The tail rotor found on conventional helicopters has always been considered a 'necessary evil'. Without it the helicopter is uncontrollable in yaw, yet the tail rotor is an expensive feature, consuming a lot of power, and it provides only marginal control authority under unfavorable wind conditions. Tail rotors are also noisy, vulnerable and dangerous to bystanders. The ideal solution to all these problems would be to design a main rotor that eliminates the need for a tail rotor. Professor van Holten started developing in 2002 a new design for a rotary wing. The Ornicopter is a single rotor helicopter without a reaction torque — it is fully controlled using only one rotor.
The secret to the Ornicopter concept is in rotor blade flapping. The rotor blades are forced to flap up and down once per revolution, thus generating a propulsive force on the blades that drives the rotor around the hub. By increasing or decreasing the amplitude of this flapping movement, the yaw motion of the fuselage can be controlled.
The first analyses of the Ornicopter showed that it had a similar power requirement to a conventional helicopter, as well as very similar longitudinal and lateral stability and controllability characteristics to a conventional helicopter. However, the Ornicopter generated higher vibratory loads than in a conventional helicopter, and its performance was strongly limited by the stall effect.
Development of the Ornicopter is an active area of research at the Delft University of Technology.