Apu

B767/49/301 APU

Boeing B767-200/300

APU Training manual For training purposes only LEVEL 3

ATA 49

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B767/49/301 APU

Training manual

This publication was created by Sabena technics training department, Brussels-Belgium, following ATA 104 specifications. The information in this publication is furnished for informational and training use only, and is subject to change without notice. Sabena technics training assumes no responsibility for any errors or inaccuracies that may appear in this publication. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of Sabena technics training.

Contact address for course registrations course schedule information Sabena technics training [email protected]

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Table of Contents 1. AUXILIARY POWER SYSTEM...................................................................6 2. APU SYSTEMS & COMPONENTS............................................................8 2.1. APU Systems...........................................................................................8 3. GTCP 331-200ER SPECIFICATIONS........................................................12 3.2. APU Door..............................................................................................14 3.3. APU support installation.......................................................................16 4. APU ENGINE..........................................................................................18 4.1. Gearbox & Accessories..........................................................................20 4.2. APU borescope provisions.....................................................................22 5. APU control unit (ECU)....................................................................24 5.2. APU Monopoles (RPM)..........................................................................28 5.3. APU EGT Thermocouples......................................................................30 5.4. APU Indication......................................................................................32 6. APU LUBRICATION SYSTEM..................................................................34 6.1. Oil supply & reservoir............................................................................36 6.2. APU Oil service......................................................................................38 6.3. APU oil quantity indication....................................................................40 6.4. Oil Pump Assembly...............................................................................42 6.5. Pump de-oiling system..........................................................................44 6.6. Oil cooler & thermal bypass valve..........................................................46 6.7. Gearbox pressurization system..............................................................48 6.8. APU & generator oil scavenge system...................................................50 6.9. APU Oil System Operation.....................................................................52 7. APU FUEL SYSTEM................................................................................54 7.1. Fuel Control Unit..................................................................................56 7.2. Fuel flow divider....................................................................................60 7.3. Fuel nozzles & manifold assembly..........................................................62 7.4. APU Drain & Vent Assembly..................................................................64 7.5. Combustor case drain check valve.........................................................66 7.6. APU Fuel System Operation...................................................................68 EFFECTIVITY ALL

8. APU IGNITION/STARTING SYSTEM.......................................................70 8.1. APU Start Motor Assembly....................................................................72 8.2. Ignition System.....................................................................................74 8.3. APU Start Acceleration..........................................................................76 9. APU air intake system.....................................................................78 9.1. APU Pneumatic System.........................................................................80 9.2. APU air intake door and actuator..........................................................82 9.3. APU air intake door operation...............................................................84 9.4. APU inlet sensors..................................................................................86 9.5. Inlet guide vanes...................................................................................88 9.6. Inlet guide vane actuator.......................................................................90 9.7. IGV control logic...................................................................................92 9.8. APU Surge Bleed System.......................................................................96 9.9. APU Surge Valve...................................................................................98 9.10. Flow Sensor Module.........................................................................100 9.11. APU Surge Bleed System Operation..................................................102 9.12. Compartment & Oil Cooling.............................................................104 9.13. APU Fan Isolation Valve.....................................................................106 9.14. APU Cooling Fan..............................................................................108 9.15. APU Exhaust Duct.............................................................................110 10. APU NORMAL OPERATION...............................................................112 10.1 Power................................................................................................112 10.2. Starting............................................................................................112 10.3. Normal Running...............................................................................112 10.4. Normal Shutdowns...........................................................................113 10.5. Protective Shutdowns.......................................................................113 11. APU PROTECTIVE SHUTDOWN.........................................................114 12. APU BITE INTERROGATION...............................................................116 13. APU INSTALLATION & REMOVAL......................................................120 13.1. APU System Deactivation..................................................................122 B.767-300 — APU GTCP 331-200 ER........................................................122 page 4 20 - 01 - 2014 rev : 5

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List of Illustrations A3 APU SCHEMATIC.............................................................................................................................................................. 125 A3 APU SCHEMATIC.............................................................................................................................................................. 126 APU AIR INTAKE DOOR & ACTUATOR...................................................................................................................................... 83 APU AIR INTAKE DOOR OPERATION......................................................................................................................................... 85 APU AIR INTAKE SYSTEM......................................................................................................................................................... 79 APU BITE INTERROGATION..................................................................................................................................................... 119 APU BORESCOPE PROVISIONS................................................................................................................................................. 23 APU COMBUSTOR DRAIN PRESSURE RELIEF VALVE.................................................................................................................. 67 APU COMPARTMENT & OIL COOLING................................................................................................................................... 105 APU CONTROL UNIT (ECU)...................................................................................................................................................... 25 APU COOLING FAN................................................................................................................................................................ 109 APU DOOR.............................................................................................................................................................................. 15 APU DRAIN & VENT ASSEMBLY................................................................................................................................................ 65 APU EGT THERMOCOUPLES..................................................................................................................................................... 31 APU ENGINE (GTCP 331-220 ER)............................................................................................................................................. 19 APU EXHAUST DUCT............................................................................................................................................................. 111 APU FAN ISOLATION VALVE................................................................................................................................................... 107 APU FLOW SENSOR MODULE................................................................................................................................................ 101 APU FUEL CONTROL UNIT........................................................................................................................................................ 59 APU FUEL FLOW DIVIDER......................................................................................................................................................... 61 APU FUEL NOZZLE & MANIFOLD ASSEMBLY............................................................................................................................. 63 APU FUEL SYSTEM................................................................................................................................................................... 55 apu fuel system operation................................................................................................................................................ 69 APU & GENERATOR OIL SCAVENGE SYSTEM............................................................................................................................ 51 APU IGNITION / STARTING SYSTEM.......................................................................................................................................... 71 APU IGV CONTROL LOGIC....................................................................................................................................................... 95 APU INDICATION..................................................................................................................................................................... 33 APU INLET GUIDE VANE ACTUATOR........................................................................................................................................ 91 APU INLET GUIDE VANES......................................................................................................................................................... 89 APU INLET SENSORS................................................................................................................................................................ 87 APU INSTALLATION.................................................................................................................................................................. 13 APU INSTALLATION & REMOVAL............................................................................................................................................ 121 APU LUBRICATION SYSTEM..................................................................................................................................................... 35 APU MONOPOLE (RPM)........................................................................................................................................................... 29 APU OIL PUMP ASSEMBLY....................................................................................................................................................... 43 APU OIL QUANTITY INDICATION.............................................................................................................................................. 41 APU OIL SERVICE..................................................................................................................................................................... 39 APU OIL SUPPLY & RESERVOIR................................................................................................................................................. 37 APU OIL SYSTEM OPERATION.................................................................................................................................................. 53 APU PNEUMATIC SYSTEM........................................................................................................................................................ 81 APU PROTECTIVE SHUTDOWN............................................................................................................................................... 115 APU SCHEMATIC................................................................................................................................................................... 127 APU START ACCELERATION..................................................................................................................................................... 77 APU START MOTOR ASSEMBLY................................................................................................................................................ 73 APU SUPPORT INSTALLATION................................................................................................................................................... 17 APU SURGE BLEED SYSTEM..................................................................................................................................................... 97 APU SURGE BLEED SYSTEM OPERATION................................................................................................................................ 103 APU SURGE VALVE................................................................................................................................................................... 99 APU SYSTEM DEACTIVATION................................................................................................................................................. 123 APU SYSTEMS & COMPONENTS.............................................................................................................................................. 11 AUXILIARY POWER SYSTEM....................................................................................................................................................... 7 ECU INPUTS / OUTPUTS........................................................................................................................................................... 27 GEARBOX & ACCESSORIES...................................................................................................................................................... 21 GEARBOX PRESSURIZATION SYSTEM....................................................................................................................................... 49 IGNITION SYSTEM.................................................................................................................................................................... 75 OIL COOLER & BYPASS............................................................................................................................................................ 47 PUMP DE-OILING SYSTEM........................................................................................................................................................ 45

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Abbreviations and Acronyms APU CTL ECS ECU EGT EICAS FCU FOD GTCP IDG IGV INFLT ISA LRU LVDT MEL MES MSG NVM OVHT PS PWR QTY RPM RVRSE TRU TST

Auxilary Power Unit Control Environmental Control System Electronic Control Unit Exhaust Gas Temperature Engine Indicating & Crew Alerting System Fuel Control Unit Foreign Object Damage Gas Turbine Compressor Powered Integrated Drive Generator Inlet Guide Vane In Flight International Standard Atmosphere Line Replaceable Unit Linear Variable Differential Transformer Minimum Equipment List Main Engine Start Message Non Voltile Memory Overheat Pressure Static Power Quantity Revolutions Per Minute Reverse Transformer Recifier Unit Test

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1. AUXILIARY POWER SYSTEM. The airborne auxiliary power system supplies electrical and pneumatic power for the airplane. On the ground, electrical and pneumatic power are available to make the airplane independent of ground support equipment. Pneumatic power is available in flight up to 17,500 feet. Electrical power is available in flight at any altitude. The Garret 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 E6 rack aft of the aft cargo door. The E6 rack also contains the APU battery, battery charger and the optional APU start TRU.

