MD-11 Flight Crew Operations Manual
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Fire Protection -
Description and Operation
Fire.10.4
In addition to the two fire outputs, a third output is also provided for cockpit aural
warning. The fire outputs will be activated in response to any one of the following
conditions:
• (Fire loop A) and (Fire loop B).
• (Fire loop A) and (Fault loop B).
• (Fault loop A) and (Fire loop B).
• (Fault loop A) and (Fault loop B) - AND both faults occurring within 5
seconds of each other.
If any of the following conditions exist, the FDCU will generate a FAIL output
signal for the affected loop:
• Loss of power for that loop.
• Fault in a detector for that loop.
• A failure within that loop’s fire detection circuit.
• Detection of fire by single loop for greater than 15 seconds while the
other loop is indicating normal (no fire and no fault).
The FDCU has a built-in test circuit capable of testing both the loop A and loop B
detection circuits and sensing loops. The circuit provides the following functions:
• During FIRE TEST (pilot initiated), both FDCU loop detection circuits
are tested and the fire warnings activate.
• During the maintenance test the FDCU performs an internal test of itself,
the detection loops, and the critical wiring. The maintenance test
automatically occurs when the system powers up and the aircraft is on the
ground.
The fire bell has the following characteristics:
• Sounds when a fire condition (engine) is detected.
• Sounds during pilot initiated fire test.
• Will stop sounding when the fire output clears.
• Is inhibited during maintenance test.
The FDCU contains two redundant control channels (loop A and loop B) in a
single enclosure, with each channel operated by one of the sensing element loops.
Alerts are activated as follows:
October 02, 2006
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