How to tell you've sheared the AP servo screw.

[tcbc8222]

Had the opportunity to work through a AP issue on my Cessna 172. When flying on a very bumpy day I set the AP up for an approach and it wouldn't capture the navigation. Upon landing and putting the plane in the hangar I opened the inspection ports to verify the servo cable hadn't slipped. I had the cable slip one time before and thought it could be a shear screw then.
The cable had a little bit of looseness to it so I tightened it up and performed the calibration test. If you haven't done one before you need to read the manual on how to do one.
Upon running the calibration test the Dynon would not complete the test successfully and the panel would say that I don't have servo's installed. The AP panel disappeared on my main screen too. The network would show the servos installed but because they didn't calibrate successfully they were "ghosted".
The servo had the screw sheared and after replacing with correct Dynon parts the AP calibrated successfully and flew great.

I posted this for those that may have this issue in the bumpy spring ahead.

 

[Rhino]

Thank you! I wish more folks would post problem resolutions here.

 

[tcbc8222]

I received an email from Dynon support walking through the steps to identify a shear screw failure. Their process is correct, however, if the clamps have slipped on the cable it will mimic a shear screw failure. I would recommend to open the inspection panels and inspect first to ensure that all items are correct prior to doing the calibration test. It could save you 20 to 30 minutes of head scratching.