Fundamental Understanding Of Helicopter Rotor Hub Vibration Reduction Using Non-Structural Lumped Masses

Abstract

Significant potential exists for reducing the vibratory hub loads generated by the rotor through optimal blade design process. An optimization study was carried out to reduce the vibratory rotor hub loads using non-structural lumped masses and twist. The lumped masses had both spanwise and chordwise location variability. Prior to the optimization, a sensitivity analysis was carried out to understand the effect of the individual parameters on the vibration index. A significant observation from the study was that a lumped mass which was placed near the tip region and aft of the elastic axis reduces the vibration index the most. Optimally locating three lumped masses along with optimal twist led to a reduction of vibration index by 65% from the baseline case. Such a significant reduction was achieved without resorting to radical design or geometries and without expensive techniques.