MD-11 Flight Crew Operations Manual
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Automatic Flight -
Description and Operation
Auto.10.20
When the FCC localizer capture criteria are satisfied, the roll control window on
the FMA changes to LOC ONLY and the AFS captures and controls to the ILS
localizer using the same FCC control laws as when APPR/LAND is selected.
Align and rollout submodes are not available.
Engaging another lateral control mode cancels the LOC ONLY mode. However,
once LOC ONLY has been annunciated in the FMA, de-selecting the LOC ONLY
prompt on the MCDU will no longer cancel LOC ONLY. This method can only
be used to cancel the LOC ARMED status.
Automatic Pitch Trim
One automatic pitch trim (APT) channel is contained in each FCC. Only one of
these channels is operational at a time. In land modes or LSAS, the second channel
auto engages if the first channel fails.
The horizontal stabilizer is automatically positioned to off-load any steady state
elevator deflections. The trim rate is varied with airspeed to provide best
performance for all flight conditions.
APT is available during LSAS operation and in all AP modes except flare.
APT is inhibited if:
• Control column force more than 2 lb.
• Bank angle more than 5 degrees.
• LSAS is in speed protection.
Nose-up trim is delayed for 10 seconds when the AP TO and GA modes are
initially engaged.
Autothrottle System (ATS) and Engine Trim
General
The ATS automatically positions the throttles to maintain engine thrust required
for the mode selected. The engine thrust trim system will maintain the engines at
a common thrust setting to eliminate the need for throttle adjustments. The trim
system can operate during manual and ATS operation. It is engaged any time two
or more engines are operating above an N1 threshold.
Each FCC contains one ATS control channel that drives a separate section of a
dual actuator. This provides two channels of control with fail passive monitoring.
The ATS is designed for full flight envelope operation. It can be engaged on the
ground. It can remain engaged until it is automatically disengaged when reverse
thrust is applied during landing rollout.
The ATS operates in the following modes:
IAS Hold - Provides control of throttles to maintain the current airspeed.
October 02, 2006
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