL PUMP ASSY

SHUTDOWNPROTECTIVEGEN FILTER

49-27-R18972M

APU AND GENERATOR OIL SCAVANGE SYSTEM



ENGINE FUEL AND CONTROLFUEL SYSTEM

General

The APU receives fuel from the left fuel feed manifold through a flexible, shrouded line. The APU uses fuel for combustion and for muscle pressure to operate the inlet guide vane actuator (IGVA).

The components of the APU fuel system include the fuel control unit, flow divider, primary and secondary fuel manifold and nozzles, and the inlet guide vane actuator.

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

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 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 UNITPOP-OUT INDICATOR

TORQUE MOTOR

FUEL CONTROL

FUEL FILTER

FRONT

FUEL SHUTOFFSOLENOID VALVE

VALVESOLENOID

INLET GUIDE VANE ACTUATOR(IGVA)

FUEL MANIFOLDSFLOW DIVIDER

(LCIT)

TEMP SENSORAPU INLET

FUELMANIFOLD

APU INLET

(P2)PRESS SENSOR

INFLOW

FUEL FILTER

(REF)MONOPOLE

OUTFLOWSECONDARY

OUTFLOWPRIMARY

(REF)

CONTROLFUEL

IGVASURGE

VALVECONTROL

(BEHIND SURGE VALVE)FUEL FLOW DIVIDER

LEFT SIDE

UNDER START

OVER

FUEL

FLOW

FUEL

REASONAPU NOTOPERATING

STATUS

FAULTYLRU

SELECTEDRECORD LRU

SUMMARYSHUTDOWN

432SHUTDOWNCURRENT/

LAST RUNSHUTDOWN

LOSSDC PWR

SPEEDNO

LIGHTOFF

MANUALSEE MNTSENSOR

SOL

SURGEVALVE

FILTER

SPEEDTESTOKKP

SENSOR

A/C STRTCIRCUIT

UNITIGN

CONTROL

ABORTED

HIGH OILTEMP

PRESSURELOW OIL

WAIT

PTSENSOR

FANVALVE

APUSTARTER

ACTIGV

SWITCH

CIRCUITO/S TEST

NODATA

SOL

CONTROLFAILURE

ECU

ECSCONTROL

CIRCUITEGT #2 SENSOR#2 SPD

FIREEMERG

OVERTEMPEGT

SPARE

SENSORLCIT

P2SENSOR

DIV SOL


STOP SIGNORMAL

SYSTEMDOOR

REVERSE FLOW

SPARE

INLETDOOR RLY

HOT

GEN

DEOIL

LOP

FILTERSW(GEN)

49-31-R18975M

FUEL SYSTEM



ENGINE FUEL AND CONTROLFUEL SYSTEM (CONT.)

General

Fuel scheduling is automatically controlled using software in the ECU. The ECU maintains APU RPM by metering fuel through signals to the fuel control torque motor. Two major schedules are utilized. One for acceleration, and one for on-speed operation. Switchover occurs at 95 percent sensed speed.

ECU fuel scheduling requires speed signals from the monopoles, EGT from the T5 thermocouples, inlet air pressure from the P2 sensor, and inlet air temperature from the LCIT Sensor. Alternate values are utilized by the ECU software if P2 or LCIT signals fail. Speed and EGT signals have redundant inputs to the ECU.

Acceleration Scheduling

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.

Fuel Shutoff Solenoid Valve

The fuel shutoff solenoid valve is energized at or above 7 percent RPM if hardware or software protective shutdowns are not detected.

Fuel Flow Divider

The fuel flow divider distributes metered fuel to the primary and secondary fuel manifold for combustion. It is located behind the surge control valve on the lower left side of the APU. It is an LRU. Components include an inlet screen, sequence valves, drain valves, and an ECU controlled solenoid. The inlet screen is a 200 micron cleanable LRU. The Flow Divider Solenoid is monitored by an ECU test of the solenoid in Prestart and Self-Test for opens, shorts and overcurrent. FLOW DIV SOL is stored in the ECU Fault memory if a fault is detected. A short causes the ECU driver to turn off to protect the ECU, leading to the same symptoms as for a solenoid valve which fails to open.

Operation

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.



(OPTION)

TANKDRAIN

MASTDRAIN

INLET GUIDE

VANE ACTUATOR

LOW PRESSURE FUEL

HIGH PRESSURE FUEL

METERED FUEL

REGULATED HIGH

PRESSURE FUEL

SEALDRAIN COMBUSTOR

OIL PUMP

GEARBOX

DRAIN

FUEL FLOWDIVIDER

VALVE

SECONDARY

VALVERUN SEQ

START SEQ

INLETFILTER

METERINGASSEMBLY

PLENUM

FUEL

FUELINLET

PUMP

DIVIDER SOLENOID

B

FUEL FLOW

VALVE 100 PSIG

VALVE 35 PSIG

FUEL

FUEL

AIR INLET

PRIMARY DRAIN VALVE

ASSEMBLY

TO ECU

FUEL NOZZLESSECONDARY

FUEL NOZZLESPRIMARY

SCREEN(SELF BYPASSING)

FLOWDIVIDER

SOLENOIDVALVE

SPRING

SCREEN

FUEL INLETOVERBOARDDRAIN PORT

SECONDARY NOZZLEPORT

PRIMARY NOZZLE PORT

FWD

FLOW DIVIDER

(LOCATED BEHIND AND UNDER SURGE VALVE)

______________

49-31-R18976M

FUEL SYSTEM



ENGINE FUEL AND CONTROLFUEL CONTROL UNIT

General

The fuel control unit filters, pressurizes and meters the fuel flow for supply to the flow divider. It is mounted to the front flange of the oil pump assembly with a quick attach/detach clamp. The fuel control unit is an LRU. The fuel control unit consists of the following components.

Inlet Filter

The FCU inlet filter is a 10 micron disposable filter. The filter housing is bolted to the FCU. The FCU contains a filter bypass valve and a filter differential pressure indicator. The differential pressure indicator activates at 5 psid across the filter. The bypass valve activates at 8 psid across the filter. The inlet filter and the bypass valve are both LRUs.

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.

Actuator Pressure Regulator

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.

High Pressure Relief Valve

The high pressure relief valve protects the fuel system against over pressurization. It has a crack point pressure of 950 psid.

High Pressure Filter

The high pressure filter is a cleanable stainless steel screen. It is an LRU.

Torquemotor Metering Valve

The torquemotor metering valve controls the fuel flow output from the fuel control unit. The valve's position is electronically controlled by the ECU. The metering valve controls the fuel supplied to the flow divider to between 0 and 660 lbs/hr (299 KG/HR). The torquemotor consists of a keyhole shaped metering port and a clevis valve. Electrical current from the ECU is sent to a coil, causing the clevis valve to move, which controls the metering port opening. The metering valve current is a function of APU speed, inlet temperature and pressure; and is limited by T5 (EGT). The torquemotor is not an LRU.

Differential Pressure Regulator

The differential pressure regulator maintains a constant differential pressure of 50 psid across the metering valve. This constant differential pressure creates a linear relationship between fuel flow and torquemotor current.

Pressurizing Valve

The pressurizing valve is a spring-loaded-closed valve. It opens at fuel pressures of 100 psid or more. It prevents a fuel flow output until at least 100 psid is present.

Fuel Shutoff Solenoid Valve

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.



FUEL SHUTOFF

ACTR PRESS REG

FUEL METERINGVALVE

PRESSURIZINGVALVE

METERED FUEL OUT

FUEL CONTROL UNIT

TORQUE MOTOR

T

APU FUELFEED SYSTEM

HIGH PRESSRELIEF VALVE

LEGEND

LOW PRESS FUEL

REGULATED HIGH PRESS FUEL

METERED FUEL

M

HIGH PRESS FUEL

PUMP

DIFFPRESS REG

TEST PORT

FUEL CONTROL (DE-ENERGIZED)

TORQUE MOTORMETERING VALVE________________

______________

_______________________

TO ECUTO ECU

IGV ACTUATOR

FUELHIGHPRESSFILTER

FUEL FILTER ELEMENT

SOLENOID VALVE

FUEL SHUTOFF

(ENERGIZED)SOLENOID VALVE

TORQUE MOTORFUEL CONTROL

SHUTOFF

TEST PORT

FILTERBYPASS VALVE

OUTPUT

ACTUATOR

METERED FUEL

SUPPLY PORTREGULATOR AND

RETURN PORT

INLET FILTERDIFFERENTIAL

FUELINLET

FUEL

VALVE

PRESSUREFILTER (POP-OUT)

PRESSURE INDICATOR

ACTUATOR PRESSURE

FUEL CONTROL UNIT

FUEL HIGH

FUEL FILTER ELEMENT

SOLENOID

QUICK ATTACHDETACH CLAMP

OIL PUMP ASSY(REF)

METERINGPORT

FUEL INLETPORT

CLEVISVALVE

49-31-R20888M

FUEL CONTROL UNIT



POWER PLANTDRAIN 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.



DRAIN MAST(RIGHT APU ACCESS DOOR)

FLOW DIVIDER& HEAT SHIELDDRAIN

BEARING SEALCAVITY VENT

TURBINEPLENUMDRAIN

_____________APU DRAINS

(BOTTOM VIEW)

FUEL-OIL PUMPS& INLET GUIDEVANE ACTUATOR

FWD

MID BEARINGSEAL CAVITY

SEAL CAVITYFORWARD BEARING

APU INLETPLENUM DRAINFUEL CONTROL UNIT/

OIL PUMP

ACTUATORIGV

(VIEW LOOKING FORWARD)TELL TALE DRAINS

OIL

PUMP

TELL TALEDRAINS

PUMP - TELL TALE DRAINFUEL CONTROL UNIT/OIL

FUEL FLOW DIVIDERAND DRAIN VALVE

LAB SEAL

MID - BEARING OIL SEAL

FUEL CONTUNIT

GEARBOX

ACTUATORIGV

OIL SEALBEARINGFORWARD

LAB SEAL

49-15-977600M

DRAIN AND VENT ASSEMBLY



APU IGNITION/STARTING SYSTEMIGNITION AND STARTING SYSTEM

General

The ignition/starting system supplies initial APU acceleration and combustion spark. The system consists of the ignition unit, igniter and the starter motor.

The ignition unit generates igniter spark energy. The igniter provides the spark to the combustor. Ignition unit power is controlled electrically by the ECU.

Operation

The main battery switch must be ON to start the APU. APU start is initiated by rotating the APU start switch momentarily to START and releasing it to ON. The APU air intake door opens, the RUN light blinks twice, indicating completion of the pre-start BITE, and the FAULT light comes on during APU fuel shutoff valve transit. After the door is open the ECU energizes the APU crank contactor to power the starter motor. A 28 VDC dc signal is sent from the starter motor to the ECU when the starter motor has power. If this signal is interrupted for more than 50 msec a DC PWR LOSS protective shutdown occurs. At 7 percent speed the ECU energizes the ignition unit. Starter cutout is a function of altitude with the -19 ECU. At 95 percent speed the ECU de-energizes the ignition unit.

To prevent damage to the APU engine during start attempts at high altitudes, only two starts may be attempted if oil pressure fails to meet the minimum pressure required. Subsequent start attempts are inhibited. See APU oil system operation for details.



49-41-977630M

IGNITION/STARTING SYSTEM



APU IGNITION/STARTING SYSTEMIGNITION SYSTEM

Ignition Unit

The ignition unit is a high energy (4 joule nominal stored energy) high voltage (18 kV) exciter mounted to the compressor case. It converts 28 volt dc into 18 kV output sparks. It generates between 2 and 10 sparks per second for supply to the combustor. The ignition unit is an LRU.

Ignition Lead / Ignitor

The ignition lead is a heavily shielded copper wire conductor that supplies the ignition spark between the ignition unit and the igniter. The lead is an LRU.

The igniter consists of an insulated tungsten alloy center electrode and a hastelloy X tip. The igniter is capable of operating at temperatures above 1500 degrees F (816 degrees C). The igniter screws into its mounting on the combustor case. The igniter is an LRU.

Failure Modes, BITE, and Troubleshooting

The ignition unit is tested in Prestart and Self-Test BITE for opens, shorts or overcurrent up through the primary coil. IGN UNIT is stored in the fault memory. A secondary coil, ignition lead, or plug fault is not detected. The ECU initiates a NO LIGHTOFF protective shutdown.

WARNING: USE CAUTION WHEN REMOVING IGNITION COMPONENTS TO ASSURE THAT RESIDUAL HIGH VOLTAGES ARE BLED, TO AVOID POSSIBLE LETHAL ELECTRICAL SHOCKS.

WARNING: DO NOT PERFORM ECU SELF TEST WHILE PERFORMING IGNITION SYSTEM MAINTENANCE. AN ELECTRICAL BURN FROM EXPOSED IGNITER LEAD COULD OCCUR.



INSULATORCERAMIC

PLUGIGNITER

_____________IGNITER PLUG

__________

AIR HOLESCOOLING

ALLOYTUNGSTEN

HASTELLOY X

RIGHT SIDE

IGNITION UNIT

POWERINPUT LEAD

IGNITION

MOUNTRIGHT REAR

PLUGIGNITER

ECU

HARDWARESOFTWAREGND

CIRCUITS

DISCHARGEAND

TRIGGER

+28V

IGN

IGNITION UNIT

IGNITE

FWD

49-41-B07657M

IGNITION SYSTEM



APU PNEUMATIC SYSTEMPNEUMATIC SYSTEM

General

Air from the intake plenum is used for pneumatic power and APU cooling. A dedicated load compressor, connected to the APU mainshaft, supplies the pneumatic power. A cooling fan supplies air for oil cooling and compartment cooling.

Aircraft Pneumatic Power

Pneumatic power for the aircraft is used for environmental control (ECS), main engine starting (MES), and the air driven hydraulic pump (ADP). Air into the load compressor is regulated by inlet guide vanes (IGV's) in response to air pneumatic demand. This improves the efficiency of the APU because the APU supplies only the pneumatic power required. The IGV's are moved by an IGV actuator that is controlled by the ECU.

A surge valve directs excess pneumatic outflow into the APU exhaust to prevent a load compressor surge. The surge valve is controlled by the ECU using inputs from a flow sensor.

Note: If pneumatic demand causes EGT to exceed operating limits, pneumatic demand is reduced.

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.



(REF)APU GEN MOUNT

(ROTATED FOR CLARITY)

FWD

FLOWSENSOR

COOLEROIL

VALVESURGE

VANE (IGV) ACTUATORINLET GUIDE

AIR DUCTCOOLINGOIL

LCITSENSOR

SPARE

EGTOVERTEMP

EMERGFIRE

#2 SPD SENSOR

EGT #2CIRCUIT

CONTROLECS

ECU

SHUTDOWN2

FAILURECONTROL

SOLFUEL

DATANO

O/S TESTCIRCUIT

SWITCHLOP

IGVACT

STARTERAPU

VALVEFAN

SHUTDOWN3

UNDER

SENSORPT

WAIT

LOW OILPRESSURE

TEMPHIGH OIL

ABORTEDSTART

CONTROLFUEL

IGNUNIT

CIRCUITA/C STRT

FILTERSW(GEN)

4SHUTDOWN

SENSOREP

OKTEST

SPEEDOVER

FILTERGEN

VALVESURGE

DEOILSOL

HOTSENSOR

SEE MNTMANUAL

SUMMARYLRU

LIGHTOFFNO

SPEED

DC PWRLOSS

RECORDSELECTED

LRUFAULTY

STATUS


DOOR RLYINLET

SPARE

REVERSE

DOORSYSTEM

NORMALSTOP SIG

#1 SPD SENSOR

EGT #1CIRCUIT

DIV SOLFLOW

SENSORP2

LAST RUNCURRENT/

FLOW

M206 ECU (E6)

ACCESS PANEL

PRESSURE SENSOR (P2)APU INLET

APU AIR INLETPLENUM

APU INLET TEMPSENSOR (LCIT)FAN

COOLING

49-52-R18797M

PNEUMATIC SYSTEM



APU PNEUMATIC SYSTEMINLET SENSORS

Inlet Pressure Sensor (P2 Sensor)

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.

P2 Sensor Troubleshooting, Failure Modes, and BITE

If the P2 sensor tube is plugged, the APU may experience an OVERSPEED protective shutdown at altitude, because fuel scheduling is excessive. (The ECU thinks it is at low altitude).

If the P2 sensor is plugged in a low pressure (high altitude) mode, the fuel scheduling is reduced. During heavy demand on the APU, the speed decays, causing loss of pneumatic output, followed by the generator going off-line when speeds decay to below 95 percent.

The P2 sensor is tested during the prestart, monitor, and self-test BITE for resistance range. If the APU inlet pressure sensor fails to meet the appropriate resistance range, P2 SENSOR is stored as a faulty LRU. If the failure occurs on the ground, the ECU substitutes a programmed value of 13.66 PSIA, and functions normally. If the failure occurs while airborne, the IGVs close, and the surge valve opens. The APU operates to supply electrical power only. The ECU uses a substitute value from the PT sensor for fuel scheduling. (Part of the flow sensor for the surge valve control.) If PT is also failed, 13.66 PSIA is utilized.

Load Compressor Inlet Temperature Sensor (LCIT or T2 Sensor)

Air inlet temperature is utilized by the ECU for fuel scheduling, IGV positioning and surge projection. The load compressor inlet temperature (LCIT) sensor consists of a chromel-alumel thermocouple assembly.

The assembly consists of two thermocouple probes enclosed in an inconel support tube attached to a common stainless steel header. The thermocouple assembly is mounted in the left side of load compressor inlet. It is an LRU.

LCIT Sensor Troubleshooting, Failure Modes, and BITE

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 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.



2 2T BA SED ON P AL TERNATE VA LUE

SL. IS A

35,000 ISA

2T C

2P PSIA

-40

-28.9

-17.8

-6.7

4.4

15.6

151050-40

-20

0

20

40

60

2T F

INLET PRESSURE SENSOR P2

LOAD COMPRESSORINLET TEMPERATURESENSOR (LCIT)

49-52-980581M

INLET SENSORS



APU PNEUMATIC SYSTEMINLET GUIDE VANE ACTUATOR

General

The inlet guide vane actuator (IGVA) is an electrically controlled hydraulically operated linear actuator. The actuator is mounted to the left side of the load compressor case. The actuator has a total stroke of 1 inch. It is an LRU.

Operation

Pressurized fuel is supplied to the IGVA from the Fuel Control Unit (FCU). This fuel is supplied within the actuator to the second stage spool and the single inlet torquemotor. The position of the single inlet torquemotor is controlled electrically by the ECU. A non-centered inlet to the servo valve causes a hydraulic pressure unbalance that drives the second stage spool off center. The second stage spool directs pressurized fuel to the actuator piston. The actuator piston drives the IGV ring gear positioning the IGV.

The Linear Variable Differential Transformer (LVDT) supplies an electrical position signal to the ECU.

The IGV's are positioned by the ECU through torquemotor commands as a function of the pneumatic demand mode, inlet air temperature, function switch settings, and EGT limit schedules. The highest priority pneumatic mode commanded is selected by ECU software. In descending order these priorities normally are: INFLIGHT, MES, ADP, and ECS. The IGV's are always closed below 95 percent RPM.

Main Engine Start (MES) Mode

During a main engine start, the IGV's are positioned to full open and the APU RPM is increased to 101 percent. The MES function switch allows positions less than full open to be selected during main engine starts. This mode allows the highest EGT vs LCIT schedule.

Air Driven Pump (ADP) Mode

The IGV's open in response to the ADP signal and function switch. (Normally 3 degrees).

Environmental Control Systems (ECS) Mode

The ECS mode is the most sophisticated, as the IGV's are modulated in response to three function switches, the air inlet temperature (LCIT sensor), and signals from the zone temperature control unit. This control unit sends an analog signal to the ECU that represents the difference between commanded and actual cabin temperatures (DELTA-T). For 767-300 models, the APU operates at 101% in the ECS mode to provide additional airflow.

Cool down

The APU is operating hot when both pneumatics and electrics are demanded. For protection, the APU continues to operate without pneumatics for the duration of the cooldown time, normally 60 seconds, after the APU switch is turned off. The bleed valve automatically closes when the APU switch is turned off, and the timer is activated. If the bleed valve switch is first turned off, the timer activates. After the cool down time has expired, the APU shuts down with the APU switch. The fire handle, remote shutdown switch (P40 panel on nose strut) and protective shutdowns all circumvent the cool down cycle. The function switch allows modification of cool down time. (See APU shutdown).



49-52-980589MM

INLET GUIDE VANE ACTUATOR

INLET GUIDE VANE ACTUATORBLOCKASSEMBLY

BUSHING(2 EA)

BELLCRANK

ROD (TO IGVS)CONNECTING

ELECTRICALCONNECTOR OPEN

CLOSE

ACTUATORIGV

TORQUE MOTOR

ygmm-49-52-0003 (mod)

ACTUATORPISTON

SERVO VALVE

SECOND STAGE SPOOL

SINGLEINLETTORQUEMOTOR

FEEDBACKTO ECU

FROM ECUEXCITATION

COMMANDSIGNALFROMECU

CONTROLUNIT

TO FUEL

PRESSURE

RETURN

VANESCLOSED

LVDT

SPRING



APU PNEUMATIC SYSTEMSURGE BLEED SYSTEM

General

The surge bleed system provides load compressor surge protection by assuring that pneumatic flow is matched to IGV position. The system consists of total pressure and static sensors, total and differential pressure transducers, a variable volume chamber, a load compressor inlet temperature sensor (T2), and a surge valve.

The flow sensor provides a mass flow signal to the ECU. The ECU modifies the position of the surge valve based on the flow signal, altitude and position of the IGVs. PCD2 air is used as the power to modulated the valve.

The LCIT sensor senses hot air back flowing through the duct from surges or other pneumatic system failures, and initiates a REVERSE FLOW protective shutdown. The pneumatic system dynamics occasionally allow a one-time surge, such as during a main engine start valve closure, because of surge valve

response time. The ECU allows a LCIT increase of 11OC in two seconds once, but not twice in a 15 second interval to prevent nuisance shutdowns due to

these dynamics. The ECU allows a maximum of 99OC for 2.5 seconds, and

initiates a shutdown immediately at 204OC.

APU Surge Valve

The surge valve is a spring-loaded open, modulating valve. It consists of a pneumatic actuator, torque motor, filter, pressure regulator and butterfly valve.The valve is clamp ring mounted in a duct connecting the load compressor output to the APU exhaust. It is an LRU. A cleanable metallic filter is located in a housing below the surge valve torque motor.

The torque motor is tested during prestart and self-test BITE for opens or shorts. If the circuit fails the test, the faulty unit SURGE VALVE is stored in the ECU. The APU operates, but pneumatic output is reduced to the airplane. The surge valve remains in the fully open position. If the surge valve fails in the closed position, a REVERSE FLOW protective shutdown occurs.

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.



49-53-B07649M

SURGE BLEED SYSTEM



APU PNEUMATIC SYSTEMFLOW SENSOR MODULE

General

The flow sensor module measures APU pneumatic output. The ECU uses these measurements to prevent load compressor surges. All components are mounted on a line replaceable flow sensor module. The module is bench calibrated. Components of the module are discussed below.

• Total Pressure (PT) • Static Pressure (PS) • Differential Pressure (DP)

Pressure Sensing

Total pressure is measured by a Total Pressure (PT) probe. A piezoresistive solid state transducer converts the total pressure to an electrical signal for the ECU.

Static Pressure (PS) is measured by a static pressure probe. PS is sensed by a differential pressure (DELTA P) transducer. The transducer measures the differential pressure between PT and PS (DELTA P = PT - PS) and sends it to the ECU.

Variable Volume Chamber

The variable volume chamber protects the transducers from pressure shock. A diaphram in the chamber isolates PT and PS.

Directional Flow Control

The directional flow control protects the DELTA P transducer and variable volume chamber from contaminates and pressure shock. It includes a filter and a one-way orifice.



