Please see attached log and screenshot.

  • Pixhawk
  • Flying wing
  • Arduplane 3.3

Flying mission with auto takeoff and waypoints. Plane perfectly executes take off and heads to first waypoint. Upon arrival at first waypoint plane pitches down until impact - even though desired pitch is up. No failsafes. No errors I can find. Z vibration low at time of failure. Any ideas?




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  • regarding your PM:

    Yes, DesRoll  & roll matches at line 48827 , but watch from ~49000  your roll does no longer follow and pitch starts dropping too.

    It was late yesterday - it seems i were reading wrong lines, at time - must stop working too much on things :)

    • So what would be the main cause of this?

      • any problem that may cause contol surface(s) not move accordingly to PWM output. , wiring, servo power, servo, etc..

        • Can you see PWM commands in the log? The plane is still intact after the crash. It is a flying wing. Both elevon servos and control linkages are good. Seems like something was lost between Pixhawk Desired Pitch Up and the servo. Also, since it's a flying wing the plane will spiral down if you lose a servo. Can you tell from the log if the plane is spiraling? Seems like the log would show an oscillation. I will take a plane out later today and send it down in a spiral in stabilize mode and see.

  • look at the crazy uncommanded roll you have after log line 47600 , it banks over for no reason (RCOU.ch1 & ch2) does nothing to cause that - it tried to roll back later, but is unable,

    most likely a control link fell apart or loose control surface.

    • Thank you Andre for the excellent analysis. I suspected mechanical failure. Please help me understand how you see the uncommanded roll in the log?



      • I see a rapid roll (before you loose altitude) , your RCIN tels me it's not manually commanded, at the same time i see  RCOUT.ch1  RCOUT.ch2 (your elevons servo signal) does not deviate from "normal"

        - then, as you got big roll angle, you can see autopilot try to correct the roll with very big servo output (compared to usual flight till then), but it does not help...

        • Is this the right graph to show the roll? Thanks! Brian

          • I've been using ATT.Roll , but it'do.

            • Sorry to beat a dead horse, but I don't see the uncommanded roll. Roll and Desired Roll are somewhat aligned. Pitch and Desired Pitch clearly diverge.3702885607?profile=original

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