MD-11 Flight Crew Operations Manual
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Flight Controls -
Description and Operation
Flt.10.11
Positive Nose Lowering (PNL)(FCC-908) will apply 3° of nose-down elevator
command when the FCC commands the Auto Ground Spoilers to extend at main
wheel spinup. As the spoilers extend beyond 10°, PNL will increase the
nose-down elevator command to 4°. The command fades out when FD mode
cycles back to T/O, or if throttles are advanced for G/A.
During take-off and landing flight phases, when PAP or PNL is active,
approximately 10-15 pounds of force on the control column is required to override
LSAS.
Upon detecting a fault, both channels of one FCC shut down. After selecting both
failed channels off, the remaining FCC is armed to revert to single LSAS channel
operation should one of the two remaining LSAS channels fail. The remaining
LSAS channels will increase deflection 2-fold (4-fold deflection occurs
automatically in case of reversion to single elevator LSAS operation).
NOTES:
• With LSAS LEFT (RIGHT) INBD off or failed, AP1 (AP2) is not
available.
• With LSAS LEFT (RIGHT) OUTBD off or failed, AP2 (AP1)
Takeoff, Go-Around, Windshear, and Land modes are not
available in the associated AP. Only SINGLE LAND will be
available.
• Only Two Channel LSAS is available if an automatic horizontal
stabilizer trim system has failed and only Single Channel LSAS
is available if both automatic trim systems have failed.
Refer to autoflight chapter for speed limiting and stall protection information.
Stall Warning System
The dual stall warning system provides indications of an impending stall.
Stall warning indications can be divided into two categories, alpha-based
(angle-of-attack) and speed-based. The two categories will not match unless the
airplane is in steady state, level, 1g, non-maneuvering flight.
During ground powerup, each FCC automatically tests the angle-of-attack sensor
and the stickshaker. Afterwards, other tests are continuously done to verify that
valid angle-of-attack data is being used for stall warning computations.
Stall warning is not affected by the AFS OVRD switch on the FCP.
Alpha-based indications are more accurate than speed-based indications during
maneuvering flight. They are generated by the FCC and are the function of alpha,
alpha rate, flap position, slat position, and Mach number.
November 10, 2008
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