DYNAMICS OF A ROTOR WITH NONHARMONIC CONTROL

McDonnell Douglas Helicopter Company is developing an experimental rotor system to demonstrate blade vortex interaction noise control using a flap near the blade tip. The flap actuation mechanism operates on each blade individually. The flap deflection is nonharmonic but identical for each blade. This paper addresses the dynamics challenges inherent in such a concept. Both rotor dynamics and flap actuation dynamics are covered. Detailed analyses show that the active control flap inputs cause a sizeable elastic torsion response of the blade, substantially increase the blade oscillatory section loads, but have little impact on stability. Small changes in the flap schedule can significantly affect loads in the actuation mechanism. In summary, a thorough and comprehensive evaluation of the dynamics of the rotor and flap actuation mechanism are required to guide and substantiate the concept design.