I saw that the version 3.2 is available and want to try out with my hexacopter (APM 2.5 with external compass, supplied from PM with extra 470uF capacity on rail)
After update I checked battery with tester (~90%) and went out for a testflight.
I did no compass calibration because I think it is not necessary if updating from 3.15.
It took about 2 min before the copter felt down then.
I started with stabilize, tried a little altitude hold and switched to loiter then.
Loiter was not stable and copter was flying around a little (by the way - why does the gps hdop and satellites always get worse when switching to loiter???)
I decided to switch back to altitude mode and then motors all turned off.
Seems like a brownout but the internal voltage looks ok even if the battery voltage is in peak just around 9.2V with is definitly not ok (this battery will go to the bin).
Is it a brownout (stupid) or does it have something to do with V3.2 and a board reset?
Check out the attached graph.
Your voltage went from over 11.6 to under 10.0 at the beginning of your flight.
I don’t know what would cause that, but it would certainly shorten flying time a lot.
I did no compass calibration because I think it is not necessary if updating from 3.15.
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I’d guess this was the problem. It is explicitly stated that its required to recalibrate after upgrading to 3.2
Good luck!
Not calibrating the compass is a problem, but not the cause of this crash.
I believe what happened is that your battery was in poor health, this is shown by the extreme amount of voltage sag in flight. It’s quite possible just 1 cell that is very bad. If you check it now, you may see that one is very much lower than the other 2.
In this case, I have seen that under load, that one cell will go open-circuit, mean the battery voltage suddenly drops to zero. Obviously this leads to a crash that looks like a brownout. After the crash, sometimes the dead cell will slowly recover to 3.0 volts. You can try to balance charge it, and you may be successful, but that battery will usually be suspect. That cell will suddenly go open circuit again, any time it gets a little low.