Performance and Loads Prediction for a High Advance Ratio Coaxial Rotor

Background and Motivation Current requirements for future helicopters as outlined by the Future Vertical Lift, Joint Multirole and DARPA X-plane competitions all call for helicopters to fly at significantly higher speeds than they can currently achieve while maintaining exceptional hovering performance. The Sikorsky X2 has flown faster than 250 kts, demonstrating that the rigid coaxial compound is a viable candidate for future helicopter configurations. In addition to the performance benefits, the rigid coaxial compound provides significant freedom in trim allowing for hover and flight in a variety of pitch attitudes as well as the use of lift offsets in the rotor. This paper presents work that has developed a comprehensive analysis technique for analyzing coaxial rotors and is used to study the impact of coaxial configuration on performance and loads.