NACA-ARR-3F29

Abstract

Force-test mea8nrenkata in two-dimensional flow have been made in the N.ACA 4- by 6-foot vertical tunnel to determine the aerodynamic characteristics of an NACA 0009 airfoil equipped with a double plain flap that consisted of a plain forward flap having a chord 20 percent of the airfoil chord (0,20c) and a plain rearward flap having a chord 15 percent of the airfoil chord. <br>The results of the present tests and a brief analysis of previously obtained data indicated that, for positive flap deflections at zero and positive angles of attack, a sealed 0.20c double plain flap would produce more lift and less hinge moment than a 0.50c single plain flap. The small double flap was not so effective as the large plain flap in producing positive lift at large negative angles of attack. With controls free, the slope of the lift curve of a surface having a 0.20c single or a 0.20c double plain flap is more than twice that of a surface having a 0.50c plan flap. Although the stick hinge moments of a small-chord double plain flap are much less than those of a larger-chord single plain flap, they are still too great for use on large high-speed airplanes. &#8216;ID order to function efficiently both gaps of double. plain flaps should be sealed.