Modeling and control of lift offset coaxial and tiltrotor rotorcraft

The US Department of Defense has established an initiative to develop a family of next-generation vertical lift aircraft that will fly farther, faster, and more efficiently than the current fleet of rotorcraft. To accomplish these goals, advanced rotorcraft configurations beyond the single main rotor/tail rotor design must be considered. Two advanced configurations currently being flight tested are a lift offset coaxial rotorcraft with a pusher propeller and a tiltrotor. The US Army Aviation Development Directorate has developed generic high-fidelity flight-dynamics models of these two configurations to provide the government with independent control-system design, handling-qualities analysis, and simulation research capabilities for these types of aircraft. This paper describes the modeling approach used and provides model trim data, linearized stability and control derivatives, and eigenvalues as a function of airspeed. In addition, control allocation for both configurations is discussed.