Two weeks ago i crashed with my hexacopter with APM 2.5 and uBlox LEA 6-H GPS. In loiter mode drone behaved unpredictably. According to symptoms, it was probably about a compass interference. I use my older APM modified to external compass and use uBlox NEO6 with external antenna. I used HMC5883L external magnetometer. GPS external antenna and compass I placed about 20 cm above the top of dome on platic water pipe. After this modification drone fly perfectly.I tested auto mission and everything was perfect. I thing that external compass is needed.
There is onboard video from automatic mission.
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There is full video H.A.L. Hexacopter with external compass and GPS antenna modification
We tested Stabilize, AltHold, Loiter, RTL and Auto Mode
What were the symptoms? Outward spiraling in loiter flight mode?
Exactly. After two circles crash
It happened the same to me last week, but it never crashed, just seemed to keep on spiral infinitely.
In auto mode yes I had bigger problems, because it failed completely the waypoints both in planimetry and altimetry, and had to call it back to stabilize to save the copter.
Anyways, I've found out at least 2 problems in my copter.
1st - The compass was decalibrated, dunno why. I had to recalibrate it again.
2nd and most important, I've found out that the loiter PID's were crasyly high. I don't know how in the hell did they changed. The problem was solved by reinstalling the firmware.
I've flown it again and it flew well again, even tough in loiter mode it isn't as stable as it used to be.
After modification i had to install new firmware because I used this APM for ardurover. And after install new firmware i had to make all calibrations. But i think that compass and GPS interference was main problem. And in first flight a made auto tune.