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49-71-31
ú ú 01 Page 504 ú Nov 12/01
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
APU INDICATING SYSTEM - DESCRIPTION AND OPERATION
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1. General
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A. The APU indicating system monitors the condition of the APU engine. The APU indicating system has the OVER SPEED light and the elapsed time indicator. The OVER SPEED light is found on the P5 forward overhead panel. The elapsed time indicator is found on the APU engine.
2. OVER SPEED Light
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A. The OVER SPEED light supplies the indication when the APU engine speed is too high. The OVER SPEED light is amber. The OVER SPEED light is energized when the APU engine speed is 110%. The 110% contact in the electronic speed switch is energized. The circuit to the OVER SPEED light is completed and the APU stops.
B. The OVER SPEED light is connected to the APU annunciator and the MASTER CAUTION lights. When the OVER SPEED light comes on, the APU annunciator and MASTER CAUTION lights also come on. For a more detailed description of the APU annunciator and MASTER CAUTION lights, refer to AMM 33-15-00/001. To do a test of the OVER SPEED light, the OVER SPEED light can be pushed or the master test switch can be pushed.
3. Elapsed Time Indicator
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A. The elapsed time indicator keeps a record of the hours of APU operation. The elapsed time indicator is an electrical clock that is closed in a hermetically sealed case. The elapsed time indicator shows the total hours of APU operation with a digital counter. The digital counter shows hours and tenths of hours. The elapsed time indicator is installed on the oil cooler.
B. When the APU engine speed is 95%, the signal from the 95% contact in the electronic speed switch energizes the elapsed time indicator. The elapsed time indicator keeps a record of the APU operation when the APU engine speed is more than 95%. The circuit for the elapsed time indicator has a circuit breaker. The circuit breaker prevents damage to the elapsed time indicator from a surge of current. When the circuit breaker opens, it can be closed with the reset button.
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49-72-00
ALL ú ú 03 Page 1 ú Nov 15/94
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
////////////////////////A / GTCP85-129 SERIES /737-300/400/500/ ENGINES /MAINTENANCE MANUAL ////////////////////////
SEE A
SEE B
A
ELAPSED TIME INDICATOR
CIRCUIT
BREAKER
FWD
BUS OFF BUS BUS
B
OFF OFF
ON ON
GEN 1 APU GEN GEN 2
APU
LOW OIL OVER
12
PRESSURE SPEED
PILOTS LIGHTSHIELD
100
6 EXH 8 7 5 C X 100 50 AC AMPERES 150 200 LIGHT OVERSPEED FIRE MASTER HSI ILS VOR/
4 3 12 TEMP 0 BELL CUTOUT WARN PUSH TO RESET CAUTION NAV
FLT CONT ELEC
IRS APU
FORWARD OVERHEAD PANEL FUEL OVHT/DET
MASTER
1 OR "MAINT" LIGHT "LOW OIL QUANTITY" LIGHT LIGHT CAUTION LIGHT APU ANNUNCIATOR
2 "HIGH OIL TEMP" LIGHT
OR "FAULT" LIGHT
APU Indicating System Component Location
Figure 1
EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú
49-72-00
ALL ú ú 02 Page 2 ú Jul 15/91
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
ELAPSED TIME INDICATOR - REMOVAL/INSTALLATION
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1. General_______
A. This procedure contains the removal and installation tasks for the
elapsed time indicator.
TASK 49-72-11-004-001
2. Elapsed Time Indicator Removal (Fig. 401)______________________________
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