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31-495: Slats are high-lift devices typically used on aircraft intended to operate within a wide range of speeds. Trailing-edge flap systems running along the trailing edge of the wing are common on all aircraft. Types include: The chord of the slat is typically only a few percent of the wing chord. The slats may extend over the outer third of the wing, or they may cover the entire leading edge . Many early aerodynamicists, including Ludwig Prandtl , believed that slats work by inducing

62-422: 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. The size and lifting capacity of a fixed wing is chosen as a compromise between differing requirements. For example, a larger wing will provide more lift and reduce

93-421: A high energy stream to the flow of the main airfoil , thus re-energizing its boundary layer and delaying stall. In reality, the slat does not give the air in the slot a high velocity (it actually reduces its velocity) and also it cannot be called high-energy air since all the air outside the actual boundary layers has the same total heat . The actual effects of the slat are: The slat has a counterpart found in

124-463: A leading edge extension (LEX). A LERX typically consist of a small triangular fillet attached to the wing leading edge root and to the fuselage. In normal flight the LERX generates little lift. At higher angles of attack, however, it generates a vortex that is positioned to lie on the upper surface of the main wing. The swirling action of the vortex increases the speed of airflow over the wing, so reducing

155-453: A mechanism that ejects air backwards over a specially designed airfoil to create lift through the Coandă effect . The Blackburn Buccaneer had a sophisticated boundary layer control (BLC) system which involved compressor air blown onto the wings and tailplane to reduce the stalling speed and facilitate operations from smaller aircraft carriers. Another approach is to use the airflow from

186-438: A patent challenge, they reached an ownership agreement with Lachmann. That year, an Airco DH.9 was fitted with slats and test flown. Later, an Airco DH.9A was modified as a monoplane with a large wing fitted with full-span leading edge slats and trailing-edge ailerons (i.e. what would later be called trailing-edge flaps) that could be deployed in conjunction with the leading-edge slats to test improved low-speed performance. This

217-410: A wing surface can change shape in flight to deflect air flow. The X-53 Active Aeroelastic Wing is a NASA effort. The adaptive compliant wing is a military and commercial effort. High-lift device 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

248-414: Is the gap between the slat and the wing. The slat may be fixed in position, with a slot permanently in place behind it, or it may be retractable so that the slot is closed when not required. If it is fixed, then it may appear as a normal part of the leading edge of a wing, with the slot buried in the wing surface immediately behind it. A slat or slot may be either full-span, or may be placed on only part of

279-508: The University of Miami . For a hybrid-electric regional aircraft based on the ATR 72 with the same wing area, size and weight, CFJ improves its cruise lift coefficient for a higher wing loading , allowing more fuel and batteries for longer range. Flaperon A flaperon (a portmanteau of flap and aileron ) on an aircraft's wing is a type of control surface that combines

310-404: The roll or bank of an aircraft, as do conventional ailerons, both flaperons can be lowered together to reduce stall speed, similarly to a set of flaps. On a plane with flaperons, the pilot still has the standard separate controls for ailerons and flaps, but the flap control also varies the flaperon's range of movement. A mechanical device called a "mixer" is used to combine the pilot's input into

341-546: The 1930s automatic slats had been developed, which opened or closed as needed according to the flight conditions. Typically they were operated by airflow pressure against the slat to close it, and small springs to open it at slower speeds when the dynamic pressure reduced, for example when the speed fell or the airflow reached a predetermined angle-of-attack on the wing. Modern systems, like modern flaps, can be more complex and are typically deployed hydraulically or with servos. Powered high-lift systems generally use airflow from

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372-522: The German patent office at first rejected it, as the office did not believe the possibility of postponing the stall by dividing the wing. Independently of Lachmann, Handley Page Ltd in Great Britain also developed the slotted wing as a way to postpone the stall by delaying separation of the flow from the upper surface of the wing at high angles of attack, and applied for a patent in 1919; to avoid

403-449: The aerodynamic purpose with the advantages of less: mass, cost, drag, inertia (for faster, stronger control response), complexity (mechanically simpler, fewer moving parts or surfaces, less maintenance), and radar cross-section for stealth . These may be used in many unmanned aerial vehicles (UAVs) and 6th generation fighter aircraft . One promising approach that could rival slats are flexible wings. In flexible wings, much or all of

434-530: The aircraft to takeoff into a light wind in less than 45 m (150 ft), and land in 18 m (60 ft). Aircraft designed by the Messerschmitt company employed automatic, spring-loaded leading-edge slats as a general rule, except for the Alexander Lippisch -designed Messerschmitt Me 163B Komet rocket fighter, which instead used fixed slots built integrally with, and just behind,

465-438: The distance and speeds required for takeoff and landing, but will increase drag, which reduces performance during the cruising portion of flight. Modern passenger jet wing designs are optimized for speed and efficiency during the cruise portion of flight, since this is where the aircraft spends the vast majority of its flight time. High-lift devices compensate for this design trade-off by adding lift at takeoff and landing, reducing

496-430: The engine to shape the flow of air over the wing, replacing or modifying the action of the flaps. Blown flaps take " bleed air " from the jet engine 's compressor or engine exhaust and blow it over the rear upper surface of the wing and flap, re-energising the boundary layer and allowing the airflow to remain attached at higher angles of attack. A more advanced version of the blown flap is the circulation control wing ,

527-516: The engines directly, by placing a flap so that it deploys into the path of the exhaust. Such flaps require greater strength due to the power of modern engines and also greater heat resistance to the hot exhaust, but the effect on lift can be significant. Examples include the C-17 Globemaster III . More common on modern fighter aircraft but also seen on some civil types, is the leading-edge root extension (LERX), sometimes called just

