Strake (aeronautics)

In aviation, a strake is an aerodynamic surface generally mounted on the fuselage of an aircraft to improve the flight characteristics either by controlling the airflow (acting as large vortex generators) or by a simple stabilising effect. In general a strake is longer than it is wide, in contrast to a winglet or a moustache. Leading edge root extensions (LERX) are also sometimes referred to as wing strakes. On both supersonic and subsonic types, smaller strakes are sometimes applied to the forward fuselage to control the fuselage flow at high angles of attack; for example, the Concorde had small nose strakes "to get a better directional stability". Double delta wing aircraft (Concorde, Tupolev Tu-144, Boeing 2707 SST project) featured a forward extended leading edge that may be considered as a wing strake; it provides the same additional vortex lift at high angle of attack by leading edge suction. On jet aircraft where the engines are mounted in nacelles slung under the wings, strakes may be added to one or both sides of each nacelle to produce vortices that energize the airflow over the wings in times of high angle of attack, such as during takeoff and landing, thus improving wing effectiveness. One or two ventral strakes are sometimes positioned under the fuselage, as large vortex generators, to provide a better tail surfaces efficiency. Typical examples can be seen on the SOCATA TB family or the Lockheed F-104 Starfighter. One or two large fins or strakes are sometimes positioned under the rear fuselage or below the empennage, to provide adequate stability at high angles of attack when the tail fin is shielded from the main airstream by the fuselage and/or the wing wake. Typical examples can be seen on the Piaggio P.180 Avanti, Learjet 60 and Beechcraft 1900D. The Grumman X-29 research aircraft had rear fuselage lateral fins or "Tail fins", sometimes called strakes, continuous with the trailing edge of the main wing. This allowed the positioning of a rear control surface at the end of each fin.