The dreaded compass error - two near identical flights - one with and one without - wondering what causes it

[Deleted member 94047]

That perhaps suggests an external influence

Sar, the AC was above the take off point and low at the time, no more than 10m at most - possibly less. I can't think of any external influences that might have caused this - other than a possible insect ingestion into one of the motors. I did find a black streak on the top shell after I landed. Didn't give it much attention as the props often catch a few insects.

 

[sar104]

Sar, the AC was above the take off point and low at the time, no more than 10m at most - possibly less. I can't think of any external influences that might have caused this - other than a possible insect ingestion into one of the motors. I did find a black streak on the top shell after I landed. Didn't give it much attention as the props often catch a few insects.

There was no recorded motor speed excursion until after the rotation, so I don't think that's the explanation.

 

[Deleted member 94047]

Thanks for ruling that out, I can't think of anything else. The video should be up now;

vlc-record-2019-12-30-18h09m02s-DJI_0404.MP4- - Streamable

Check out this video on Streamable using your phone, tablet or desktop.

streamable.com

The un-commanded rotation happens around 10s into the video; starts violently and then eases off into a gradual yawing to the left. I start rotating the AC around 20s.

 

[sar104]

Thanks for ruling that out, I can't think of anything else. The video should be up now;

vlc-record-2019-12-30-18h09m02s-DJI_0404.MP4- - Streamable

Check out this video on Streamable using your phone, tablet or desktop.

streamable.com

The un-commanded rotation happens around 10s into the video; starts violently and then eases off into a gradual yawing to the left. I start rotating the AC around 20s.

Yes - that's weird. Almost looks like a collision, but it wasn't. The rate gyros clearly show the rotation but the accelerometers didn't detect anything except the start and end of the climb:





I'm not sure what to suggest at this point.

 

[Deleted member 94047]

Well, if you can't make sense out of it, I don't think anyone can. Thanks for taking the time sar, really appreciate it. I posted this thinking it was a case of compass error and unable to figure out why a compass error would occur in one flight and not in the other in two flights that were near identical. I guess it will have to go into the unexplained events list which I should start compiling. Thanks again!