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RickSolana
06-14-2017, 01:19 PM
I have a new Dynon Skyview HDX system in a new RV-10. For 6 weeks now, several things are occurring and seem to be getting worse:
- on glide slope, the a/p will decide to go into altitude hold mode, or to begin a climb with no mode annunciation.
- in cruise and altitude hold, the a/p will randomly decide to climb.
- when commanding a climb or descent with VS, either the a/p will respond correctly while the flight director shows an incorrect suggestion, or the flight director will show the proper guidance while the autopilot ignores it.

Any thoughts?? Dynon has been given several diagnostic files, but to date has made no suggestions on how to fix the problem.

Thanks in advance!

Don Jones
06-14-2017, 01:40 PM
I have a new Dynon Skyview HDX system in a new RV-10. For 6 weeks now, several things are occurring and seem to be getting worse:
- on glide slope, the a/p will decide to go into altitude hold mode, or to begin a climb with no mode annunciation.
- in cruise and altitude hold, the a/p will randomly decide to climb.
- when commanding a climb or descent with VS, either the a/p will respond correctly while the flight director shows an incorrect suggestion, or the flight director will show the proper guidance while the autopilot ignores it.

Any thoughts?? Dynon has been given several diagnostic files, but to date has made no suggestions on how to fix the problem.

Thanks in advance!

Rick, have you checked the shear screws? Mine broke both of them at one time or another and it acted a lot like you describe. The roll would be flying along fine and suddenly try to make a 60 degree bank turn. The pitch acted exactly as you describe. There is enough friction in the servo to arm interface to allow some operation of the a/p.

RickSolana
06-14-2017, 02:23 PM
Thanks Don. I will check it when I'm back at the airport on Friday. I never would have thought this behavior was from a shear screw!

bruceh
06-14-2017, 02:56 PM
Run the AP servo calibration? It should move the stick around the entire range. That would show you if it is the shear pin.

Carl Froehlich
06-14-2017, 05:14 PM
I just replace the pitch servo shear screw. I seems the new owner muscled the stick when in AP. This is the second time I replaced the screw. The first was me doing a jerk when I hit a hard air pocket.

I understand Dynon got a rash of broken shear screw and set up a reporting process to track. The new screw I just got from them (no charge) was noticeably thicker where they machine down the neck.

Carl

Ironflight
06-14-2017, 05:48 PM
We are using the big Dynon AP servos in our four-place bush plane...can you say HEAVY?! At first, we sheared screws every time we tried to test the AP on the ground - the servo just couldn't lift the big elevator. Dynon then sent us the latest, upgraded screws, and we haven't had a problem since.

Good upgrade Dynon!

RickSolana
06-14-2017, 06:05 PM
Bruce, I got out to the airport today and I did something similar. Commanded a left turning climb and guess what: the stick went left but not aft!

RickSolana
06-14-2017, 06:08 PM
At the airport, I put the autopilot in a climb (in the hangar) and went in the back. That autopilot was clicking away and you could see the empty shear pin hole and the autopilot wheel turning behind it! Dynon has one of the beefier pins on its way.

Thanks for the help, guys!

Jesse
06-14-2017, 08:31 PM
In well-trimmed flight in calm air, there is often just enough tension on the main nut to function with a broken shear screw, but then it acts up. Rick, I hope that solves the problem.

RickSolana
06-21-2017, 10:39 AM
It was the shear screw! Replaced it yesterday and all is well!