KikoL,
That set of conditions is true, but for most of today's helicopters it's way too conservative I would think.
My point is that for example in a Bell 407 that has a very high disk loading to enter VRS you would have to descend with at least 1,000 plus feet per minute to even get near VRS, plus you would need to have at least some forward airspeed, very little but some forward airspeed.
Then another thing that is a myth about VRS and it keeps on being told is that the the higher altitude you are or the heavier you are the easier it is to enter VRS, and this it simply not true, it's the opposite way around. (athough it would be a lot easier to Settle for Lack of Power in these conditions)
To enter true VRS you must get close to your downwash velocity, and the higher and heavier you are, the faster your downwash speed will be, the faster you will have to descend to catch up with it and actually get VRS.
A lot of people at all levels seem to be confused by this, and always blame VRS for not being able to stop a descending aircraft because of high DA, weight, etc.
Remember that you can have power to hover OGE at 100% power, but if you are in a descent you will need more than a 100% to kill the downwards inertia of the machine, if you don't take that into account it could easily mean bent skids.
Nick Lappos created a document in which he clearly showed all of this, and where he gave the VRS numbers for a Bell 206, I remember that he demostrated that the ONSET of VRS in a heavy 206 started around 900 FT/MIN descent, and the center of the VRS was at somewhere 1,500 FT/MIN descent.
I sincerely thank Nick Lappos for having previously explained this to all of us.