TUNNEL TEST BY

Blade airloads data were acquired for a 1/4-scale tiltrotor model tested at the Duits-Nederlandse Windtunnel in The Netherlands. For the first time, detailed airloads measurements were acquired for an isolated tiltrotor model utilizing one hundred and fifty dynamic pressure transducers. Simultaneous acoustic measurements were made in a plane below the model rotor to correlate airloads with tiltrotor noise. Rotor performance data and wake geometry data were also acquired. Samples of the airloads data are presented for several key operating conditions. The effects of rotor thrust and model shaft angle on the blade airloads are discussed. Comparisons are made between blade pressure data, acoustic data and laser light sheet results. Negative lift at the blade tip was found over a wide range of conditions for the tiltrotor in helicopter mode. Single and multiple blade-vortex interactions were measured and correlated with acoustic data and measured wake geometry. The data acquired during this test provide a fundamental set of aeroacoustic measurements that can be used to validate tiltrotor analyses