First, let me say that I am a novice. I have been flying APM quads for a little over a year starting with a 3DR quad. I am now on my 5th APM based quad and keep having a similar situation cause me to crash. I don't know whether it is an equipment problem or pilot error and would greatly ppreciate some help.

Yesterday I was flying my Talon Quad shooting video with Mobius actioncam on a brushless gimbal. I flew the first part of my flight starting in stabilized mode and switched to alt hold, flew around for a couple of minutes, switched back to stabilized and landed so I could switch settings on the camera. I then took off again following the same scenario, flew out about 150 feet from me at an altitude of about 20 feet. I tried to come back towards me (flying in SIMPLE mode) and just "lost it". Quad got really unstable and crashed.

I have attached a log file. I do not have telemetry on this quad and am not real good at reading and understanding log files. I do see a GPS error in the log analysis, but believe this is after the quad crashed.

Can anyone give me some idea of what's going on? This is the forth or fifth time I have experienced the same situation and I'm getting really frustrated. I've been through vibration dampening, GPS/compass isolation, light shielding...

Here's my setup:

  • APM 2.6
  • NEO 6M gps/compass module (eBay, but I have had the same situattion with 3DR on earlier quads) on 3" mast
  • FrSky D8R II plus reciever 
  • TX9 with FrSky module
  • 2 axis brushless gimbal
  • Mobius actioncam

Thanks for any help.


2014-05-05 11-47-50.log

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  • Developer

    It looks like a mechanical failure to me.  The GPS failsafe happens around line 3800 but the vehicle is in AltHold mode so it doesn't matter.  The crash happens 1min later at 7400.  I don't see anything in particular in the parameters which point to a problem... for example very bad tuning could sometimes cause a flip but this copter's values look ok to me.


    • Thanks Randy. I'd have never known what that indicated or what to look for. Maybe someday if I keep pluggging along I'll get logs figured out.

      I've got the quad back together and am going to swap out props (see Gustav reply) I was using 10x4.7 carbon fibre I bought on eBay. I had one broken prop that I thought happened on impact as I also broke an arm, but who knows. I'll go back to APC 10x4.7 SF and see how it works.

    • Jim, I too had crashes that I couldn't "explain"

      And found prop blades further away than expected.

      Do yourself a favour, get the new APC Multi Rotor props.

      The SF's flex too much.

    • Ah,

      A guru weighs in:-)

      Obviously, the next question is, what propellers were you using ?

      (SO wish I could read logs, and SEE.....)

  • The interference caused by Mobius is very distance dependant I find, and it has not been difficult for me to find a way to make enough space between the camera and the GPS that reduces it to almost nothing. I have 2 Mobius which I interchange between a plane, 3 quads and a hex and just use separation as my remedy.

  • Lots of the FAQs and best practices that on this site recommend becoming proficient in STABILIZE mode before moving on Alt Hold and Loiter.  Being the nerd that I am, I of course completely ignored that and went right to flying around in alt hold and loiter.  It is great because the flight computer does all the hard work for you.  It is bad, because the flight controller does all hte hard work for you.  Now I'm trying to work my way into playing around in stab mode to re-train myself the way I should have in the first place.

    Last month I almost lost my quad because I stupidly had the GPS/Compass mounted sideways. In any GPS guided mode, it took off on a wild tangent off to lala land.  It got very far away, almost gone.  I took it back home in stabilize mode, which was terrifying. All over the place and very difficult to control since I wasn't experienced with it, and it was windy.  It was at a drone meet, so it was kind of like "OK everyone, make a hole cause this thing is coming home!"  I'd like to no have to do that again.

    • HOW TRUE!

      There is no "easy way". Couple that with the fact that I'm a slow learner and old, shortcuts sound tempting. I'm just going to havr to back up a few steps on not be in such a hurry.

      I am going to look into ways of reducing the interference from the Mobius as it is a great little camera.

      I assume it is sage to shoot Mobius video if I'm only using manual or stabilized modes?

  • Developer

    Simple is a bad way to recover your quad if you don't understand what position it is, especially when something doesn't work.
    Before using the all the automatic mode try your quad several times at very low altitude, especially when you add or change hardware.

  • Thanks for all of the input and the link to RCGroups Mobius forum. I AM going to get this worked out. I guess the greatest fun is overcoming the frustration.


  • RF noise from the camera.

    Except on my quad it played havoc with the Spektrum RX, I think......

    Unfortunately, it was the one time I did not use telemetry.

    Managed to regain control by running towards the quad.

    Mmm, wait a bit, also running towards the quad, I switched to manual.

    So yes, RF interference, GPS, RX, all bad.

    Wrapping the camera with aluminium foil, with just the lens peeking out, might do the job.

    I would place some plastic or electricians tape over the heatsinks, just to make sure the foil is isolated from the internal noise.

    And no, this isn't a design fault of the camera, most electronic devices generate huge amounts of RF noise.

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