Two-way racing street

Max Kingsley-Jones (Flight International, 25 June-1 July) describes how aero engineers are improving racing cars. In the case of the Gurney flap, innovation travelled the other way. Dan Gurney, car owner and one-time racer, was challenged by test driver Bobby Unser to do something about the cornering of a car they were testing. Gurney responded with a very narrow trailing-edge flap, deflected 90°, that increased the downforce of racing car wings and at the same time reduced drag.

The surprising result (described by Robert Liebeck of McDonnell Douglas at an American Institute of Aeronautics and Astronautics Symposium, "The Evolution of Aircraft Wing Design", at Dayton, Ohio in 1980) focused attention on what happens in fact, as opposed to theoretical approximation, at the trailing edge of a wing. It may not be coincidence that McDonnell Douglas later introduced aerofoils that thickened toward a down-hooked, blunt trailing edge.

Charles McCutchen

Bethesda, USA

Source: Flight International