Dave, S69 would have varied the swashplate lead by altering both swash plate control mechs. Crossover point would be defined by main g/box synchronisation of rotors, so would not alter. Crossover points would be every 30 degrees, so if there was one on the left there would be one on the right. Statement about clearance with blade flexure still stands.
Not sure if S-69 was FBW or not - did it preceed Shadow version of S-76? Also i'm not sure how much control pilot (ie Nick) had over swash plate lead angle, but my guess would be this was an automated function of the control system (Nr and IAS).
BTW did some back of envelope calcs today, in the best engineering tradition. I was mistaken about roll torque variation being reduced with blade number - once you go to 3 or more blades per rotor roll torque remains smooth. So only reason for RAH-66 to have had 5 blades over 4 is for a flexural mode near 4P, unless there is a survivability benefit. More likely machine started with 4 blades, then increased MAUM.
Unless you have internal damping, stick with 4 blades per rotor for an effective hinge offset less than 15%. But if blade 3/4 wave mode is well damped, with a fail safe system, the 3 blade rotor will be more cost effective.
Mart
Last edited by Graviman; 13th April 2007 at 09:33.
Reason: Tidy up after reread Dave's last post. Understand what is being said now.