ANALYSIS OF ROTOR BLADE DYNAMICS USING EXPERIMENTAL UH-60A AIRLOADS OBTAINED AT THE DNW

A structural dynamics model of a modern articulated helicopter rotor is validated by applying measured airloads as a forcing function to the structural model. The validation is conducted on the model as it is implemented in a comprehensive aeroelastic analysis. Measured airloads and blade bending moments are obtained from a UH-60A BLACK HAWK model rotor test conducted at the DNW. Test conditions selected for the validation effort included cases in which blade modal frequencies were very close to rotor harmonics. Though such conditions are a severe test for a dynamic analysis, the structural model performed favorably. Accurate documentation of blade structural properties results in good blade modal predictions and an excellent agreement between predicted and measured flatwise bending moments. Good edgewise bending moment predictions prove sensitive to coupling between the rotor system and fixed system, coupling of blade modes, and the non-linear characteristics of the lag damper. Torsional bending moment predictions are only fair, with disagreement possibly due to inadequate modeling of the rotor control system. The generally high quality of agreement between calculated and measured blade response, and the excellent agreement between calculated blade modal frequencies and rap-test data, yields a mutual validation of the experimental data and the dynamic model.