Flyover-Noise Reduction of Commercial Aircraft via Reduced Slat Deflections and Modified Flight Procedures

Current regulation and operation of commercial aircraft result in flyover noise that generates public protest well outside the recognized noise footprint of modern airports. This noise issue was recently exacerbated by the implementation of NextGen air-traffic control which uses GPS-based navigation for predictable flight paths and improved efficiency. This study documents flyover noise in residential communities during early approach (15-20 nautical miles from landing). Since airframe noise is significant during approach, reduced slat deflections are explored as a potential noise-reduction configuration. To document the aerodynamic effects of lower slat deflections, CFD simulations were conducted for an aircraft configuration representative of early approach. Additionally, modified flight procedures are proposed to mitigate existing flyover noise levels. Field measurements of flyover noise indicate a 5-8 dB difference between commercial aircraft with and without slats deployed. Both noise-mitigation strategies have promise, but reduced slatdeflection configurations will not likely be adopted without additional noise-certification requirements. Hence, the most promising near-term noise mitigation is to modify flight procedures to delay slat deployment and/or provide multiple approach flight paths.