QTD 2 (Quiet Technology Demonstrator 2) Main Landing Gear Noise Reduction Fairing Design and Analysis

Abstract

The advances in aircraft engine noise reduction and the increasing demand for quieter aircraft has led noise research to focus more attention on airframe noise. Landing gears and high lift systems have been known to significantly contribute to the total aircraft noise at approach idle conditions, especially in cases where high by-pass ratio engines are used, when noise from the engines is low enough that it could be considered comparable or lower than the noise from the airframe. Landing gears in service on today’s aircraft were not designed with noise impact in mind and contain a myriad of possible noise generating features. Today’s landing gear designer is challenged to consider noise among many other factors when designing efficient aircraft landing gear systems. It is a challenge further complicated if noise reduction solutions are required for retro-fit applications. Much of the experimental noise research conducted on landing system noise has centered around the understanding of noise generating mechanisms and evaluation of noise reduction concepts in model-scale environments such as wind tunnel tests. These experiments have provided valuable insight into landing gear noise sources. However, little effort has been made to integrate noise reduction research with full-scale landing gear design and evaluate noise reduction potential in a full-scale flight environment. The work conducted under the Quiet Technology Demonstrator 2 (QTD2) program marks a first step in the successful integration of noise research with landing gear design with the focus being to design, implement and evaluate noise reduction solutions in a full-scale flight environment. This paper discusses the design and analysis of a ‘toboggan’ shaped main landing gear noise reduction fairing for full-scale flight evaluation on a B777-300ER aircraft in the QTD 2 program. The fairing was selected for flight evaluation after a series of model-scale wind tunnel acoustic experiments were conducted in conjunction with full-scale feasibility studies. The fairing design addressed issues such as gear kinematics and stowing, brake cooling, ground operations and noise reduction potential. The design was supported by static stress analysis and flutter analysis to ensure that the fairing was flight worthy.