Nick,
I had a look at your website (very good!) and have a couple of questions. In your formula for downwash speed, you have the three variables, weight, density and disc area. I would have imagined that angle of attack and possibly rotor rpm would have to be in this formula somewhere. If I'm on the ground at 104% (in the Robby say), with no pitch, then my downwash velocity is zero (correct me if I'm wrong). As I increase pitch and subsequently AOA, my downwash speed increases until such point that I can take off. So I see a downwash speed varying with AOA. By inference I assume my downwash speed in a descent will be lower than in straight and level flight everthing else being equal, thus permitting me to descend. So is your formula valid for a concrete flight situation or is it valid for all flight situations? My worry is that I could calculate my 700fpm (50%) and 2100fpm (150%) as being the avoid descent rates for a given all up weight and air density, only to find that these can dramatically lower, with decreasing downwash speeds due to lowered collective.
I may of course be talking utter non-sense.
If you could point me on the straight and narrow, I would be very grateful!
Irlandés
