Nick, based upon your formula to calculate the downwash velocity and the following data:
R22, at MAUW=1370lbs, rotor diam=7.7m/25.26ft, I calculate the downwash velocity to be 1440 fpm. Am I right? Is the 0.002378 number in your formula, is that specific to a particular rotor system or a constant for all helos?
When I used to demonstrate VRS to students, I would get it into the hover (obviously with at least 3000 feet to spare) and in the R22 this would usually require pretty much max power. I would then very slowly lower the collective. As the ROD got to around 500-900 fpm or so, (and sometimes you would have to gently search for the downwash with cyclic), bingo you would be into it and most times so quickly you would lose your stomach. All the normal control sloppyness, pitch and roll and vibrations just prior to it. On a windy day often you couldn't get into VRS no matter how hard you tried for obvious reasons. From your formula it seems like a higher ROD is necessary but experience tells me otherwise, maybe I am under-estimating the lag in the VSI? Or does the downwash velocity vary considerably depending upon the power being applied at the time?
Thanks for your input and a Disclaimer for students: DONT do the above solo.