The airborne auxiliary power system is controlled from the APU control panel on the P5 panel. This panel has a three position rotary switch and fault and run annunciator lights. EICAS displays APU exhaust gas temperature (EGT), RPM and oil status. To shut down the APU, turn off the control switch. To shutdown the APU during an emergency, pull the APU fire handle on the P8 panel or use the APU shutdown switch on the APU fire shutdown panel (P40) on the aft side of the nose gear. When the APU is shutdown with the P40 fire shutdown switch, cycle the main battery switch before attempting an APU start. APU circuit breakers are located on the P49 panel in the E6 rack.

The ECU coordinates the starting sequence, monitors the operation and pneumatic output of the APU and ensures proper shutdown. The ECU has extensive built in test equipment (BITE) that monitors many line replaceable units. It also performs protective shutdowns if damage to the APU is possible. These shutdowns and failed components are displayed on the front face of the ECU.

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AUXILIARY POWER SYSTEM EFFECTIVITY ALL

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2. APU SYSTEMS & COMPONENTS. 2.1. APU Systems. Primary APU systems include : - Air intake, - APU & generator lubrication, - Engine fuel, - Ignition/starting, - Air, - Control, - Indicating. The APU interfaces with the following systems that are covered elsewhere : - Electrical power (Chapter 24), - Pneumatics (Chapter 36), - Fire protection (Chapter 26), - EICAS (Chapter 31).

Air system. Air that enters the APU air inlet plenum is used for cooling, supporting combustion and as a pneumatic power source. A high speed cooling fan circulates air to cool the APU compartment and supplies air to the oil cooler. A fan isolation valve closes off supply air to the cooling fan in case of an APU fire. The inlet guide vane (IGV) actuator controls the pneumatic output of the APU. The inlet guide vanes (IGVs) open and close in response to aircraft pneumatic demand to regulate the amount of air entering the load compressor section of the APU. A flow sensor measures pneumatic output. The ECU uses this information to prevent a load compressor surge by positioning a surge valve.

APU 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.

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APU & 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, nonbypass oil filter. If the generator should fail, the filter protects the rest of the APU from damage. A de-oil system allows the oil pressure pump to draw air from the gearbox. This unloads the oil pump of cold oil, allowing easier starting at cold temperatures. The low oil pressure switch signals the ECU to initiate a low pressure (LOP) protective shutdown when there is low oil pressure in the pressure supply line. The oil temperature sensor supplies oil temperature information to the APU control unit (ECU). The gearbox pressure regulating valve controls gearbox pressurization. At lower altitudes the gearbox is vented to ambient. At higher altitudes, high pressure air is used to pressurize the gearbox to prevent oil foaming in the oil pump. The gearbox shutoff valve controls the input of high pressure air to pressurize the gearbox above 18,000 feet. The shuttle valve selects the source of buffer air for the compressor and cooling fan bearings.

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B767/49/301 APU

APU engine fuel system. The APU engine fuel system regulates and distributes fuel for engine combustion and pneumatic control. The fuel control unit shuts off, filters, pressurizes and meters the fuel supply. The fuel control unit is electrically controlled by the ECU. The flow divider and solenoid valve separates fuel flow into primary and secondary flows. The solenoid valve prevents excessive fuel flow into the combustion chamber during start. Fuel manifolds and nozzles provide even distribution of primary and secondary fuel flows into the combustion chamber. APU ignition & starting system. The APU is started by using a 28V DC powered electric motor. A single ignition unit sends a high voltage to the igniter plug that sparks combustion.

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APU control system. All operations of the APU are controlled and monitored by the APU 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 and oil status as well as fault messages. Oil level information is sent from the oil quantity sensor directly to EICAS. EGT thermocouples measure exhaust gas temperature.

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APU SYSTEMS & COMPONENTS EFFECTIVITY ALL

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3. GTCP 331-200ER SPECIFICATIONS. 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 17,500 feet. The APU supplies enough pneumatics to start the main engines up to an altitude of 14,000 feet and to maintain a 24° C cabin on a 40° C day at sea level. Pneumatic modes & 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.

3.1. APU Installation. General. The APU is located in the aft portion of section 48 of the fuselage. It is suspended in its compartment from the APU air intake plenum. Access into the APU compartment is through the APU doors. APU 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. APU air intake & 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. APU drains & 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.

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3.2. APU Door. Access to the APU compartment is through the clam shell APU access doors. The doors are attached to the fuselage using piano-type hinges. They are held closed by 4 flush mounted door latches. When the latches are released, the spring clip door restraint on the right access door prevents it from opening until the restraint is released. When open, the doors are held in place by 4 locking struts. The APU drain mast is installed in the right access door.

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APU DOOR EFFECTIVITY ALL

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3.3. APU support installation. The APU is suspended in the compartment from the APU air inlet plenum. The APU is secured by three mount brackets on the APU. These three brackets mount to the APU forward support and vibration isolator mount in one place and to the APU aft support and vibration isolator mounts in two places. The three vibration isolator mounts prevent transmission of APU vibration to the airplane structure. Each vibration isolator has a cone bolt. The cone bolts attach to the mount brackets with cone bolt nuts. The APU air intake plenum flange seal reduces APU vibration to the airframe and leakage into the APU compartment.

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APU SUPPORT INSTALLATION EFFECTIVITY ALL

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4. APU ENGINE. 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 compressor, a reverse flow annular combustor, and a three stage axial turbine. The inlet bearing has a labyrinth seal pressurized with PCD1 or PCD2 buffer air. Load compressor. The load compressor is a centrifugal 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.

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APU ENGINE (GTCP 331-220 ER) EFFECTIVITY ALL

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4.1. Gearbox & 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. APU generator seal plate. The APU generator seal plate is installed on the APU with a rubber gasket when it leaves the Garret 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.

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4.2. APU borescope provisions. General. The load compressor and power section first stage compressor borescope access is through the plenum access panel, on the bottom of the APU plenum, or the air inlet to the APU. The inlet guide vanes (IGVs) must be opened to inspect the load compressor. The fuel lines connected to the inlet guide vane actuator must be disconnected to allow manual opening of the IGV. The combustor and first stage turbine borescope access is through one of the 12 fuel nozzles or the single ignitor plug.

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5. APU control unit (ECU). 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 governoring, - Inlet guide vane (IGV) control, to regulate pneumatic output, - Surge valve control, - Built-in-test (BITE), - Protective shutdown, - Load sequencing; to prioritize electrical and pneumatic loads.

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ECU BITE functional description. The ECU performs 15 protective shutdowns and stores 24 faulty LRU’s in nonvolatile memory when necessary. To accomplish this, 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 :

The same as prestart, self-test BITE is initiated by the SELFTEST switch on the face of the controller. Any LRU faults detected at the time of the test are stored in the ECU.

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APU CONTROL UNIT (ECU) EFFECTIVITY ALL

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5.1. ECU inputs/outputs. Control. The ECU may be powered-up 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 the START has been selected on the APU Control Panel. Once the APU is on-speed (over 95 percent rpm), the operator may draw electrical power, and/or pneumatics as desired. System monitoring and protective shutdown functions are automatically performed by the controller.

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5.2. APU Monopoles (RPM).

Sensing & failure modes.

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, resistort 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 ECU tests the APU Monopoles (RPM) 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% (40 msec delay) to the ECU. A detected monopole failure stores N° 1 SPD SENSOR or N° 2 SPD SENSOR in the ECU. N° 2 is the left monopole. If both monopoles fail, a FAILED SENSOR protective shutdown occurs.

Construction & installation. Screw threads near the tip are used to install the unit in the APU. It should be screwed in only hand-tight.

The speed signal is sent by the ECU to EICAS to provide an APU RPM indication in the flight compartment. Note : The monopoles are not tested during Prestart BITE. If they are faulty on the APU start (disconnected or wiring problems) the starter motor begins to rotate the APU, but since a speed signal is not sensed, the ECU initiates a SLOW START protective shutdown after 30 seconds and incorrectly stores the APU STARTER 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.

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. Note : 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 resistor inside which makes the monopole unusable.

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5.3. APU EGT Thermocouples. General. APU exhaust gas temperature (EGT) is measured by 4 individual chromelalumel 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 rake N° 1. The two on the right side are wired together to form rake N° 2. These rakes supply two redundant EGT signals to the ECU. The EGT thermocouple assemblies are LRU. Sensing & failure modes. The ECU tests the rakes during prestart, monitor and self-test for an output signal greater than -100° F (-88° C). The highest output signal (EGT) is utilized for operation. When APU speed is greater than 95%, the two rakes cannot disagree more than 150° F (66° C). The rake reporting the lower temperature is considered failed and the ECU records NO. 1 T/C RAKE or N° 2 T/C RAKE as a faulty unit. If both rakes fail for more than 50 msec, the ECU initiates a FAILED SENSOR protective shutdown. Only one of the 8 thermocouple probes is necessary for APU operation. The EGT signal is sent by the ECU to EICAS, to provide an APU EGT display in the flight compartment.

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APU EGT THERMOCOUPLES EFFECTIVITY ALL

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5.4. APU Indication. General. The APU control unit (ECU) sends analog signals to the EICAS computers for display of RPM and exhaust gas temperature (EGT). Discrete signals are also sent to the EICAS computers for display of protective shutdowns or faulty LRUs, stored in NVM. 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. A customer option allows RPM to be displayed on the status page also. The EICAS advisory message APU FAULT appears and the FAULT light illuminates to annunciate a protective shutdown of the APU. The fault light also shows transit of the APU fuel shutoff valve. (See chapter 28 - Fuel.) APU BITE appears on the ECS/MSG page to indicate that a faulty LRU is stored in the ECU. If the faulty LRU also caused a protective shutdown; the APU BITE message and the APU FAULT message may appear simultaneously. The white RUN light on the APU control panel comes on when the APU is operating above 95 % speed. The RUN light also blinks two times during starting. This indicates that the prestart BITE has been completed. An APU hour meter shows total APU operating hours. The hour meter runs when the APU is starting or running and the APU fire switch is normal.

