I took off the copter using Stabilize mode, switched to AltHold mode and it all works fine.
Then I flip Ch8 switch to AUTOTUNE.
In a split second, all the motors seem to lose power and the copter fell from the air.
Can anyone help to have a look at the log and parameters file to see what happened?
Log and param file:
The crash caused the power cable to disconnect so the data after the crash is not in the log.
your front right motor failed to provide thrust (motor/ESC/propeller) , so it tilted in that direction, as a response you can see RCOU.C1 being commanded to a high level , and the opposite motor (2) go to idle.
you were flying at about 50% of the available throttle level, so with the effective loss of two motors, it surely looked as if it just dropped down.