I had a few successful flights while using autotune, stabilize, cruise, loiter and RTL modes. (I read the wiki on autotune and was doing many hard banks and hard elevator changes to help train it.) I then went to a park. I used mostly autotune and stabilize, and the plane gradually got harder and harder to roll left, until inevitably was stuck rolling right. My guess is that autotune was adjusting things to a worse and worse state but would appreciate some help by someone more experienced in analyzing logs.
Ideally there would be a Log Browser view of stick inputs vs FC servo outputs. This would help determine if ardupilot was trying its best to (max roll-left servo position) and the plane wasn’t cooperating, or if ardupilot was for some reason not giving a full roll-left servo output, even though the stick input was asking for it.
The inability to roll left starts at 3:40.
Google Drive folder containing the log from the crash, and the flights before the crash.
2021-06-19 16-41-48.bin is the relevant log from the crash.
Just before the crash, RC input, RC output, and desired roll are all left, but the plane is still doing clockwise barrel rolls.
I think this was a servo failure. Maybe the servo was getting hot? It still works. It was also not responding a little a previous points in the flight.