Low Speed Aerodynamics for Ultra-Quiet Flight

Abstract : A combined aerodynamics, acoustics and bionics study was conducted in an attempt to discover novel mechanisms to reduce the noise associated with aircraft flight. The strigiformes order of birds, selected in the bionics effort as possessing characteristics of silent flight, was studied extensively. Three mechanisms producing the potential for acoustic quieting were discovered as a result of this study. These are: vortex sheet generators, compliant surfaces, and distributed wing porosity. An experimental program aimed at initiating full scale flight evaluation of these concepts was outlined. The detailed results of these studies are included. The report develops design concepts which may be applied to obtain ultra quiet flight for convert/reconnaissance/surveillance aircraft such as the YO-3.