MD-11 Flight Crew Operations Manual
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Fuel -
Description and Operation
Fuel.10.11
Fuel Dump System
Fuel dumping uses all main tank and upper aux tank pumps to pump the fuel
overboard through exits on each wing located at the trailing edge between the
outboard aileron and the outboard flap. The dump flow is controlled by two
electrically operated shutoff valves, and the low level shutoff float switches in the
three main tanks. The dump valves are dc motor operated valves. They are
energized by a dedicated dump control network which is activated by a guarded
DUMP switch. An alert will be displayed to indicate that the fuel dump system has
been activated.
The fuel dump operation is initiated by pushing the guarded DUMP switch on the
FUEL control panel. The dedicated dump control network then commands all
transfer and boost pumps on, all crossfeed valves open, and the dump valves open
in a controlled sequence. The sequence will not overload the electrical system or
adversely affect engine feed capability.
The FSC monitors the state of the fuel dump valves. Left or right dump valve
disagree alerts are displayed on the SD if one or both of the dump valves are not
in the commanded position.
The dump valves are on separate electrical buses. If the FSC is in auto mode,
backup commands will be sent to the crossfeed valves and the pumps to ensure
that they are properly activated in the event of a malfunction of the dump control
network. The FSC performs fault checking of the fuel dump system by monitoring
the sequencing of the pumps and valves. Any faults in the operation of the system
are isolated and recorded. The FSC has no control over the operation of the dump
valves. This feature ensures that fuel can not be inadvertently dumped due to a
malfunction of the FSC.
At any time during the fuel dumping operation a crew member can stop the flow
of fuel overboard by pushing the DUMP switch again. This action causes the
dump valves to close, all crossfeed valves to close, and the transfer pumps to be
commanded off. If fuel dumping is started a second time during a single flight,
dump continues to low level dump cutoff or until the DUMP switch is pushed
again. If a malfunction of the DUMP switch occurs, the fuel dump sequence can
be overridden by pushing the FUEL DUMP EMER STOP switch.
When dumping fuel from the aux tanks, both upper and lower pumps turn on.
After the lower aux fuel has been pumped to the upper aux tank, then tail tank fuel
is pumped to the upper aux tank and dumping continues using the upper pumps.
The aircraft can carry dedicated ballast fuel in either tank 2 or the upper aux tank.
Tail ballast fuel will remain on board and will not be moved during fuel dump.
Ballast fuel in the upper aux tank will also remain on board, but may be relocated
(to tank 2) in the dump process. Total fuel quantity remaining on board following
dump will be the low level dump cutoff quantity plus any dedicated ballast.
October 02, 2006
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