NASA-TP-1498

Abstract

An investigation was conducted in the Langley low-turbulence pressure tunnel to determine the low-speed two-dimensional aerodynamic characteristics of a 13-percent-thick medium-speed airfoil designed for general aviation applications. The results are compared with data for the 13-percent-thick low-speed airfoil section. Also, theoretical predictions of the drag-rise characteristics of the medium-speed airfoil are provided. The tests were conducted over a Mach number range from 0.10 to 0.32, a chord Reynolds number range from 2.0 x 10⁶ to 12.0 x 10⁶, and an angle-of-attack range from about -8&#176; to 20&#176;. <br>The results of the investigation indicate that the objective of retaining good high-lift low-speed characteristics for an airfoil designed to have good medium-speed cruise performance was achieved. Maximum section lift coefficients at a Mach number of 0.15 increased from about 1.70 to 2.06 as the Reynolds number increased from about 2.0 x 10⁶ to 12.0 x 10⁶. Stall characteristics were of the trailing-edge type and were docile at the lower Reynolds numbers. The application of a roughness strip near the leading edge of the airfoil resulted in only small effects on maximum section lift coefficients. Increasing the Mach number from 0.10 to 0.32 at a constant Reynolds number of 6.0 x 10⁶ decreased the maximum section lift coefficient about 0.08. The magnitude of the quarter-chord pitching-moment coefficient was decreased about 25 percent for the medium-speed airfoil compared with the low-speed airfoil.