558-474: The flaperons. While the use of flaperons rather than ailerons and flaps might seem to be a simplification, some complexity remains through the intricacies of the mixer. Some aircraft, such as the Denney Kitfox , suspend the flaperons below the wing (rather in the manner of slotted flaps ) to provide undisturbed airflow at high angles of attack or low airspeeds. When the flaperon surface is hinged below

589-482: The functions of both flaps and ailerons. Some smaller kitplanes have flaperons for reasons of simplicity of manufacture, while some large commercial aircraft such as the Boeing 747 , 767 , 777 , and 787 may have a flaperon between the flaps and aileron. The 787 has a configuration known as a SpoileFlaperon that combines the action of spoilers , flaps and ailerons into one control surface. In addition to controlling

620-767: The latest fighter aircraft . These research approaches include flexible wings and fluidics: In flexible wings, much or all of a wing surface can change shape in flight to deflect air flow. The X-53 Active Aeroelastic Wing is a NASA effort. The Adaptive Compliant Wing is a military and commercial effort. This may be seen as a return to the wing warping used and patented by the Wright brothers . In fluidics , forces in vehicles occur via circulation control, in which larger, more complex mechanical parts are replaced by smaller simpler fluidic systems (slots which emit air flows), where larger forces in fluids are diverted by smaller jets or flows of fluid intermittently, to change

651-424: The massive lift required during takeoff. Another common high-lift device is the slat, a small aerofoil shaped device attached just in front of the wing leading edge. The slat re-directs the airflow at the front of the wing, allowing it to flow more smoothly over the upper surface when at a high angle of attack . This allows the wing to be operated effectively at the higher angles required to produce more lift. A slot

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682-408: The pressure and providing greater lift. LERX systems are notable for the potentially large angles in which they are effective. A Co-Flow Jet (CFJ) wing has an upper surface with an injection slot after the leading edge and a suction slot before the trailing edge, to augment lift, increase the stall margin and reduce drag. CFJ is promoted by the mechanical and aerospace engineering department of

713-407: The speed and distance required to safely land the aircraft, and allowing the use of a more efficient wing in flight. The high-lift devices on the Boeing 747-400 , for example, increase the wing area by 21% and increase the lift generated by 90%. The most common high-lift device is the flap, a movable portion of the wing that can be lowered to produce extra lift. When a flap is lowered this re-shapes

744-748: The trailing edge of a wing, they are sometimes named "Junkers flaperons", from the doppelflügel (lit., "double wing") type of trailing edge surfaces used on a number of Junkers aircraft of the 1930s, such as the Junkers Ju 52 airliner, and the iconic Junkers Ju 87 Stuka World War II dive bomber . Research seeks to coordinate the functions of aircraft flight control surfaces (ailerons, elevators , elevons , flaps, and flaperons) so as to reduce weight, cost, drag, and inertia , and thereby achieve improved control response, reduced complexity, and reduced radar visibility for stealth purposes. Beneficiaries of such research might include drones (UAVs) and

775-621: The upper surface remains either fixed to the wing or moves independently. Travelling flaps also extend backwards, to increase the wing chord when deployed, increasing the wing area to help produce yet more lift. These began to appear just before World War II due to the efforts of many different individuals and organizations in the 1920s and 30s. Slotted flaps comprise several separate small airfoils which separate apart, hinge and even slide past each other when deployed. Such complex flap arrangements are found on many modern aircraft. Large modern airliners make use of triple-slotted flaps to produce

806-409: The wing (usually outboard), depending on how the lift characteristics need to be modified for good low speed control. Slots and slats are sometimes used just for the section in front of the ailerons, ensuring that when the rest of the wing stalls, the ailerons remain usable. The first slats were developed by Gustav Lachmann in 1918 and simultaneously by Handley-Page who received a patent in 1919. By

837-456: The wing panel's outer leading edges. Post-World War II, slats have also been used on larger aircraft and generally operated by hydraulics or electricity . The A-4 Skyhawk slats were spring loaded and deployed by the air load below certain speeds. Several technology research and development efforts exist to integrate the functions of flight control systems such as ailerons , elevators , elevons , flaps , and flaperons into wings to perform

868-430: The wing section to give it more camber . Flaps are usually located on the trailing edge of a wing, while leading edge flaps are used occasionally. There are many kinds of trailing-edge flap. Simple hinged flaps came into common use in the 1930s, along with the arrival of the modern fast monoplane which had higher landing and takeoff speeds than the old biplanes. In the split flap, the lower surface hinges downwards while

899-588: The wing, a design that was used on a number of STOL aircraft. During World War II, German aircraft commonly fitted a more advanced version of the slat that reduced drag by being pushed back flush against the leading edge of the wing by air pressure , popping out when the angle of attack increased to a critical angle. Notable slats of that time belonged to the German Fieseler Fi 156 Storch . These were similar in design to retractable slats, but were fixed and non-retractable. This design feature allowed

930-532: The wings of some birds, the alula , a feather or group of feathers which the bird can extend under control of its "thumb". Slats were first developed by Gustav Lachmann in 1918. The stall-related crash in August 1917 of a Rumpler C aeroplane prompted Lachmann to develop the idea, and a small wooden model was built in 1917 in Cologne . In Germany in 1918 Lachmann presented a patent for leading-edge slats. However,

961-597: Was later known as the Handley Page H.P.20 Several years later, having subsequently taken employment at the Handley-Page aircraft company, Lachmann was responsible for a number of aircraft designs, including the Handley Page Hampden . Licensing the design became one of the company's major sources of income in the 1920s. The original designs were in the form of a fixed slot near the leading edge of

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