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) is a critical system that complements the autopilot by relieving forces on the pitch servo, enabling hands-off flight, but introduces complex failure modes and operational risks.
Dangers arise from the autotrim system operating normally but unmonitored (e.g., maintaining altitude in icing conditions, leading to extreme trim and stall), true "trim runaway" due to sensor failure, or dangerously trimming in the opposite direction when a pilot attempts to overpower an engaged autopilot.
To prevent hazardous situations, pilots must constantly monitor trim indicators, be aware of warning signs, know how to quickly disable the trim system, and critically, never attempt to overpower an engaged autopilot, as this can lead to severe out-of-trim conditions upon disengagement.

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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