Automatic Autopilot and Yaw Damper Disengagement
Automatic autopilot/yaw damper disengagement is indicated by a flashing red and white 'AP'/'YD'
annunciation and by an Autopilot disconnect tone. The automatic disengagement
indications will continue until acknowledged by the pilot which is accomplished by
touching the AFCS Status Box on the PFW. Automatic autopilot disengagement occurs due
to:
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System Failure.
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Invalid sensor data.
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Stall warning (YD also disengages).
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Inability to compute default flight director modes (FD also disengages automatically).
If automatic autopilot disengagement is caused by failure in a parameter also affecting the yaw damper then the yaw damper may also automatically disengage. Otherwise, the yaw damper can remain operational in some cases where the autopilot automatically disengages.
Automatic yaw damper disengagement is indicated by a five-second flashing amber ‘YD’ annunciation. A localized failure in the yaw damper system or invalid sensor data can cause automatic yaw damper disengagement.