Unexplained crash with Pixhawk

an unexplained crash with Pixhawk. 20 seconds after RTL. high drift uncontrollably, motors go shortly before the crash at full speed.
switch to a different mode, no control.
Broken camera
Frame broken
1 motor broken
This is the 1 crash that is inexplicable to me for me after a few years of APM.
am grateful for each idea

The Log

Are you able to get the .BIN log from the pixhawk SD card?


Hello Jschal

thanks for the quick reply.
the logs BIN are here:

last week I had this error before, but was able to land in Stabilize after switch

Next week I have to provide a OKTO to a customer, would be good for my sleep if the error would be found

thank you for your interest in this problem

What are the specs of the esc and motors
Simon-K (HK afro esc 30a) and pixhawk causes unexplained crashes with my quad.


ESC HK F20 with Simon, K. to T -Motors.
The controllers are OK

What’s happening is that the inertial navigation velocity is ceasing to track the GPS velocity. See fig. 1.

Possible causes:

  • Bad compass
  • Vibrations
  • GPS glitch (does not appear to be this)

I’ll post again when I’ve found the most likely cause.

Just took a look at your params:
Those motor compensations are 8 times what I have.

You don’t have mag logging enabled, but I can graph your rotated accelerometer (used for INAV) against your GPS acceleration (the second derivative of position)

For most of the flight, it is good (see fig.1). At the end of the log, it goes bad (see fig. 2).
We can take a look at what would happen if we put a yaw offset into the calculation of rotated acceleration. In this case, -60 degrees seems to work somewhat (see fig. 3).

Anyway, your yaw was off by a lot. This indicates compass problems.

So, to fix this problem:

  1. Zero your compassmot calibration gains: COMPASS_MOT_X, COMPASS_MOT_Y, COMPASS_MOT_Z
  2. Elevate the GPS/compass module away from any high-current wires or devices (ESC, ESC wires, battery wires, power distribution board)
  3. Redo compass calibration
  4. Re-run compassmot

many thanks for your work Jonathan

it is true, it is something seen with the Compass.habe in the t-logs and there were bad compass.
just got an external compass mounted compassmot
2% I found very good. But the internal compass runs. is that ok? fly is not possible.
I take to a hardware error. I’ve bought here a Pixhawk 3 days ago has a Compass error.
I connect an external everything OK.
this error does not have the APM. 5 piece Pixhawk and 2 pieces with errors is not ok.
The software of APM and Pixhawk is very very good.
only the hardware errors must be removed, I can not find me such things as seller not good.
Please, please 3DR checking the hardware, then everything is ok.

my thanks go to them johnathan