Prediction of UH-60A Structural Loads using Multibody Analysis and Swashplate Dynamics

The current paper uses multibody approach to model the dynamics of the rotor blade. The first half of the paper deals with the verification and validation of the current methodology. For this purpose analytical solution for elastica, static Princeton Beam test and full scale UH-60A flight test airloads for high speed and dynamic stall conditions are used. The measured airloads are imposed on the UH-60A blade structural model and flap, lag, torsional moment, and pitch link loads are compared. The multibody model is compared to full finite element and finite element with modal reduction. It is observed that the predictions for the UH-60A rotor under given conditions are equally accurate for multibody, FEM, and FEM with modal reduction methods. A three degree of freedom swashplate model is developed in the second half of the paper which is coupled with a simple rigid blade model, and then with multibody blade model to predict the servo loads.It is observed that swashplate dynamics has insignificant effect on overall blade dynamics, but it is important for prediction of servo loads.