A leading-edge extension (LEX) is a small extension to an aircraft wing surface, forward of the leading edge. The primary reason for adding an extension is to improve the airflow at high angles of attack and low airspeeds, to improve handling and delay the stall. A dog tooth can also improve airflow and reduce drag at higher speeds.
Leading-edge slats deployed on an Airbus A318-100
Dog tooth on the wing of a Hawker Hunter
Experimental drooped leading-edge cuff on an American Aviation AA-1 Yankee
Condensation vortex flows along the LERX of an F/A-18
In fluid dynamics, angle of attack is the angle between a reference line on a body and the vector representing the relative motion between the body and the fluid through which it is moving. Angle of attack is the angle between the body's reference line and the oncoming flow. This article focuses on the most common application, the angle of attack of a wing or airfoil moving through air.
Angle of attack of an airfoil
Coefficients of drag and lift versus angle of attack. Stall speed corresponds to the angle of attack at the maximum coefficient of lift (CLMAX)
Su-27M / Su-35 at high angle of attack