Evaluation of Gritting Strategies for High Angle of Attack Using Wind Tunnel and Flight Test Data for the F/A-18

A subsonic study of high-angle-of-attack gritting strategies was undertaken with a 0.06-scale model of the F/A-18, which was assumed to be typical of airplanes with smooth-sided forebodies. This study was conducted in the Langley 7- by 10-Foot High-Speed Tunnel and was intended to more accurately simulate flight boundary layer characteristics on the model in the wind tunnel than would be possible by using classical, low-angle-of-attack gritting on the fuselage. Six-component force and moment data were taken with an internally mounted strain-gauge balance, while pressure data were acquired by using electronically scanned pressure transducers. Data were taken at zero sideslip over an angle-of-attack range from 0 deg to 40 deg and, at selected angles of attack, over sideslip angles from -10 deg to 10 deg. Free-stream Mach number was fixed at 0.30, which resulted in a Reynolds number, based on mean aerodynamic chord, of 1.4 x 10(exp 6). Pressure data measured over the forebody and leading-edge extensions are compared to similar pressure data taken by a related NASA flight research program by using a specially instrumented F/A-18, the High-Alpha Research Vehicle (HARV). Preliminary guidelines for high-angle-of-attack gritting strategies are given