Pixhawk fall from the sky in altitude hold mode

Another crash caused by a switch to a different flight mode....

After several good flights with my pixhawk equipped quad, i had a crash soon after take off immediately after switching to alt hold flight mode. The quad immediately rolled over and fell from the sky...

I don't understand the cause, especially because i had several good flights with the same configuration, i didn't change anything since then...

If somebody can give me a hint based on the log file i attach to this thread i will be very grateful.

I also attached the video taken from the go pro on the gimbal.

Thank you in advance...


alt hold crash.mp4

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          • This is in line with the log and video. Copter fall on the left. Pixhawk reduce motors on the right and increase on the left to come back to a stable position but probably no reaction from the motors. What I noticed this morning from the video is the noise variation. It's like the motors nearly don't spin anymore. It start just after the copter noise going down (sport mode). As pixhawk asked for full power on 2 motors we should hear it. Have you checked the main power distribution to all motors ? Are you sure that this strongly attach to allow the amperes to go thought during vibrations (clean contact) ? My feeling is more on main power distribution related issue.

            PS: I guess your camera is on a stabilized gimbal, so the camera movement are perhaps not in direct relation to the real copter movement.

  • I find out that the copter didn't go to halt hold straight away from stabilized mode. It was in stabilized mode, then went to Sport and only then to HaltHold (at row 5026, then 5109, 83 rows). During the 83 rows period, you can see the pitch going down to -1 in IMU and in IM2. You can see this movement also from the film. And only then the behavior got crazy. During the mode change, the RC2 is at 1300 while the others are around 1500 (neutral). Is the RC2 link to pitch which could explain the pitch movement ?

  • Don't understand what you mean...
    • like this


      • For sure not at close distance, also on google maps i can't see any in the area, do u think those antennas could interfere with the pixhawk? If so why would it do that at the moment of the flight mode switch?

  • Is that environment have an internet or stanchion pillar

    • Son, do you have bad experience around comm tower like the one pictured?

      I am asking because I fly an Iris close to one of the towers, and sometimes I have funny glitches, but mostly poor 915 telemetry.

      Thank you.


  • I think maybe motor,prop or esc issue

    Firmware version?

    Esc type?

    • FW is the latest, 3.1.5, I can exclude prop issue, about motor and esc i must check, but it's not likely, the drone rolled over exactely when i switched to alt hold, till that moment it was flying nicely as always.

      • Motors are Sunnysky V3508 580kv and ESCs are Afro 30 amp.

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