An aeromechanics and stability investigation has been conducted for the Boeing 222 proprotor wind tunnel data set in hover, transition and cruise with the comprehensive analysis RCAS. The RCAS model of the proprotor was validated with blade frequency response data before stability calculations were made of the air resonance boundary in cruise, as a function of RPM, between 50 and 192 knots. RCAS' calculations of critical damping agree with test data at low wind speeds, but over-predict damping at high wind speeds. The aeromechanics investigation compared the calculations of trim and blade oscillatory structural loads from two inflow models, prescribed vortex wake (PVW) and Viscous Vortex Particle Method (VVPM), in one cruise condition at 170 knots, two transition conditions at 80 and 45 knots, and in hover. In cruise, the analyses predict similar trim and loads. In transition, the wake trajectories differ between the wake models resulting in different cyclic control angles, with VVPM in closer agreement with the test. In general the calculated A_1 cyclic (approximately cosine pitch component) is offset by about 1° from measurements for all test cases. The calculated root flap bending oscillatory magnitudes represent the measured loads well, whereas chord bending and pitch link loads are under-predicted by both analyses.
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