Airframe Noise Research at DLR

The expected increase in stringence of the ICAO Chapter-3 noise certification limits necessitates the development of source noise reduction technologies for subsonic commercial aeroplanes. The noise from such aeroplanes during landing approach is largely dominated by airframe noise, i.e. the noise generated by the interaction of flow and those aircraft components deployed for landing, such as the landing gears and the wing high-lift devices. In the mid-nineties, DLR had been under contract to Airbus Industrie to investigate the noise from Airbus-type aircraft landing gears. More recently, DLR has entered into two major - still ongoing - pertinent research programs: first, a German National Program on commercial aeroplane airframe noise reduction (sponsored by the German Ministry of Research and Education, BMBF) to specially investigate the noise from high-lift devices, and, second, a European program under the auspices of the EU entitled Reduction of Airframe and Installation Noise (acronym RAIN), dealing with airframe noise from both landing gears and high lift devices. This paper will present Highlights from these research projects, indicating the source noise reduction potential of design changes on landing gears and on wing high lift devices which could be employed without hampering the basic functionality of such components