Originally Posted by
Robbiee
No, I got that your point was about not freaking out. My point however, was simply, they say it stalls at 80, so why is it not stalling at 70?,...as I don't recall them mentioning that you must have forward speed to get low rpm rotor stall?
I will consult my texts then.
The 80% is predicated on an engine failure where the helicopter starts to descend... As the helicopter descends the relative wind from below increases the angle of attack, stalling the blade.
I flew with one person who described a demo a cfi gave him where they flew around the pattern at 70%... The problem being that if the engine had failed, the rotor would have stalled no matter how fast the collective had been lowered.
Of all the interesting things to explore in helicopter aerodynamics, this is one corner of the envelope I've never been tempted to play in...