Two questions of technical clarification:
With the engines off, the rad alt loses it's power
Are the EC-135's generators run by the engines or by the transmission? Don't know the type, which is why I ask.
SHED BUS activates on 2 x GEN failure.
Thanks.
henra made a point about stalled main rotor blades a few pages back. With the thought that EC-135 is a low inertia rotor head ... I will walk through this and see if the logic holds, or if it doesn't. Please critique.
For reason "X" drive to the rotor head stops abruptly and rotor RPM begins to decay. Poster henra pointed out that there is a "point of no return" where the blades are likely to stall. Once stalled, the amount of time/alt/control manipulation to unstall is, for the sake of discussion, more altitude and time than was available to the crew on this occasion.
Following along this train of thougth: with the rotors slowed and then stalled, but still rotating at "Y" percent, does the finestron (still rotating as far as one can tell from info available) still produce thrust of a nominal amount?
If yes, one could perhaps explain the tumbling/rotating that the witness reported as residual thrust about the vertical axis overcomes roughly "no" torque from a stalled rotor head (finestron being there for anti-torque). Even though the Nr decay continues for whatever reason, monentum sustains that rotation/tumble since there is insufficient force to counteract it (lack of Nr generated thrust and torque) and also less finestron residual thrust to try getting the thrust heading the other direction as Nr further decays, thus slowing the finestron to an eventual stop.
Feel free to shoot holes in that idea.
As to why the thrust goes away: I think the AAIB would have reported if they found bird remains in the engine/engines by now. Pretty sure that likelihood has been covered and can be safely put to bed.