chopjock, No that is not a helicopter "tumbling end over end", it is one which is merely rotating in the horizontal plane about its own axis, the M/R Mast.
Hey Sid 'ol mate don't get too hyped up, ducks will fly at night between their daytime pond and their nightime feed range. In fact I had one impact the sidemirror of my motor car one night, wiped the mirror and the duck out. I was at 140 klicks, it possibly was doing their normal cruise range of 90 or so. It could easily have hit further back. Also one of our machines crashed during a fast run on a couple of years back but during the run on hit an obstruction. The Emerg landing was caused by a sudden wild vibration and loss of T/R control. Nothing had been seen but a subsequent detailed ground search discovered a very dead wedge tail eagle and some time later, the missing T/R blade complete with feathers and blood, so it can and does happen.
I agree the gentleman concerned had little prospect of control, at least in the latter stages, as did Sasless I believe, who hypothised on the clear areas which were not used..
Not too long back we had a double fatality in an R22 which appeared to have been overpitched as low as between 30 and 40 feet. The blade damage to the surrounding light brush was minimal as was the damage to the blades other than the typical operpitching initialised bending moment evidence which is usual on that type. What i am saying is they don't have to fall too far for the blades to virtually stop and to do lots of damage to the aircraft and its occupants. And oh yes, that machine was nearly full of fuel and did not burn.
cheers tet.