Wind tunnel investigation of the transonic aerodynamic characteristics of forward swept wings

Abstract

This paper discusses some of the results of a series of wind tunnel investigations conducted on forward and aft swept wings in order to compare the relative drag performance of both wings at a transonic maneuver condition and to determine the associated drag penalty of the forward swept wing for a high supersonic cruise condition. At the transonic maneuver design point, the results indicate a significant reduction in the profile drag of the forward swept wing relative to the aft swept wing. The forward swept wing exhibits extreme sensitivity to wing root height and incidence variations. A drag penalty was recorded at M— 2.0 for the forward swept cruise wing. The cruise wings have the same sweep and box geometries as the transonic maneuver wings. The difference in supersonic cruise drag is attributed to the difference in the leading-edge sweeps (ALE = +48.7 and -28 deg for the aft and forward swept wings, respectively). This drag penalty decreases at lower supersonic Mach numbers. The results of the test indicate that the aft swept wing aerodynamic design and analysis methods used in the study can be used on forward swept wings with only minor modifications.