Trailing Edge Tabs

Reduction of pitching moments on a given airfoil can be achieved by using a reflex trailing edge either as an integral part of the airfoil design or as an add-on flat tab. Several wind tunnel tests of airfoils with tabs have been made. Figure 6.37 summarizes the results presented in references 6.9,6.10,6.21, and 6.49 in terms of the effect of tab deflection on both cm and c, as a function of the ratio of tab to airfoil chord. The test results for pitching-moment sensitivity correlate well with those obtained from thin airfoil theory as given in reference 6.1. It may be seen that the larger tabs are desirable for their ability to produce a pitching moment

while minimizing the penalty to maximum lift coefficient. Drag penalties of tabs appear to be small—in most cases not much more than the accuracy of the drag measurement.