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APU INDICATION EFFECTIVITY ALL

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6. APU LUBRICATION SYSTEM. The lubrication system consists of: - A pressure system for oiling the bearings, generator and starter clutch - A scavenge system for returning oil to the sump from the bearings and generator. - A gearbox pressurization system and an oil cooler with bypass Oil supply. The APU gearbox serves as an oil reservoir (5,9 liters). 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 transmitter send quantity information 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. 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.

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Oil scavenge system. Three scavenge pumps return oil to the reservoir, compressor bearing scavenge, generator scavenge and turbine bearing scavenge. 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). Operation is automatic and controlled pneumatically. ECU bite. Protective shutdowns occur for low oil pressure (LOP), high oil temperature (HOT), and for a blocked generator oil filter while oil temperature is above 46°C (GEN FILTER). The faulty units stored in the ECU memory include LOP SWITCH, DE-OIL SOL, HOT SENSOR, and FILTER SWITCH.

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APU LUBRICATION SYSTEM EFFECTIVITY ALL

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6.1. Oil supply & 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 or an oil quantity transmitter (See APU oil indication page 38 & 39).

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APU OIL SUPPLY & RESERVOIR

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6.2. APU Oil service. Servicing. The oil reservoir is the bottom of the APU gearbox. Capacity is 6.2 quarts (5.9 liters). Normally the same oil as the engine is used. A manual fill port, scupper drain, sight glass, and optional provisions for pressure filling are located on the left side of the gearbox. The sight glass shows FULL and ADD levels. An oil level switch or transmitter signals EICAS when the oil level reaches approximately 4.2 quarts (4.0 liters) or less (engine not running) generating the status and maintenance message APU OIL QTY. An optional oil quantity transmitter may replace the low level switch. EICAS then shows oil level as FULL, 0.75, 0.50, 0.25 and ADD. When a decreasing quantity reaches ADD (approximately 4.2 quarts (4.0 liters), engine not running or 2.7 quarts (2.6 liters) engine running) the APU OIL QTY message also appears.

B767/49/301 APU

If the oil reservoir is overfilled, oil foaming can occur in the gearbox. Oil foaming can cause low oil pressure shutdowns. To replenish the APU oil using gravity fill, clean and remove the cap. Then slowly add oil until the reservoir oil level is at the top of the oil fill port. Install the cap, assuring that it is secure. To replenish the APU Oil using Pressure Fill, remove the caps from oil pressure fittings. Clean the fittings. Connect the supply and overflow lines to the pressure fittings. Slowly add oil until oil appears in the overflow line. To prevent overfilling the reservoir, remove the lines when flow from the overflow line has reduced to a slow drip. Install caps on pressure fittings. EICAS message APU OIL QTY. The EICAS maintenance and status message APU OIL QTY is latched. To clear these messages, perform the EICAS latched message erase procedure. The EICAS APU Auto Event must also be erased.

The APU OIL QTY message causes an EICAS APU system auto event. Note : Oil level sight glass shall not be used for filling, but can be used to determine an approximate level in gearbox. CAUTION : SOME OILS ARE NOT COMPATIBLE WHEN MIXED. UNLESS COMPATIBILITY IS ASSURED, DO NOT MIX BRAND NAME OILS. OVERFILLING OIL RESERVOIR CAN CAUSE SHUTDOWN DUE TO LOW OIL PRESSURE.

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APU OIL SERVICE

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6.3. APU oil quantity indication.

APU oil level (U.S. quarts)/EICAS indication.

There are two ways to determine the oil level in the gearbox reservoir. The first way is to use the sight gauge window. The oil level should appear in the safe area, color coded yellow, of the sight gauge. One side of the sight gauge is calibrated to show the safe area with the APU running, the other side is calibrated to show the safe area with the APU shutdown. When the oil level is at the add line, the oil quantity is approximately 2 quarts low, and servicing is required.



APU RUNNING

GULP/FULL GULP/FULL GULP/FULL 3.0/FULL 2.5/75% 2.0/50% 1.5/25% 1.0/ADD

APU NOT RUNNING

6.2/FULL 5.7/75% (.5 qt low) 5.2/50% (1 qt low) 4.7/25% (1.5 qt low) 4.2/ADD (2 qts low) /ADD /ADD /ADD

The second way to determine the oil level is to use EICAS. A dual magnet float-type oil quantity transmitter is mounted on the bottom of the APU oil reservoir. The transmitter sends oil quantity information directly to the EICAS computers. Oil quantity is then displayed on the EICAS STATUS and PERF/ APU pages as FULL, .75, .50, .25, or ADD. ADD appears on the STATUS and PERF/APU pages when oil quantity is approximately 2 quarts below the full APU not running level. When the ADD appears, approximately 30 hours of operation remains at a normal oil consumption rate. The latched EICAS message APU OIL QTY appears on the STATUS and /CS/ MSG pages, and is an auto event whenever ADD appears on EICAS. The oil level in the reservoir lowers approximately 2-3 quarts whenever the APU is operating. This is due to the gulp of the system. The EICAS display automatically compensates for the gulp when the APU is running. A 60 second time-delay prevents the ADD from appearing during starting or shutdown. The following table relates sensed oil level in the reservoir to the EICAS display.

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APU OIL QUANTITY INDICATION EFFECTIVITY ALL

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6.4. Oil Pump Assembly. General. 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. Pressure pump. 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.

B767/49/301 APU

Pressure regulator valve. 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. 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.

Pump relief valve. The pump relief valve prevents oil system overpressurization. The valve is a spring loaded piston and sleeve unit. The valve opens at 200 ± 5 psid. It is an LRU. Oil filter. 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. It is an LRU. Oil filter differential pressure indicator. 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° C. This prevents viscous cold oil from activating the indicator. It is an LRU.

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APU OIL PUMP ASSEMBLY EFFECTIVITY ALL

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6.5. Pump de-oiling system. General. Cold, viscous oil causes a high drag on the APU during starts, possibly leading to SLOW START 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 deoils 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 ± 6.6° C 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 deoil low temperature switch energizes the solenoid.

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B767/49/301 APU

The de-oil solenoid low temperature switch is mounted in the generator scavenge cavity. When 28V DC is available at the starter terminal, and the cavity oil temperature is less than approximately -4° C, the deoil solenoid energizes. An in-line fuse protects the wiring. If the fuse is open, STARTER 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 4° C. It remains open until memory oil temperature falls below -4° C. 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 SLOW START 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. Note : If the de-oil system is not operational, the time limit for a LOP protective shutdown is reduced to 1 second. This is to protect the APU from damage caused by lack of lubrication. 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 LOP protective shutdown. ECU is stored as a faulty unit.

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PUMP DE-OILING SYSTEM EFFECTIVITY ALL

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6.6. Oil cooler & thermal bypass valve. General. Oil is cooled by inlet air. When PCD2 pressure reaches 7.5 psig on APU start, the fan isolation valve opens, allowing the gearbox driven cooling fan to blow air through the oil cooler and also into the APU compartment. 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. Two check valves prevent back-flow and drain-down. These check valves are LRU‘s Oil cooler. The cooler is an air/oil exchanger, designed to maintain the oil temperature at approximately 66° C above ambient, and below 152° C 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° C and fully closed at 77° C. 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. BITE & troubleshooting. A blocked cooler may cause a HOT protective shutdown. The two check valves are not interchangeable, and have different screw thread sizes.

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OIL COOLER & BYPASS EFFECTIVITY ALL

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6.7. Gearbox pressurization system. General. The gearbox pressurization system maintains gearbox pressure at 4 psi above ambient. This 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, PCD1 air 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.

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GEARBOX PRESSURIZATION SYSTEM EFFECTIVITY ALL

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6.8. APU & 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 page 40 for details.). Turbine bearing scavenge pump. This pump is a gerotor type. The pump is press fitted 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.

B767/49/301 APU

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 (FILTER SW). 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 46°C. 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 46° C. A failed open or disconnected switch is faulted in Prestart and Self-Test. If the switch is detected open during Prestart BITE, the APU then operates without protection from a blocked filter. The switch is an LRU.

Generator oil 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 LOP protective shutdown occurs (See the oil supply system.).

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APU & GENERATOR OIL SCAVENGE SYSTEM EFFECTIVITY ALL

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6.9. APU Oil System Operation. 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 (LOP), high oil temperature (HOT) or generator filter blockage (GEN FILTER). The APU FAULT light and APU FAULT advisory EICAS message appear until the APU control switch is turned OFF. All three switches are LRUs. L.O.P. 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 LOP protective shutdown. If a LOP 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 start attempt. If the start fails to meet the new oil pressure requirements, all further starts are inhibited. H.O.T. A protective shutdown is initiated at a sensed oil temperature greater than 154° C. 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 46° C or less.

