Wing fence

A boundary layer fence is an aerodynamic aids to improve the Strömungsabreißverhalten on aircraft wings. Of the boundary layer fence is attached to the supporting surface in the direction of flow rib to inhibit the cross- flow in the boundary layer, and thus a flow of the fluid to the airfoil tip. Of the boundary layer fence is mainly used in highly swept wing so as to prevent the flow separation at the wing tip in the region of the ailerons which leads to a tilting of the aircraft.

Boundary layer fences divide while the wing into several sections. Modern design methods for hydrofoil usually allow the renunciation of boundary layer fences, which are thus increasingly seen as a last resort.

History

The boundary layer fence in 1938 was developed from the Messerschmitt AG working Wolfgang love and patents pending. The first flight with wing fences took place on September 16, 1939 in Augsburg with a Messerschmitt Bf 109 B -1 ( D- IHHB, WNr. 290) instead. The experiments led to the success and brought significant improvements in the slow flight characteristics. However, there was no series production.

Only after the Second World War came with the MiG -15 aircraft with extensive boundary layer fence use in the application. The corresponding wing had been previously tested with the La -160. Boundary layer fences were then also widespread among civilian patterns for use, including the first jet airliners Comet, Tu -104 and Caravelle. A unique embodiment of a boundary layer fence uses Tupolev Tu -160, as it is only when a tilt angle of the wing of 65 ° folded upwardly. At smaller angles, the fence serves as cover the gap between the wing and fuselage.

Disadvantage of radar echo

The aerodynamic benefits is offset by the disadvantage of strong radar echoes. The smooth wing surface itself raises radar echoes back only at certain angles. Boundary layer fences ( metal ) on the upper wing surface but act as reflectors and thus powerful radar echoes ( technical term " radar flares " ), which may lead to a slight positioning of the aircraft. After this effect was detected, the boundary layer fences disappeared in newer military aircraft again very soon. Modern military aircraft designs come entirely without boundary layer fences. A similar effect also underwing pylons, which is why these two features are no longer found on modern stealth aircraft at the wing base.

More options

In addition to boundary layer fences, there are other possibilities that flow over the wing - especially on the outside - to stabilize: