HeliTester:
I realize what Part 27 and Part 29 say.
If what you say is true, why is minimum airspeed IFR for so many helicopters well above 20 Knots?
Or why are so many Vtoss figures also so high?
My experience is that on takeoff, the airspeed indicators read consistently lower than actual speed (tests done at zero wind and using GPS groundspeed for equivalent to airspeed).
The regulations may say one thing, but the practical reality is that very few, if any airspeed system works well below 40 KIAS -there just isn't enough difference between dynamic and static pressure to be accurate.