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B767/49/301 APU

BITE, troubleshooting & failure modes. If the APU LOP protective shutdown occurred with the lowered time limit, performing a faulty display test causes the LOP light to blink. Further start attempts are inhibited until the fault memory is erased. The following oil system LRUs are detected as faulty and stored in the ECU during the prestart and self-test BITE routines. L.O.P. 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 LOP protective shutdown. Gen. filter switch. The switch is normally closed. If it is found open during the prestart BITE, FILTER SW 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 GEN FILTER protective shutdown occurs. De-oil solenoid. Tested for open, short, and overcurrent. APU start and operation is not inhibited if it is found faulty. Hot sensor. The ECU tests the oil temperature sensor during pre-start, monitor and selftest BITE. If the sensor is detected as failed, the ECU uses 60°F (16°C) for the first three minutes of operation and 120°F (49°C) for the remainder of operation. The de-oil solenoid valve is deactivated at start and the APU runs without high oil temperature protection. HOT SENSOR is stored as a faulty unit. page 52 20 - 01 - 2014 rev : 5

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APU OIL SYSTEM OPERATION EFFECTIVITY ALL

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7. APU FUEL SYSTEM. The APU fuel system receives fuel from the airplane wing tanks through a shrouded line. The system then pressurizes, filters, and meters fuel for combustion and to operate the inlet guide vane actuator (IGVA). The primary components are the fuel control unit, flow divider, primary and secondary fuel manifolds and nozzles; and the inlet guide vane actuator. The APU is a constant speed engine. Speed control is accomplished automatically by the ECU through torquemotor inputs to the fuel control unit, resulting in fuel flow regulation. The acceleration schedule is also torquemotor controlled. Air inlet pressure (P2) and inlet temperature (T2 or LCIT) are sensed by the ECU to adjust fuel flow for ambient conditions. The torquemotor also responds to T5 (EGT limits) if necessary to prevent an OVERTEMP protective shutdown. Fuel control unit. This unit accomplishes all pressurizing, filtering, and metering for the APU. It mounts to the front of the oil pump. Electrical connections include the torquemotor and fuel shutoff valve solenoid. Both are ECU controlled.

Fuel manifold/nozzles. The two fuel manifolds encircle the APU combustion chamber. Each has six fuel nozzles permanently attached. The nozzles and manifold are an LRU as an assembly only. ECU BITE. APU protective shutdowns that are associated with the APU fuel system include NO FLAME, NO ACCEL, SLOW START, OVERTEMP, and OVERSPD. NO ACCEL and SLOW START are often caused by too little fuel, while OVERTEMP and OVERSPD are often caused by excessive fuel flows. Faulty LRU‘s that can be displayed on the face of the ECU include the FUEL CONTROL, FUEL SOL. and FLOW DIV. SOL. APU drain & vent assembly Four drain lines drain fluids overboard through the APU drain mast installed in the right access door.

Inlet guide vane actuator. This actuator utilizes fuel pressure for muscle. Operation is discussed in the APU pneumatics section. Flow divider. The fuel flow divider separates the metered flow into two manifolds; primary and secondary. The primary manifold is used full time. The secondary manifold is used when flow demands are increased. A electric solenoid valve modifies secondary flows to accommodate APU starting requirements. The solenoid is ECU controlled. EFFECTIVITY ALL

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APU FUEL SYSTEM EFFECTIVITY ALL

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7.1. Fuel 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.

B767/49/301 APU

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. 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. 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.

Fuel pums. The fuel pump is a gear pump that provides up to 1980 lbs/hr of fuel. It is spline driven from the oil pump assembly. 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.

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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 springloaded-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.

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Troubleshooting, failure modes, and BITE. 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. If the APU oil reservoir is overserviced, and a fuel odor is present at the oil fill port, fuel is entering the oil return from the fuel pump drive spline. Replace the FCU. The fuel control torquemotor is tested in Prestart, Monitor, and Self-Test for opens, shorts, and overcurrent. FUEL CONTROL is stored as a faulty LRU. During start, an electrical open causes a SLOW START or NO FLAME protective shutdown, and FUEL CONTROL as a faulty LRU. If the APU is on speed, an electrical open causes a NO ACCEL shutdown, and FUEL CONTROL faulty LRU. If the torquemotor shorts during APU operation, the ECU driver is turned off, and an ECU shutdown occurs, with FUEL CONTROL as a faulty LRU. The fuel shutoff solenoid valve is tested for opens and shorts during prestart and self-test BITE; and for overcurrent during monitor BITE. The ECU stores FUEL SOL as the faulty LRU. A failed open-solenoid (valve closed) causes a SLOW START or NO FLAME shutdown, with FUEL SOL as the faulty LRU. During APU operation, an open solenoid causes a NO ACCEL shutdown and FUEL SOL faulty LRU. During shutdown, if the valve mechanically sticks open, the APU would continue to run, and an ECU LRU fault would be stored after 20 seconds. The ECU would then de-energize the airplane fuel shutoff valve relay, to shut down the APU, and erroneously store S/D CKT as a protective shutdown, with ECU as the faulty LRU. A subsequent start attempt causes either a NO FLAME shutdown (igniter plug wet) or OVERTEMP (fuel available too soon). Note : An S/D CKT protective shutdown trips an internal breaker in the ECU, requiring it to be replaced before subsequent starts. EFFECTIVITY ALL

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APU FUEL CONTROL UNIT EFFECTIVITY ALL

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7.2. Fuel flow divider.

Troubleshooting, failure modes and BITE.

General. 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.

Solenoid valve fails to open (mechanically stuck closed or fails to energize). - The APU operates normally at lower altitudes through the start sequence valve. At higher altitudes and low fuel flows, the start valve may cycle open and closed, causing RPM surges and cycling. Possible NO ACCEL protective shutdown.

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 .

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Solenoid valve sticks open. - Excessive secondary fuel causes an OVERTEMP, NO FLAME, SLOW START, or NO ACCEL protective shutdown. The type of shutdown is a function of ignition, battery condition, altitude, and other external parameters. Flow divider solenoid monitoring. - The ECU tests the solenoid in Prestart and Self-Test for opens, shorts and overcurrent. FLOW DIV 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. Primary drain valve sticks closed. - Fuel flow is through the secondary manifold only. A NO FLAME or OVERTEMP protective shutdown occurs. NO FLAME if the igniter gets flooded before light-off. OVERTEMP if ignition occurs. Start sequence valve sticks closed. - No secondary fuel flow. A SLOW START or possible NO ACCEL protective shutdown occurs.

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APU FUEL FLOW DIVIDER EFFECTIVITY ALL

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7.3. Fuel nozzles & manifold assembly. Purpose. The fuel manifolds distribute fuel to the nozzles. The nozzles inject the fuel into the combustion chamber. Location. The manifolds encircle, and are mounted to, the APU combustor case. Description/operation. There are two manifold assemblies, designated primary and secondary. Each manifold assembly has six nozzles, or atomizer assemblies. The manifold assemblies are connected to the fuel flow divider with separate hoses. The manifold assemblies have no moving parts. Fuel flow distribution and flow rate are controlled through the FCU and the flow divider. The primary atomizer tips are sized with a small orifice that supplies proper atomization of fuel for light off. The secondary atomizer tips are sized with a larger orifice to supply adequate fuel flow for all other phases of operation. Each manifold assembly is an LRU. The primary and secondary nozzles have different alignment pin orientation to prevent improper installation. Individual nozzles can not be replaced.

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APU FUEL NOZZLE & MANIFOLD ASSEMBLY EFFECTIVITY ALL

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7.4. APU Drain & Vent Assembly. 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. 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.

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APU DRAIN & VENT ASSEMBLY EFFECTIVITY ALL

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7.5. Combustor case drain check valve. General. A drain valve is located in the lowermost portion of the combustor case to prevent an accumulation of un-ignited fuel in the case. The valve is an LRU. Installation is by a screw thread and O-ring. Operation. The valve is spring loaded open when the APU is not operating, and is closed by air pressure within the case at 9-16 psig. The valve should reopen at 5 psig, allowing any fuel present to flow through the valve and overboard through the drain mast on the right access door.

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APU COMBUSTOR DRAIN PRESSURE RELIEF VALVE

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7.6. APU Fuel System Operation. General. Fuel scheduling is automatically controlled using software in the ECU. The ECU maintains 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. Switch over occurs at 95% sensed speed. Sensor inputs. 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 programming if P2 or LCIT signals fail. Speed and EGT signals have redundant inputs to the ECU. If, however, both of these inputs fail for either EGT or RPM, a FAILED SENSOR protective shutdown occurs. Acceleration scheduling. The APU is in the acceleration mode when the APU control switch is on, prestart BITE is complete, speed is below 95%, and no software protective shutdowns are present. The torquemotor current is a function of APU speed and is modified per the timed acceleration schedule and the T5 (EGT) temperature trim schedule. Updates occur every 20 millisec. A digital overtemperature schedule initiates a protective shutdown if EGT limits are exceeded. The acceleration schedule is also monitored to maintain RPM, EGT and acceleration limits. If the APU fails to meet the RPM VS time schedule targets, a slow start protective shutdown occurs. If the APU fails to meet EGT minimums a no flame protective shutdown occurs.

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If the RPM and EGT meet the requirements, but the APU fails to accelerate by a given amount, a no accel 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% speed the ECU switches from acceleration to onspeed scheduling. The APU operates at either 100%, or 101% 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 (torquemotor current vs speed) are provided for flameout and surge protection. The minimum fuel schedule prevents flameout. The maximum fuel schedule prevents power section compressor surge. The torquemotor current is adjusted as necessary to meet these minimum and maximum current requirements. The minimum and maximum schedules are based on standard sea-level ISA conditions. The actual inlet pressure and temperature are input from the sensors (P2 & T2) to adjust torquemotor current for OFF-ISA conditions. Fuel shutoff solenoid valve. The fuel shutoff solenoid valve is energized at or above 7% RPM if hardware or software protective shutdowns are not detected. Fuel flow divider solenoid valve. The flow divider solenoid valve is energized at 95% speed.

