SUMMARY
Wind-tunnel tests have been made to determine the aerodynamic section characteristics of an NACA 0009 airfoil with a plain flap having a chord 25 percent of the airfoil chord and a balancing tab having a chord 50 percent of the airfoil chord or 200 percent of the flap chord so linked that the tab would deflect at a given rate with respect to the flap. Three linkage ratios were tested on the model.
The tests indicated that the flap and tab could be linked to give hinge-moment balance with flap deflection and with angle of attack and yet have greater lift effectiveness than a plain flap of similar size with a conventional balancing tab having a chord 20 percent of the flap chord linked to give hinge-moment balance with flap deflection only.