Aeromechanics Analyses of a Modern Lift-Offset Coaxial Rotor in High-Speed Forward Flight

Abstract

This study conducts an aeromechanics analysis of a modern lift-offset coaxial rotor in high-speed flight. A lift-offset coaxial rotor of the Sikorsky X2 technology demonstrator (X2TD) is considered for the present study. For the analyses of rotor performance, blade airloads, and hub vibratory loads, a rotorcraft comprehensive analysis code, CAMRAD II, is used. For the rotor performance analysis at a flight speed of up to 250 knots, which is the maximum level flight speed of X2TD in flight test, the present prediction of rotor power is compared well with the flight test data. For the blade section airload analysis at 250 knots, the impulses of the section lift forces are observed because of the aerodynamic interactions between the upper and lower rotors. The 4/rev hub vibratory loads are predicted, and its variation trend is moderately compared with the previous analysis results. Furthermore, the rotor vibration index increases significantly in high-speed flight with an increase in the flight speed, and this is well correlated with the previous rotorcraft comprehensive analysis result. This study shows that the present modeling and analysis techniques are appropriate to analyze the aeromechanics, including the performance, blade airloads, and hub vibratory loads of a modern lift-offset rotor in high-speed flight.