S PROBEP

PROBE

FLEX LINES

CHAMBERVARIABLE VOLUME

FLOW CONTROLDIRECTIONALTO SURGE VALVE

FROMAPU

VOLUMECHAMBER

DIRECTIONAL

FILTERS

TOTAL PRESS

TO AIRPLANE

PS

PT

PT-PS

PT

VALVE

SURGE

SOFTWAREFLOW CONTROL VALVE

ORIFICE

ECU

TRANSDUCER

PT

TRANSDUCER

TRANSDUCERPRESSUREDIFFERENTIAL

TOTAL PRESSURE

49-53-980587M

FLOW SENSOR MODULE



ENGINE CONTROLSPROTECTIVE 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.

Analog (Hardware) Protective Shutdown

Analog protective shutdowns are initiated by either a 107 percent overspeed or by an EGT in excess of 621 degrees C if the RPM is greater than 95 percent. Analog protective shutdowns cause the ECU to de-energize the fuel shutoff solenoid valve, ignition unit, and starter motor. Enabling signals are removed for the air valve and the APU generator. The ECU opens the APU inlet door driver when speed is less than 15 percent, closing the APU air inlet door.

Digital Protective Shutdown

Digital protective shutdowns are initiated by the following:

• 109% overspeed (OVER SPEED) • EGT overtemperature (EGT OVERTEMP) • High oil temperature (HIGH OIL TEMP) • Low oil pressure (LOW OIL PRESSURE) • Loss of dc power (DC PWR LOSS) • APU air inlet door not full open (DOOR SYSTEM) • APU fire (FIRE EMERG) • Reverse flow (REVERSE FLOW) • Loss of both monopoles UNDER SPEED • Shutdown circuit failure (O/S TEST CIRCUIT) • Internal ECU Failure (CONTROL FAILURE) • Generator oil filter differential pressure (GEN FILTER) • APU speed greater than 95% then drops below 88% (UNDER SPEED) • EGT not greater than 150F (65C) above stored valve of EGT at 7% within

30 seconds. (NO LIGHTOFF) • APU SPEED (START ABORTED)

A digital protective shutdown initiates the same signals as an analog shutdown, but in addition also removes signal to the FCU torquemotor.

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.



FUEL S/O VLVDC PUMP

"FAULT" LIGHT

RELAYAPU FAULT

GENERATOR

AIR VALVE

STARTER MOTOR

IGNITION UNIT

APU FUELSOLENOID VALVE

EICASCOMPUTERS

TORQUE MOTORFUEL CONTROL

PROTECTIVEDIGITAL

SHUTDOWNS

BREAKER

ANALOG OVERSPEED SHUTDOWN

OIL TEMP >46C

GEN OIL FILTER P

CONTROL FAILURE

LOSS OF MONOPOLE NO. 2

LOSS OF MONOPOLE NO. 1

REVERSE FLOW

NO LIGHTOFF

UNDER SPEED

START ABORTEDFIRE EMER

DOOR SYSTEM

DC PWR LOSS

LOP 95%

OVERSPEED

109%

621C

LATCH

107%

>95%

LATCH

WINSHIGHEST

WINSHIGHEST

MONOPOLE NO. 2

MONOPOLE NO. 1

HOT 95%

DIGITAL

RPM

40% 100%

899C

649C

EGT

ANALOGPROTECTIVESHUTDOWNS

M206 ECU

OVERTEMP

EGT #1 CIRCUIT

EGT #2 CIRCUIT

CIRCUIT FAILURE (O/S TEST CIRCUIT)

MANUALSW(GEN)VALVE

SENSORCIRCUITSTARTERCONTROL

SOLUNITACTCIRCUIT

SWITCHSENSOR#2 SPD

VALVECONTROL

SENSORSENSORSOLSENSOR

TESTOK

NODATA

SPEEDTEMPCIRCUITEMERG

LOSS FILTERPRESSUREOVERTEMP

SPEED LIGHTOFFABORTEDFAILURENORMAL

STOP SIG

REVERSE FLOW

DOORSYSTEM

INLETDOOR RLY

#1 SPD SENSOR

EGT #1CIRCUIT

MEMORYERASE

OCER

DR

TCEL

SE

REASON

LRUTLUAF

STATUS

DC PWR

NO

SEE MNT

HOT

DEOIL

SURGE

GEN

OVER

VP

FILTER

A/C STRT

IGN

FUEL

START

HIGH OIL

LOW OIL

WAIT

PT

UNDER

FAN

APU

IGV

LOP

O/S TEST

FUEL

CONTROL

ECU

ECS

EGT #2

FIRE

EGT

SPARE

LCIT

SPARE

APU NOTOPERATING

REASON

LRUFAULTY

SELECTEDRECORD

LAST RUNCURRENT/

2SHUTDOWN

3SHUTDOWN

4SHUTDOWN

SUMMARYLRU

SENSORP2

DIV SOLFLOW

NORMAL SHUTDOWNSIGNAL 107% FOR INJECTED OVERSPEED1

1

49-61-R20207M

PROTECTIVE SHUTDOWN



ENGINE CONTROLSELECTRONIC 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:

• Fuel Control, both timed acceleration and on-speed governing • Inlet Guide Vane (IGV) control, to regulate pneumatic output • Surge Valve Control • Built-In-Test (BITE) • Protective Shutdown • Load Sequencing; to prioritize electric and pneumatic loads

ECU BITE Functional Description

The ECU performs three types of BITE:

• Prestart BITE - Tests the LRU's when the APU start sequence is initiated with the APU control switch. The ECU stores the faults, and in some cases prevents APU start.

• Monitor BITE - Monitors the LRU's from prestart to below 7 percent RPM on shutdown. The ECU stores the faults, and undertakes alternate action or shuts down the APU as necessary.

• Self-test BITE - Self test BITE and Prestart BITE are the same. Self test BITE only operates with the APU shutdown. Self test BITE is initiated by moving the test switch to the SELF position. If a faulty LRU is found, a faulty LRU lamp(s) is displayed.



