I think the nose down pass is main rotor thrust only, so a helo mode pass with the prop disengaged. There’s a nice side shot where you can see the exhaust gasses... as close as they are to the prop, I can imagine that you’d never want to have the prop truly stopped and stationary. So it looks like it’s spinning, but probably just from windmilling and or torque from a disengaged wet clutch.
Definitely sounds like a hornets with the prop engaged, but it should be pretty quiet with the prop off.
Originally Posted by
SansAnhedral