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 essential for hands-off flight by relieving control surface servo forces, but it can create dangerous situations if pilots fail to monitor aircraft parameters (e.g., airspeed decay) or if a trim runaway occurs.
A significant "trim failure" is caused by pilots attempting to overpower an engaged autopilot, which leads the autotrim to run in the opposite direction of pilot input, making manual recovery exceptionally difficult, especially if the trim reaches its limit.
Pilots must actively monitor trim indicators, be alert to any warning signs of trim malfunctions, and know how to quickly disengage the autopilot or trim system instead of fighting control forces.

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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