Flight error without sensors error?

Today, after 30-50 normal flights, strange things start to happen with my copter on APM 1. 

At first 1-2 seconds of flight in any mode tried (stabilize, alt_hold, loiter, acro, simple) it behaves as normal, but than things look like if there was a ball on an equilibrist's pole: when I move ale/elev stick a bit, copter leans to the same side as stick, but even more and more, and when I try to restabilize the drone, it quickly overjumps the balance point and overwhelms to other side, this time dropping on the ground. 

We tried to find any error in sensors and IMU data, but haven't find anything go wrong. Maybe sensors - too noisy, but the noise is significantly lesser than signal level (see chart)

Logs: 1,2

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  • Well, yesterday I had a strange behaviour from my copter after running "level" command from within the Planner. Looks like it did not run it properlly, I was having 1 motor accelarating much more than the others, motors pulsing etc, so I did another ESC calibration etc and nothing worked, then I runned "level" again from within the Planner and the copter was ok. Perphaps corrupt level calibration, so, you have nothing to loose, try to run the "level" from planner with the copter connected via USB (leveled) and see if it gets better (or good preferebly).

  • Moderator

    Did your PIDs change?

  • Moderator

    I would also re-calibrate the ESCs, and then repeat the auto-trim process a couple of times, rotating the system 90 degrees each time, and auto-trim at least four times. Something is tickling my brain, about this leaning... something Jason Short said to someone else who had that problem, but it's not coming to me right now...

  • Moderator

    I have also seen cases where the electrical connections on the board for the sensors have broken, and this can cause similar behavior. This usually happens from hard impacts. You can sometimes check for this by pressing lightly on the board (avoid ESD) in different spots while watching the status and HUD. If it goes crazy, you might have some micro fractures in the surface mount between the board and the gyro and/or accelerometer chips. A second idea, maybe worth checking. Of course, it can easily be something else entirely.

  • Moderator

    What are you doing for vibration isolation? Tie it down, and run the motors up. Watch the HUD. Does it roll? It may be sensor aliasing from vibration. There are good reasons why you might have been find for a lot of flights, then had this start.... the frame might have loosened up, your vibration suppression might have gotten worn, your motors and props might be vibrating more or the props might be less balanced, etc. Just one idea of something to check.

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