Design and Initial Flight Testing of a Coaxial Tilting-Head Compound Rotorcraft

This paper describes the design and initial flight testing of a compound coaxial tilting head rotorcraft (CCT-HR). Control is provided by titling the rotor head for roll and pitch, differential rotor speed for yaw rate, and rotor speed for total thrust. In addition, a longitudinal thruster is incorporated to enable higher speed forward flight and to add a degree of freedom for longitudinal trim in forward flight. The intent is to explore the feasibility of this vehicle concept and to develop a vehicle that can be used to explore control strategies. The steady state flight envelope is developed analytically; a simulation of longitudinal degrees of freedom is described and a control method for forward flight that incorporates the thruster is proposed. Results of near-hover flight tests are described and initial tests of forward flight using the thruster are described. The vehicle is shown to be stable and easily controllable near hover; in thruster-powered forward flight unmodeled rotor dynamics result in instability.