North American T-6 trainer showing its split flaps Flaps may be fully extended for landing to give the aircraft a lower stall speed so the approach to landing can be flown more slowly, which also allows the aircraft to land in a shorter distance.
When in the extended position, it could be angled up to a negative angle of incidence so that the aircraft could be dived vertically without needing excessive trim changes.
In this region of high local airspeed, skin friction viscous force is very high and the boundary layer arriving at the slot on the upper wing has lost much of its total pressure or total mechanical energy due to this friction. The mixing of the upper surface boundary layer with air arriving through the slot re-energises the boundary layer which then remains attached to the upper surface of the wing to a higher angle of attack than if the slot were not there.
This high-speed flow then mixes with the boundary layer attached to the upper surface and delays boundary layer separation from the upper surface. When the flap's leading edge moves aft along the track, the triangle formed by the track, the shaft and the surface of the flap fixed at the pivot gets narrower and deeper, forcing the flap down.
It boosts the efficiency of even basic theoretical airfoils made up of a triangle and a circle overlapped to the equivalent of a conventional airfoil.
This increases the camber and thickness of the wing, which in turn increases lift and drag. At progressively higher angles of attack, the flow of air through the slot becomes increasingly significant, accelerating from the higher pressure region below the double slot flaps to the lower pressure region on top of the wing. It also adds a little to lift coefficient.
The thrust gate on the Boeing was provided by a single-slotted flap in between the inboard and outboard double-slotted flaps. Krueger flap A hinged flap which folds out from under the wing's leading edge while not forming a part of the leading edge of the wing when retracted. Gouge flap A type of split flap that slides backward along curved tracks that force the trailing edge downward, increasing chord and camber without affecting trim or requiring any additional mechanisms.
Winds across the line of flight, known as crosswinds, cause the windward side of the aircraft to generate more lift and drag, causing the aircraft to roll, yaw and pitch off its intended flight path, and as a result many light aircraft land with reduced flap settings in crosswinds.
Split flap[ edit ] The rear portion of the lower surface of the airfoil hinges downwards from the leading edge of the flap, while the upper surface stays immobile. Air from below the wing can accelerate through the slot towards double slot flaps low pressure region above the wing, and exit from the slot moving parallel to the upper wing surface.
It was named for racing car driver Dan Gurney who rediscovered it inand has since been used on some helicopters such as the Sikorsky SB to correct control problems without having to resort to a major redesign.
Blown flap A type of Boundary Layer Control System, blown flaps pass engine-generated air or double slot flaps over the flaps to increase lift beyond that attainable with mechanical flaps.
Flexible flap[ edit ] Also known as the FlexFoil. Some flaps increase the wing area and, for any given speed, this also increases the parasitic drag component of total drag. Thrust gates[ edit ] Thrust gates, or gaps, in the trailing edge flaps may be required to minimise interference between the engine flow and deployed flaps.
While thermallingflaps may be partially extended to reduce the stall speed so that the glider can be flown more slowly and thereby reduce the rate of sink, which lets the glider use the rising air of the thermal more efficiently, and to turn in a smaller circle to make best use of the core of the thermal. One way to reduce the cruise drag of slots is to make them able to be closed.
It may have a flexible gap seal at the transition between fixed and flexible airfoils.
Aerodynamically, slats work in the same way as fixed slots but slats can be retracted at higher speeds when they are not needed. The higher lift and drag associated with fully extended flaps allows a steeper and slower approach to the landing site, but imposes handling difficulties in aircraft with very low wing loading i.
The amount of flap used on takeoff is specific to each type of aircraft, and the manufacturer will suggest limits and may indicate the reduction in climb rate to be expected. This arrangement is known as leading edge slats. Pale lines indicate line of movement, and green indicates flap setting used during dive.
Therefore, for any given weight and airspeed, flaps increase the drag force.
The three orange pods are fairings streamlining the flap track mechanisms. Fairey was one of the few exponents of this design, which was used on the Fairey Firefly and Fairey Barracuda. Plain flap[ edit ] The rear portion of airfoil double slot flaps downwards on a simple hinge mounted at the front of the flap.
