The research organizations ONERA and DLR initiated a common programme supported by Eurocopter (EC) and Eurocopter Deutschland (ECD) as industry partners within the Active Blade Concept (ABC). The content is to investigate in theory and experiment the possible benefits and the phenomena associated with an actively controlled flap located at the trailing edge of a helicopter rotor blade. The main focus is put on the reduction of vibration and noise radiation of the complete helicopter rotor and the expansion of the flight enve-lope by the use of multi-frequency higher harmonic flap control. The first phase of the research programme was dedicated to the numerical assessment of flap geometry, radial location, and optimal control inputs. The simulations showed best results for a 15% chord flap, with different optimal radial locations, depending on the distur-bance considered. A more inboard flap location is most suitable for vibration reduction, while for noise reduction the best results were obtained with a more outboard position. The design, manufacturing and experimental wind tunnel testing of a 4-bladed Mach-scaled rotor model in high speed and descent flight is realized during the second phase
