Lessons learned from comparision between ground-based tests and flight measurements for the high-angle-of-attack programs on the F-18 High Alpha Research Vehicle (HARV), the X-29 forward-swept wing aircraft, and the X-31 enhanced fighter maneuverability aircraft are presented. On all three vehicles, Reynolds number effects were evident on the forebodies at high angles of attack. The correlation between flight and wind tunnel forebody pressure distributions for the F-18 HARV were improved by using twin longitudinal grit strips on the forebody of the wind-tunnel model. Pressure distributions obtained on the X-29 wind-tunnel model at flight Reynolds numbers showed excellent correlation with the flight data up to [alpha]=50 deg. Above [alpha]=50 deg. the pressure distributions for both flight and wind tunnel became asymmetric and showed poorer agreement, possibly because of the different surface finish of the model and aircraft. The detrimental effect of a very sharp nose apex was demonstrated on the X-31 aircraft. Grit strips on the forebody of the X-31 reduced the randomness but increased the magnitude of the asymmetry. Nose strakes were required to reduce the forebody yawing moment asymmetries and the grit strips on the flight test noseboom improved the aircraft.

Static aerodynamic forces and moments were measured to study the effects of Reynolds number and body corner radius on the aerodynamic characteristics of a straight wing space shuttle orbiter at subsonic speeds. A 0.02-scale model was tested at Mach numbers from 0.3 to 0.9 and Reynolds numbers from about 600,000 to 3 million, based on body width. The body alone and the body with its wing and horizontal tail attached were tested at angles of attack from 35 to 75 degrees. The effects of rounding the body corners at the junctures connecting the bottom and sides were investigated for corner radii from 0 to 8.5 percent of the body width. At low subsonic Mach numbers (free stream Mach number approximately equal 0.3) the aerodynamic characteristics are affected significantly by changes in Reynolds number and body corner radius. With increase in Mach number to free stream Mach number = 0.9 the effect of Reynolds number seems to vanish, but a significant effect of body corner radius remains.