787 Flight Crew Operations Manual
DO NOT USE FOR FLIGHT
Fuel -
System Description
Copyright © The Boeing Company. See title page for details.
12.20.2 D615Z003-TBC
When less than all engines/generators are operating, there may not be sufficient
electrical power to operate all fuel pumps. In such cases, the fuel system
automatically determines the best pumps to operate depending on how much
electrical power is available. Certain fuel pumps may be load shed until enough
electrical power is available. The indications that a fuel pump has load shed are
that the pump switch PRESS light is illuminated and the pump is labeled LOAD
SHED on the fuel synoptic.
The left main tank contains a DC–powered fuel pump. It has no controls or
indicators, other than the fuel synoptic display. The DC pump operates
automatically to provide fuel to the APU when AC power is not available and the
APU selector is ON.
Surge tanks are provided in each wing, outboard of each main tank. Fuel in the
surge tanks and fuel remaining in the refueling manifold is drained into the main
tanks.
Fuel Pump Operation
Before start, the main tank pump switches should all be pushed ON. If the FUEL
IN CENTER message is displayed, the center tank pump switches should also be
pushed ON.
During flight, when the FUEL LOW CENTER message displays, the center tank
pump switches should be pushed off. The condition statement for this message is
contained in Section 12.30, Fuel System EICAS Messages.
If a center pump has low output pressure, the fuel pump switch PRESS light
illuminates and the message FUEL PUMP CENTER (L or R) displays.
[Option – English / Metric units]
With the main tank pumps ON, a scavenge system operates automatically to
transfer any remaining center tank fuel to the main tanks. Fuel transfer begins
when either main tank quantity is less than approximately 35,000 pounds / 16,000
kilograms (depending on fuel density) and the center tank pumps are off. The
system is inhibited if the engine is on suction feed.
Suction Feed
When main tank fuel pump pressure is low, each engine can draw fuel from its
corresponding main tank through a suction feed line that bypasses the pumps. As
the airplane climbs, dissolved air is released from the fuel in the tank due to the
decrease in air pressure. This air may collect in the suction feed line and restrict
fuel flow. At high altitude, thrust deterioration or engine flameout may occur as a
result of the fuel flow reduction.
February 15, 2010
To Next Page
Loading...
