NACA-RM-A57E02

Abstract

INTRODUCTION <br>It has been previously demonstrated that a thin highly swept wing is capable of large lift-drag ratios at speeds well into the supersonic regime. Reference 1 reports lift-drag ratios of 9 at a Mach number of 1.5 for one such wing-body combination in which the wing had a thickness-chord ratio of 0.05, a leading-edge sweepback of 63&#176;, and an aspect ratio of 3.5. This lift-drag ratio was achieved despite the lack of body indentation, which has since been shown to be beneficial (see ref. 2, for example). This wing has a disadvantage that is typical of a wide range of plan forms with high sweep: The static longitudinal stability decreases abruptly at some moderate lift coefficient. Reference 3 and showed that a model geometrically similar to that of reference 1 had this unfavorable stability characteristic at all subsonic speeds. Reference 5 discusses the phenomenon and concludes that it is a result of leading-edge flow separation. One method of delaying the separation is to provide camber and twist in the wing; these improvements were already incorporated in the wings of references 1,3, and 4. There are also certain devices, such as wing fences, to control the span wise location of the separation so as to improve the pitching-moment characteristics of highly swept wings. Reference 6 describes the partially successful results of using such devices. A third method of improving stability characteristics is to place a horizontal tail in the downwash filed of the wing so that it provides increases in stability at the angle of attack where the wing loses stability. <br>The purpose of the present investigation was to use all three methods of improving the longitudinal stability of a thin highly swept wing and to assess the resulting lift and drag penalties. For this purpose a model configuration similar to that of reference 1 was tested in the Ames 12-foot pressure wind tunnel at mach numbers from 0.20 to 0.95 and at Reynolds pressure wind tunnel at Mach numbers from 0.20 to 0.95 and at Reynolds numbers from 2 million to 7 million. The test data are reported herein.