GPS link lost mid flight

[SamaraMedia]

Had a disturbing thing happen over the weekend while out for a little flight with my P2/GoPro. Used it for a week while on vacation and had no issues (thankfully since I was flying over the ocean) but once I returned home and went back to a field I fly in a lot I had some issues. First it took me about four attempts to finally get a GPS lock with 7 or more satellites. I'm using the DJI 5.8 vtx/rx, DJI miniOSD and a RMRC 9" monitor for FPV. The first three calibration attempts failed, the fourth I got 7 sat's. I took off in ATTI mode and started flying my usual path, about 1 minute in I noticed the quad starting to drift, then the Zenmuse H3-2D started to lose its orientation and horizon. I glanced at the screen and noticed I had 0 satellites locked. I didn't think that it mattered since I was in ATTI mode and not GPS but I was wrong. It was difficult to navigate since the stick input wasn't always what I was getting on the other end. I was able to bring it back to home without a crash but it never gained GSP lock again and I had decided to ground it (maybe the best decision yet) until I can figure out what happened. Glad none of this happened while out over the ocean.



<iframe src="//player.vimeo.com/video/101508185" webkitallowfullscreen="" mozallowfullscreen="" allowfullscreen="" frameborder="0" height="281" width="500"></iframe> Lost Satellite on DJI P2 from John Woike on Vimeo.

 

[Cheshirecat]

Sounds like a compass issue, you should be able to fly correctly without any GPS in ATTI mode.
You said you had 3 calibration failures, did you mean compass calibration if so does it calibrate reliably in a different location? there may be environmental ineterference at this location affecting the compass module.
I have a P1 and the compass module is on the landing skid (not 100% if the P2 is the same) there was a video explaining how to reset a compass module that has been corrupetd by a magnetic field, may be worth a search or maybe get a replacement Compass module, the P1 is readily available and not too expensive.
Maybe pop the hood and check the connections to the GPS Puck as well.

 

[SamaraMedia]

Thanks Cheshire. I fly at this location just about every weekend and had no issues up to this point. Yes, compass calibration, yes, located on landing skid. I thought I could fly in ATTi mode no problem too so I was surprised when it gave me problems. It even effected the Zenmuse horizon orientation, good thing the miniOSD gave me a horizon plane to judge the flight position.

I'll look into the compass trouble, check the GPS puck connection and connect up to the P2 assistant and see if something shows up there. 'til then I'm keeping it grounded.

 

[Cheshirecat]

Good luck.
I did have an issue with the P1 Compass module, and could not calibrate it. In the Naza assistant you can see the compass data jumping around wildly when the aircraft is sitting still on a desk.
the fix involved waving a magnet around it in different planes, seems counter intuative but it did work for me.
Here is the link:

http://youtu.be/kCT1rRE_UIg

 

[SamaraMedia]

Thanks Cheshirecat

 

[Benjamin Kenobi]

Agree with above. Certainly sounds like a compass issue. I would say re-calibrate again. I had something like this when flying near a large magnetic source. Also affected the Zenmuse horizon. Re-calibration took care of it.