NACA-ACR-4B28

Abstract

Wind-tunnel tests have been made in two-dimensional flow to investigate the aerodynamic characteristics of a flap balanced by a large overhang linked to deflect more slowly than the flap. Three lengths of blunt-nose overhang were tested linked to & 0.30-airfoil-chord straight-contour flap on an NACA 66-009 airfoil. <br>The test results indicated that the linked overhang was capable of producing as highly balanced flap hinge moments as can be obtained with other types of aerodynamic balance. At the same time, the linked-balance flap produced slightly higher lift at large deflections than the corresponding unbalanced or internally balanced flap and much higher lift than flaps balanced by smaller conventional type overhangs. Such characteristics can be obtained with a linked balance because much balance can be obtained without the nose of the overhang protruding sufficiently far into the air stream to cause severe air-flow separation at large deflections. <br>Because the hinge-moment parameters are functions of the rate of balance deflection, adjustment of the balancing characteristics of a control surface can be made on each individual airplane merely by changing the length of a link.