MD-11 Flight Crew Operations Manual
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Fuel -
Description and Operation
Fuel.10.5
The transfer pump supplies fuel directly to the crossfeed manifold. One of the
boost pumps is mounted to the rear spar next to the transfer pump to minimize the
unusable fuel during nose up or level flight attitudes. The other boost pump is
mounted to the bottom wing skin in the forward part of the tank to minimize
unusable fuel during nose down flight attitudes.
The aft engine is fed by tank 2 which contains four fuel pumps. These four pumps
are:
• Two aft mounted boost pumps.
• One forward mounted boost pump.
• One forward mounted transfer pump.
The boost pumps feed directly to the aft engine.
A dc powered APU start pump is also located on the right side of tank 2.
In each tank, the pumps are all powered from different electrical buses. In case of
electrical failure, the left aft boost pump in tank 2 can be run from the Air Driven
Generator (ADG).
The aft feed pump(s) in each tank (one each in tank 1 and 3 and two in tank 2) and
the two upper aux transfer pumps have a jet pump installed in the inlet. Each boost
pump is capable of supplying fuel at the takeoff fuel flow rate to two engines.
Each tank mounted pump is provided with a pressure sensor which provides
information to the FSC.
In auto mode the FSC uses this input combined with fuel quantity information to
decide if a tank is empty or a pump is inoperative. If the quantity is above the
preset limit when a low pressure situation is sensed, the FSC turns the pump off
and logs a fault in the CFDS. The appropriate PUMP OFF alert will be displayed.
The forward pumps and tank 2 transfer pump will not be turned off if pump
pressure is low due to a high pitch angle with a low fuel level. In manual mode, a
pumps LOW light on the FUEL control panel is illuminated if all boost pumps that
have been commanded on in a tank have low discharge pressure.
Suction feed is accomplished for the wing engines only through the aft pump inlet.
The engine feed pump suction line contains a bypass with a check valve. This
allows the inlet to be used for suction feed.
Electrically operated crossfeed valves provide crossfeed capability from any tank
to any engine or to any other wing tank. In auto mode, the FSC controls crossfeed
and will compensate for failed components.
In either mode of operation, lights on the FUEL control panel illuminate to
indicate valve disagreement with switch position. A short time delay is provided
in the annunciation logic to allow for normal valve transition. The valve has a
manual override for ground use.
October 02, 2006
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