Motor failure octo causing crash or not?

Interesting. I flew my big 12kg octo and suddenly I went out of control. After checking the hardware I found a bad wiring on one of the motors. I cannot find any error in the log file.(see link). But, it is still not clear for me how arducopter is handling a motor failure. You should expect to have some redundancy on an octo?

The crash seems to have been caused by a brown out of the flight controller.
No motor failure is indicated.
The craft is overweight/underpowered and you have very little headroom for attitude control.
Your Vcc is quite noisy indicating some issue with the boards power supply.
Are you getting power from the power module?
Do you have a backup BEC connected?

It is battling to keep actual pitch and roll in line with desired pitch and roll

thanks Mike! However, I can’t figure this out. Pixhawk is powered by a Mauch BEC including a Mauch backup BEC.
During this flight, we had a wind speed of aprox. 18 knts. and system seems (visual) very stable. I have a weight - thrust ration of 1:2
One motor wiring was loose for sure and not because of the crash.
I still have my doubts about the PID values (which I set manually as autotune crashed the system for 3 times.)
This is the bin file of the flight just before the other one.

This doesn’t look like a 2:1 thrust ratio to me.

And your PID’s could do with some work as they are making the response quite twitchy (technical term :slight_smile: )

Your Rate Pitch and Roll Filters are only at 15, I would reduce them to at least 10.
And your aggressiveness is also mid range at 0.075.
For this size copter I would start at the minimum of 0.005 and work up from there.
Maybe that’s why the last 3 attempts at autotune resulted in a crash.

But I still hark back to your crash log ending in mid air.
That’s an indication of a Flight Controller malfunction or software crash.
Looking at the Vcc I see a swing of .25v which is not very good and indicates something amiss.
.15v is considered normal, so .25v, although not good, would be surprising if on its own caused a brownout.

But you did have a brownout, or the SD card came loose - just a thought as I write this.