Trim slipping

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JU343

Trim slipping

Post by JU343 » Sun Oct 28, 2018 7:07 am

I have noticed that the trim wheel is unable to hold selected position during high speed descents (150KIAS). Unless I keep holding the trim wheel, it rolls backwards. Thus I need constantly to keep stick pressure forward.

Is this normal or is the trim clutch worn out?
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Steve
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Re: Trim slipping

Post by Steve » Sun Oct 28, 2018 2:00 pm

Not normal, but may simply need adjustment.
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CFIDave
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Re: Trim slipping

Post by CFIDave » Sun Oct 28, 2018 3:42 pm

I experienced something similar on a DA40 last year, where the autopilot couldn't hold elevator trim when in "high-speed" cruise: The autopilot would add more nose-down trim, the wheel would then slip backwards to T/O trim, the autopilot would move the wheel forward again, and the cycle would repeat.

The first (and easiest) fix is to adjust (tighten) the friction block in the tail that's easily visible right under the elevator. If that doesn't work, then your mechanic/tech will need to take apart the center console to adjust the friction on the elevator trim wheel. A spring scale is used to measure the appropriate force (described in the DA40 AMM).
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