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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  • I place a small torroid with max amount of turns as close to the GPS as possible. Especially doing fpv. Many cameras are known to be noisy.
    • Martin, the GPS would be mostly interfered by RF fields hitting the ceramic antenna, than creeping along the power/signal cable.

      But then, every little bit helps :-)

    • Your correct. We also don't want a Faraday Shield with a outward Resonant antenna lead creeping into the electronics. hehe

  • There is a known issue with the mobius radiating RF interference from the heat sinks.  The RFI happens to not play with GPS. Stab and Alt Hold do not use the GPS.  It is quite likely the interference was there all along, but because you weren't using a flight mode the utilizes GPS, you were none the wiser to it.  Once you switched to Loiter, it tried to use the GPS which was experiencing serious interference.

    The log file shows an HDOP of 100.  It should less than 2. And basically no sats.  I'd be willing to bet if you watch the HDOP with the copter on the ground, and move the camera towards or away, you'll see it change.

    Oddly, it doesn't seem to consistently effect everyone.  It depends greatly on the placement of you GPS receiver and the mobius.  But as soon as you said Mobius, I knew where this was going!

    Mine doesn't do it. In fact right now, I have my mobius sitting directly next to the GPS, TRYING to get it to mess up and it won't.  But others, it renders them completely inop.

  • Just a long shot but the Mobius causes issues with your gps, I have three setups all with APM 2.6/GPS/COMPASS that each had issues with the Mobius camera, I ended up having to cover the Mobius with MuMetal which fixed the issue.

    just a thought 

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