Refined Performance and Loads of a Mach-Scale Rotor at High Advance Ratios

Abstract

This work will investigate the performance and vibratory loads of a Mach-scale rotor with highly similar, non-instrumented blades at advance ratios (µ) up to 0.9. Wind tunnel tests were performed on a 4-bladed, articulated rotor with a diameter of 2.78 ft. The slowed rotor was operated at 30%, 40%, and 50% of nominal speed,corresponding to advancing tip Mach numbers up to 0.53, and shaft tilt angles

of -4◦, 0◦, and 4◦ were tested. Collective sweeps from -2◦ to 12◦ were performed for each flight condition, and blade motion, control cyclics, and hub loads were measured. Blade similarity was shown to improve rotor track and trim at high µ. Thrust reversal was observed at µ = 0.9, but positive (aft) shaft tilt increased lift at high µ. Vibratory hubloads are shown to increase with advance ratio. Correlations performed using the comprehensive analysis code UMARC show good agreement for rotor performance.