LOADING CONSEQUENCES OF THE WlING UPPER SURFACE AIR BRAKE

Abstract

The continuous trend to improve sailplane performance leads to new design conceptions aimed at reducing drag as far as possible. It is well known that competing pilots seal all the slots and grooves on the external surfaces of the ship to avoid any leakage in the air flow and to preserve the "healthful" stream over the surfaces of the sailplane, especially on the wing. The slots or grooves produce discontinuities of the aerofoil contour, so contributing extra drag as a result of "turbulization" of the flow. The upper surface wing air brake seems to be an attractive solution in respect to its advantages: - small decrement of braking effectiveness when compared with the conventional upper and lower surface air brake, - reduction in flow disturbance since slots on the lower wing surface are avoided, - and some simplification in production. 0n the other hand, the upper surface air brake wing configuration produces greatly modified lift distribution along the span when compared with that of the smooth wing configuration. This modification leads to very serious increment of wing loading. Before the application of the upper surface air brake is decided, close calcuation of loadings and structural analysis should be performed to be sure that the required safety level of the wing structure is maintained.