Correlation of RCAS load predictions for an active flap rotor

The next generation of helicopters will incorporate advanced technologies into their rotor systems to improve overall vehicle performance. One such technology that is being investigated is an active trailing-edge flap. The ability to accurately predict the effect these devices have on the rotor is a key capability that is required for future vehicle integration. This study shows the first correlation study using the Rotorcraft Comprehensive Analysis System (RCAS) to predict the loading due to active trailing-edge flaps. The experimental data collected through the testing of the full-scale Smart Material Advanced Rotor Technology (SMART) rotor at the NASA Ames Research Center is used for correlations. In addition, results from previously conducted studies of a similar nature using the Comprehensive Analytic Model of Rotorcraft Aerodynamics and Dynamics (CAMRAD II) are shown as further comparison. Correlations for flapwise, chordwise, and torsional moments are performed for a baseline rotor, with no flap deployment; as well as, for four cases in which the flap is actuated at different harmonics, amplitudes, and phases. Overall, the RCAS predictions show fair correlations with the experimental data. For a majority of the bending moment time histories, the features are captured but the peak values are underpredicted. Finally, a phase offset between the experimental and predicted values demonstrates the effect that unsteady aerodynamics has on high-frequency flap deployments.