What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Trim Up issue following Trim runaway in flight.

NZ_Pompey

Member
I have a strange issue on my 12is (Single screen Dynon with AP) -
I had a trim-up runaway happen mid-flight, luckily during straight and level, which I was able to reverse using pitch down and then pulling the fuse when it got to neutral, as it kept on wanting to go up! Luckily AP wasn't engaged at the time so I noticed it straightaway.

Upon landing I put the fuse back and all was good during ground tests. I assumed there must be an intermittent short to ground somewhere in a pitch up wire, but upon powering up today to test it my pitch up does not work now from either the pilot or co-pilot stick buttons.
However if I go into the setup menu on the Dynon I can pitch up fine when testing it using the soft keys - so to my mind the circuit back to the trim motor from the power module must be ok?
As I'm having this no trim-up issue on both pilot and co-pilot sticks, I'm looking for any ideas on where to start troubleshooting.
From the schematics, it looks like the wiring is independent from the pilot and co-pilot sticks and goes back to separate pins on the AP module and so given that both up buttons are not working, does this point to an issue with the AP module? Any ideas appreciated to help troubleshoot!!

Thanks
Paul
12-iS #121263
 
The trim switch on one of the sticks might be stuck in the closed position. If you unplug the stick harness at the DB9 connector at the bottom of each stick one at a time that would easily confirm or rule out that possibility.
 
Wiring for both sticks checked out fine - It looks like the issue was with the pre made harness where it goes into the autopilot module and splits off to the power module.
Remaking those connections seems to have cleared the fault.
 
Back
Top