Gurney Flaps on Slender and Nonslender Delta Wings

*† ‡ A parametric low-speed wind tunnel study has been undertaken of the effect of Gurney flaps on the aerodynamic characteristics of slender and non-slender delta wings with sweep angles of 40°, 60° and 70°. In contrast to published data, no fundamental difference in behaviour with sweep angle was found. Gurney flaps were found to give similar lift and pitching moment changes to conventional hinged control surfaces, but with a much greater drag penalty. Gurney flap effectiveness was found to increase as sweep angle is reduced; a characteristic explained by a simple analysis of lift and drag on a sharp-edged delta wing. For a 40° sweep angle (typical of a UCAV configuration), Gurney flap deployment can significantly improve lift/drag ratio at higher incidences. Further improvements can be obtained by tapering or serrating the flap.