1Calculation of Tilt Rotor Aeroacoustic Model (TRAM DNW) Performance, Airloads, and Structural Loads

Comparisons of measured and calculated aeromechanics behavior of a tiltrotor model are presented, with an emphasis on performance and structural loads. The recent test of the Tilt Rotor Aeroacoustic Model (TRAM) with a single, 1/4-scale V-22 rotor in the German-Dutch Wind Tunnel (DNW) provides an extensive set of aeroacoustic, performance, and structural loads data. The calculations were performed using the rotorcraft comprehensive analysis CAMRAD II. The comparison of measurements and calculations includes helicopter mode operation (performance, airloads, and blade structural loads), hover performance, and airplane mode performance. The correlation establishes the level of predictive capability achievable with current technology; identifies the limitations of the current aerodynamic, wake, and structural models of tiltrotors; and leads to recommendations for research to extend tiltrotor aeromechanics analysis capability. Nomenclature. a speed of sound cn blade section normal force coefficient, N/(1/2rU 2c) cref blade reference chord CP rotor power coefficient, P/r(WR)3A = Q/r(WR)2RA CT rotor thrust coefficient, T/r(WR)2A (shaft axes) CX rotor propulsive force coefficient, X/r(WR)2A (wind axes, positive forward) M2cn blade section normal force coefficient times Mach number squared, N/(1/2r