Research into Landing Gear Airframe Noise Reduction

Servere air-traffic constraints are imposed by commercial airports following public complaints about the ever increasing noise impact. This situation lead to renewed emphasis by aviation industry into aircraft noise source research. While the engine noise still dominates during aircraft full-power take-off, it is the airframe noise which represents the essential contributor to the overall flyover noise signature in the landing phase for today's high-bypass ratio engine powered large commercial aircraft. Therefore in Europe a research project was launched aiming at the reduction of landing gear noise, which is the dominant airframe noise component for wide-body aircraft and the subject area of this paper. Based on the knowledge of a state-of-the-art full scale A340 nose- and main-landing gear baseline noise test, realistic noise reduction add-on devices were developed for these gears and the devices' effectiveness tested in a dedicated wind tunnel study. Both farfield noise data were taken and techniques employed for noise source localization. By removing the noise reduction devices orderly, their individual effectiveness were assessed. It was demonstrated that significant noise reduction can be achieved with add-on devices which have been designed to cause minimum interference with respect to the gears' functionality and maintainability