Vibration Prediction for Rotor System with Faults Using Coupled Rotor-Fuselage Model

A coupled rotor-fuselage vibration analysis is formulated to analyze the effect of rotor system faults on fuselage vibrations and rotor-blade displacements in both hover and forward-flight conditions. Two groups of rotor-system faults, adjustable and nonadjustable component faults, are modeled. Results are presented for an SH-60 helicopter and are compared with available flight-test data. A detailed aeroelastic analysis is carried out where each rotor blade is modeled individually such that rotor dissimilarity can be considered. A fuselage NASTRAN model is incorporated and coupled with the rotor model analysis. The centrifugally tuned, hub-mounted bitilar vibration absorbers are also modeled, and the coupled rotor-fuselage-bifilar nonlinear equations are solved using finite element method in space and time. Predicted 1/rev and 4/rev vibrations at pilot and copilot seats showed acceptable trends for magnitude and phase with flight-test data.