Originally Posted by
Ascend Charlie
Can you explain, then, why an R22 only needs 72 degrees of advance? If it was a gyroscope, it has to be 90 degrees flat.
The R-22 main rotor head has delta-3, which affects the phase angle between control input and rotor response. There are other factors that affect that angle, but if there is delta-3 involved, that has to be accounted for. I don’t have a drawing of the head to calculate delta-3 from, but looking at photos and the lack of a hub spring, I’d guess 18 degrees.