Evaluation of Wind Tunnel and Scaling Effects with the UH-60A Airloads Rotor

Abstract : Data obtained during the recently completed full-scale UH-60A Airloads wind tunnel test have been compared with measurements from the full-scale UH-60A Airloads flight test and the UH-60A small-scale test in the German-Dutch Wind Tunnel (DNW). Rotor power, airloads (section normal force and moment), and structural loads have been examined and compared to help understand the effects of the wind tunnel and model scale on the measured data. The measured power matched well with both flight and small-scale results, suggesting that the procedures and trim targets used to match the rotor conditions were fundamentally sound. For the flight test comparisons, rotor airloads were generally well simulated in the wind tunnel, although there were noticeable differences in the waveforms at the outboard radial stations that can t be explained by bad measurements or integration errors. Rotor structural loads were also well simulated with the exception of chord bending moments. Further investigation is necessary to determine the exact cause of these differences. For the DNW test comparisons, the rotor airloads and structural loads showed significant differences in waveform, especially for 3/rev torsion loads. These results are consistent with those found during earlier DNW/flight test comparisons and provide additional verification that the different blade modal properties of the DNW model had a significant effect on blade response and ultimately, blade airloads.