Uncontrolled take off.

[Phantom of the Gorge]

I setup to fly under a bridge way up over my head but a little off to the side. I notice before taking off that I only have 7 satellites acquired but think once I get airborne I'll get more. I also notice that the concrete below me must have a ton of rebar because I'm getting compass errors so I set the bird on top of a rock off the sidewalk. Admittedly I was surrounded by heavily reinforced concrete and a steel bridge about 100 ft above.
The bird rises up about 2 feet and pitches to one side at what seemed a 45° bank and heads straight at a concrete column about 15 feet away. I did everything I could to regain control but it was all I could do to soften the blow. The bird got a little dirty but seems fine (in fact seems more stable now ).

So my question is; what would cause the erratic behavior, the metal affecting the compass or the GPS positioning throwing a wandering position because of so few satellites being aquirred?

 

[msinger]

what would cause the erratic behavior, the metal affecting the compass or the GPS positioning

This type of erratic flight is most often caused by nearby magnetic metal objects.

 

[GMack]

Wonder if there would be any benefit to turning off the compass at times in GO (If it could be done.) and just letting the GPS be "good 'nuff?"

 

[msinger]

The compass cannot be turned off/ignored. Without the compass data, your Phantom would not be able to steer itself back to the home point.

 

[Gearbox]

I remember reading a Thread around here somewhere ( with Video ), where the Drone did the same thing under a Bridge , only his was damaged & I think DJI wouldn't repair it under warranty .

 

[MacPhantom]

GPS can tell you with where you are but it can't tell which way you are pointing without first going in a specific direction. The compass provides details on which heading the device has so that it can then follow that up with control inputs to go in that direction. Once moving, GPS technically can derive the heading but I am unsure if DJi utilizes GPS for heading while underway. If this was the case that they use it, the problems come when GPS and the Compass showing different directions while underway.

In the aviation industry they utilize Compass, GPS along with Inertial Navigation to gain accuracy and reliability.

 

[solentlife]

Its not unknown for the compass to be 'stuck' ..... I note that after the 'bang' you say it tends to fly more steady ? It may have 'bumped' the compass into working ?

Strong magnetic influence can in fact lead to apparent failure of a compass ... mechanical and electronic until it gets a 'nudge' back to normal ...

I'd find a nice quiet open field and fly her to see what she is like overall .... tentative few test flights to determine if OK or not.

Nigel

 

[Phantom of the Gorge]

Sorry for the delay in getting back, it's been an incredibly busy week for me but I appreciate all the responses.

 

[Phantom of the Gorge]

Its not unknown for the compass to be 'stuck' ..... I note that after the 'bang' you say it tends to fly more steady ? It may have 'bumped' the compass into working ?

Strong magnetic influence can in fact lead to apparent failure of a compass ... mechanical and electronic until it gets a 'nudge' back to normal ...

I'd find a nice quiet open field and fly her to see what she is like overall .... tentative few test flights to determine if OK or not.

Nigel

The stuck compass might explain the problems I was having before. I have had it out since the crash and it does seem to fly better but I suspect it might be something else, hard to say for sure.

Pre-crash I was getting the dreaded wobble and I saw a post suggesting to change the gain to 80,80,80 and 100. I did that but then it seemed a little sluggish to respond and was wandering a bit more than before so (before the crash) I tried 90,90,90 and 100 and it's buttery smooth now. I flew an entire battery before the crash with the new gain settings and all looks good, I've since flown 3 or 4 batteries out and haven't had any issues. The video is smooth as silk, no jello effect and stills are as sharp as ever.