Dave,
Originally Posted by DaveJackson
mention "Higher Harmonic Control" Perhaps, I should have said, 'Independent Blade Control', not 'Higher Cyclic Control'.
As for Higher Harmonic Control, one report states "The results show that properly phased 2/rev inputs can reduce the rotor required power by up to 3.8%. The improvements are very small."
For Independent Blade Control, any appropriate types of sensors and actuators might be employed.
How do you distinguish Independant Blade Control from Higher Harmonic Control? 3.8% fuel saving for higher harmonic is not to be sneezed at - remember we were disputing 15% payload capacity in Nick's Ballistic Recovery System thread. Agreed that the more control you can give a blade the better it will slip through the air.
Originally Posted by DaveJackson
If your mention of "tip servo" is in reference to a trailing edge servo flap, I would be concerned. The sequence of events that must take place for the above flap to change the lift of the blade may be too slow for a high speed craft.
I do not know what success or otherwise Kaman had with tip servos. I imagine that as long as they were large enough to overcome the tip rotational inertia, response would be fast enough. The possibility is to have the tip self optimise to the local airflow, with the control system gently keeping the pitch/roll moment tally around the azimuth.
Originally Posted by Dave Jackson
You are absolutely correct. This is where utilizing a [Slowed Rotor Speed] during cruise is an advantage.
Reduced rotor RPM is something that only becomes possible to consider with X2 15% effective hinge offset. Even then i bet Big Sky don't rush in to it. The problems are variation of blade eigenmode by RPM stiffening, and increased cone angle. Designing a blade with torsional compliance for active twist, and variable RRPM would be challenging.
Mart