Quote Scattercat
"To me, the rapid ROD from the "point of failure", is more indicative of a sudden collective pitch change, rather than simply the loss of drive to the rotor system. If the collective was held, in what would normally be a relatively high position given the approach phase, followed by a loss of drive, I would expect to see an engine over-speed & an increase in the ROD, but not that sudden. Collective control failure perhaps?" Quote Scattercat
Are you serious dude? If you lose drive to the rotor system and hold the collective in position and you will drop like a brick. The RPM decay is massive in the event of a total drive or proper engine failure. These things tend to fly better with rotor RPM, when you lose it, you lose flight.