Autopilot Trim

Wednesday, July 26, 2023 at 08:58 AM ET

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Cygnet Aerospace Photo In the event of a trim runaway, can you identify and pull the correct circuit breaker in a hurry? A collar could help.

Key Takeaways:

Autopilot pitch trim (autotrim) helps relieve control forces, but its proper function requires careful pilot monitoring as it can mask critical flight parameter changes, such as airspeed decay during icing or prolonged climbs.
Significant hazards include both "trim runaway" caused by sensor failures, and pilot-induced problems arising from attempting to overpower an engaged autopilot.
Overpowering an engaged autopilot causes it to trim *opposite* the pilot's input, leading to an extremely out-of-trim condition that makes manual recovery exceptionally difficult upon autopilot disengagement.
Pilots must diligently monitor trim indicators, understand system behavior, know how to quickly disable the trim system in emergencies, and always disengage the autopilot before taking manual control.

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The autopilot interaction with the aircraft’s trim system is a gray area for many pilots. You can easily overpower the autopilot, but overcoming the trim that the autopilot may have run to the stop is another matter. This article will give you background information on how the autopilot trim works, a trim runaway, and how the autopilot can also slowly run the trim to the stop and then disengage.

Pitch Trim