AERODYNAMIC AND AEROACOUSTIC LAYOUT OF THE ATR (ADVANCED TECHNOLOGY ROTOR)

In the framework of the ATR (Advanced Technology Rotor) research program a new main rotor design was developed to achieve a stepforward in performance, noise emission and economy. The aerodynamic and aeroacoustic layout of the ATR is presented and the choice of rotor parameters like blade planform, twist distribution and blade tip shape are discussed. Previous research programs, in which the influence of these parameters were studied, are briefly reviewed. Results of flight tests conducted on a BK117 helicopter equipped with the ATR and two different blade tips (with parabolic and elliptic leading edge sweep back) are presented with respect to rotor performance and noise emission. The noise measurements on ground were performed for approach, flyover and takeoff flight procedures specified in the ICAO (International Civil Aviation Organisation) certification rules and included also additional descent angles, flight and tip speeds. The noise radiation of the ATR is evaluated for the two blade tips and compared to the standard rotor of the BK117.