(2)
AMM 28-26-01/401, Manual Defueling Valve
C.
Access
(1)
Location Zones 543 Outbd Main Tank (Part), Front Spar to Mid Spar, Left 643 Outbd Main Tank (Part), Front Spar to Mid Spar, Right
(2)
Access Panels
546AB Fuel Tank Access Door
646AB Fuel Tank Access Door
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747-400
MAINTENANCE MANUAL
Defuel Check Valve
Figure 401
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747-400 MAINTENANCE MANUAL
D. Procedure
S 434-009
(1) Install a new gasket seal (2) on the defueling check valve (1).
S 424-010
(2) Put the defueling check valve (1) in its position on the front spar with the HINGE mark on the valve body in 45 degrees of the top.
S 434-018
(3) Install the bolts (3).
S 434-011
(4) Put new packings (5) in the coupling (4).
S 434-019
(5) Connect the coupling (4) to the fuel-feed manifold.
S 864-012
(6) Go out of and close the fuel tank (AMM 28-11-00/201).
S 414-013
(7) Install the manual defueling valve (AMM 28-26-01/401).
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747-400
MAINTENANCE MANUAL
FUEL JETTISON SYSTEM - DESCRIPTION AND OPERATION
________________________________________________
1. General
_______
A. The fuel jettison system supplies a means for dumping fuel overboard during an in-flight emergency to reduce the weight of the airplane to a permitted landing weight. Fuel from the tanks is pumped into the fuel jettison manifold and then discharged through fuel jettison nozzles found on the two wingtips of the airplane.
B. The fuel jettison system is operated and controlled automatically by a fuel jettison control card which is active when the system is armed and the fuel jettison nozzle valves in the wingtips are opened. The system will jettison fuel until the fuel quantity remaining onboard decreases to a preset level. Power to the system is 28 volts dc supplied from the P180 dc power distribution circuit breaker panel and 115 volts ac from the P414 and P415 main power distribution panels.
C. These components are used for fuel jettison:
(1)
Two fuel jettison nozzles in the wingtips
(2)
Two fuel jettison nozzle valves
(3)
Two override/jettison pumps in the center wing tank
(4)
Two jettison pumps in each of the inboard main tanks
(5)
The fuel jettison manifold
(6)
Two main tank transfer valves
(7)
Four transfer valves for the reserve tanks
D.
Fuel jettison system components, such as pumps, valves and controls, are also used for pressure fueling and defueling while airplane is on the ground (AMM 28-21-00/001 and AMM 28-26-00/001).
E.
Fuel jettison operation can be monitored by viewing fuel synoptic on EICAS auxiliary display.
2. Fuel Jettison Manifold (Fig. 1)
______________________
A. The fuel jettison manifold supplies a passage for fuel to be dumped overboard during a fuel jettison operation. The fuel jettison manifold is found in the fuel tanks and extends from wingtip to wingtip of the airplane. Found at each end of the fuel jettison manifold is a fixed fuel jettison nozzle. The continuous fuel jettison manifold permits dumping of fuel from one side of the wing to the other wingtip should the fuel jettison nozzle valve on that side fail to open. The fuel jettison manifold is also used for pressure fueling of the tanks (Ref 28-21-00/001).
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