A Study on Landing Gear Wake - Flap Interaction Noise

Abstract

Landing gear noise represents for nearly all transport aircraft one, if not the dominant, airframe noise source during the final landing phase of the aircraft. This can be roughly defined to start at about 2000 ft altitude above ground level and ends with the aircraft’s touch down. Accordingly, landing gear noise is a significant contributor to both, the certification noise level as well as community noise levels. Past and current research activities on landing gear noise focused at a first glance on the noise generated due to the interaction between a turbulent flow and the landing gear structure such as wheels and brakes, struts, links and dressings. Less emphasis was spent on the fact that the main landing gear related wake impinges on the flap and thus could generate landing gear wake – flap interaction noise. The aim of the present study was to identify and quantify gear wake flap interaction noise. The study is based on flyover noise measurement data gathered in 2004 in the mainframe of the German national funded research project FREQUENZ. Noise tests were conducted with an Airbus A319 100 aircraft which can be considered representative for the fleet of narrow body short and medium range aircraft. The obtained results can be summarized as follows: gear wake flap interaction noise increases the airframe noise signature by up to 3 dB at medium frequencies and is most pronounced for forward and rear arc radiation directions. High as well as very low frequency noise levels are not significantly contributing to gear wake - flap interaction noise. For future attempts to reduce airframe noise and in particular landing gear noise gear wake flap interaction noise needs to be considered.