Leading edge extension

Leading edge extensions or LEX (also referred to as leading edge root extensions) are fillets added to the front of a modern fighter aircraft's wings in order to provide usable airflow at high angles of attack. They are typically roughly triangular in shape, running from the leading edge of the wing root to a point near the cockpit along the fuselage. They tend to be fairly small in span, extending out less than a metre.

Related Topics:
Fillet - Fighter aircraft - Wing - Airflow - Angles of attack - Wing root - Cockpit

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In cruising flight the effect of the LEX is minimal. However: when the angle of attack increases, as in a dogfight, the LEX starts to generate a high-speed vortex that remains attached to the top of the wing. Due to the effects described by Bernoulli's principle the wing therefore has a low pressure zone on top, and continues to generate lift past the normal stall point. The F/A-18 Hornet has especially large examples of LEX, as does the Sukhoi Su-27. The F-16 and its unsuccessful competitor the YF-17 also took advantage of the increases in maneuverability.

Related Topics:
Dogfight - Vortex - Bernoulli's principle - Stall - F/A-18 Hornet - Sukhoi Su-27 - F-16 - YF-17

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A concept similar to LEX can be found on many aircraft, including airliners. These vortex generators take the form of small fins sticking up from the surface of the wing just behind the leading edge. In this case the purpose is to generate small vortices that ensure airflow over the control surfaces at high angles of attack, typically during takeoff and landing.

Related Topics:
Airliner - Vortex generator - Control surface

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