Originally Posted by
rotorspeed
But HC surely the issue here is not primarily on whether IAS or VS coupling was used - it is that the crew were supposed to be monitoring a parameter and weren’t. With AIS hold, that type of error could have caused them to not monitor VS sufficiently with the result they dived the aircraft into the sea with a grossly excessive ROD and not enough time to recover.
No I disagree. There is a massive difference between response to the collective with high RoD and low airspeed, vs the response with high Rod and airspeed around Vy. In the former case, as the accident demonstrates, pulling up the collective doesn’t do much. In the latter case, pulling on the collective has a nearly immediate result of stopping and reversing RoD. And of course there is scope to raise the nose too, to convert horizontal speed into vertical speed which isn’t the case with very low airspeed.
Just like a fixed-wing, IAS is THE most important parameter because with adequate airspeed, the helicopter is easily controllable. With inadequate airspeed, the helicopter is barely controllable as this accident demonstrates. If the collective had been raised at the same altitude as it was raised in this accident, but with plenty of airspeed, the accident wouldn’t have happened.