Some Applications of the Method of Multiblade Coordinates

The dynamic linearized problem of a lifting rotor with rigid flapping blades having elastic root restraints, with rigidly or elastically supported hub and with various control feedback systems is solved for high rotor advance ratio with the method of multiblade generalized coordinates. Dynamic stability limits are substantially affected by the number of blades per rotor. Constant coefficient representations can be considerably in error even for low advance ratios and do not account properly for blade number effects. Lifting rotor whirl flutter at high advance ratio is briefly studied and found to be a potentially critical condition. The method of multiblade coordinates has also been used to study the alleviation of random blade flapping response to atmospheric turbulence by using control feedback systems.