Performance and loads correlation of the UH-60 rotor at high advance ratios

Abstract

The comprehensive analysis code UMARC is validated at high advance ratios with the UH-60A full-scale slowed rotor test data in a wind tunnel and then used to analyze the high advance ratio aerodynamic environment. UMARC predicts the sensitivity of thrust to collective well up to ? = 0.7, but thrust reversal is predicted at lower collectives (negative) than are evident in the wind tunnel tests. Including a drag model for the blade shank is shown to improve the prediction of rotor drag and the effect of fuselage upwash is shown to further improve the correlation. The sectional normal force shows very good correlation in phase and magnitude and the effect of wake model resolution on the loads is evaluated. Flapwise bending moments at 50% span are well predicted by the analysis up to ? = 0.9. The mean values of the torsional moments are predicted satisfactorily, but the analysis does not capture the high harmonic content.