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apu fuel system operation EFFECTIVITY ALL

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8. APU IGNITION/STARTING SYSTEM. General. The ignition/starting system provides Initial APU acceleration and combustion spark. The system consists of the ignition unit, igniter and the starter motor. The ignition unit provides igniter spark energy. The igniter provides the combustion spark to the combustor. The supply of ignition unit power is controlled electrically by the ECU. The starter motor provides APU initial rotation and acceleration. It is powered by the APU TRU if the right main ac bus is powered, and by the APU battery if the TRU is not powered. AC TRU enable relay determine the power source used. 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 or TRU start relay as appropriate, to supply power to the starter motor.

APU Start TRU. (a) When an APU start signal is received (Ref 49-41-00)., the TRU APU start relay energizes, applying power to the APU start TRU. The relay also turns on the internal cooling fan for the TRU. The cooling fan stays on until TRU temperature drops below 125°F (52°C). (b) If TRU temperature exceeds 250°F (121°C), TRU overheat relay energizes. When TRU OVHT relay energizes, APU BAT/TRU select relay de-energizes, connecting the APU start signal to the crank contactor. The crank contactor connects the APU battery to the APU starter motor. (c) In event of the APU start TRU malfunction, the APU may be started by the APU battery by opening the TRU APU START CONT circuit breaker located on the overhead circuit breaker panel. This will de-energize the TRU OVHT and APU BAT/TRU SEL relays, apply 28 volt dc from the APU START circuit breaker through the APU BAT/TRU SEL relay to energize the APU crank contactor. The APU crank contactor thus connects the APU battery to the APU start motor.

A 28 volt 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 POWER LOSS protective shutdown occurs. At 7% speed the ECU energizes the ignition unit, Starter cutout is a function of altitude. At 95% ,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 detatis. EFFECTIVITY ALL

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8.1. APU Start Motor Assembly. General. The start motor rotates the gearbox drive train through a sprag clutch. The starter motor is a 28 volt DC motor. It receives power from the APU battery or an optional APU TRU. Starter duty cycle: 3 consecutive start attempts then a 60 minute cooldown period. Starter motor details. The starter motor has a brush wear indicator. When the brush wear indicator is not visible, replace the starter. Remove the starter motor end cap to access a 5/16 inch hex shaft. Rotate the hex shaft to rotate the APU. Sprag clutch details. The sprag clutch prevents the starter motor from overspeeding. During start initiation, the sprag clutch is connected to both the starter motor and the gearbox drive train. After starter cutout, the sprag clutch mechanically disengages from the starter motor.

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APU START MOTOR ASSEMBLY EFFECTIVITY ALL

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8.2. Ignition 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. 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.

B767/49/301 APU

Failure modes, BITE & 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 FLAME 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.

Igniter. 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°F (816°C). The igniter screws into its mounting on the combustor case. The igniter is an LRU.

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IGNITION SYSTEM EFFECTIVITY ALL

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8.3. APU Start Acceleration. General. The APU control unit (ECU) completely controls start and acceleration. It controls the supply of fuel, the starter motor, and the ignition unit. After START is initiated and the air intake door is fully open, the ECU enables the starter motor. The torquemotor metering valve in the fuel control unit is opened to supply enough fuel to run the APU at 16% speed. At 7% speed the ECU opens the fuel shutoff solenoid valve, enabling fuel flow to the combustor, and energizes the ignition unit. With fuel and ignition to the combustor, the APU accelerates under its own power. As the APU accelerates, the fuel supplied by the metering valve is increased to match acceleration to that shown on the speed vs time graph. The ECU de-energizes the starter motor at 42% on the ground, 50% inflight below 36,000 feet and 55% above 36,000 feet. Above 30,000 feet, the APU acceleration between the time when starter cutout occurs and the time when 95% RPM is attained, changes with altitude. This allows the APU more time to come up to speed before a protective shutdown occurs, when the air is less dense. At 95% speed the ignition unit is deenergized. Also at 95% speed the ECU sends signals that allows electrical and/or pneumatic power to be used. The APU has two different speeds : 100% (39,850 RPM) and 101% (40,400 RPM), selected as a function of the pneumatic mode. The APU operates at the higher speed if pneumatics are being supplied for starting the main engines or inflight. It operates at the lower speed at all other times. Note : To improve fuel scheduling during starts at high altitudes, the time acceleration slopes are different above approximately 30,000 feet.

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APU START ACCELERATION EFFECTIVITY ALL

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9. APU air intake system. 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. APU 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. The ducting is approximately 15 by 8 inches (38 by 20 cm) in cross section. Access is through the service access door in the fuselage. APU 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.

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APU AIR INTAKE SYSTEM EFFECTIVITY ALL

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9.1. APU Pneumatic System. General. Air enters the APU inlet plenum from the air intake duct. This air is used for pneumatic power, APU cooling and combustion. A dedicated load compressor, connected to the APU mainshaft, supplies the pneumatic power. A cooling fan supplies air for oil cooling and compartment cooling.

B767/49/301 APU

ECU BITE. A REVERSE FLOW protective shutdown occurs if the compressor surges. An INLET DOOR protective shutdown occurs if the intake door is sensed as not being fully open when the APU is running. The LCIT SENSOR, ECS CONTROL, IGV ACT, FAN VALVE, PT SENSOR, DELTA-P SENSOR, and SURGE VALVE can be stored in the ECU as faulty units.

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. The inlet guide vanes are a pneumatic valve designed to control the volume of air into the compressor. 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. Switches behind a panel on the face of the ECU adjust IGV position. The switches are not for on-line adjustments. Cooling air. Air from the plenum is drawn by the gearbox-driven fan through the fan isolation valve to cool the oil, and to blow air into the APU compartment. The fan isolation valve is open when the APU is running.

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APU PNEUMATIC SYSTEM EFFECTIVITY ALL

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9.2. APU air intake door and actuator. APU 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° 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. APU 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.

B767/49/301 APU

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 locknuts 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.

APU air intake door actuator. The APU air intake door actuator is an electrically operated linear actuator. A 28 volt DC 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.

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APU AIR INTAKE DOOR & ACTUATOR EFFECTIVITY ALL

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9.3. APU air intake door operation. Power. Power for operation of the APU air intake door actuator is supplied by the 28 volt DC APU battery bus. Power for the APU control circuits is supplied by either the main battery bus or the APU 28 volt DC battery bus by a diode circuit. 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.

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The two door position switches internal to the actuator have been modified to avoid nuisance messages when the door and actuator are in the correct position. - 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.

A ground for K176 is supplied by an electronic switch inside the ECU whenever the speed is 15% or greater, to assure that the door remains open during APU shutdown until RPM is less than 15%, and also allows the door to remain open in the air with the main battery switch OFF. 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.

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APU AIR INTAKE DOOR OPERATION EFFECTIVITY ALL

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9.4. APU inlet sensors. APU 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 piezo-resistive 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%. 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.

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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 chromelalumel 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 -100°F to 450°F (-73.3°C to 232.2°C). 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.

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APU INLET SENSORS EFFECTIVITY ALL

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9.5. Inlet guide vanes. General. There are 28 radial articulated inlet guide vanes (IGV) regulating the airflow into the load compressor inlet. The vanes have a fixed leading edge and a moveable trailing edge. The vanes are supported with sleeve bearings at both ends. They are actuated by individual sector gears and a ring gear. The ring gear is positioned by the inlet guide vane actuator (IGVA). The vanes are full open at minus 20° angle and are full closed at 85° angle.

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APU INLET GUIDE VANES EFFECTIVITY ALL

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9.6. Inlet 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. 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. Troubleshooting. The actuator is connected to the IGV linkage bellcrank with a trunnion and bushing. Wear in this linkage may cause the IGVS to open partially during APU start, leading to a protective shutdown.

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APU INLET GUIDE VANE ACTUATOR EFFECTIVITY ALL

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9.7. IGV control logic. General. 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, & - ECS. The IGV’s are always closed below 95% RPM. Function adjustment switches. Eight screwdriver slot type fiveposition switches are located behind a screwattached cover plate on the face of the ECU. These switches are designed to facilitate software modifications as operational experience and environmental conditions dictate. They are not to be used for calibration or on-line adjustments. The switches are preset by the vendor as shown on the graphic. Six switches modify the IGV positioning vs pneumatic mode. One modifies the maximum allowable EGT vs LCIT schedule, and one modifies the cool-down time.

B767/49/301 APU

Duct pressurization mode. The APU bleed valve is open, but the airplane does not require pneumatics (on the ground, MES, ADP, ECS off). The IGV’s open (normal setting 37°) to pressurize the airplane pneumatic ducting to check for leaks, and to confirm the availability of pneumatics prior to activating a system by monitoring the duct pressure gages. A function adjustment switch allows modification. Inflight Mode. Whenever the ECU senses the air/ground switch in the air, and the airplane altitude is below approximately 18,000 feet, the IGVs are commanded full open (-20°) unless the EGT vs LCIT schedule is exceeded. The ECU receives the altitude signal from the P2 sensor. 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.

