Description and Operation 1 ALL General 1 Light - HIGH OIL TEMP or FAULT 1 Light - LOW OIL PRESSURE 1 Light - LOW OIL QUANTITY or 4
MAINT Switch - Low Oil Quantity 4 SWITCH - LOW OIL QUANTITY 49-94-11 Removal/Installation 401 ALL SWITCH - OIL TEMPERATURE 49-94-21 Removal/Installation 401 ALL
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BEJ Page 13 Mar 12/02
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
AIRBORNE AUXILIARY POWER - DESCRIPTION AND OPERATION
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1. General
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A. The airborne auxiliary power for the airplane is supplied by a gas turbine auxiliary power unit (referred to as the APU). The APU can supply pneumatic bleed air and electrical power to the airplane while the airplane is on the ground or in flight. The APU operation is controlled by the APU control unit. The APU control unit is found on the E3-3 electrical shelf.
B. The APU has a gas turbine engine (referred to as the APU engine), APU electrical generator and electronic controls. The APU engine turns the APU electrical generator through the gearbox assembly. The electronic controls make sure that the APU operates safely and continuously. The airplane pneumatic system connects to the APU bleed system (AMM 36-11-05/001). The APU electrical generator supplies the electrical power to the airplane electrical system (AMM 24-21-00/001). The APU has a fire protection system (AMM 26-22-00/001).
C. The APU is found in a compartment in the airplane tail section. To get to the APU, the APU cowl door must be opened and the lower shroud must be removed.
D. The No. 1 fuel tank supplies the fuel for the APU operation. The airplane battery supplies the electrical power for the APU. To start the APU operation, the APU master switch is moved to the START position and released to the ON position. The APU fuel valve and the air inlet door open. The fuel, ignition, and acceleration are controlled to permit the APU engine to operate safely and quickly. When the APU speed gets to 100%, pneumatic power and electrical power are available for the airplane operation. If a large quantity of pneumatic power is necessary, the electrical load must be decreased.
E. The APU stops when the APU master switch is moved to the OFF position. The APU will stop automatically because of an engine overspeed, low oil pressure, high oil temperature, or APU fire (AMM 26-22-00/001).
2. Airplanes with the Electronic Temperature Control (ETC) (Fig. 3)
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A. Some of the airplanes have a later configuration APU. This APU has the electronic temperature control (ETC). It is not easy to see the differences with this later configuration APU. To do the maintenance on the APU, you must correctly identify the APU. In the Maintenance Manual, the procedures that are not common between the APU's have an effectivity of AIRPLANES WITH THE ETC and AIRPLANES WITHOUT THE ETC.
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49-00-00
ALL ú ú 01 Page 1 ú Mar 15/92
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
////////////////////////A / GTCP85-129 SERIES /737-300/400/500/ ENGINES /MAINTENANCE MANUAL ////////////////////////
SEE B
SEE A
SEEC
SEE D
EXHAUST DUCT
AUXILIARY POWER UNIT (SHROUDED)
FUEL LINE
FLIGHT COMPARTMENT
COMPRESSOR
AIR DUCT
COOLING
TORQUE AIR DUCT
BOX LINER
AIR DIFFUSER DUCT
AIR INLET DOOR
BLEED AIR
VALVE BLEED AIR DUCT
Auxiliary Power Unit Component Location Figure 1 (Sheet 1)
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49-00-00
ALL ú ú 01 Page 2 ú Mar 15/92
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
THE "TEST PASS" AND "TEST FAIL" LIGHTS
Auxiliary Power Unit Component Location Figure 1 (Sheet 2)
A09824
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