NACA-RM-A54F18

Abstract

INTRODUCTION <br>Commercial and military needs for long-range airplanes Capable of relatively high subsonic speeds have stimulated much research aimed toward the development of suitable airframe configurations. Indications are that these performance requirements can be met best by airplanes with sweptback wings of relatively high aspect ratio. <br>A wing of this type has recently been investigated in the Ames 12-foot pressure wind tunnel and the results are presented in reference 1. In an effort to obtain good stability characteristics, the reference wing used NACA 4-digit sections in combination with moderate amounts of camber and twist. However, the data in references 2 and 3 indicate that in two-dimensional flow at speeds below the Mach number for drag divergence and at the lift coefficients required for cruising flight of long-range airplanes, cambered NACA 6-series wing sections (of laminar-flow type) have less drag than cambered NACA 4-digit sections. The two-dimensional data also show about equal drags for the two types of section at super critical speeds and about equal Mach numbers for drag divergence. <br>In order to assess the anticipated drag penalties at sub-critical speeds as well as the probable gains in stability resulting from the use of 4-digit wing sections with sweptback wings of relatively high aspect ratio, the present investigation was undertaken in the Ames 12-foot pressure wind tunnel. Two series of twisted and cambered wings, identical in all respects except the thickness distributions of the ting sections, were tested. One series employed NACA 4-digit sections and the other NACA 64A sections. The sweepback angle of the wings was varied from&#160;40&#176; to 50&#176; to determine if the Mach number of drag divergence could be raised by increasing sweepback without introducing severe stability problems. <br>The experimental data include longitudinal aerodynamic characteristics for both series at sweepback angles of 40&#176;, 45&#176;, and 50&#176;. The tests covered a range of Mach numbers up to 0.94 at a constant Reynolds number of 2 million and a range of Reynolds numbers up to 10 million at low speeds.