Noise Sources Control of an Aircraft Landing Gear

Abstract

3 Landing gears are one of the major sources of airfr ame noise at approach and previous studies have shown that fairings can be used succes sfully to reduce broadband noise radiation in the mid- and high-frequency ranges 1 . In flight tests 2,3 , however, the overall benefit of the fairings was offset by an increase i n low frequency broadband noise and a new tonal noise source that was believed to originate f rom the leg-door or hinge-door of the gear. This paper describes an experimental study on a 1/4 scale model of the main landing gear of the aircraft to control the low-frequency broadband noise and to identify and eliminate the source of the tone, whilst retaining the noise redu ction capability at higher frequencies. The aeroacoustic and aerodynamic characteristics of the model were assessed in a low-speed closed-loop wind tunnel using phased microphone arrays on the roof and wall of the tunnel and surface pressure transducers on the gear. The t one could be readily suppressed or reduced by a number of different treatments. Control of low frequency noise was less straightforward, although some preliminary solutions have been identified.