Identification and Attenuation of a Tonal-Noise Source on an Aircraft's Landing Gear

Aircraft landing gear noise is a major contributor to the overall airframe noise during the landing approach of a commercial aircraft. Fairings covering geometrically complex areas of the gears have proved to be very effective in noise reduction. However, in tests on an A340’s main landing gear, the overall benefit of the fairings was offset by both a slight increase in low-frequency broadband noise and a strong tonal noise. In this study, the identification and attenuation of the tonal-noise source has been carried out using a one-quarter-scale A340 main-landing-gear model. Aeroacoustic and aerodynamic tests were conducted in a closed-section wind tunnel, using a phased microphone array on the ceiling of the test section, flush-mounted pressure transducers on the model surface, and the particleimage- velocimetry technique. Far-field noise tests were then taken in an open jet aeroacoustic facility, using far-field microphones to verify the wind-tunnel test results. The experiments demonstrated the tonal-noise mechanism and a number of different control methods.