S-97 RAIDER® Propulsor Flight Loads and Validation

The S-97 RAIDER® helicopter uses a pusher propeller to provide forward and reverse thrust capability to Sikorsky's X2 Technology™ design. Due to the propeller's aft mounting location on the aircraft it experiences aerodynamic interactions with both the airframe wake and main rotor wake across the flight envelope. This paper details the inclusion of an aerodynamic interference flow field near the propulsor disk plane in a CSD (Computational Structural Dynamics) propulsor model used to predict blade loads. The interference flow field uses either wind tunnel measurement or CFD (Computational Fluid Dynamics) to define the aerodynamic flow near the propeller plane. The predicted blade loads were compared with flight test data at a variety of steady flight conditions and overall good agreement is found between simulation and test. The simulation methodology is also expanded to simulate transient hover and acceleration conditions using a quasi-steady trim approach at multiple discrete time points of the maneuver. Overall good correlation of the measured blade maximum, minimum, and vibratory loads are achieved.