Further Noise Reduction of Regional Jet Two-Wheel Main Landing Gear

Noise reduction design concepts have been applied to the two-wheel main landing gear of a regional jet in order to reduce airframe noise during approach. Several of the concepts were initially developed for the main landing gear of the Japan Aerospace Exploration Agency’s experimental aircraft, “Hisho,” based on a Cessna Citation Sovereign business jet, and were tailored to the larger regional jet main landing gear after a careful investigation of the flow fields around it by computational fluid dynamics simulations, far-field noise measurements with a 10%-scale wind tunnel model, and an evaluation of structural feasibility. The initial design was then improved upon by further investigations with a 20%-scale wind tunnel model and additional computational simulations. New noise reduction concepts in addition to those applied to Hisho were also evaluated and adopted to enhance the overall noise reduction performance. Six types of noise reduction devices were chosen: a porous-plate cover around the tire axle and the lower half part of the strut, a plate between the mid door and strut, a porous plate on the side brace, a porous door arm, porous material with open cells affixed to the inner surfaces of the landing gear doors, and sealed wheel holes. Compared with a baseline configuration, significant noise reduction, 5.5 dB(A) in overall sound pressure level at a position directly below the main landing gear and 4.5 EPNdB, was achieved in a wind tunnel test with the 20%-scale model.