High-alpha aerodynamic characteristics of crescent and elliptic wings

Static longitudinal and lateral-directional forces and moments were measured for elliptic- and crescent-wing models at high angles of attack in the NASA Langley 14-by-22-ft Subsonic Tunnel. The forces and moments were obtained for an angle-of-attack range including stall and post-stall conditions at a Reynolds number based on the average wing chord of about 1.8 million. Flow-visualization photographs using a mixture of oil and titanium-dioxide were also taken for several incidence angles. The force and moment data and the flow-visualization results indicated that the crescent wing model with its highly swept tips produced much better high-angle-of-attack aerodynamic characteristics than the elliptic model. Leading-edge separation-induced vortex flow over the highly swept tips of the crescent wing is thought to produce this improved behavior at high angles of attack. The unique planform design could result in safer and more efficient low-speed airplanes.