Craziest tlog and fly away in Stab mode

I had a great flight yesterday on my 3DR Quad-C with 880 motors that ended in a flyaway in Stab mode. I was flying in a school yard in a residential neighborhood and had to do something to stop it from climbing away and drifting with the wind so I switched to RTL. It immediately fell out of the air. Lesson learned. Do all test flying in remote wide open spaces.

It was the first flight with an external magnetometer, the first flight with telemetry (3DR), and the first flight with Andropilot. This may be too many firsts in one flight. All seemed well...right up to the point where it flew away after several minutes of very smooth normal flight. It was a gentle flight where I was giving the compass time to self calibrate and make sure there were no surprises. I did do a manual compass calibration before this flight and heading hold seemed to be locked in. The compass offsets were off the charts. This is much worse than before the addition of the external mag.

COMPASS_OFS_X    226.787
COMPASS_OFS_Y    66.172
COMPASS_OFS_Z    -711.784

Looking at the log, the APM was rapidly switching between Stab mode and Unknown, Armed and Disarmed.

The copter is new with only a few flights with 2.81 and two flights including this one with 2.91 and default tuning.

Any ideas?


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  • The "Unknown" mode may be Position Hold mode.  When I switch to Position Hold Mode the APM Mission Planner shows and calls out "Unknown."  Obviously this is a software issue.  The other modes report and call out fine. 


    The rapid switching back and forth - could it be the radio/receiver on the ragged edge of the propper PWM for Stablaize mode?  IF you are using the F Mode switch to get many modes on one radio channel it could be worth a look. 

  • One flight with andropilot and Arduplane 2.70 with APM 1.0

    Finally I found thismode twisting  thread ;-)

    At home everything is solid.(of course)

    I know there is some radio interference, but it should'nt so bad.

    First manual, then mostly stabilize, one trial to Auto, and back (lost my nerves), one test radio shut down-> circle-rtl (deep nose dive)

    Quite messy I know, gusty N/NE wind and flight ended to ditch with minor injuries ;-)


  • Kevin,
    I've been experiencing the same thing. Mode is not changing.
    When you say 'ignore those messages' are you removing them? KMZ in GE is constantly alternating between current mode and unknown. 313 points!

  • Developer

    Re: switching modes between stab and unknown etc...

    I don't think this is really the case.  I looked at the tlog here:

    And I think what you saw for mode changes is actually a (minor) bug in mission planner.  Andropilot tlogs store _all_ mavlink packets (including packets sent from the GCS).  The 'unknown' mode changes are actually MP misinterpreting the heartbeat message from andropilot.

    If I ignore those messages (since they are from the GCS) I see only stabilize & RTL mode changes (most easiliy seen by downloading the kmz from the link above and viewing in google earth)

  • why did you use Andropilot ??? and not Mission Planner ????

    did you get the copter in one piece ???

  • Developer

    I'd guess the mode switching thing is likely related to the new Andropilot because it doesn't appear that your flight mode channel (ch5) moves around at all.

    The altitude issue could be vibration, it's hard to be sure because the accelerometer values are logged at a very low rate in these tlogs.

    3692641250?profile=originalThe compass offsets are terrible however.  I wonder if it's mounted in the wrong orientation or perhaps you just have very bad motor interference.  -711 is amongst the worst I've ever seen.  It was actually this bad for the entire flight so even before you took off your heading was very inaccurate it think.  It's no wonder RTL had no chance of bringing it home.


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