Mitchell Attitude Indicator
The refurbishment of the old Piper Autocontrol autopilot is not looking good at the moment. The attitude indicator is not co-operating. While it erects promptly and seems to be very stable the moment the aircraft moves or turns the instrument pitches up or down.
In the air it will eventually erect close to vertical, and will allow the autopilot to trim out and it works very well when it does. But any pitch up or pitch down movement can cause a very erratic reading.
So, now I am off to find out if there is any place that can refurbish or re-build one of these.
In the air it will eventually erect close to vertical, and will allow the autopilot to trim out and it works very well when it does. But any pitch up or pitch down movement can cause a very erratic reading.
So, now I am off to find out if there is any place that can refurbish or re-build one of these.
Sounds like the gymbal bearings need replacing. Outer gimbal bearings (in the roll axis) being rough or sticky will cause a precession in pitch when banking while the inner bearings (which allow the A/C to rotate about the pitch axis of the gyro) will cause a roll indication when pitching. Assuming the instrument is of a certain age and is probably air driven it's not surprising. Best to replace them all AND make sure your air inlet filter is good. So many times have I seen this filter "forgotten" about or even removed to save a few pennies... If you could see the state of the inside of those instruments when I opened them up for overhaul you'd never miss a filter replacement again.
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