DAPT said:
"Robinson video vs UK military primary training
The explanation and graphic video is the best way to understand how a helicopter can drop like a stone with rotors not turning.
The only way for that to happen is delayed entry into autorotation it does not matter where you received your training."
There are other factors that could make the autorotation a hopeless maneuver- control rigging, for example. Once flew a fleet spare (twin) on an autorotative check that wouldn't maintain NR in the green as I pulled power back in an established AR profile. Don't know how low it would have fallen with with further power reduction.
How often do you check yours?