Performance Wind Tunnel Testing of an X2 Technology® Mach-Scaled Powered Model

A 1/5th scale powered coaxial rotor and propeller system has been developed and tested in the National Full Scale Aerodynamic Complex (NFAC) 40x80 ft Wind Tunnel. Test conditions include airspeeds in excess of 250 kts, the highest recorded for a rotor in edgewise flight at the NFAC. The system was studied in four configurations: a powered coaxial rotor, a powered coaxial rotor with a propeller wake rake, a powered coaxial rotor with a powered propeller, and a bare hub rotor with a propeller wake rake. The high-quality data from the test included propeller, fuselage and main-rotor performance; aerodynamic-interactions between the rotors, fuselage, empennage, and propeller; acoustics and handling-qualities attributes. These results have been used to validate physics-based rotorcraft modeling tools and enhance the quality of full-scale X2 Technology® aircraft designs. Innovative solutions to test measurement challenges included rotor shaft strain gages, balance thermal control systems, and a dual arm rotating rake to measure inflow at the propeller plane. Main rotor hub and blade system performance trends are presented as functions of speed, thrust, and body attitude. Time-averaged and unsteady pressure measurements on the fuselage, empennage, and propulsor plane characterized the interactions between the fuselage, rotor hubs and blades, empennage, and propeller over a wide range of operating conditions.