Investigation of Rotor Performance and Loads of a UH-60A Individual Blade Control System
ARMY RESEARCH DEVELOPMENT AND ENGINEERING COMMAND MOFFETT FIELD CA AVIATION AEROFLIGHT DYNAMICS DIRECTORATE
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Wind tunnel measurements of performance, loads, and vibration of a full-scale UH-60A Black Hawk main rotor with an individual blade control IBC system are compared with calculations obtained using the comprehensive helicopter analysis CAMRAD II and a coupled CAMRAD IIOVERFLOW 2 analysis. Measured data show a 5.1 rotor power reduction 8.6 rotor lift to effective-drag ratio increase using 2rev IBC actuation with 2.0 deg amplitude at mu 0.4. At the optimum IBC phase for rotor performance, IBC actuator force pitch link force decreased, but both flap and chord bending moments did not change much. CAMRAD II predicts the rotor power variations with IBC phase reasonably well at mu 0.35. However, the correlation degrades at mu 0.4. Coupled CAMRAD IIOVERFLOW 2 shows excellent correlation with the measured rotor power variations with IBC phase at both mu 0.35 and mu 0.4. Maximum reduction of IBC actuator force is better predicted with CAMRAD II, but general trends are better captured with the coupled analysis. The correlation of vibratory hub loads is generally poor by both methods, although the coupled analysis somewhat captures general trends.