I've been flying my heli for a while but I came across a problem, which doesn't happen quite often but it may be important for safety. It's the power failure and autorotation.
Recently I had a major failure of my battery during the flight, the battery just suddenly died that my motor has stopped but the servos were still working thanks to the separate battery for servo and PX4. Luckily I was about to land my heli about 4m high so I heard that the motor had stopped.
I changed to stab mode, and tried to do my first autorotation in my life without any experience and I'm glad I was not panic. Although my autorotation was not well performed, the stab mode helped a lot. In the end I just had a slight hard landing, nothing was broken.
After this accident I was thinking, whether it's necessary to have some way (from our PX4/Pixhawk) to perform the autorotation or maybe a warning to the pilot when such failure happens. If I wasn't close enough to my heli I'll have no idea that the motor had failed and the heli will sure lose all its power before I realized what was going on.
If it's a large heli like 600 or 700, it will sure turn out to be a disaster. Afterall for a UAV a lot of things are controlled by the FC, we may not notice it until it's too late, and unlike the 3D pilots, our heli can be far away and we won't feel anything. So yeah, I kind of feel that we may need some safe mechanism through Ardupilot, to protect the heli, and maybe protect other people.