Quad crush

Hi all.

I ran into this problem. When starting the quadcopter in position mode, it abruptly gave off the throttle, made a roll and fell down

More about my quadcopter:
It is a large quadcopter with 30 inches of propamy, power and control (via joystick) comes with a wire (Tethered drone).

Below I will provide a link to the log file that was recorded. Please disregard the errors until 4:14 - before that time the quadcopter was being positioned on the landing site and it was affected by interference.

Maybe I have some simple setup error here, because before that I was flying only on AP firmware.

Thanks in advance for the help

Log File

Sorry to hear about the crash.

When you post the flight log, please upload it to: logs.px4.io. I have done that here:


It seems like it only shows 2 plots, and indicates that you probably have custom changes & are not logging all the topics that official PX4 releases do, is this a processed (certain topics removed) log by any chance?

Yes, unfortunately, that’s all that was recorded. Apparently I did not keep track of the fact that the logging of the main parameters was turned off…

We briefly discussed this during Community QnA call. There can be few possible issues:

  1. Your Multirotor tuning parameters are default, but they should be reduced (as it’s not as agile), for example attitude P gain is 6.5, which is for sure too high for drone with 30 inches prop. So it could have been tuned improperly, leading to a crash.
  2. Your PWM minimum output are all 1000 us, which could lead to motors coming to a stop mid-air, when it saturates to the minimum value, especially if your ESCs were not calibrated.


  • It seems like drone was in Hold mode, before switching to Position mode, why was that?
  • Did you calibrate your ESCs?

For the PWM issue 2. please refer to this comment:

If there were more topics in the log about controller tracking and motor commands we could analyze it in more detail. The suggestions are just our guesses based on the logged parameters.

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