Spec,
Your description is a lot clearer.
As I understand it;
Raising the collective during autorotation causes; the Stall region to move out into the Driving region, and the Driving region to move out into the Driven region. On a helicopter with one rotor, this will reduce the rotor RPM but it does not effect the descent rate.
Raising the collective on one of the coaxial's rotors will also cause the three regions to move out, as mentioned above. It appears that the coaxial's problem is based upon the amount of the collective increase. Small collective increases will cause this rotor to become the Driving rotor, because it's Driven region has been reduced and its Stall region is insignificant. Larger collective increases will cause this rotor to become the Driven rotor, because its Stall region has now become the predominant region.
If this is true, then only small amounts of yaw control can be applied to the coaxial configuration during autorotation.
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CJ Eliassen,
You're correct.
Mia culpa.
