A European Study on Landing Gear Airframe Noise Sources

Flyover noise of modern aircraft in their approach configuration can be dominated by airframe noise. Relevant flow noise sources are high lift devices and landing gears. Therefore aeroacoustic tests were performed in the German Dutch Wind Tunnel employing full-scale landing gears of an A340 aircraft. Farfield noise characteristics were determined for both a nose- and a main landing gear, the latter in a 4-wheel and a 6-wheel mock-up configuration, at wind speeds ranging from 50 to 78 m/s. DNW's 3m acoustic mirror and a planar microphone array served for source localization and ranking. Excess tone noise was detected and originated from pin-cavities. Broadband noise levels were confirmed to increase with the 6th power of flow velocity. Noise directivities feature weak level maxima both in the forward and rear arc. Based on results from earlier testing on a smaller A320 gear the effects on noise of gear size and configuration were evaluated. By covering different gear components with streamlined fairings an overall noise reduction on the order of 3 dB was achieved