Tourist: your response was only in part to what I commented upon. The rest you seem to be thinking out loud.
No, as with just about all helicopters, 2500-3000ftpm is more realistic, to descend faster you would either need high angle of bank, or a temporary dive, and neither would give a straight cut.
"Just about all helicopters?"
Not going down that rat hole, but I'll accept I may have been a bit high on the ball park. As I've not flown any Mi I'll take your word for it.
How fast you descend depends on how fast you want to fall, if you fly max glide or max range auto, if you slip, gross weight of the helo, density altitude ... but you know most of that.
High speed descents are a small arms fire procedure, so usually start approx 2000ft agl as that is the threat zone. There is no point whatsoever in starting the dirty dive at 10000ft agl.
Agreed, from my own experience, apart from the fact that I never suggested a "dive" dirty or otherwise.
What I was talking about was that he may have been flying that high to AVOID small arms fire.
The dive can only go on for a little while in a helicopter before vmax at which point you are stabilised at a low rate of descent again.
Dive? Anyone who has flown military helicopters knows the limitations of the airframe in regards to missile avoidance maneuvers. And small arms fire avoidance maneuvers. You seem to be using "dive" where I did not.
Are we even having the same conversation?
There is a max airspeed that you limit yourself to in order to avoid retreating blade stall, if you know your aircraft. That does not preclude a high speed descent, nor an autorotative descent. FWIW, I'd suggest you
1. Try not to teach your grandmother to suck eggs, and
2. remember that I know how to fly helicopters.
3. See above comment on why the helicopter may have been up that high.
I speak as one of the few( only ) people on here to fly both types of aircraft involved.
Cheers.
Had you understood my point about high altitude to avoid small arms fire, you'd most likely not have responded as you did.