Types include the original internally blown flap which blows compressed air from the engine over the top of the flap, the externally blown flap, which blows engine exhaust over the upper and lower surfaces of the flap, and upper surface blowing which blows engine exhaust over the top of the wing and flap.
Slotted flap[ edit ] A gap between the flap and the wing forces high pressure air from below the wing over the flap helping the airflow remain attached to the flap, increasing lift compared to a split flap. No thrust gate is required in the continuous, single-slotted flap.
In contrast, the air passing through the slot has not experienced this high local airspeed or high skin friction, and its total pressure remains close to the free-stream value. Flaps increase the drag coefficient of an aircraft due to higher induced drag caused by the distorted spanwise lift distribution on the wing with flaps extended. Their primary purpose is to allow the aircraft to fly at a higher angle of attack before reaching the stalling angle.
The flaps two on each side, on the Airbus A lie directly above these. Short Brothers may have been the only company to use this type.
Late marks of the Supermarine Spitfire used a bead on the trailing edge of the split 9s blackjack, which functioned in a similar manner. Fowler flap[ edit ] A split flap that slides backwards, before hinging downward, thereby increasing first chord, then camber.
It was invented by Orville Wright and James M. Slats, in turn, are heavier and more complex than slots. Leading edge flap[ edit ] The entire leading edge of the wing rotates downward, effectively increasing camber and also slightly reducing chord.
The slotted flap was a result of research at Handley-Pagea variant of the slot that dates from the s, but wasn't widely used until much later. As a defining feature - distinguishing it from the Gouge Flap - it always provides a slot effect. Fairey-Youngman flap[ edit ] Drops down becoming a Junkers Flap before sliding aft and then rotating up or down. Invented by Otto Mader at Junkers in the late s, they were most often seen on the Junkers Ju 52 and the Junkers Ju 87 Stuka dive bomber, though the same wing control surface can be also be found on many modern ultralights, like the Denney Kitfox.
Jacobs inbut only became common in the s and was then quickly superseded. Extending the flaps also increases the drag coefficient of the aircraft. While testing was done in Britain and Germany before the Second World War and flight trials started, the first production aircraft with blown flaps wasn't until the Lockheed T2V SeaStar.
They were first used on the Martin prototype inand in production on the Lockheed Super Electra and are still in widespread use on modern aircraft, often with multiple slots. Interference in the go-around case while the flaps are still fully deployed can cause increased drag which must not compromise the climb gradient. The leading edge of the flap is mounted on a track, while a point at mid chord on the flap is connected via an arm to a pivot just above the track.
Control line model aircraft built for precision aerobatics competition usually have a type of maneuvering flap system that moves them in an opposing direction to the elevators, to assist in tightening the radius of a maneuver.
Furthermore, once the aircraft is on the ground, the flaps may decrease the effectiveness of the brakes since the wing is still generating lift and preventing the entire weight of the slot machine band wiki from resting on the tires, thus increasing stopping distance, particularly in wet or icy conditions.
This ensures the wing root stalls first and contributes to docile stall behaviour and maintaining aileron control throughout the stall. Gurney flap exaggerated for clarity. At high angles of attack the fastest airspeed relative to the airfoil is very close to the leading edge, on the upper surface.
Usually, the pilot will raise the flaps as soon as possible to prevent this from occurring. This reduces the balancing load required on the horizontal stabilizerwhich in turn reduces the trim drag associated with keeping the glider in longitudinal trim.
Flap tracks[ edit ] Extending flaps often run on guide tracks. This is because they contribute to drag compared to an unslotted wing.
Slots naturally exact a penalty on the aircraft in which they are used. In the absence of an inboard aileron, which provides a gap in many flap installations, double slot flaps modified flap section may be needed. Where these run outside the wing structure they may be faired in to streamline them and protect them from damage.
Some flaps use multiple slots to further boost the effect. Blown flap skipped as it is modified from any other type. The principle was discovered in the s, but was rarely used and was then forgotten. At full deflection, a split flaps acts much like a spoiler, adding significantly to drag coefficient.
A modern interpretation of wing warping, internal mechanical actuators bend a lattice that changes the airfoil shape.