A radio-controlled tailless model helicopter will be used later this year to test a "flapping blades" propulsion concept that avoids generating the torque associated with conventional rotors.
In a traditional helicopter torque from the shaft-driven rotor reacts on the fuselage and is countered using a tail rotor. In the flapping blades concept each blade generates a propelling force when flapped up and down that rotates the rotor without the conventional mechanical drive that causes the reaction torque.
During each flapping motion the blade tip transitions from maximum height above the rotor plane on one side to maximum depth on the other. Cyclic and collective control are still achieved using a swashplate that modulates blade pitch. Yaw control is by over- or under-flapping the blades. Designed at the Delft University of Technology in the Netherlands, the tailless model helicopter's blades are to be "flapped" by a gearwheel mechanism. "The concept has been proven in the windtunnel. Later this year the model will fly," says research leader Theo van Holten.
Source: Flight International
