Abstract:
In an effort to assess the suitability of the U. S. Army's Rotorcraft Comprehensive Analysis System (RCAS) for calculating tiltrotor aeromechanics characteristics, comparisons of rotor performance and blade loads between calculations and test data are presented for the TRAM rotor in helicopter mode at an advance ratio of 0.15. For rotor performance, the comparisons are with test points that form shaft angle sweeps for two different thrust levels. These calculations include those from a free vortex wake model and those from coupling the comprehensive analysis to a viscous vortex particle method. The emphasis of this work is on the comparisons of blade loads, which are analyzed in detail for two test points with 3° forward shaft tilt and different thrust levels. Blade airloads calculations include the two aforementioned sets of calculations while blade structural loads calculations also include those from prescribing experimentally measured airloads. The level of agreement between calculations with the free vortex wake model and test data are generally comparable with those of helicopter rotors at similar conditions. The level of agreement improves with the viscous vortex particle method. Meanwhile, some deficiencies in structural loads calculations with prescribing measured airloads are noted and lead to further investigations.