Copter flipped again. Hardware, Software or adjustment?

ArduCopter Copter 3.1
1

After some successful starts, the copter flipped in the flight and crahed with the top down into the ground.

Did I have the flip function active by mistake or does the hardware or software have a problem.
The copter did sometime also flip at the start before but some flights were okay between.

I hope somebody can see the reason for the problem in the logfile.

2

Hi,

There’s not a lot visible in that log. Generally, it appears the Rate PID tuning is not very good. Also, it appears the logs stopped mid-flight, so it probably had a brownout for some reason.

I notice the Vcc is a bit high at ~5.5V, how are you powering the system?