Zorab, such a situation would indeed result in the drive to the rotors stopping and seems very possible.
Whatever it was, something happened that stopped the engine providing drive to the rotors, that much is evident. There is then the question of why there was no/little Nr at the ground.
Even assuming that a pilot recognises what has happened and is able to understand what needs to be done, it doesn't take very long at all before Nr will decay to the point at which there isn't anything that can be done if the collective is not lowered extremely quickly. Failure to respond sufficiently quickly has been seen more than once in an accident report.
There's also the possibility that the blades were rigged incorrectly i.e. too much residual pitch on the blades even with collective fully down and thus won't allow for autorotation - unlikely as an autorev check should capture this, but it wouldn't be the first aircraft where there is an issue with the blade rigging.
Finally, there's the possibility that something interfered with the collective such that it wasn't able to be lowered fully when the need arose. Cockpit was dark, who's to say that something hadn't slipped under the collective and wasn't noticed?
Fundamentally, what concerns me is that the SOP / RFM seems to allow for a latent failure mode to go unchallenged. To my mind, a 20 min / 30 min fuel allowance should allow 20 mins / 30 mins until the engine(s) stop. That's why it's a reserve fuel allowance; if you can't use it, it's not in reserve. I don't think it is a reserve fuel if you need to remember to switch something on or off to make use of it, because you are designing into the system a latent cause of potential cognitive error. I accept that if there is a failure of a subsystem then there may be fuel that becomes unusable: for instance, an A109 has some cheeky gotchas with booster pump failures if you fail to close the cross feed. However, you are not saying that. What you are saying is that there is a SOP that allows a pilot to get to a situation where under normal circumstances the minimum usable fuel is below the minimum fuel reserve?
If a procedure offers up the possibility of making a mistake, sooner or later, someone will make that mistake. That's life. That's why parts for aircraft should never be designed so they can be put onto the aircraft the wrong way round. The same should apply to SOPs. Does anyone else agree, or am I in a minority of one in this regard?
Puntosaurus, you appear to have arrived at the same conclusion whilst I was typing.
Last edited by sarboy w****r; 10th Dec 2013 at 12:36.