Validation of Rotorcraft Comprehensive Analysis Performance Predictions for Coaxial Rotors in Hover

Comparisons of rotor aerodynamic performance parameters in hover, between rotorcraft comprehensive analysis predictions using a free vortex wake model and measured data, for two model–scale and two full–scale coaxial rotors are provided. Predictions from a computational fluid dynamics analysis are also included for one of the full–scale rotors to provide additional insights. Test points evaluated form sweeps in both the coaxial rotor system thrust and the axial separation distance between the two rotors. The comprehensive analysis predictions are mostly in good agreement with measured data, which includes reflecting the same trends from all sweeps. While the comprehensive analysis predictions are mostly in good agreement with measured data and computational fluid dynamics predictions for individual rotor thrust, good agreement for individual rotor torque is more elusive. The comprehensive analysis predictions also show that even though the coaxial rotor figure of merit is not strongly dependent on the thrust sharing ratio between the two rotors, the figure of merit of the two individual rotors are highly sensitive to the thrust sharing ratio.