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Defuel valve control relay
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Defuel valve.
The EEU sends the position signals to the FQIS processor unit (FQPU) on the ARINC 629 system buses. When the valve is open, the FQPU turns on the blue defuel valve light. You push the defuel valve light to do a test of it.
If there is a disagreement between the switch position and the defuel valve control relay, the FQPU sends a fault signal to the AIMS.
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DEFUEL -FUNCTIONAL DESCRIPTION -ELECTRICAL
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DEFUEL -OPERATION
General
The defuel procedure is on a placard on the refuel station door. The procedure is also in the maintenance manual.
Defuel Procedure
This is a brief summary of the pressure-defuel procedure:
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Connect the fueling nozzles
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Move the defuel lever on refuel adapter to the defuel position
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Move the defuel valve switch to OPEN
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Turn on the fuel pumps in each tank that you want to defuel
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Open crossfeed valve if necessary
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Move the defuel valve switch to CLOSE when the tanks are empty
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Turn off the fuel pumps
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Move the defuel lever on the refuel adapter to the refuel position
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Remove the fueling nozzles
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Do a test of the defuel valve open light.
The suction-defuel procedure is the same as the pressure-defuel procedure except you do not turn on the fuel pumps. Suction defueling stops when one of the bypass valve inlets is uncovered. Thus, if the tanks do not become empty at the same time, there may be fuel remaining in one of the tanks.
Tank-to-Tank Transfer
To move fuel from one tank to another you must use the engine feed, defuel, and refuel systems. These steps are necessary for tank-to-tank transfer:
*
Do a test of the indicators and defuel valve open light
*
Move the defuel valve switch to OPEN
*
Turn on the fuel pumps in the tank you want to defuel
*
Open crossfeed valve if necessary
*
Move the refuel valve switches to OPEN in the tank you want to put the fuel into.
If you want to defuel the tank, let the pump operate until the tank is empty. If you want to move only part of the fuel, use the refuel valve control switches to stop the fuel flow.
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777 AIRCRAFT MAINTENANCE MANUAL
DEFUEL -OPERATION
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FUEL JETTISON -INTRODUCTION
Purpose
The fuel jettison system dumps fuel overboard to reduce the landing weight. You operate the jettison system from the fuel panel on the P5 overhead panel.
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777 AIRCRAFT MAINTENANCE MANUAL
FUEL JETTISON -INTRODUCTION
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FUEL JETTISON -GENERAL DESCRIPTION
General
The fuel jettison system dumps fuel overboard to reduce the landing weight. You operate the jettison system from the fuel jettison panel (P5). The ELMS controls the fuel jettison system.
Jettison Pumps
There are two override/jettison pumps in the center tank and one fuel jettison pump in each main tank.
Each pump has a pressure switch that sends a signal through the ELMS to the systems ARINC 629 buses. The signal goes to the jettison panel and the AIMS for fault indication.
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