Toward Improved UH-60A Blade Structural Loads Correlation

This study is focused on the improvement of UH-60A blade structural loads correlation with flight and wind-tunnel test data. The blade airloads prediction has been proven to be reasonably good from past studies. However, the blade structural loads, especially the edgewise bending moment, were poorly predicted, and these are the subject of the current study. Several variations of modeling effort have been examined. This includes the drive-train model, refined grid, lag-damper model variation, hub impedance with test stand, tunnel wall, and dis-similar blades. The drive-train and refined grid showed noticeable improvement in edgewise bending moment, but not enough to close the gap between measured data and prediction. A lag damper study indicated that the current nonlinear damper seems to be adequate, and variations to the lag damper had a limited impact to inboard region only. The influence of dis-similar blades provides further insight into the sensitivity of the edgewise bending moment. The largest difference was observed to be due to the presence of the fuselage-like wind tunnel mount, indicating that a rotor analysis should include the fuselage.