Exploration of a Low-Speed, Flapped, Slotted, Natural-Laminar-Flow Airfoil

A 12.91%-thick, flapped, slotted, natural-laminar-flow (SNLF) airfoil, the S702, intended for a low-speed, fixed-wing aircraft, has been designed, analyzed theoretically, and verified experimentally in The Pennsylvania State University Low-Speed, Low-Turbulence Wind Tunnel. The two primary objectives of high maximum lift that is insensitive to roughness and low-profile drag have been achieved. The use of a simple flap for manipulation of the low-drag region and control purposes was also explored and found to provide the desired characteristics. The airfoil exhibits a sharp stall that is less abrupt than the stalls of earlier SNLF airfoils, which meets the design objective. The constraint on the pitching moment has been satisfied. Comparisons of the theoretical and experimental results show reasonably good agreement overall, given the complexity of the configuration.