D-10 Uncommanded Pitch Up

Flying along yesterday with my wife and a few bags in back, stable at the capture altitude (6500) and on autopilot. The AP is always a bit "nervous" - like its had WAY too much coffee...

Anyway, out of nowhere it decided to depart the commanded altitude with a 3 G pullup to about 45 degrees nose high. I disconnected, pushed back over to level flight and re engaged. The AP behaved normally for the duration of the flight.

Anyone seen this before?

The airplane has a very small stick force gradient when loaded, so that may contribute to pitch sensitivity, but I dont understand the sharp pull FROM the assigned altitude.

I have seen something similar, but in roll, when I was a beta tester for these autopilots.

We traced it back to a problem with the Garmin 496 that was putting out bogus waypoints every so often. We would be cruising along and all of a sudden the airplane would turn to knife edge because the Garmin put out a waypoint in Europe. Dynon was able to fix it by checking to see if the next waypoint was "real" or not.

Assuming your D10 software is up to date, that is a strange one and you are lucky it didn't push over. I would contact Dynon on Monday, they might already have a solution for this.

Micheal, yes this has happened to me as well. In my case, wife in the back, luggage etc and I was reading a map, auopilot on, life was good. Suddenly I experienced what you described. How could this happen?
In my case, it was the folded map, resting firmly on the top of the stick This activated the trim switch, commanding trim to the point that the servo could not take the load.
Is it possible that loaded as you were that the servo was at the limit of it's max break-out force? Did you trim for level flight or did the autopilot level at a preselected altitude?

What is your max speed set at? If you exceed the max speed it will pitch up.

Tom Martin said:

Micheal, yes this has happened to me as well. In my case, wife in the back, luggage etc and I was reading a map, auopilot on, life was good. Suddenly I experienced what you described. How could this happen?
In my case, it was the folded map, resting firmly on the top of the stick This activated the trim switch, commanding trim to the point that the servo could not take the load.
Is it possible that loaded as you were that the servo was at the limit of it's max break-out force? Did you trim for level flight or did the autopilot level at a preselected altitude?

Click to expand...

Like Tom mentioned, take a very hard look at an out of trim condition causing the event. I have had it (the full trip out pitch up described) happen a couple of times, plus when the pitch trim is preloading the autopilot but not enough to cause a full trip out, the autopilot action will be one sided. Think intercepting a glideslope and the autopilot not tracking the vertical very well.

Is there any trim sensing/warning on the D10?

I have seen the AP struggle with out of trim conditions before so I am sensitive to trim to zero stick force (despite the fact that I still see the out of trim indication on the D-10). In this case the airplane was in trim throughout the event.

And max speed was not the issue, as I was flying with a buddy in his RV-7. We were only going about 170 KTAS which is about 50 knots under my max AP speed.