I was testing out the Autotune feature with my drone, which has a Pixhawk with ArduCopter 3.2.1 on it. I have autotuned before with another drone and didn't have any issues on that one. The battery was at 65% after it landed.
I am attaching the log file. Could anyone please help with this?30.BIN
Without a battery monitor it's hard to tell but the motors went to max and it still lost altitude so I would say it ran out of power coming from the battery. Possibly a weak battery.
you have no power logging (vbatt/current) - so it's hard to tell you the battery performs, but it's apperently hovering at 73% throttle, and while falling it's going to 100%
so it needs much more thrust.
plot CTUL.ThrOut to see for yourself, the official maximum is 70% , , but I'd say it should be below 60 at most.