(5)
Fuel Quantity Indicator (AMM 28-41-0/001)
(a)
Fuel tank No. 1 must contain a specified amount of fuel for APU operation (AMM 49-11-0/201).
(b)
The APU fuel inlet line must be filled with fuel before attempting to start the APU. During start, the fuel is fed to the fuel control unit by (1) ac boost pump if ac power is available (2) suction feed only - no boost pump available.
(6)
APU Controls and Indicators
(a)
The APU control panel on forward overhead panel P5 provides the controls and indicators required to operate the APU. The controls and indicators on the APU panel are listed in Fig. 101.
(b)
The APU control unit (M280 module), located in the lower 43 section on the E3-3 electrical and electronic equipment rack has one board in it containing micro circuits that may be damaged by electrostatic discharges. A decal attached to the module indicates that special handling of the unit is required.
540
49-00 Page 102 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. Aug 15/80
CAUTION: STATIC SENSITIVE. DO NOT HANDLE BEFORE READING PROCEDURE FOR HANDLING ELECTROSTATIC DISCHARGE SENSITIVE DEVICES (AMM 20-40-12/201). CONTAINS DEVICES THAT CAN BE DAMAGED BY STATIC DISCHARGE.
565
Aug 01/95 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 49-00 Page 103
CONTROL/INDICATOR FUNCTION Battery Switch 1. Provides power to APU control system. Master Switch ON 1. Provides dc power to open fuel shutoff valve and
air inlet door. Master Switch START 1. Initiates starter sequence (start relay R5). (Momentary Position) 2. Center spring-loaded return position to ON.
3. Opens fuel shutoff valve and air inlet door.
STOP 1. Power is supplied to the overspeed oscillator in the electronic speed switch to simulate an engine (APU) overspeed.
Bus Tie Breaker Switches Connects APU generator to the airplane electrical system, (Ref Chapter 24, Electrical).
FIRE SWITCH When pulled will shut down an operating APU and energize fire-extinguishing circuit (Ref Chapter 26, Fire Protection).
APU Bleed Valve Switch Operates the APU bleed air valve (Ref Chapter 36, Pneumatics).
FIRE WARN Indicator Indicates fire condition in APU compartment (Ref Chapter 26, Fire Protection).
APU Generator Ammeter Indicates APU generator load current (Ref Chapter 24).
EGT Indicates APU exhaust gas temperature.
APU Controls and Indication 540 49-00 Figure 101 (Sheet 1) May 20/82
Page 104
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
CONTROL/INDICATOR FUNCTION
LOW OIL PRESSURE LIGHT (amber) NORMAL Illuminates when master switch placed in ON position. Extinguishes when the oil pressure reaches 55 psig. ABNORMAL
Illuminated when oil pressure decrease to 45 + 3 psi.
Automatic shutdown in 10 + 2 seconds. Master caution light and
APU annunciator illuminates. LOW OIL QUANTITY LIGHT (blue) Illuminates when APU oil quantity is low. (1.5 + 0.5 qt.) HIGH OIL TEMP LIGHT (amber) Illuminates when APU oil temperature exceeds high oil
temperature switch set point range (250° + 10°F or 285° + 10°F). MASTER CAUTION light and APU annunciator illuminate. APU GEN OFF BUS LIGHT (blue) Illuminates when APU is not supplying a generator bus and APU turbine speed reaches 95% RPM. OVERSPEED LIGHT (amber) Illuminates under the following conditions:
1.
When the APU MASTER switch is turned to OFF following an unsuccessful APU start.
2.
When the APU is shut down by turning the MASTER switch to OFF (normal shut down) if there is a malfunction.
3.
When the APU automatically shuts down due to over-speed during APU operation either on the ground or in the air.
It is important that conditions under which the over-speed light is illuminated be determined and that correct maintenance procedures be used to avoid damage to the APU.
The most common occurrence of overspeed light operation is the overspeed light coming ON when the APU master switch is turned OFF following an unsuccessful APU start.
504 APU Controls and Indicators
Feb 20/86 Figure 101 (Sheet 2) BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 49-00 Page 105
OVERSPEED LIGHT (Cont.) Depending on the point reached in the start cycle during the attempted start, the light will come on either immediately after the APU is switched 'OFF' or within 5 seconds after switching the APU 'OFF'. Before attempting another start two minutes should elapse with the APU switch in the OFF position to allow for the time delay system in the APU start system to recycle.
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