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collector tank.
MAIN EJECTOR
Two main ejectors are operated by motive flow created by the high-pressure output of the engine-driven fuel pumps. Each
ejector pump takes fuel from its associated collector tank and delivers the fuel to the engine. The main ejectors are installed
on the bottom of the collector tanks.
FUEL SYSTEM CONTROLS
The fuel system controls are as follows:
- L PUMP and R PUMP standby boost pump rotary switch (OFF, AUTO, ON)
- XFER SWITCH
- GRAVITY XFLOW switch
- L (R) ENG FIRE switches
In order to provide pressure during engine start or in the event of feed ejector failure, a standby boost pump is fitted in
parallel with each feed ejector. When the engine RUN switch is selected ON and the respective standby boost pump is
armed, it will be commanded ON as long as the feed ejector does not deliver sufficient pressure to the dedicated engine.
For added safety, when sufficient pressure is achieved at the primary ejector outlet, a time delay will command the boost
pump to remain ON for an additional 10 seconds.
The standby boost pumps are also used for lateral balance of the fuel load by pumping fuel from one wing to the other. If
lateral imbalance of fuel loads occur (e.g. after engine failure), fuel can be pumped from wing to wing by means of the
standby boost pumps which are interconnected by a transfer valve. The transfer valve is closed in order to isolate left and
right engine feed systems from each other except when restoring balance. Transfer is achieved by opening the transfer valve
and then switching on the standby boost pump. Fuel will be pumped from the wing through the transfer valve and the inactive
standby boost pump into the other wing to restore fuel balance.
A secondary means of balancing fuel completely independent of the pumped system is provided by a gravity crossflow
system that provides a direct flow path between the wings and is controlled by the opening and closing of a gravity crossflow
shutoff valve. While the gravity transfer shutoff valve is opened, aircraft maneuvering (steady heading sideslip) may
be required to achieve transfer of fuel if the initial imbalance is minimal. Aircraft maneuvering is not required when the
imbalance between the two tanks is large.
Whether performing balancing by means of the standby boost pumps or by gravity, the action is controlled manually by the
pilot while visually monitoring the fuel contents and messages on the EICAS.
An independent operated fuel shutoff valve for each engine feed is located forward of the engine rotor burst areas. In the
event of an engine fire the valves are closed by the activation of L (R) ENG FIRE switches. on the center pedestal. They
can be subsequently reopened if required by depressing the switches once more.
ENGINE FUEL SHUTOFF VALVE (SOV)
The engine fuel shutoff valves are located on the aft spar of the wing box in the main landing gear bay and are controlled
by the L (R) ENG FIRE switches on the ENGINE control panel located on the center pedestal. The engine fuel shutoff
valves are electrically operated valves that stop the flow of fuel to the engines.
FUEL HEATER/OIL COOLER
The fuel heater/oil cooler (FHOC) is located in the engine accessory gear box. The engine FHOC purpose is to heat the fuel
sufficiently to prevent ice formation in the engine fuel system, while maintaining the engine oil temperature within limits.
FUEL FILTER
The fuel filter assembly is mounted just aft of the oil tank on the engine. The filters are monitored for contamination by an
impending bypass switch. If the fuel pressure parameters are exceeded, a signal is sent to the EICAS. REV 1
FUEL
Sep 13/2004 Flight Crew Operating Manual Volume 2
REV 1 CSP 100-6 12-01-07
FUEL DISTRIBUTION (Cont)
APU FUEL SHUTOFF VALVE (SOV)
The APU fuel feed SOV is an electrically operated shutoff valve. In case of an APU fire, pushing the APU FIRE switch on
the ENGINE control panel, located on the center pedestal, closes the SOV. During normal operations, the SOV is automatically
controlled.
REFUELING/DEFUELING
DESCRIPTION
Refueling can be accomplished using either pressure or gravity refueling procedures. Pressure refueling is preferred, while
overwing gravity refueling is only used when single-point refueling capabilities do not exist.
Suction defueling of the fuel tanks is accomplished by applying suction to the single-point refuel/defuel adapter with the
refuel/defuel control panel configured for defueling. Defueling of the aircraft is not a pilot function and is carried out only
by maintenance personnel.
COMPONENTS AND OPERATION
FUEL COMPUTER
The dual-channel fuel system computer monitors and controls the refueling process. Each channel receives signals from
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