Leading-edge extension
Strakes (also Leading Edge EXtension, LEX) are aerodynamic components to the modern (usually military ) aircraft, affecting the flow over the wings at high angles of attack.
Operation
On wings of small aspect ratio, such as delta wings and tapered wing combat aircraft, the flow with increasing angle of attack at the leading edge dissolves and forms a stable leading edge vortex over / along the wing. This generates strong negative pressures on the upper wing surface, thus increasing the buoyancy. This leads to the so-called non-linear buoyancy.
At high angles of attack of the leading edge vortex is not completely on the leading edge to, but " bends " the main flow over the wing from the following. About the outer wings arise so-called backflow. The positive effect of the vortex then acts only on the inside of the blade, while the flow at the outside of collapsed. This decrease buoyancy and control effect.
Strakes to prevent this collapse of the outer flow and stabilize the vortex system of the wing. On the side of the fuselage, the front edge of the main wing is strongly swept pulled forward. This extension is the Strake (LEX). When inflow positive pitch on both the strake and at the leading edge of the main wing ever an eddy peel off. The Strakewirbel displaces the " -turning " main vortex outward and stabilized him on the outer wing. For larger areas of the wing for generating lift can still be used and the flow to the control surfaces remain effective.
More options
Side strakes may be other ways to stabilize the flow over the wing, v. a to the outer area:
Examples
- Various aircraft with strakes in the aerodynamic design
F/A-18 at high angle of attack with a visible vortex generation on the strakes.
F -16 with visible vortex generation to "small" strakes between the cockpit and the wing leading edge.
Space Shuttle with strakes that extend to the forward cockpit.
The wings of the Concorde go in the front area flows into strakes.
- Aeronautical engineering
- Military Aviation