APU FUEL FEED -FUNCTIONAL DESCRIPTION -APU DC FUEL PUMP & ISOLATION VALVE
Fault Indications
The P310 EEU monitors the status of the APU dc pump pressure switch and the APU isolation valve position. If the pressure switch does not agree with the dc pump command status, the EEU sends a fault message to the systems ARINC 629 buses. If the APU isolation valve position does not agree with the isolation valve command status, the EEU sends a fault message to the systems ARINC 629 buses. The fault messages cause EICAS advisory and status messages.
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APU FUEL FEED -FUNCTIONAL DESCRIPTION -APU DC FUEL PUMP & ISOLATION VALVE
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APU FUEL FEED -FUNCTIONAL DESCRIPTION -APU FUEL SHUTOFF VALVE
General
The ELMS automatically controls the APU fuel shutoff valve. The EEU in the P310 panel uses inputs from the APU controller and the APU selector to control the valve.
Control
The P310 EEU sends a valve open command when any of these conditions occur:
*
APU is running
*
APU selector is in the ON or START position.
It sends a valve close command when any of these conditions occur:
*
APU is not running
*
APU fire switch closes
*
APU fire shutdown switch closes
*
APU fire.
The APU running signal comes from the APU controller.
Power
The APU fuel shutoff valve gets power to open or close from the fuel shutoff valve bus. The P310 EEU sends a command to operate the valve. This energizes the open or close coil of the APU fuel shutoff valve control relay and permits power to go to the valve.
Power to operate the valve goes through limit switches to the actuator. The actuator moves the valve to the commanded position. When the valve is in the commanded position, the limit switches remove power from the actuator.
If you pull the APU fire switch or push the APU fire shutdown switch, power goes directly to the APU fuel shutoff valve to close it. Pushing the APU fire shutdown switch energizes the APU remote shutdown relay. APU fire control circuits keep it energized.
Fault Indications
The P310 EEU monitors the positions of the APU fuel shutoff valve control relay and the APU remote shutdown relay. The EEU gets the APU fuel shutoff valve position from the OPAS on the systems ARINC 629 buses. If there is a disagreement between the valve position and the relay positions, the EEU sends a fault message to the AIMS. The fault message causes EICAS advisory and status messages.
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APU FUEL FEED -FUNCTIONAL DESCRIPTION -APU FUEL SHUTOFF VALVE
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APU FUEL FEED -INDICATIONS
Fuel Synoptic Display
The fuel synoptic display is a simplified schematic of the fuel system. It shows the system configuration for the APU fuel feed system.
The configuration in the fuel synoptic display below shows the left forward boost pump feeding the APU. The inset display shows the APU dc fuel pump feeding the APU.
Fuel Management Maintenance Page
The fuel management maintenance page shows commanded and actual status for the APU fuel feed system components.
The AC PUMP data tell you about the left forward boost pump.
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777 AIRCRAFT MAINTENANCE MANUAL
APU FUEL FEED -INDICATIONS
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DEFUEL -INTRODUCTION
General
The defuel system moves fuel from the airplane tanks to the refuel station, or from one airplane tank into another. You operate the defuel system with the refuel station controls.
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DEFUEL -INTRODUCTION
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DEFUEL -GENERAL DESCRIPTION
General
The defuel system moves fuel from the airplane tanks to refuel station. It also moves fuel from one airplane tank into another (tank-to-tank transfer). There are two ways to get fuel out of the tanks:
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