A signal for valve fault indication goes to the fuel jettison panel and the AIMS.
General Operation
In the air, you push the arm switch to operate the fuel jettison system. The arm switch sends a signal through the systems ARINC 629 buses to the ELMS.
The jettison system has two operating modes:
*
Maximum landing weight (MLW) mode
*
Manual (MAN) mode.
When you arm the jettison system, it is in the MLW mode. The ELMS calculates the quantity of fuel to remain after it jettisons fuel to the MLW. The ELMS subtracts zero fuel weight (ZFW) from MLW to get the fuel to remain. It gets the MLW and ZFW from the AIMS. The quantity of fuel to remain in the airplane shows on the EICAS display.
The ELMS gets actual fuel quantity from the FQPU. It uses this information to calculate the time to jettison.
When you pull out the fuel-to-remain selector, the jettison system is in the MAN mode. You can use the fuel-to-remain selector to increase or decrease the quantity of fuel to remain.
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FUEL JETTISON -GENERAL DESCRIPTION
In the air, the jettison nozzle valve switches cause the ELMS to open the nozzle valves. Each switch also causes the ELMS to open the isolation valves and start the fuel jettison pumps. You must use the center tank pump switches to start the override/ jettison pumps.
On the ground, the arm switch causes the ELMS to open the two jettison isolation valves and start the fuel jettison pumps.
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777 AIRCRAFT MAINTENANCE MANUAL
FUEL JETTISON -GENERAL DESCRIPTION
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FUEL JETTISON -COMPONENT LOCATIONS -FUEL TANKS
General
The jettison system has these components:
*
Override/jettison pumps
*
Jettison pumps
*
Jettison isolation valves
*
Isolation check valves
*
Refuel/jettison manifold
*
Jettison nozzle valves.
Override/Jettison Pumps
There are two override/jettison pumps in the center tank. They are in the left and right wheel wells on the rear spar. The engine feed section describes these pumps.
Fuel Jettison Pumps
There is one fuel jettison pump in each main tank. They are on the rear spar forward of the flaperons. These pumps are interchangeable with the override/jettison pumps.
Fuel Jettison Isolation Valves
There is one fuel jettison isolation valve in each section of the center tank. The valve actuators are on the rear spar just outboard from the fuselage.
These are the same kind of valve as the other motor-actuated valves in the fuel system.
Jettison Isolation Check Valve
There is a jettison isolation check valve in each section of the center tank. The valve prevents fuel jettison by the left and right main tank fuel boost pumps.
Refuel/Jettison Manifold
The refuel/jettison manifold is in both wings and goes through the end of the main tank and surge tank. The end of the refuel/ jettison manifold has a nozzle. The nozzle comes out of the trailing edge of each wing between the outboard flap and the aileron.
Fuel Jettison Nozzle Valves
There is one jettison nozzle valve near each end of the refuel/ jettison manifold. They attach to the refuel/jettison manifold.
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FUEL JETTISON -COMPONENT LOCATIONS -FUEL TANKS
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FUEL JETTISON -COMPONENT LOCATIONS -REAR SPAR
General
The fuel jettison pumps are on the rear spar, aft of each engine.
There are two fuel jettison isolation valves. The valve actuators are on the rear spar. There is an actuator in each main landing gear wheel well.
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FUEL JETTISON -COMPONENT LOCATIONS -REAR SPAR
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