Book Description

Summary: Wind-tunnel tests have been made in two-dimensional flow to investigate the aerodynamic characteristics of a double flap with an internal and an overhang balance. Three sizes of each type of balance were tested with three relative rates of deflection of the two flaps. An NACA 66-009 airfoil having a 0.30-airfoil-chord straight-contour forward flap and a 0.20-airfoil-chord straight-contour rearward flap was used. The test results indicated that a balanced double flap produced the same lift as a single plain flap of the same chord and also produced highly balanced hinge moments. High lifts and low hinge moments were obtained with a double-flap arrangement if either an overhang or an internal balance having a chord 50 percent of the flap chord was incorporated on the forward flap. The overhang-balance flap showed a lower value of the hinge-moment gradient due to flap deflection than the internally balanced flap.