Fly away after take off in PosHold mode Navio2/PXFmini ArduCopter3.4.3 and 3.4.4

I have encountered 2 fly aways after taking off in PosHold mode using RPi 3 running Navio2/ArduCopter 3.4.3 and PXFmini/ArduCopter 3.4.4

In both cases I was using a single compass parameter
In both cases this event occured ONLY during take off+PosHold. When I take off in AltHold or Stabilize and switch to Loiter or PosHold I get no issue

Here are my compass parameters on my PXFmini

Here are the flight logs!GMVAXKwb!Bo3n5r0AhxzCUzMSPQ5-sUAID5QVcEGPxAMx67425NQ

Does somebody know where it could be coming from?

Thanks for your help

Hi Guillaume,

I had a quick look at both logs, each of them shows that you took off in stabilize. In one of them you are in stabilize for more than 3 minutes before switching to alt hold. In the other you take off in stabilize, switch to alt hold 15 seconds or so later, and then switch to poshold around the 1 minute mark.

Could it be that you thought you were in PosHold, but where actually in manual?

Hello Olivier
Thanks for this analysis
Sorry for not having been more precise : in the log called 2017-01-17 10-56-16, my 3rd take off is done in PosHold (take off at 11:07 if looking at Altitude parameter, just before the EKF-CHECK-2 error). This is the one where I have had a fly away.
By the way the aircraft did not detect its crash and was continously attempting to fly even on its back on the ground. (same situation on both fly aways I have had after PosHold take off)
I confirm in both situations I have encountered I was in PosHold, unfortunately :frowning:


Here is my interpretation of what finally happened:
-Take Off in PosHold
-EKF CHECK error due to high magnetic interference with compasses (high current)
-Automatic switch to Alt Hold (I changed the default value since LAND can be dangerous in remote autonomous missions)

  • Loss of heading (quad turning clockwise around himself) --> as I use “simple” mode commands are not properly interpretated
  • Wind pushes the drone away while I cannot attempt to recover control
    …but RTL should in this theory have worked? Shouldn’t it?



Bad compass = no navigation (RTL)