ENGINE FUEL FEED -INTRODUCTION

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ENGINE FUEL FEED -GENERAL DESCRIPTION

General
The engine fuel feed system controls and supplies fuel to the engines. It uses these inputs:
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Fuel panel

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Fuel control switches

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Engine fire switches

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The ELMS.

The engine fuel feed system uses these components to supply fuel to the engines:
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Fuel pumps

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Fuel pump pressure switches

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Crossfeed valves

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Spar valves

The engine fuel feed system uses power from the ELMS and the engine fuel spar valve battery.
Fuel Pump Control
Each fuel pump has a switch on the fuel panel. The switches control relays in the ELMS to supply power to the pumps.
Fuel Pump Pressure Switches
Pump pressure switches send low pressure signals to the ELMS. The ELMS sends the signals through OPAS to turn on the low pressure lights on the pump switches.
Crossfeed Valves Control
The crossfeed valve switches on the fuel panel directly control the crossfeed valves. The ELMS supplies the power that opens or closes the valves.
Spar Valve Control
The fuel control switches control relays to open and close the spar valves. The engine fire switch must be down to permit the power to get through the relays to the spar valve.
The fire switch also has a direct circuit to the spar valve. This closes the valve when you pull the fire switch.
The hot battery bus (ELMS) or the engine fuel spar valve battery supply the power to open or close the spar valve.
Fault Indication
The ELMS compares fuel panel switch positions with crossfeed valve and fuel pump relay positions to look for disagreements. The ELMS receives switch positions on the systems ARINC 629 buses. The OPAS reports faults of the spar valves and the engine fuel spar valve battery. Faults go to the AIMS for indication.
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777 AIRCRAFT MAINTENANCE MANUAL

ENGINE FUEL FEED -GENERAL DESCRIPTION

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777 AIRCRAFT MAINTENANCE MANUAL

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ENGINE FUEL FEED -COMPONENT LOCATIONS -TANKS

General
The engine fuel feed system has these components:
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Fuel suction bypass valve (2)

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Outlet float-operated shutoff valve (2)

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Crossfeed valve (2)

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Engine feed manifold

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Override/jettison pump (2)

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Scavenge jet pump (6)

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Inlet float-operated shutoff valve (2)

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Boost Pump (4)

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Spar valve (2).

Main Tank Fuel Suction Bypass Valves
There is one fuel suction bypass valve in each main tank. It attaches to the engine feed manifold. You get access to the bypass valve through the fourth fuel tank access door.
Fuel Crossfeed Valves
The forward and aft crossfeed valves isolate the left and right sides of the engine feed manifold. Both valve bodies are in the left side of the center tank. You get access to the valve bodies through the first fuel tank access door in the left wing. The valve actuators are on the rear spar aft of the first fuel tank access door.
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Engine Feed Manifold
The engine feed manifold connects the output of the fuel pumps to the engine fuel main supply line. Sections of the manifold are in the center dry bay, the center tank, and the main tanks.
Center Fuel Tank Override/Jettison Pumps
There are two override/jettison pumps, one for each section of the center tank. Both pumps attach to the rear spar of the center dry bay. You get access to the pumps in the main wheel wells.
Scavenge Jet Pumps
There are four water scavenge jet pumps and two center tank fuel scavenge jet pumps. Each main tank has one water scavenge jet pump on the rear spar aft of the Fourth fuel tank access door.
Each side of the center tank has a water scavenge jet pump and a fuel scavenge jet pump. The water scavenge jet pumps are on the rear spar of the center dry bay. The fuel scavenge jet pumps are on the rear spars of the wings.
Float-Operated Shutoff valves
Each center tank fuel scavenge jet pump has an inlet and an outlet float-operated shutoff valve. You get access to the inlet valve through the first fuel tank access door. You get access to the outlet valve through the fourth fuel tank access door.
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ENGINE FUEL FEED -COMPONENT LOCATIONS -TANKS
　
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