God. Excuse me, <img src="wink.gif" border="0"> Nick
Thanks for providing information related to the sources of rotor induced vibration. The fact that vibration is an intrinsic part of a rotor, which is flying edgewise into the airflow, is also understandable.
The alternatives of being 'minimized or absorbed' is the intriguing part, especially when it seems that minimization would be the preferred method. I assume that higher harmonic control (incorporating efficient algorithms, parallel processing and rapid cyclic pitch actuators) is the primary area of research at present for minimizing vibration.
It would appear, from a relatively naive perspective, that more could be done with the actual rotor to reduce this vibration. Retreating blade stall can be eliminated by the advancing blade concept. Vortices from the previous blade might be reduced by blades with high rigidity, and the compressibility effect might be somewhat reduced by the combining of ABC, blade rigidity, a high lift airfoil and a slightly slower RRPM.
It also appears that primary source of vibration, the in-plane and out-of-plane moments, might also be reduced by the application of ABC and rotor rigidity. In fact, I have the audacity to think that the intermeshing configuration might be better than the coaxial. The intermeshing rotors have their centers of rotation laterally offset from the centerline of the craft and this means that the 75%R position on the advancing blades is closer to the craft's longitudinal centerline.
No doubt, it's a long trip from the scratch pad to the helipad, but on some trips, the journey is half the fun; ~ and theorizing sure is fun.
If you find fault with any of the above, please criticize: tenderly. <img src="smile.gif" border="0">
[ 15 January 2002: Message edited by: Dave Jackson ]</p>