MD-11 Flight Crew Operations Manual
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Fuel -
Description and Operation
Fuel.10.2
• Corrects for tank overfill.
• Reconfigures the fuel system for failure of various elements.
• Reconfigures for a dump valve failed open.
• Employs special management procedures to compensate for various
components being inoperative at the beginning of flight.
• Monitors itself and other fuel system components for proper operation
and detects and reports faults to the Centralized Fault Display System
(CFDS).
• Reverts to manual for certain failure modes.
Fuel Tank Arrangement
Three main fuel tanks are installed in the wings. These main tanks are tank 1, 2,
and 3. The numbers correspond to the engine which the tank feeds. Additional fuel
is contained in a center wing auxiliary tank consisting of upper and lower sections
and a tail tank located in the horizontal stabilizer.
All of the tanks are integral except for the lower auxiliary which contains a bladder
cell.
Tanks 1 and 3 in the left and right wings respectively are identical. Each has an
outboard compartment and a main compartment. The main compartment is further
divided by a check valve bulkhead which allows inboard fuel flow to the boost
pump reservoir but prevents outboard fuel flow that could occur under some flight
conditions such as a steep climb or uncoordinated maneuvers.
Tank 2 supplies fuel to the APU and the aft engine. It is a split tank with half of
the volume in the left wing and half in the right wing. Gravity flow and vent lines
connect the two tank sections. This tank has a greater fuel capacity than tank 1 or
3.
Manifold drain/outboard fill valves are located at the outboard ends of the
fill/crossfeed manifold in tanks 1 and 3. These valves serve the dual function of
controlling manifold venting for drainage and providing an alternate fill path for
tanks 1 and 3. A manifold drain float valve is located at the low point of the
fill/crossfeed manifold. This valve allows drainage of the manifold into tank 2
when the fuel level in tank 2 is below 815 kilograms. In auto mode, the FSC
commands the manifold drain/outboard fill valves open at the appropriate time
allowing fuel drainage. In manual mode, a crew member operates the MANF
DRAIN switch which opens the same valves. The MANF DRAIN switch is a
guarded switch.
October 02, 2006
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