49-61-R18774M

ELECTRONIC CONTROL UNIT (ECU)

E6 AFT EQUIPMENT CENTER ACCESS DOOR

CONTROL

SHUTDOWN


STATUS

FAULTYLRU

SELECTEDRECORD

LOSSDC PWRSPEED

NOLIGHTOFF

LRUSUMMARY

MANUALSEE MNTSENSORHOTSOLDEOIL

SURGEVALVE

GENFILTEROVERSPEEDTESTOKÄP

SENSOR

SHUTDOWN4

SW(GEN)FILTER

A/C STRTCIRCUIT

UNITIGN

FUELCONTROL

STARTABORTED

HIGH OILTEMP

PRESSURELOW OIL

WAIT

PTSENSOR

UNDER

3

FANVALVE

APUSTARTER

ACTIGV

LOPSWITCH

CIRCUITO/S TEST

NODATAFUELSOL

FAILURE

2SHUTDOWN

ECU

ECSCONTROL


FIREEMERG

OVERTEMPEGT

SPARE

SENSORLCIT

CURRENT/LAST RUN

P2SENSOR

FLOWDIV SOL


STOP SIGNORMAL

SYSTEMDOOR

REVERSE FLOW

SPARE

INLETDOOR RLY

STARTON

OFF

STEP

ENSURE APU START SWITCH IS IN

S351T020-18 AND PRIOR S351T020-19 AND ON

"OFF" POSITION.

APU CAN BE OPERATING OR SHUT-

DOWN DURING BITE PROCEDURE.

TEST" POSITION.

(LAMPS THAT DO NOT ILLUMINATE).

1

10

9

8

7

6

5

4

3

2

FLIGHT DECK

EICAS MAINTPAGE

APU RPM%

FLIGHT DECK

TESTLAMP

E.C.U.

E.C.U.

E.C.U.

E.C.U.

E.C.U.

ERASEMEMORY

E.C.U.

E.C.U.

TESTSELF

APU SPEED MUST BE BELOW 7% RPM.

POSITION 1.

a) PLACE TOGGLE SWITCH TO "LAMP

TEST" POSITION.

NOTE POSITION OF FAULTY LAMPS


b)

NOTE: "LAMP TEST" UNAVAILABLE

WITH APU RUNNING.

PLACE "FAULT SELECT" SWITCH TO PLACE "RECORD SELECT" SWITCH TO

"LAST RUN" POSITION.

NOTE POSITION OF FAULTY LAMPSb)

PLACE TOGGLE SWITCH TO "LAMPa)

DISPLAY" POSITION.

(IF DISPLAYED).

a) PLACE TOGGLE SWITCH TO "FAULT

REASON" POSITION.

RECORD "REASON APU NOT OPER-

ATING" LAMP THAT ILLUMINATES.

RECORD ALL "FAULTY LRU" LAMPS

THAT ILLUMINATE.

PLACE TOGGLE SWITCH TO "FAULT

LRU" POSTION.

b)

d)

c)

UNIT" POSITION.

(IF DISPLAYED).

b) REPEAT STEP 5 EACH TIME.

a)

PREVIOUS SHUTDOWN, 2 THRU 5.


a) PLACE "FAULT SELECT" SWITCH TO PLACE "RECORD SELECT" SWITCH TO


a)

RECORD "FAULTY UNITS"

a) PLACE TOGGLE SWITCH TO "FAULT PLACE "RECORD SELECT" SWITCH TO

"SUMMARY" POSITION.


LRU" POSITION.

b)

RECORD "FAULTY LRU" LAMPS

ILLUMINATED.

c)

b)

RECORD "FAULTY UNIT"c)

RECORD "FAULT DISPLAY".b)


REPAIR/REPLACE FAULTY UNITS AS

INDICATED.


INDICATED.

TO CLEAR ECU MEMORY, PUSH

"ERASE MEMORY" TOGGLE SWITCH UP,



LOCATED BEHIND PROTECTIVE COVER. LOCATED BEHIND PROTECTIVE COVER.

NOTE: "ERASE MEMORY" UNAVAILABLE

WITH APU RUNNING.

b)

a) PLACE TOGGLE SWITCH TO "SELF

TEST" POSITION.

"WAIT" LIGHT ILLUMINATES.

c)

b)


TEST" POSITION.


"TST OK" LIGHT ILLUMINATES WHEN

FAULTS CORRECTED.

c)

NOTE: "SELF TEST" UNAVAILABLE

WITH APU RUNNING.

BAC27TAP45

APU CONTROL UNIT (ECU)

BUILT IN TEST (BITE) INSTRUCTIONS

WHEN FAULTS CORRECTED.

"TST OK" LIGHT ILLUMINATES

SEE MAINTENANCE MANUAL FOR COMPLETE INSTRUCTIONS.

LAST RUN

LRU SUMMARY - Record of all Faulty LRUs detected since thelast Memory Erase.

Displayed Faulty LRUs are only the failed LRUs that could cause2.3.4 - Second, third, and fourth historical fault shutdowns.

the associated shutdown.


the shutdown.

run can be displayed. If Reason is an automatic shutdown,displayed Faulty LRUs are only the failed LRUs that could cause


D

OCER

R CT

ELES

TLUAFREASON

LRUMEMORY

ERASE

TSET

SELF

LAMP

ROTARY SWITCH OPERATION

________

_____

___________

S351T020-19 CONTROL UNIT



ENGINE CONTROLSECU FRONT PANEL/BITE TEST INSTRUCTIONS (-19 ECU)

General

There are three BITE routines:

• 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.

Reason APU Not Operating

This lamp field identifies either the type of protective shutdown or it identifies that a normal shutdown has occurred.

Status

This lamp field identifies the current status of the APU.

Faulty LRU

This lamp field identifies the faulty LRU that was detected during any of the three BITE routines.

Record Selected

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

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.



E6 AFT EQUIPMENT CENTER ACCESS DOOR

CONTROL

SHUTDOWN


STATUS

FAULTYLRU

SELECTEDRECORD

LOSSDC PWRSPEED

NOLIGHTOFF

LRUSUMMARY

MANUALSEE MNTSENSORHOTSOLDEOIL

SURGEVALVE

GENFILTEROVERSPEEDTESTOKÄP

SENSOR

SHUTDOWN4

SW(GEN)FILTER

A/C STRTCIRCUIT

UNITIGN

FUELCONTROL

STARTABORTED

HIGH OILTEMP

PRESSURELOW OIL

WAIT

PTSENSOR

UNDER

3

FANVALVE

APUSTARTER

ACTIGV

LOPSWITCH

CIRCUITO/S TEST

NODATAFUELSOL

FAILURE

2SHUTDOWN

ECU

ECSCONTROL


FIREEMERG

OVERTEMPEGT

SPARE

SENSORLCIT

CURRENT/LAST RUN

P2SENSOR

FLOWDIV SOL


STOP SIGNORMAL

SYSTEMDOOR

REVERSE FLOW

SPARE

INLETDOOR RLY

STARTON

OFF

STEP

ENSURE APU START SWITCH IS IN

S351T020-18 AND PRIOR S351T020-19 AND ON

"OFF" POSITION.

