3.6 Airframe Noise Reduction Flap airframe noise model in Wind Tunnel During an aircraft approach, the noise the community hears is more than just the engine. Airplanes take off and land at slow speeds of 140 to 180 knots, compared with cruise speeds of 550 knots. To ensure adequate lift and stall margin during the critical take-off and landing, wings are enhanced with such lift-enhancing systems as trailing-edge flaps and extendible slats on the wing's leading edge. Exposed edges and gaps of high lift systems, not to mention the deployed landing gear, create airframe noises that can be as loud as the engines. NASA has developed a flow-physics-based technology that reduces the noise created by the air passing over flap edges. This technology is a micro piece of hardware that can be easily added to existing airplanes. The technology has been validated in small-scale-model tests and full-scale numerical simulation. Flap airframe noise reductions of 4 decibels have been demonstrated experimentally with little degradation in lift performance. Not only can adoption of this technology benefit the community, but it can also aid the airline industry in meeting the more stringent noise certification standards of the future. NASA POC: William Wilshire (757) 864-5270 W.L.Willshire@larc.nasa.gov

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