Out of respect for Nick's question about vibration, the following is added
Nick,
If your concern is about the vibration within an absolutely rigid rotor blade, then I would suggest that the attempted solutions should be addressed at a lower level in the development hierarchy. If your concern has to do with the craft, as a whole, then it is an uppermost concern.
Regarding the second; The Prewitt evaluation of the Flettner Fl-282 was extremely flattering, however, it did express a concern about the high level of vibration. It appears that this vibration is mainly the result of a rotor to rotor aerodynamic interaction.
The following are the approaches that are been taken to minimize this problem;
- The blade count has been increased from 4 to 6. This increases the blade-to-blade passages per revolution from 4 to 9. This in turn, reduces the amplitude of the vibration and takes its frequency above that which is uncomfortable for occupants.
- The craft is to have a pusher propeller and one of the advantages of this is a reduction in the thrust of the rotors during forward flight.
- Independent Root and Pitch Control plus 2P Higher Harmonic Control on the root will provide a better distribution of thrust.
- Future improvements to rotor induced vibration should be more meaningful to the intermeshing and the interleaving configurations than the single rotor configuration.
For the perverse and the bored their is more on
UniCopter ~ Vibration
Whew!
Dave