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Aircraft does not remain in trim


Toasty

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I saw similar questions in the last few pages, so I don't think I'm alone on this one.

I'm a real world pilot, and it really concerns me when the Otter doesn't behave accurately, especially hand-flying climbs and descents. It appears to "fall out of trim", even though airspeed hasn't changed. This is very noticeable on descents- if I disengage AP, and reduce power...the airplane should begin descending. Instead, it actually pitches up. Also, the trim requirement on a constant speed descent seems to change as you come down. It makes smooth transitions very difficult, and doesn't behave properly.

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I presume the pitching on power changes is correct behaviour. The engines are above the longitudinal axis of the aircraft (I think above the centre of gravity is the significant factor), hence the pitching effects. The rest I'd have to think about.

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I presume the pitching on power changes is correct behaviour. The engines are above the longitudinal axis of the aircraft (I think above the centre of gravity is the significant factor), hence the pitching effects. The rest I'd have to think about.

I'd assume the opposite. It's a blown wing design- any power reduction immediately reduces lift over the wings. Besides, as long as the CG is forward of the center of lift, the nose should always fall first. Unless there's something screwy going on with the trim.

After some more testing, I think it's related to trim and AP pitch knob. The other day I was trimmed in level flight, but it took 100% down trim to fly straight and level. The aircraft was moderately loaded, well below gross (9-10k lbs), with weight spread across all stations. The elevator was full nose-up on external view just holding level. The second I engaged autopilot (which should hold the level flight), the nose pitches wildly downwards. I would have to fight the AP manually until the AP trim corrected to follow the knob (I even had the knob pointing the FD above the horizon, and it continued to nose down). Something's amiss.

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