Idle mode. The APU operates in Idle pneumatic mode when RPM is greater than 95% and the bleed valve is closed. The IGV’s are closed (90°). The APU also automatically reverts to idle mode above approximately 18,000 ft altitude.

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Air driven pump (ADP) mode. The IGV’s open in response to the ADP signal and function switch. (Normally 3°). 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. ECS MIN. The ECU always initializes in ECS minimum, and does not revert to max. norm. or max. cold when T2 is between minus 10 and plus 60° Fahrenheit. The IGV‘s modulate in response to the MIN. function switch and zone temperature control unit signals. MAX NORM. If T2 is 60° F or warmer and DELTA-T is 10° F or greater, the IGV‘s modulate open in response to the MAX NORM function switch and DELTA-T. MAX COLD. If T2 is minus 10° F or colder and DELTA-T is 10° F or greater, the IGV‘s modulate open in response to the MAX COLD function switch and DELTA-T.

EFFECTIVITY ALL

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EGT vs LCIT schedule. For all pneumatic modes of operation, a maximum EGT is programmed vs ambient temperature (LCIT). The current to the IGV actuator torquemotor is reduced when this trimline is exceeded, reducing the pneumatic output. The normal schedule may be shifted by 40° increments with the EGT function switch. In position ‘E’ an extra duty cycle is available for the MES schedule should insufficient air be available for main engine starts in position ‘D’. This allows adjustments for high altitude airports, and similar circumstances. Cooldown. The APU is operating hot when both pneumatics and electric 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 cooldown 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 cooldown cycle. The function switch allows modification of cooldown time. (See APU normal operation - shutdown).

EFFECTIVITY ALL

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APU IGV CONTROL LOGIC EFFECTIVITY ALL

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9.8. APU Surge Bleed System. 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 IGV‘s. PCD2 air is used as the power to modulated the valve. The LCIT sensor senses hot air backflowing 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 11° C 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 99° C for 2.5 seconds, and initiates a shutdown immediately at 204° C.

EFFECTIVITY ALL

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APU SURGE BLEED SYSTEM EFFECTIVITY ALL

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9.9. 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.

EFFECTIVITY ALL

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APU SURGE VALVE EFFECTIVITY ALL

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9.10. Flow Sensor Module. 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. Pressure sensing. Total pressure is measured by a total pressure (PT) probe. A piezo-resistive 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 diaphragm in the chamber isolates PT & 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.

EFFECTIVITY ALL

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APU FLOW SENSOR MODULE EFFECTIVITY ALL

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9.11. APU Surge Bleed System Operation. Surge protection is maintained by modulating the surge valve to assure that load compressor output is matched to IGV position. As the IGV‘s 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 T2, the torquemotor signal is removed and a protective shutdown occurs. The surge valve is always open below 95% RPM.

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APU SURGE BLEED SYSTEM OPERATION EFFECTIVITY ALL

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9.12. Compartment & Oil Cooling. General. A gearbox-driven fan draws air from the plenum, through an isolation valve, and discharges air into a duct to the oil cooler. A port in the duct allows air into the APU compartment for cooling. Oil cooling air is discharged overboard through a duct to the bottom-left side of the compartment. Compartment cooling air vents overboard through a louvered blow-open door on the left side of the compartment. The door will open at a pressure differential of 2 psid.

EFFECTIVITY ALL

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APU COMPARTMENT & OIL COOLING EFFECTIVITY ALL

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9.13. APU Fan Isolation Valve. The fan isolation valve prevents a fire in the APU compartment from spreading through the inlet plenum to the forward side of the APU firewall. The valve is spring loaded closed when the APU is not running. PCD2 air opens the valve. The valve is a disk valve with a pneumatic actuator. It is bolted to a support on the upper right side of the APU and clamped to the ducting. It is an LRU. Operation. When PCD2 air is greater than 7.5 psig, the pneumatic actuator overcomes the spring force and fully opens the valve. A switch closes to signal the ECU that the valve is open. If the ECU detects the valve open when the APU is not running, or closed when the APU is running, the faulty unit FAN VALVE is stored in the ECU. APU operation is not inhibited. If the valve has failed closed, an eventual HOT protective shutdown may occur.

EFFECTIVITY ALL

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APU FAN ISOLATION VALVE EFFECTIVITY ALL

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9.14. APU Cooling Fan. The cooling fan supplies cooling air for the APU compartment and oil cooler. It is located in ducting downstream of the fan isolation valve. A screen is installed in the air inlet to protect the fan from foreign-objectdamage (FOD). The cooling fan is a 37 blade axial flow fan driven by and mounted to the gearbox. There are 31 stator vanes to direct the flow. Approximately one fourth of the output is used for compartment cooling, and three-fourths, for oil cooling. Buffer air is used as a secondary seal for the fan bearings. This reduces the likelihood of oil leakage into the fan housing. If oil leaks into the fan housing, then it could be carried by cooling airflow into the oil cooler. This would allow dirt and other contaminates to clog the cooler. The fan is attached to the gearbox with a V-band clamp. The fan inlet and outlet ducts along with the buffer air connection, must be removed to remove the fan. It is an LRU.

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APU COOLING FAN EFFECTIVITY ALL

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9.15. APU Exhaust Duct. General. The exhaust duct is a 11.5 inch diameter single piece welded inconel 625 duct. A bellows assembly attached to the turbine exhaust end of the duct allows relative movement between the APU and exhaust duct. The exhaust duct is attached to the APU with a V-band clamp. The aft end of the duct is supported by a leaf spring support ring attached to the airplane tail cone. A two-piece, 0.9 inch thick stainless steel foil insulation blanket is wrapped around the duct. The blanket is held on with safety wire lacings and is sealed to prevent the entrance of fluids.

EFFECTIVITY ALL

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APU EXHAUST DUCT EFFECTIVITY ALL

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10. APU NORMAL OPERATION. 10.1 Power. ECU power is supplied by both the main battery and the APU battery through a diode circuit. The APU starter motor is powered by the APU battery only. If a start is attempted when the main battery is removed or uncharged, the starter current decreases the APU battery voltage to the ECU to unacceptable levels, causing a DC POWER LOSS protective shutdown.

10.2. Starting.

If the fire handle is normal, no detected fire, no faults, and the main battery switch is on, (K175) has a ground through the main battery switch. This opens the APU fuel shutoff valve and enables the DC fuel pump. K175 is latched by the same driver that controls the intake door. The driver is energized when a start/on signal is present, or during shutdown until APU speed is less than 15%. The ignition unit is energized between 7% & 95% if protective shutdown signals are not present. The fuel solenoid valve is energized at 7%. The ECU de-energizes the solenoid valve to shut down the APU.

The start sequence is completely automatic and is controlled by ECU software. To start the APU, rotate the APU control switch to start and release ito (It is spring loaded to ON). This causes two things to happen; the logic in the ECU changes from high to low and the APU fuel control relay (K175) energizes.

10.3. Normal Running.

The ground at the main battery switch changes the logic in the ECU from high to low. This signals the ECU to perform the pre-start BITE and energize a driver allowing the APU air intake door to open. With no faults, pre-start BITE complete and the intake door open, the ECU energizes a driver. 28V DC is then supplied to the starter motor. The driver also causes the APU cycle meter to count another start attempt. The starter motor de-energizes when APU speed reaches 42% on the ground, 50% while inflight below 36,000 feet, or 55% while inflight above 36,000 feet.

In the air, electrical loads are available. Pneumatics are available up to 17,500 ft (approximately). The battery switch may be turned OFF, as K1 is latched through K203, K175, and the driver. The APU hourmeter records the number of hours the APU is operated above 95%. The number of hours operated is recorded to the nearest tenth of an hour.

EFFECTIVITY ALL

On the ground, electrical and pneumatic loads are available. The battery switch must be ON, to assure fire detection and automatic shutdown for an operating unattended APU.

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10.4. Normal Shutdowns. Normal shutdowns occur by turning the APU control switch to OFF or by turning the battery switch to OFF with the aircraft on the ground. All other shutdowns are protective shutdowns. The following normal shutdowns are possible. Control switch OFF prior to attaining 95% speed on start : - The APU shuts down immediately. Control switch OFF after 95% speed is attained : - Air valve closed for more than 60 seconds (or as set) : the APU shuts down immediately. - Air valve closed for less than 60 seconds (or as set) : the APU operates until the valve has been closed for 60 seconds, and then shuts down. - Air valve open : the air valve closes, and the cool-down timer starts, keeping the APU operational for 60 seconds, (or as set on the controller). The APU shuts down at the end of the cool down cycle. The generator is enabled during the cooldown cycle. All normal shutdowns are accomplished by removing the ground for the start/ on signal, causing the signal to go high. K175 is latched through the ECU driver until APU speed is below 15%. This keeps the APU fuel shutoff valve open and the dc pump enabled. The same driver also keeps the air intake door open until APU speed is below 15%. Both analog protective shutdowns are tested during all normal shutdowns. First an overtemp signal is injected into the overtemp logic. A signal is also sent to the shutdown and fault storage logic to deactivate those functions.

EFFECTIVITY ALL

After removing the overtemp and inhibit signals, an overspeed signal is injected into the overspeed logic. Fault storage is inhibited, allowing an analog overspeed protective shutdown. If this analog overspeed shutdown fails, and APU speed is greater than 85% after 20 seconds, the ECU performs a digital S/D CKT protective shutdown by tripping an internal magnetic breaker. If the ECU S/D CKT circuitry fails to trip the breaker and the APU RPM is above 7% after two minutes, the ECU initiates a protective shutdown. ECU is stored as the cause of the shutdown and also as a faulty LRU.

