Loiter mode causes fly away, good calibration etc etc,

Can you try the flight again but with the logging bitmask set to it’s highest, not sure what that is on the apm but 655358 might work.
The other things are, have you tried an autotune? and does it behave differently in GPS modes when your in an open area and not between two buildings?

WEll, I found something

FAIL - ERR found: GPS

That was in my last log, the GPS shows a perfect lock in mission planner, and I am getting the lock light after arming, but that is what the log is showing,.,

logging bitmask set to it’s highest

No idea what that is.

You GPS still thinks home is China. :slight_smile:

Had a similar problem. Replaced the GPS with a new NEO 8M unit and made a huge difference. Not only that, even a cold start in the house had lock on 20 satellites consistently in about 12 seconds. Outdoors it was almost instant.

Hey all - I hope it’s OK to necro this thread, but the advice in here got my Cheerson CX-20 flying safely again. Quite a while ago my stock CX-20 started to misbehave, and I determined the problem to be the compass. I moved the compass on to a pylon external to the aircraft. It was fine for a while, then went all crazy again, trying to fly away in loiter mode. I replaced the compass, and its behaviour was slightly different but STILL it wanted to fly away. Thanks to this thread I discovered that the compass setting of roll 180 was wrong - in my case, with the new compass, it should be yaw 180. Now it holds position perfectly once more :slight_smile: Thanks guys :slight_smile: