Parametric Investigation of The Aeromechanic Stability of Bearingless Rotors

The objective of this investigation is to conduct a parametric investigation on the aeromechanic stability of modern bearingless rotors. To ensure aeromechanic stability, modem bearingless; rotors use elastomeric dampers to augment the blade inplane damping. The augmented dampers are necessary to avoid aeromechanic instabilities such as air and ground resonance on soft-inplane rotors. The prevention of air and ground resonance depends largely on the damping level of the rotor-fuselage system during the critical frequency-crossing between the rotor and the fuselage inplane motions. The blade inplane damping, critical in ensuring aeromechanic stability of a rotor, depends not only on the damper sizes but also on the aeroelastic properties of the rotor blade. The results of this investigation provide insight into the source of inplane damping. The parametric study is carried out analytically using the University of Maryland Advanced Rotorcraft Code, or UMARC.