APU CAN BE OPERATING OR SHUT-

DOWN DURING BITE PROCEDURE.

TEST" POSITION.


1

10

9

8

7

6

5

4

3

2

FLIGHT DECK

EICAS MAINTPAGE

APU RPM%

FLIGHT DECK

TESTLAMP

E.C.U.

E.C.U.

E.C.U.

E.C.U.

E.C.U.

ERASEMEMORY

E.C.U.

E.C.U.

TESTSELF

APU SPEED MUST BE BELOW 7% RPM.

POSITION 1.

a) PLACE TOGGLE SWITCH TO "LAMP

TEST" POSITION.

NOTE POSITION OF FAULTY LAMPS


b)

NOTE: "LAMP TEST" UNAVAILABLE

WITH APU RUNNING.

PLACE "FAULT SELECT" SWITCH TO PLACE "RECORD SELECT" SWITCH TO

"LAST RUN" POSITION.

NOTE POSITION OF FAULTY LAMPSb)

PLACE TOGGLE SWITCH TO "LAMPa)

DISPLAY" POSITION.

(IF DISPLAYED).


REASON" POSITION.

RECORD "REASON APU NOT OPER-

ATING" LAMP THAT ILLUMINATES.

RECORD ALL "FAULTY LRU" LAMPS

THAT ILLUMINATE.


LRU" POSTION.

b)

d)

c)

UNIT" POSITION.

(IF DISPLAYED).


a)



a) PLACE "FAULT SELECT" SWITCH TO PLACE "RECORD SELECT" SWITCH TO


a)

RECORD "FAULTY UNITS"

a) PLACE TOGGLE SWITCH TO "FAULT PLACE "RECORD SELECT" SWITCH TO

"SUMMARY" POSITION.


LRU" POSITION.

b)

RECORD "FAULTY LRU" LAMPS

ILLUMINATED.

c)

b)

RECORD "FAULTY UNIT"c)

RECORD "FAULT DISPLAY".b)



INDICATED.


INDICATED.





LOCATED BEHIND PROTECTIVE COVER. LOCATED BEHIND PROTECTIVE COVER.

NOTE: "ERASE MEMORY" UNAVAILABLE

WITH APU RUNNING.

b)


TEST" POSITION.


c)

b)


TEST" POSITION.


"TST OK" LIGHT ILLUMINATES WHEN

FAULTS CORRECTED.

c)

NOTE: "SELF TEST" UNAVAILABLE

WITH APU RUNNING.

BAC27TAP45

APU CONTROL UNIT (ECU)

BUILT IN TEST (BITE) INSTRUCTIONS

WHEN FAULTS CORRECTED.

"TST OK" LIGHT ILLUMINATES

SEE MAINTENANCE MANUAL FOR COMPLETE INSTRUCTIONS.

LAST RUN

LRU SUMMARY - Record of all Faulty LRUs detected since thelast Memory Erase.

Displayed Faulty LRUs are only the failed LRUs that could cause2.3.4 - Second, third, and fourth historical fault shutdowns.



the shutdown.

run can be displayed. If Reason is an automatic shutdown,displayed Faulty LRUs are only the failed LRUs that could cause


D

OCER

R CT

ELES

TLUAFREASON

LRUMEMORY

ERASE

TSET

SELF

LAMP


________

_____

___________

S351T020-19 CONTROL UNIT

49-61-R19065

ECU FRONT PANEL/BITE TEST INSTRUCTIONS



ENGINE CONTROLSMINI-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: Outside of rare internal ECU failures, there are no LRU faults which appear only on a mini-flag test. Any faults displayed on a mini-flag test will also be displayed with other BITE tests.



M206 ECU (E6)

PROPER MINI-FLAG TEST VIEWING ANGLE___________________________________

OKNO MINI-FLAG FAULTS

CODE 34

DOOR RLYINLET

SPARE

FLOWREVERSE

DOORSYSTEM

NORMALSTOP SIG

#1 SPD SENSOREGT #1CIRCUIT

DIV SOLFLOW

SENSORP2

LAST RUNCURRENT/

LCITSENSOR

SPARE

EGTOVERTEMP

EMERGFIRE

#2 SPD SENSOREGT #2CIRCUIT

CONTROLECS

ECU

SHUTDOWN2

FAILURE

SOLFUELDATANO

O/S TESTCIRCUIT

SWITCHLOP

IGVACT

STARTERAPU

VALVEFAN

3

UNDER

SENSORPT

WAIT

LOW OILPRESSURE

TEMPHIGH OIL

ABORTEDSTART

CONTROLFUEL

IGNUNIT

CIRCUITA/C STRT

FILTERSW(GEN)

4SHUTDOWN

SENSOREPOKTESTSPEEDOVERFILTERGEN

VALVESURGE

DEOILSOLHOT

SENSORSEE MNTMANUAL

SUMMARYLRU

LIGHTOFFNO

SPEEDDC PWRLOSS

RECORDSELECTED

LRUFAULTY

STATUS


SHUTDOWN

CONTROL

DOOR RLY

INLET

SPARE

FLOW

REVERSE

DOOR

SYST

EM

NORM

AL

STOP SIG

#1 SPD

SENSOR

EGT #1

CIRCUIT

DIV

SOL

FLOW

SENS

ORP2

LAST RUN

CURRENT/

LCIT

SENSOR

SPARE

EGT

OVERTEMP

EMERG

FIRE

#2 S

PD

SENSOR

EGT #2

CIRCUIT

CONTROL

ECS

ECU

SHUTDOWN 2

FAILURE

SOL

FUEL

DATANO

O/S TEST

CIRCUIT

SWITCH

LOP

IGV

ACT

STARTER

APU

VALVE

FAN 3

UNDER

SENS

OR

PT

WAIT

LOW OIL

PRESSURE

TEMP

HIGH OIL

ABORTED

START

CONTROL

FUEL

IGN

UNIT

CIRCUIT

A/C

STRT

FILTER

SW(GEN)

