Experimental study of effects of forebody geometry on high angle-of-attack stability

A series of low-speed wind-tunnel tests on a generic airplane model with a cylindrical fuselage are made to investigate the effects of forebody shape and fineness ratio, and fuselage/wing proximity on static and dynamic lateral/directional stability. During the stability investigation ten forebodies were tested including three different cross-sectional shapes with fineness ratios of 2,3, and 4. In addition, the wing was tested at two longitudinal positions to provide a substantial variation in forebody/wing proximity. Conventional force tests were conducted to determine static stability characteristics, and single-degree-of-freedom free-to-roll tests were conducted to study the wing rock characteristics of the model with the various forebodies. Flow visualization data were obtained to aid in the analysis of the complex flow phenomena involved. The results show that the forebody cross-sectional shape and fineness ratio and forebody/wing proximity can strongly affect both static and dynamic (roll) stability at high angles of attack. These characteristics result from the impact of these factors on forebody vortex development, the behavior of the vortices in sideslip, and their interaction with the wing flowfield.