28-25-00
ALL ú ú 01 Page 2 ú Oct 10/88
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL
SHROUD MANIFOLD HOSE FLEXIBLE MANIFOLD
SHROUD BULKHEAD AIR SEAL
DECK PRESSURE
VALVE FUEL SHUTOFF FROM APU DUST COVER
MANIFOLD SHROUD
FITTING ADAPTER REAR SPAR SHROUD DRAIN FLEXIBLE HOSE MANIFOLD FWD OUTBD
SHROUD DRAIN HOLE B
SHROUD DRAIN MANIFOLD
FLAME ARRESTER DRAIN VALVE PRIMARY POPPET
DRAIN VALVE A ELEMENT
A FWD INBD
C A-A
Figure 1 (Sheet 2) APU Fuel Feed System Component Location
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400 MAINTENANCE MANUAL
SHROUD
FUEL LINE UNION
SHROUD FUEL
FUEL FITTING
LINE
FWD
INBD
(TYPICAL)
D
APU FIREWALL
APU FUEL LINE BELLOWS
SHROUD DRAIN LINE
APU FUEL LINE
SHROUD
APU FUEL LINE
FLAME ARRESTER
FWD INBD
E
APU Fuel Feed System Component Location Figure 1 (Sheet 3)
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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747-400
MAINTENANCE MANUAL
B. The forward drain consists of aluminum tubing extending from the adapter fitting at the center wing tank rear spar to the drain valve located between the body landing gear doors. The aft drain consists of aluminum tubing extending from the shroud immediately forward of the APU firewall to a fitting on the aft drain mast. Each drain contains a flame arrester.
4. APU Fuel Shroud Drain Flame Arrester (Fig. 1)
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A. The drain line flame arresters prevent flame from entering the APU fuel supply line shroud drain lines. A flame arrester is located at the lower end of each drain line. The arrester consists of a housing, an explosion-proof element and provisions for connecting the drain tubing. The flame arrester element is made of corrugated steel tape contained in a manner that will allow unrestricted fuel drainage but will not allow flame to enter the drain line.
5. APU Fuel Line Shroud Drain Valve (Fig. 1)
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A. A manually-operated drain valve is installed at the lower end of the forward APU fuel supply line shroud drain line. The valve is a spring-loaded, poppet-type valve consisting of a housing, mounting base, stainless steel primary poppet, a plastic secondary poppet, and a removable seat for the primary poppet.
B. When the seat for the primary poppet is removed, the secondary poppet closes to prevent accumulated flow of fuel from the drain line. The drain valve is attached to the fuselage skin with two bolts. To drain the fuel shroud, the poppet is manually pushed from its seat allowing fuel to drain through the drain hole in the center of the valve.
6. APU DC Fuel Boost Pump (Fig.______________________1)
A. The APU dc fuel boost pump provides fuel to the APU when ac power is not available. The pump is mounted in a plug-in manner through the rear spar of the No. 2 main fuel tank. The unit is a 28-volt dc electrically driven pump with a capacity of approximately 1300 pounds of fuel per hour at 18 psi. The pump assembly consists of a motor/impeller assembly and, installed on the inside of the tank, a pump receiver. An inlet shutoff valve in the housing makes it possible to remove the motor/impeller assembly without defueling the tank. The inlet shutoff valve is actuated by the end of the motor/impeller shaft. The housing also includes a discharge port and a mounting flange.
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