Hi gurus!

Just did a flight in -17C. The quad stopped listening to me...

  1. Take the quad from indoor temps to outdoor -17C. Power up right away.
  2. Takeoff in STAB. Everything works.
  3. Some seconds later ALTHOLD
  4. Some seconds later LOITER. All well so far.
  5. Slow climb and fly the quad 30 meters to the side while in loiter.
  6. Still in loiter, start steering back, slow decent. 
  7. Still in loiter. Steering or any control input don't work! Quad keeps descending slowly and moving towards me. As it was stuck in my old input. Radio (FrSky DJT + V8R-II) not beeping about loss of signal. Radio failsafe would be Thr 50% and mode = LAND. According to logs quad stays in Loiter. Slow movement back towards me also points to old input sticking.
  8. MinimOSD crashed by now (overhead layer disappears)
  9. Switch to ALTHOLD. Nothing changes.
  10. Switch to STAB. Nothing changes. 
  11. Quad reaches the groud, soft landing as the decent was nice and easy. I drop the throttle but nothing happens.
  12. 3-4 seconds later props stop and I disconnect battery.

.log file attached.


What could have caused this?

  1. The cold? I flew plenty in up to -20C last winter but that was with older FW...
  2. Stupid user?
  3. Bug?

I tested the RC link afterwards and that seems fine so I dont think the problem is here..

My board is APM 2.6 with ext compass. Enabled logs ATTITUDE_MED GPS PM CTUN NTUN CMD CURRENT

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Even if the flight was basically a failure I took my first ortho images on this flight which turned out ok. :-) 

Like you say, APM never left Loiter.

Also, your ThrIn decreased in steps ? your PitchIn is gone after before log line 5000, your RollIn is then stuck at ~-10

This is a mess, and I think you are lucky it came down the way it it did.

Anyway - you should use the APM's failsafe, not reciever. That's the only correct thing to do, and then you know what to expect.  Configure throttle failsafe, then , when throttle channel sinks below  a threshold, (or goes away), then APM takes over fully, and ignore other invalid input.

Thanks Andre for your comment.

I set up the APM failsafe and it works as intended. I have done three 2 minute flights after the weird one and everything has worked as expected. But I would love to know what happened because before that it does not feel safe to fly... :-/

I told you what happened, from the view om APM :)
your FT_THR_VALUE is 975
What PWM do you get on Thr channel after switching off TX ?

yeah... :-)

When I switch off TX Thr drops to ~900 as it should, but note that I did not have APM failsafe set during the above flight. Then I used radio failsafe with Thr at ~50%.

Any one else out there that has a theory of what happened with the APM? Too cold?

Not too cold. I've flown in mid -20s many times without issue.

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