RPA (Rotor à Pales Actives) Franco-German project was launched three years ago to study the possible benefits of implementing active trailing edge flaps on a helicopter main rotor. The main expected effects concern the decrease of BVI noise in descent flight and the improvement of the dynamic behaviour of the rotor throughout the largest possible flight domain. The technological solution adopted to deflect the flap of an 1/3rd scale rotor demonstrator, uses an off-the-shelf elliptic amplified actuator, from Cedrat Recherche Company, driving an innovative patented mechanism.