TRK autopilot bug went ... buggy!

[Sportsman7064]

Tooling along this evening using the TRK+ALT mode. All was fine for 15-20 minutes. Then the TRK bug just started to move on its own. The uncommanded turn got my attention fairly quickly, and I hit the disconnect and returned to hand-flying. Looking at the primary display, the TRK bug was circling the compass rose at about 20 rpm! I changed buttons that were assigned to the TRK function and the bug stopped spinning.

Thought I'd post somthing before giving it another try on Saturday...

Any thoughts??

Thanks

 

[Dynon]

It sounds like there an issue with the knob that was assigned to TRK. If you scroll to the bottom of SETUP MENU > LOCAL DISPLAY SETUP > DISPLAY HARDWARE INFORMATION, you can see that the joystick state line has to counters that should only move when you rotate the knob. If there is an issue with the rotation function of the knob, you'd see it in those counters incrementing or decrementing without you turning them.

 

[DBRV10]

I had the CRS function do some wild eratic changes yesterday. Sounds very much like this.

I swept the knob around and reset the value it was meant to be, and the CRS stayed very stable. This sounds like a hardware issue, so what is the history of this? I would not like this happening on an instrument approach in the soup so a good understanding of what happened or could happen would be good.

 

[Dynon]

There's no systemic problem, but it's possible for the joystick knobs to fail in a way that they either stop responding, or register extra clicks, or otherwise misbehave. Incredibly rare - like you can count all such failures on one hand, probably.

As for your issue David - what GPS or NAV device was the HSI tuned to when you saw that?

 

[DBRV10]

GTN 750 via the ARINC module.

This was very fast oscilating data, no way it could be done by hand even.

A quick twist of the knob and reset it was all fine.

Happy to retest somehow if you can give guidance.

 

[JTD]

I had a similar experience. Once when using the OBS mode on the 430 to fly a hold, the course needle oscillated 180 deg in rapid secession. I had used the Dynon course knob to set the OBS course. Only happened once.

 

[Sportsman7064]

Dynon - I went into the Set-Up menu and when I got to the Display Hadware Information screen, the counter for that knob indeed started incrementing. In fact, it causes the highlighted item on that menu to change, as if I wanted to see something else on that screen...

Guess I'll need to get an RMA for a return on this screen.

Meantime I'm just ensuring that I don't use the knob in question for any critical parameters (like Baro, Alt, Trk,...) so if it moves it is not changing something important.

 

[Dynon]

Yep, give our support team a call at 425-402-0433 or support at dynonavionics dot com for further help here.