The Gurney flap (or wickerbill) is a small tab projecting from the trailing edge of a wing. Typically it is set at a right angle to the pressure-side surface of the airfoiland projects 1% to 2% of the wing chord.This trailing edge device can improve the performance of a simple airfoil to nearly the same level as a complex high-performance design. It is named for its inventor and developer, American race car driver Dan Gurney.