Sensitivity of Rotor-Fault-Induced Vibrations to Operational and Design Parameters

A coupled rotor-fuselage vibration analysis is carried out to study the sensitivity of fuselage vibration induced by rotor system faults to operational and design parameters, such as aircraft configuration, aircraft gross weight, aircraft center of gravity location, airspeed and fuselage natural modes. Predicted airframe vibration results for an SH-60 helicopter with prescribed faults are presented and compared with flight test data. Three types of rotor system faults are considered; imbalanced mass, misadjusted pitch-control rod and misadjusted trim-tab. Results show that the first fuselage lateral mode has the largest effect on 1/rev fuselage roll vibration and that the first fuselage vertical mode has the largest contribution to the fuselage vertical vibration among all the elastic airframe modes. Fuselage vibrations were also found to be sensitive to operational parameters in some cases as well.