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". [1]
Double delta wing aircraft (Concorde, Tupolev Tu-144, Boeing 2707 and Lockheed L-2000 SST projects) 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. [2]
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", [3] sometimes called strakes, [4] continuous with the trailing edge of the main wing. This allowed the positioning of a rear control surface at the end of each fin. Together with the main and forward (canard) wing control surfaces, this effectively gave it a three-surface configuration.
Anti-spin leading edge strakes, or spin strakes, or antispin fillet [5] may be placed at the tailplane roots of generally aerobatic aircraft, such as the de Havilland Tiger Moth (British version), Scottish Aviation Bulldog, and de Havilland Canada DHC-1 Chipmunk. [6] Ventral or dorsal fins increasing the directional stability are also used as anti-spin devices.
Certain air-deployed munitions, particularly "dumb" or unguided 500-pound (230 kg) bombs, are often retrofitted with bolt-on strake sets. Designed as an open collar with strakes fitted to the outside face, these strake sets are used to alter and normalize the aerodynamics of the weapon, yielding greater accuracy. As most such munitions were manufactured with only tail-mounted stabilizer fins, the addition of longitudinal strakes proves a much cleaner flow of air around the weapon during its glide, reducing the tendency to yaw and improving terminal accuracy.[ citation needed ]
Strakes are also often found on "smart" or guided munitions as an aid to the guidance system. By stabilizing the slipstream of air traveling over the weapon, the actions of control surfaces are much more predictable and precise, again improving the accuracy of the weapon.[ citation needed ]
A wing is a type of fin that produces lift while moving through air or some other fluid. Accordingly, wings have streamlined cross-sections that are subject to aerodynamic forces and act as airfoils. A wing's aerodynamic efficiency is expressed as its lift-to-drag ratio. The lift a wing generates at a given speed and angle of attack can be one to two orders of magnitude greater than the total drag on the wing. A high lift-to-drag ratio requires a significantly smaller thrust to propel the wings through the air at sufficient lift.
In fluid dynamics, a stall is a reduction in the lift coefficient generated by a foil as angle of attack exceeds its critical value. The critical angle of attack is typically about 15°, but it may vary significantly depending on the fluid, foil – including its shape, size, and finish – and Reynolds number.
A delta wing is a wing shaped in the form of a triangle. It is named for its similarity in shape to the Greek uppercase letter delta (Δ).
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.
A vortex generator (VG) is an aerodynamic device, consisting of a small vane usually attached to a lifting surface or a rotor blade of a wind turbine. VGs may also be attached to some part of an aerodynamic vehicle such as an aircraft fuselage or a car. When the airfoil or the body is in motion relative to the air, the VG creates a vortex, which, by removing some part of the slow-moving boundary layer in contact with the airfoil surface, delays local flow separation and aerodynamic stalling, thereby improving the effectiveness of wings and control surfaces, such as flaps, elevators, ailerons, and rudders.
The Lockheed L-2000 was Lockheed Corporation's entry in a government-funded competition to build the United States' first supersonic airliner in the 1960s. The L-2000 lost the contract to the Boeing 2707, but that competing design was ultimately canceled for political, environmental and economic reasons.
A T-tail is an empennage configuration in which the tailplane of an aircraft is mounted to the top of the fin. The arrangement looks like the capital letter T, hence the name. The T-tail differs from the standard configuration in which the tailplane is mounted to the fuselage at the base of the fin.
In aircraft design and aerospace engineering, a high-lift device is a component or mechanism on an aircraft's wing that increases the amount of lift produced by the wing. The device may be a fixed component, or a movable mechanism which is deployed when required. Common movable high-lift devices include wing flaps and slats. Fixed devices include leading-edge slots, leading edge root extensions, and boundary layer control systems.
In aeronautical and naval engineering, pusher configuration is the term used to describe a drivetrain of air- or watercraft with propulsion device(s) after the engine(s). This is in contrast to the more conventional tractor configuration, which places them in front.
An aircraft fairing is a structure whose primary function is to produce a smooth outline and reduce drag.
A leading-edge cuff is a fixed aerodynamic wing device employed on fixed-wing aircraft to improve the stall and spin characteristics. Cuffs may be either factory-designed or an after-market add-on modification.
A vertical stabilizer or tail fin is the static part of the vertical tail of an aircraft. The term is commonly applied to the assembly of both this fixed surface and one or more movable rudders hinged to it. Their role is to provide control, stability and trim in yaw. It is part of the aircraft empennage, specifically of its stabilizers.
An aircraft stabilizer is an aerodynamic surface, typically including one or more movable control surfaces, that provides longitudinal (pitch) and/or directional (yaw) stability and control. A stabilizer can feature a fixed or adjustable structure on which any movable control surfaces are hinged, or it can itself be a fully movable surface such as a stabilator. Depending on the context, "stabilizer" may sometimes describe only the front part of the overall surface.
Vortex lift is that portion of lift due to the action of leading edge vortices. It is generated by wings with highly sweptback, sharp, leading edges or highly-swept wing-root extensions added to a wing of moderate sweep. It is sometimes known as non-linear lift due to its rapid increase with angle of attack and controlled separation lift, to distinguish it from conventional lift which occurs with attached flow.
The Handley Page HP.115 was an experimental delta wing aircraft designed and produced by the British aircraft manufacturer Handley Page. It was built to test the low-speed handling characteristics to be expected from the slender delta configuration anticipated for a future supersonic airliner.
In aeronautics, a canard is a wing configuration in which a small forewing or foreplane is placed forward of the main wing of a fixed-wing aircraft or a weapon. The term "canard" may be used to describe the aircraft itself, the wing configuration, or the foreplane. Canard wings are also extensively used in guided missiles and smart bombs.
In aeronautics, a tailless aircraft is an aircraft with no other horizontal aerodynamic surface besides its main wing. It may still have a fuselage, vertical tail fin, and/or vertical rudder.
The Focke-Wulf F 19 Ente was a experimentalcanard aircraft designed and produced by the German aircraft manufacturer Focke-Wulf.
The wing configuration of a fixed-wing aircraft is its arrangement of lifting and related surfaces.
In aircraft design, a chine is a longitudinal line of sharp change in the cross-section profile of the fuselage or similar body. The term chine originates in boatbuilding, where it applies to a sharp profile change in the hull of a boat. In a flying boat hull or floatplane float, the longitudinal line of sharp change in cross-section where the bottom plane meets the sidewall is an example of a chine.