After 2 weeks of building, reading and testing, I took my quad out for its first flight today. I hated every minute of it. I had flight modes set set to Stabilize on all three positions on the assigned switch on my transmitter.

I had about 5 seconds of stabilized flight before it switched to RTL and started ascending. It kept switching between stabilize and RTL throughout the entire flight, with a loiter mode thrown in for good measure. It ascended to 480m AGL (1600f).

It seems like it changed from Stabilize to RTL when I throttled down. Is this the correct behaviour? ALT_HOLD_RTL is 0 (return at current altitude), but it climbed in altitude while in RTL. Is this also correct? 

While I was doing preflight checks, I had it powered and was alternating between armed and disarmed to do a range check, confirm prop direction and to warm everything up. I lost sight of it multiple times, until I spotted it tumbling down into a tree. 

I had a GoPro mounted on the underside and captured most of the flight. From the looks of the video, there was some violent swinging that started. I think the GoPro got loose, hit a prop, snapped it and tore a motor off the frame. This is the only explanation I have for the video ending where it did.

Frame is a 3DR quad with: APM 2.5 (ArduPilot 2.8.1), 880kv motors and mediatek GPS.

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  • Damn, what a hell of a ride, thank god the problem has been sorted out for you!!! Hopefully the repairs are not too expensive.

    BTW: I programmed my Frsky RX to give the following command to APM on signal loss: Flightmode: RTL, Ail/Ele/Yaw Sticks center, Thr a little below middlestick (in any case....). On APM side i didn't set special Failsave options except: RTL hight 30m (avoid trees) and approach high 1m. I didn't dare to test this out but i hope that these settings will save me when my TX dies on me during flight or i get out of range.

    So long

    Kraut Rob

  • Developer

    Wow. That quad really wanted to get out and see the world.

    I know most of the settings are tempting, but the defaults are where you want to be for the features. I've never used failsafe in two years of standard flying and I doubt I will unless I'm flying FPV. Even then I would verify RTL was working on each and every flight before depending on it. (RTL requires GPS lock and setting home by arming *before* taking off! Otherwise, how would it know where home was?)

    Your motors must be higher KV or you have larger props because your gains for Rate_roll_P and rate_pitch_P are too high. bring them down by 30%. Rate_Yaw_P is most likely too high as well, but sort that out later.

    Good job hanging in there. I would have crapped my pants.


  • 100KM

    Wow !!!  That's some impressive video !  I don't think many people watched it, since it seems to me you have more problems then just switching into RTL unwanted.  

    I gues it's not you who is rotating the copter like that ?  

    I also gues it's not you who's shaking the copter like it's doing the boogy woogy.  

  • 3D Robotics

    It sounds like you've got an issue with your RC setup. It should never switch automatically between modes unless:

    1) You're losing RC connectivity and it's going into some failsafe mode

    2) Your Channel 5 (Mode switch) is somehow set right in-between the two modes, and random noise is flipping between them. 

    You can check for the second by just starting off with all the modes set to Stabilize  so even if it does switch from one to another it won't change the behavior. 

    What RC gear are you using? And did the RC setup go normally?

  • Hi, sorry if my posting is a little disjointed, my nerves are still going wild.

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