10.5. Protective Shutdowns. Protective shutdowns cause the APU to shut down immediately, without the benefit of the cool-down cycle. Protective shutdowns are initiated by the following : - Pulling the fire switch (S39), - APU fire detected (K2), - APU fault detected by the ECU (K442), - Pushing the remote shutdown switch (S484 on the nose strut). For all protective shutdowns, K175 is de-energized, causing the APU fuel shutoff valve to close. The ECU is reset in most cases by turning the APU control switch OFF. Remote Shutdown. The remote shutdown switch on the nose strut (P40 panel) is not intended for convenience shutdowns. Pushing the switch shuts down the APU without cooldown by energizing the APU fire relay, causing a FIRE EMERG protective shutdown. Also, K421 is latched through the battery switch. The battery switch must be cycled OFF and ON before restarting the APU after a remote shutdown.

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11. APU PROTECTIVE SHUTDOWN. 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% overspeed or by an EGT in excess of 621° C if the RPM is greater than 95%. Analog protective shutdowns cause the ECU to deenergize 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%, closing the APU air inlet door. Digital (software) protective shutdown. Digital protective shutdowns are initiated by the following : - 109% overspeed (OVERSPEED), - EGT overtemperature (OVERTEMP) (See RPM vs EGT schedule), - high oil temperature (oil temperature above 154 degrees C) (HOT), - low oil pressure (Oil pressure below 35 psi) (LOP), - loss of dc power (Batteries or diodes) (LOSS DC PWR), - APU air inlet door not full open (INLET DOOR), - APU fire (FIRE EMERG), - loss of both thermocouple rakes (FAILED SENSOR) (EGT sensing), - reverse flow (RVRSE FLOW) (sensed by the LCIT), - loss of both monopoles (rpm sensing) (FAILED SENSOR), - shutdown circuit failure (S/D CKT) (Trips an internal breaker), - ECU failure (ECU), - Generator oil filter differential pressure (35 psid) (GEN FILTER), - No acceleration : EGT over 204° C, acceleration less than 2% RPM for previous 5 seconds (NO ACCEL), - No flame (RPM over 7% for 10 sec, EGT less than 204° C) (NO FLAME), - Slow start - RPM fails to meet following schedule (SLOW START) : 7% RPM within 30 sec; 20% RPM within 50 sec; 50% RPM within 70 sec. EFFECTIVITY ALL

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 non-volatile memory for later recall on the FAULT DISPLAY 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 a S/D CKT shutdown and certain LRU faults. If the fault is still present, a new protective shutdown is initiated. S/D CKT - This shutdown trips an internal breaker in the ECU. The ECU must be replaced. LRU FAULTS - Some LRU‘s are tested in prestart BITE, and terminate the start if detected as faulty. (No starter engagement.)

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APU PROTECTIVE SHUTDOWN EFFECTIVITY ALL

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12. APU BITE INTERROGATION. The requirement to interrogate the ECU for fault information is annunciated in the flight compartment by the APU FAULT light, the EICAS APU FAULT advisory message, or by the EICAS APU BITE message on the ECS/MSG page. Faulty LRU‘s are stored in ECU memory during any one of three BITE routines; prestart BITE, self-test BITE, and monitor BITE. Prestart BITE is started when the APU control switch is rotated to START/ON. Monitor BITE is active during all operational phases of the APU. Self-test BITE is started using a switch on the front of the ECU. Pre-start BITE and self-test BITE perform the same routine. Some faulty LRU‘s do not inhibit APU operation or cause a protective shutdown. In these cases the faulty LRU is stored in the ECU memory and the EICAS level M APU BITE message appears. In general, those faulty LRU‘s that manifest themselves by other indications, such as through a protective shutdown, or loss of pneumatic output, do not cause the APU BITE message. The instructions for accomplishing the BITE check are placarded on the door of the E-6 rack. Note : If APU starting is inhibited due to certain LOP protective shutdowns, performing an APU BITE test causes the LOP protective Shutdown Light to blink. ECU fault memory must be erased to allow the APU to start.

EFFECTIVITY ALL

ECU front panel configuration. The ECU front panel allows fault recall, reset, and display by use of 2 light arrays and 3 switches. The light arrays are words etched into a plastic faceplate with two LEDs to back-light each fault when necessary. The LEDs are not LRUs. Two toggle switches are threeposition momentary, spring-loaded to the center. To start the procedure, hold the switch for one second then release it. A five-position rotary FAULT SELECT switch allows selection of the cause of the last five protective shutdowns. A toggle switch is located under the ERASE MEMORY plate to clear the fault memory. BITE interrogation conditions. The ECU is not powered unless the APU control switch is ON or commanded on by the ECU switches. Prerequisites for BITE interrogation include : - APU or main battery power, - APU control switch in the flight compartment OFF, - APU RPM below 7%.

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BITE sequence. LAMP TEST. - Each column of lamps comes on for four seconds each, in a lefttoright sequence. If a lamp does not come on, BITE is not inhibited, but the fault is not displayed if present. The ECU should be removed for bench-repair when convenient. FAULT SELECT - FAULT DISPLAY. - Place the rotary FAULT SELECT switch in position 1 and activate the FAULT DISPLAY switch (up). The most recent protective shutdown comes on for 4 seconds, followed by any faulty unit lamp that caused the shutdown, also for 4 seconds. If no protective shutdown is stored, the TST OK lamp comes on for 4 seconds. Repeat this procedure for fault select switch positions 2, 3, 4 & 5 to recall the cause of previous protective shutdowns. The FAULT SELECT switch operates only in conjunction with the FAULT DISPLAY switch. It does not affect normal operations, or the other ECU switches.

FAULTY UNIT. - Toggle the FAULTY UNIT switch (down) to display all faulty units stored in the FAULTY UNIT lamp array. The lamps come on from top to bottom, left to right across the array. Faults are not sequenced in the order stored. TST OK illuminates if no faults are stored. The lamps come on for 4 seconds each.

SELF-TEST. - Toggle the self/lamp test switch to self. WAIT comes on for 2 seconds, followed by any faulty units discovered. If no faults are detected, TST OK comes on. APU BITE EICAS message. Twelve LRU faults stored in the ECU NVM cause the EICAS maintenance message APU BITE to appear. These LRU‘s include : - P2 sensor, - flow divider, - de-oil solenoid, - low oil pressure sw., - generator filter delta-P sw., - oil temp sensor (HOT), - fan valve, - monopole 1, - monopole 2, - thermocouple rake 1, - thermocouple rake 2, - LCIT. Protective shutdowns caused by faulty LRU‘s.

ERASE MEMORY . - Push the toggle switch under the ERASE memory cover to clear ECU memory. The WAIT lamp comes on for 15-22 seconds while the procedure is in progress, followed by TST OK.

EFFECTIVITY ALL

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A protective shutdown caused by an LRU fault is indicated during BITE when FAULT DISPLAY is activated. The shutdown is illuminated for 4 seconds, followed by the associated LRU for 4 seconds. Only one LRU appears, except for dual speed sensing failures or dual thermocouple rake failures. Possible combinations include :

Protective Shutdown

ECU No accel. Slow start LOP S/D CKT No flame Gen. filter Overtemp. Failed sensor

EFFECTIVITY ALL

LRU ECU Fuel solenoid ECU Fuel solenoid Ing. unit APU starter Starter circuit ECU ECU ECU Fuel sol. Ignition unit ECU Filter sw. ECU Both speed ckts. Both thermocouple rakes

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APU BITE INTERROGATION EFFECTIVITY ALL

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13. APU INSTALLATION & REMOVAL. The APU may be removed using two fishpole hoists or a single hydraulic lift. Both methods require installation of an APU cradle that supports the APU during installation and removal. The cradle attaches to the left forward and both right side mounting brackets. Removal of the APU requires disconnection of APU electrical connections, fuel line, air ducts and installation of the APU cradle, fishpole hoists and ground support equipment. The APU harness, generator and starter motor electrical connections, APU fuel line and three air ducts (pneumatic system air supply duct, oil cooling air discharge duct and the exhaust duct) must be disconnected for removal. A ground support saddle assembly and clip assemblies maybe installed to support the exhaust duct and secure the tubular supports during APU removal. The left side fishpole hoist is installed in a keyhole slot permanently attached to the bottom of the APU air inlet plenum. The right side fishpole hoist is installed in a keyhole slot in a support beam that must be installed between the airframe and the air inlet plenum for APU removal. With the hoist installed the APU’s weight can be removed from its support installation. The APU can then be disconnected from its tubular support and lowered out of the airplane. Removal of the APU with the APU generator not installed requires installation of a 78 lb. ballast weight on the cradle for balance purposes.

EFFECTIVITY ALL

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13.1. APU System Deactivation.

B.767-300 — APU GTCP 331-200 ER.

General. If MEL requirements are met and the conditions below are satisfied, the airplane may be dispatched with the APU removed. For extended range operations both IDG’s and the hydraulic motor generator must be operable.

