AUTOTUNE crash and strange logs


During autotune the plane stopped reacting on elevators and eventually crashed.
In log I found very strange autotune graphs:

Is this explainable at all?

Full log: (2.5 MB)

After investigation I tend to believe that this behavior of autotune somehow got through the output stage for servos (without being logged somehow) and lead to servo overheating due to oscillations.

the servos didn’t oscillate, or even move fast at all. The graph looks like oscillation as its switching between roll and pitch tuning data rapidly but actually its fine.
The autotune didn’t actually do much, it didn’t have time to do any learning.
Has this plane been flown at all before? It looks like a physical setup issue with the airframe.

Yes, it flies in FBWA and manual.
In FBWA during level flight the elevator servo is very close to middle position and in manual it continues to fly leveled so the balancing is fine.
First time this happened after about 15 minutes in autotune when I switched back to FBWA.
Second time is this log, 30 seconds after autotune engage when speed has built up.

does it fly OK in FBWA if you do the same sort of rocking motion you did for autotune?

As for roll, yes it is fine.
As for pitch, I have not realy tried to rock it back and forth, but full pitch up is fine, full pitch down is also fine.

However when doing first autotune it was rocking both roll and pitch for about 15 minutes and when the results were fine, I switched back to FBWA and elevator stoped responding.
Second time the same issue after 30 seconds.

Tail is reverse V-type and servos have separate DC/DC for each one with two power lines for redundancy. First crash was hard and autopilot with electronics did not survive. After second crash checked all servos, connections, all was fine and moving like should.

If this graph for autotune is OK, then I will look for some other issues. This was the only strange thing I saw from logs.

can you post the log of the other crash as well?

Autopilot with SD card was damaged and unfortunatelly I don’t have that log.