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The dissolved air in the fuel tank will eventually deplete after reaching cruise
altitude. The depletion time is dependent upon airplane altitude, fuel temperature,
and type of fuel. Once the dissolved air is depleted, the engine should effectively
operate on suction feed.
787 Flight Crew Operations Manual
Fuel -
System Description
Boeing Proprietary 12.20.3
Fuel pressure can be provided from a main tank with operating fuel pumps to both
engines by opening the fuel crossfeed valve. Continued crossfeed use results in a
progressive fuel imbalance.
Fuel Crossfeed
The fuel manifolds are arranged so that any fuel tank pump can supply either
engine. The crossfeed valve is closed during normal operations. The closed
crossfeed valve isolates the left and right systems. The valve can be opened to feed
an engine from the opposite fuel tank. If the valve position does not agree with the
switch position, the CROSSFEED switch VALVE light illuminates and the
EICAS advisory message FUEL CROSSFEED displays.
Fuel Balance System
Fuel can be transferred from main tank to main tank using the fuel balance system.
Fuel transfer is initiated by pushing the fuel balance switch ON. Fuel from the
higher quantity main tank is transferred through its defuel/jettison valve to the
lower quantity main tank through its inboard refuel valve. Transfer stops
automatically when fuel is balanced. If there is a system failure, the balance
system shuts down, the BALANCE switch FAULT light illuminates, and the
EICAS advisory message FUEL BALANCE SYS displays.
Fuel balance operation is automatically terminated when fuel jettision is
commanded. If fuel balancing is desired after jettision is complete, fuel balance
must be re-selected ON.
Fuel Imbalance
When the fuel quantity in left and right main tanks differ by an allowable quantity,
the EICAS alert message FUEL IMBALANCE displays.
Fuel balancing is accomplished either by using manual crossfeed or the fuel
balance system.
Crossfeed is initiated by opening the crossfeed valve and turning off the fuel pump
switches for the fuel tank that has the lower quantity. Fuel balance is done by
pushing the fuel balance switch.
Fuel balancing may be done in any phase of flight. The fuel balance system is
inhibited on the ground unless the engines are shutdown and the APU is running.
787 Flight Crew Operations Manual
Fuel -
System Description
12.20.4 Boeing Proprietary
Fuel Tank Locations and Capacities
Fuel Tank Locations
Fuel Tank Capacities
Tank Gallons Pounds *
Left Main 5,500 37,100
Right Main 5,500 37,100
Center 22,500 150,400
Total 33,500 224,600
* Usable fuel at level attitude, fuel density = 6.7 pounds per US gallon.
Main
Tank
Surge
Tank Tank
Center
787 Flight Crew Operations Manual
Fuel -
System Description
Boeing Proprietary 12.20.5
Fuel System Schematic
BALANCE
FAULT
ON
FUEL
PRESS
FWD
ON
PRESS
ON
PRESS
VALVE
L - - R
PRESS
ON
ON
PRESS PRESS
ON ON
PUMPS
CENTER
CROSSFEED
FWD
L PUMPS
AFT
R PUMPS
AFT
FWD FWD
AFT AFT
33.2
149.0
33.1
FUEL215.3
TOTAL
LBS X 1000
L MAIN
L R
CENTER
R MAIN
CROSSFEED
Fuel pump Fuel valve closed Fuel valve open
787 Flight Crew Operations Manual
Fuel -
System Description
12.20.6 Boeing Proprietary
APU Fuel Feed
APU fuel is supplied from the left fuel manifold. APU fuel can be provided by any
AC fuel pump supplying fuel to the left fuel manifold or by the left main tank DC
fuel pump.
On the ground, with the APU switch ON and no AC power available, the DC
pump runs automatically. With AC power available, the left aft AC fuel pump
operates automatically, regardless of fuel pump switch position, and the DC fuel
pump turns off.
Fuel Jettison
The fuel jettison system allows jettison from all fuel tanks. Fuel is jettisoned
through jettison nozzle valves inboard of each aileron. Override/jettison pumps in
the center tank and main tank pumps transfer fuel overboard through the jettison
nozzle valves.
Fuel jettison is initiated by pushing the FUEL JETTISON ARM switch to select
ARMED. The jettison system automatically sets the fuel–to–remain to the
maximum landing weight (MLW) fuel quantity. The TO REMAIN quantity
replaces fuel temperature on the EICAS display.
Pull on and rotate the TO REMAIN selector to manually decrease or increase the
TO REMAIN quantity.
　
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