Structural Design Flight Maneuver Loads Using PDP-10 Flight Dynamics Model

Military and commercial helicopter customers are demanding improvements in both structural integrity and performance simultaneously; i. e. , stronger and lighter. One element of the Sikorsky structural integrity program modified toward this objective is the flight maneuver loads program; now using a nonlinear flight dynamics model to significantly improve the accuracy of the applied loads used for structural design. Sikorsky has developed non-linear flight dynamic models for evaluation of helicopter handling qualities and control system design. This flight dynamics model has been modified to allow its use in the development of specification required flight maneuver loads. It provides a significant improvement in the accuracy of the predicted applied loads and inertial reactions used for structural design. The flight dynamics model is basically a total force, non-linear, large angle representation in six rigid body degrees of freedom. In addition, rotor blade flapping, lagging, and hub rotational degrees of freedom are represented. The control system representation includes the effects of mechanical coupling and the FAS, SAS and AFCS systems. Fuselage and empennage airloads are represented by univariate and bivariate non-linear airload maps generated from wind tunnel test data. Main rotor wash effects on the fuselage, empennage and tail rotor are incorporated in the model.