Question on 1.5.2 Stable


I decided to try 1.5.2 Stable on my small quad and after calibration the motors don’t spin up at the same time, only two motors spin until I throttle up quite high.
Log is here:

Some other notes:

  • Before I calibrated the sensors I got warning messages in QGC but the sensors were all green in the GUI.
  • QGC constantly tells me that RC link is lost during calibration even though I don’t have an RC connected.

Thanks for any inputs!


  1. make sure you have the right PWM_MIN value set for your motor & ESC
  2. calibrate your ESCs


When locking at the logs it seems to me that the autopilot controls different pwm set points so the pwm_min parameter should not be the issue?

I also tried with ardupilot and it works good so I don’t think it is the esc calibration.


Try again with a completely flat setup and without any stick inputs. Your log shows that the roll / pitch set points are not at zero when you arm.

No, the PWM_MIN value is exactly your issue. You need to set a higher value for your ESCs.

Ok thanks will do.
Now I flashed 1.5.2, calibrated everything but was not able to level horizon:

When I re-powered all calibrations was lost

I redid the calibration and now It worked, however I can’t arm because I don’t have a safety switch plugged in. What is the parameter to disable the switch?

Its in the circuit breaker section. Is it possible that you didn’t choose a racer airframe but generic? If you had chosen a racer you would have also gotten good defaults.

In the circuit breaker section I don’t see any cbrk for safety switch?

I did not pick the racer airframe since it is not really a racer, only 2s battery and smaller motors, but now I changed but I still can’t arm since I only get the message “preflight check failed”, however I don’t know what exactly failed?

Its the circuit breaker for safety (named safety). It should be set now. As for your preflight check failure - that sounds like a good thing to debug now. You can run the check again with commander check which works with Tools/ in case you don’t have FTDI on the board (remember to disconnect QGC first).

We need in situations like these the community (you) pitching in when they have a case they can reproduce. These things are almost impossible to debug remotely.

I suspect its a supply voltage check or so failing. Check first on the console.

Yes you were right, when I changed the airframe to generic racer the number of cells changed to 3s. I created an issue for it. I also increased the pwm_min parameter to 1300 and now it flies! At least indoor, we have around 30 m/s wind here atm so will have to wait with tuning outside…