Lu: Sinusoidal With Respect to PHASE
Lu:"If you were to use a true sinusoidal wave it would mean that the closer you got to the peak of the wave either + or – the rate of change would decrease. And it would begin to speed up as you went on the downward side of the wave and then slow down as it approached the bottom end of the wave. That would mean that the rate of pitch change is not constant around the tip path. "
That's right - now you are learning! ... I think if we came to an American school we would have no problem in understanding that the plot which you say the Sikorsky school uses is against LONGDITUDINAL POSITION - which you are just misinterpreting... simple really.
Crab and Shy express the other point well, try re-reading it with an open mind - then you'll learn more...
(There's just a slightly subtle error with crab ... the AoA's aren't actually equalised ... because the airspeeds are different Clv2 same thing really tho')
Helicopters still fly in the US because none of this really matters....