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TruTrak Gemini autopilot, altitude hold issue

mgasper

Member
I have a new installation of a Gemini autopilot with auto trim in my RV-6. The unit works fine except for the altitude hold mode. The aircraft pitches up and down randomly and suddenly as if it is overcorrecting for the selected altitude. For short periods it appears to work normally then starts with the pitching movements. I have adjusted the vertical activity level, Tested the static system for leaks without any resolution. I have standard instruments with a Dynon D10a. The aircraft is equipped with a piper style pitot mast and two side static ports on the aircraft. I have contacted Trutrak but have not found a solution. Any assistance or ideas on how to trouble shoot and fix this issue would be appreciated.
 
Gemini AP

I recently installed the same unit in my RV-3.
Have not tested yet and plan to do so tomorrow.
I will let you know if I have the same problem.
 
Check to make sure the pitot and static lines are not reversed at the AP. I will not confess as to why I know to check this. If reversed, it's AP will act as you describe.
 
Good to hear your install works fine. I will verify the static line and pitot lines are not crossed but I do not think that is the case mine are color coded and difficult to mistake. The manual talks about possibly running a separate static line just for the autopilot with a tee fitting at the source, I may give that a try.
 
Also, be sure your autotrim speed is not set too high. If it is, it'll basically WAY over trim the aircraft and cause it to oscillate.
 
That depends on which version you have. If it was purchased in the last 12 months, it should be the new style. I will email you rev G of the autotrim manual. It describes how to check and set it. Let me know if you have any questions. Thanks!
 
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Similar problem with my TruTrak

I was having a similar problem with my TruTrak Digiflight II. I called them and they said it was possible the manifold on the rear of the autopilot was cracked between the static and pitot fittings.

I pulled my autopilot and that was the case. I returned it to TruTrak with a couple of fitting and they fixed me up. It has worked great ever since. I don’t know if Gemini has a comparable manifold or not.

Just my experience.

Good luck,
 
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Problem Solved, auto trim speed

With the help from TruTrak the problem was solved the auto trim speed was set to high. What was missed and being misinterpreted was the information being provided by the "indicator light". First the light seen on the auto trim module is not the indicator light they are referring to in manual when referencing trim speed settings. A separate indicator light is wired from the auto trim connector, to be place within the pilots view. My harness was built by Steinair who did not provide a wire for the light so it was missed during the install. After finally realizing I was referencing the wrong "indicator light" the problem I was experiencing was quickly resolved. Thanks for help!
 
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