4

SHUTDOWN

SENSOR

EPOK

TEST

SPEE

D

OVER

FILTER

GEN

VALV

E

SURG

E

DEOI

L

SOL

HOT

SENSOR

SEE

MNT

MANUAL

SUMMARY

LRU

LIGHTOFF

NO

SPEED

DC P

WR

LOSS

RECORD

SELECTED

LRU

FAULTY

STAT

US

OPERATING

APU NOT

REASON

SHUTDOWN

CONTROL

DOOR RLY

INLET

SPARE

FLOW

REVERSE

DOOR

SYST

EM

NORM

AL

STOP SIG

#1 SPD

SENSOR

EGT #1

CIRCUIT

DIV

SOL

FLOW

SENS

ORP2

LAST RUN

CURRENT/

LCIT

SENSOR

SPARE

EGT

OVERTEMP

EMERG

FIRE

#2 S

PD

SENSOR

EGT #2

CIRCUIT

CONTROL

ECS

ECU

SHUTDOWN 2

FAILURE

SOL

FUEL

DATANO

O/S

TEST

CIRCUIT

SWITCH

LOP

IGV

ACT

STARTER

APU

VALVE

FAN 3

UNDER

SENSOR

PT

WAIT

LOW OIL

PRESSURE

TEMP

HIGH OIL

ABORTED

START

CONTROL

FUEL

IGN

UNIT

CIRCUIT

A/C STRT

FILTER

SW(GEN)

4

SHUTDOWN

SENSOR

EPOK

TEST

SPEED

OVER

FILTER

GEN

VALVE

SURGE

DEOIL

SOL

HOT

SENSOR

SEE

MNT

MANUAL

SUMMARY

LRU

LIGHTOFF

NO

SPEED

DC PWR

LOSS

RECORD

SELECTED

LRU

FAULTY

STAT

US

OPER

ATIN

G

APU NOT

REASON

SHUTDOWN

CONTROL

___________

_____

________


displayed Faulty LRUs are only the failed LRUs that could cause

run can be displayed. If Reason is an automatic shutdown,

the shutdown.




Displayed Faulty LRUs are only the failed LRUs that could cause

last Memory Erase.


LAST RUN


LAMP

SELF

ERASE

MEMORY

S

E

L

E

T

CR

R

E

CO

DLRU

REASON

___________

_____

________




the shutdown.





last Memory Erase.


LAST RUN


F A U L T

T E S

LRU

REASON

RR E C O D

S E L E TC

ERAS

E

MEMO

RY

LAMP

SELF

T

FAULT

T

EST

___________

_____

________




the shutdown.





last Memory Erase.


LAST RUN


F A U L T

T E S T

LRU

REASON

S E L E TCRR E C O D

ERAS

E

MEMORY

LAMP

SELF

49-61-R19125

MINI-FLAG TEST



APU INDICATIONINDICATION 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.



49-72-R78293M

INDICATION GENERAL DESCRIPTION



APU INDICATION - MONOPOLES (RPM)

General

There are two APU Monopoles (RPM) mounted to the inlet plenum to sense APU speed. They supply redundant APU speed signals to the APU Control Unit (ECU). The monopoles consist of a housing with a magnet, coil, transformer, resistor, and electrical connector. The monopoles are magnetic non-contact, variable reluctance transducers, that convert the mechanical motion of the APU drive shaft into an electrical signal. Each time the ferromagnetic nut on the drive shaft passes the monopole tip, the change in the magnetic field generates an electrical signal in the monopole coil. The monopole sends this frequency signal to the ECU. The ECU converts frequency into a speed signal and uses the highest of the two inputs. The speed signal is also sent by the ECU to EICAS for display of APU RPM.

Installation

The monopoles consist of a housing with a magnet, coil, transformer, resistor, and electrical connector. Screw threads near the tip are used to install the unit in the APU. It should be screwed in only hand-tight.

Removal

There is a knurled section on the monopole near the electrical connector with two slots that accepts a special monopole removal tool. The monopole may be removed by unscrewing it with this tool after disconnecting the electrical connector. The monopole cover should not be removed.

Sensing and Failure Modes

The ECU tests the APU Monopoles during Monitor BITE only. A monopole is considered failed after the APU runs greater than 50% and the monopole reports a speed drop below 30% to the ECU. A detected monopole failure stores #1 SPD SENSOR or #2 SPD SENSOR in the ECU. #1 SPD SENSOR is the right monopole. #2 SPD SENSOR is the left monopole. If both monopoles fail during start (APU SPEED < 50 %), the APU shuts down due to START ABORTED and the ECU identifies APU STARTER as the faulty LRU.

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.



(MONOPOLE)#2 SPD SENSOR

#2 SPD SENSOR#1 SPD SENSOR

WRENCHMONOPOLE

SECTIONKNURLED

TIP

MAGNET & COIL

RETAINING NUT)SECTION BRG.NUT (POWERFERROMAGNETIC

SEALS

MONOPOLE (2 PLACES)

PULSE SENSORFOR INSTALLATION

CONNECTORELECTRICAL (2 PLACES)

REMOVAL SLOT

THREADSMOUNTING

SCREW THREADS

SHAFTAPU DRIVE

TRANSFORMER

FWD

49-61-R18957M

MONOPOLES (RPM)



APU INDICATIONEGT 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.



CIRCUIT

EGT #1

CIRCUIT

EGT #2

TUBESUPPORT

THERMOCOUPLE

INCONEL(2 PLACES) (2 PLACES)

WELDSREINFORCING

PROBE TIPSTHERMOCOUPLE

THERMOCOUPLES

APU EGT

STEEL HEADERSTAINLESS

APU EGT THERMOCOUPLE

ASSEMBLIES (4 PLACES)

49-71-R18958M

EGT THERMOCOUPLES

b767 ata 49 student book

Documents

oil system

ignition system

fuel system

starting system

lubrication system

pneumatic system

powerplant air intake

gearbox pressurization