Ok......power push over.......you’re on a powered nose high climb, and you shove stick forward to commence a descent. The gyro will pendulum at a point at that roll over and the rotors will strike the tail...game over. 1 alternative is.....power off, EASE stick forward, so you gently roll over, over she goes then commence descent in the normal safe way. there are several ways to go from hard climb to immediate descent, but i won’t explain here, it needs to be hands on with suited instructor, don’t want a pilot reading here, and going out to give it a try.
loss of control........mechanical failure of some kind, pilot seriously stuffed up and was unable to gain control.....hard question to answer, sorry