Breakers location. C5 C20 C780 C1052 C1058 C1063 C1333 C 1336 C1383 C1385 C1391

The APU air intake door and APU fuel valve must be closed prior to APU removal. Placard the associated circuit breakers, the APU generator control and manual reset switches, the APU start control panel and the APU bleed air control switch all as inoperative. Remove the APU and cap all electrical connectors. Remove the fuel hose and the APU bleed air duct and cap at the firewall. The oil cooling discharge air duct must be removed and the discharge port capped. Remove the exhaust duct and plug the port. CAUTION : ADEQUATELY SUPPORT EXHAUST DUCT. EXHAUST DUCT WEIGHS APPROXIMATELY 60 POUNDS. INSULATING BLANKET CAN BE EASILY CRUSHED OR PUNCTURED. KEEP DUCT AWAY FROM SHARP EDGES. Tie the right forward support and the left and right aft supports with a nylon retaining cord. Affix these cords to the APU compartment wall. The weight difference will be 526 pounds.

EFFECTIVITY ALL

APU Hour meter APU Start FIRE Extinguising D.C. Fuel pump CTL D.C. Fuel pump power APU Fuel valve Air supply APU bleed power Air supply APU bleed power APU prime control APU intake door actuator APU Alternate control

Relays location. K1 K2 K2 K3 K23 K117 K175 K176 K191 K197 K203 K421 K442 K496 K505 K793

APU Start Left pump low press APU Fire Fire Time delay Bleed airvalve APU Crank contactor APU Fuel control APU Air intake door D.C. pump control APU Start enable System n°2 Air-ground External shutdown APU Fault Air supply override Boost pump transfer N > 95 %

Switches location. S1 APU control switch S5 APU air supply S39 APU fire switch S484 APU fire shutdown S2 Main battery switch R10/11 R111/112 M208 APU battery

P5, P6, P49, E6 E6 G1 D35 D34 P6 P11-6 P11-6 E6 E6 P11-4

P5 P5 P5 P5 P49 P49 P37 P49 P37 P49 P37 P37 P37 P37 P37 P37

P5 P5 P8 P40 P5 P49 P34 E6

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A3 APU SCHEMATIC

EFFECTIVITY ALL

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A3 APU SCHEMATIC

EFFECTIVITY ALL

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115V AC R BUS APU TRU START

IN LINE FUSE

M

APU BATTERY

STARTER

TRU

APU START TRU

APU START TRU FAN POWER

TRU TEMP > 51,7¡C

* TRU OVHT RELAY - LATCH TO OPEN SWITCH IF TRU OVERHEAT - RESET TO CLOSE SWITCH AFTER STARTER RELAY DISENGAGEMENT

APU START TRU

28V DC R-BUS

APU TRU ENABLE RELAY

APU START RELAY APU BAT / SEL RELAY

CL

C20

K175 FUEL CTL

ON

AIR

20 sec TIMER

R11

C1391

K176

ON

M.D. & TEST

K203

TO EICAS

GND

ON

C780

OFF

EXT. S/D K421

BATTERY BUS C1052

C1058

FIRE

HOT BATT. BUS C1063

NORM

RUN

M.D. & TEST

∆P PT

28V DC

80 90

CL

115V AC R. BUS C1336

M

COOLING AIR FOR APU COMPT.

OP

APU

APU BLEED VALVE

SURGE VALVE DRIVER

FROM PRESTART BITE

FIRE

DISCH

K23

28V DC R. BUS C1333

AIR SPLY VALVE CTL.

S39

FIRE SW. NORM

K496

M FUEL S.O.V.

K793

TYPICAL

20 40 60 IGV ANGLE (¡)

FULL CLOSED

COMPRES. SURGE LINE

CONTROL LINE

SCHEDULED FLOW

N < 95% ∆P FAILED PT FAILED P2 < 7.5psi

∆P PT

FULL OPEN 0

ANALOG S/D DIGITAL S/D

N > 7% N < 95%

P2 & T2 IGV POSITION

-20

APU AIR SUPPLY S5

K505

M DC PUMP

AIR SPLY OVERRIDE K191

K2

L. PUMP LOW PRESS.

(ATA 24) GEN LOAD AVAIL

BLEED VALVE DRIVER

S/D TO DRIVER LOGICS

N > 95%

APU BAT BUS C20

BOOST PUMP XFER.

25 ms

OV. t¡ S/D

S/D LOGIC

DC PUMP CTL.

FIRE S/D REMOTE CTL. S485

INTAKE DOOR & FUEL DRIVER

+

DIGITAL S/D

-

N< 2 ANALOG S/D DIGITAL S/D

107%

INJECTED OVERSPEED SIGNAL

ANALOG OVERSPEED PROTECTIVE S/D INTERNAL MAGNETIC BREAKER

TO FUEL TM DRIVER LOGIC

ANALOG S/D

ÓS/D CKTÒ PROTECTIVE S/D

FIRE ENERG

.1 sec

OFF ST

ON

=0

FAULT INHIBIT

INJECTED OVERTEMP SIGNAL

ANALOG OVERTEMP PROTECT. S/D INHIBIT

N < 7%

INTAKE DOOR OPEN

PRESTART OK = 1 BITE

OFF

FAULT

FROM FUEL S.O.V.

FIRE

S1

START ST

FIRE S/D

COOL DOWN TIMER RESET

N > 85%

PROT S/D

MAIN BATT. SW.

FROM FIRE DETECTION

OFF

K1 START

FIRE SW. NORM S39

R12

C1383

APU BATT. BUS

OP

C1385

APU HOUR S

APU HOURMETER N19O

APU HOUR METER

K442

FAULT

K2 T.D. 1 sec. FIRE K3

INTAKE DOOR ACTUATOR

C5

TIMER

K793 APU N > 95%

2

OIL TEMP 1 < -6.7 ± 6.6 ¡C SENSING START RLY. ENERGIZED

STARTER DRIVER

1 PULSE/ 6 sec.

DE-OIL SOL. VALVE

APU CYCLES

APU CYCLEMETER N170

TRU OVHT*

APU CRANK CONTACTOR

APU TRU START RLY

> 4 ¡C < 4 ¡C OIL TEMP. SWITCH

28V DC

SIG. COND.

STARTER LOGIC

N > 95%

N < 95%

START/ON SIGNAL SPEED < 95% SPEED > 7%

N > 15%

APU AIR SPLY SW OFF AIR SPLY VALVE OPEN

POWER SUPPLY SHUTDOWN OCCURS WHEN ANY DETECTED FAILURE AND N < 7%

SOFTWARE HARDWARE

GND - 42% ALT < 34.000 - 50% ALT > 34.000 - 55%

2

GEN ∆P-SW.

DC PUMP

L. WING TAI L. ENG START VALVE

GEN.

THERMAL BYPASS VALVE

L.O.P.

OIL T¡ SW. OIL QTY. XMTR.

GEAR BOX

L. ISLN. VALVE

1

FUEL S.O.V.

R. ISLN. VALVE

R. PR. S.O.V.

CTR. ISLN. TO R. A/C PACK VALVE

HYDRAULIC RES. PRESS.

OP.

R. WING TAI

R. ENG START VALVE

PRESS. REL. V.

PCD AIR FILTER

PRESS. REGUL.

VENT QUICK DUMP V.

SURGE CONTROL VALVE

WATER TANK PRESS.

AFT CARGO HEAT

APU BLEED VALVE

SURGE ACTUATOR

(N.O.)

CL.

SERVO VALVE

CL. OP.

∆P IND

BYPASS V.

ACT. PRESS. REG. PR. REL. V.

INLET GUIDE VANE ACT.

TO INLET GUIDE VANES

IGV A TORQUE M.

LVDT

FUEL CONTROL UNIT

FLOW DIV. SOL. V.

FLOW DIVIDER

RAKE 2

TAILPIPE VENTILATION FROM SURGE RAKE 1 CONTROL V.

SEC. DRAIN VALVE

RUN SEQUENCE VALVE

FUEL SOL. V.

PRESSURIZING V.

TM

TM METERING V.

H.P. FILTER

L.P. FLTR.

∆P REG. VALVE

SELF BYPASS FILTER

START SEQ. V.

DRAIN

PRIMARY DRAIN V.

DRAIN VALVE

MANIF.

IGNITION UNIT

PRIM.

P2 SENSOR

PCD 2 PCD 1

TO TAIPIPE VENT

INLET SCREEN

DRAIN

AIR BUFFERING

MESH SCREEN

FAN ISOL. V. SW.

FAN ISOLATION VALVE

TO EXHAUST

SURGE CTL. V. TM VENT

TO IGV ACT.

LCIT T2 SENSOR

HOT

INLET SCREEN MAGNETIC CHIP DETECT.

INLET DOOR ACT.

INLET GUIDE VANES

DRAIN

AERATION

PR. REGUL. VALVE

∆P

Pt

SURGE TORQUE MOT.

TO ADP

TO L. A/C PACK

L. PR. S.O.V.

DE-OIL SOL. V.

∆P IND.

P. REG. V.

P. REL. V.

PRIM. OIL PUMP

GEN. HOT SENSOR

SCREEN

GEN. SCAV. PUMP

STARTER ∆P IND

GEN. OIL FILTER

PRESS. TEST PORT H.P. OIL FILTER

OIL COOLER

APU SCHEMATIC

SEC. MANIFOLD

FROM H.O.T. SENSOR

1

POWER SUPPLY

E.C.U. - M206

2

ACTUAL FLOW

A

B

C

D

E

F

G

H

J

page 127 20 - 01 - 2014 rev : 5

EFFECTIVITY ALL

INCREASE

B767/49/301 APU Training manual

Training manual

B767/49/301 APU

technics copyright U BR

sabena EFFECTIVITY ALL

page 128 20 - 01 - 2014 rev : 5