Preliminary investigation at supersonic speeds of triangular and sweptback wings

A series of thin, triangular plan-form wings have been investigated in the Langley model supersonic tunnel. The series consisted of eight triangular wings of vertex angles such that a range of leading-edge positions both inside and outside the Mach cone at the two test Mach numbers of 1.43 and 1.71 was obtained. Three sweptback wings having angles of sweep of 45 deg, 55 deg, and 63 deg were also tested at a Mach number of 1.43. These sweptback wings had circular-arc sections with rounded leading edges and thicknesses of 13.3 percent of the chord measured normal to the leading edge. For each angle of sweep, wings having two values of aspect ratio were tested. Lift results for the triangular wings indicated that Jones' theory for the lift of slender pointed wings is applicable for thin wings in the range of selected test Mach numbers. The center of pressure of the triangular wings was coincident with the center of area for all the wings tested at both Mach numbers. The lowest minimum drag coefficients were obtained for the wings with smallest vertex angles relative to the Mach angle. Also in this smallest vertex-angle region, the highest values of maximum lift-drag ratio of about 7 for both Mach numbers were obtained. The tests indicated that wings having triangular plan forms should be operated well within the Mach cone for maximum efficiency. Results of the sweptback-wing tests compared with triangular wing results for a Mach number of 1.43 show the same trends of lift and drag as the sweep angle is changed. For corresponding sweep angles, the swept-wing lift curve slopes were lower than those for triangular wings, probably because of the increased thickness. The tests indicate that for a Mach number of 1.4, the angle of sweep must be increased to about 60 deg to obtain low drag coefficients of the same magnitude as those due to skin friction.