Slat (aircraft)
   HOME

TheInfoList



OR:

Slats are
aerodynamic Aerodynamics, from grc, ἀήρ ''aero'' (air) + grc, δυναμική (dynamics), is the study of the motion of air, particularly when affected by a solid object, such as an airplane wing. It involves topics covered in the field of fluid dyn ...
surfaces on the leading edge of the
wing 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 e ...
of a fixed-wing aircraft which, when deployed, allow the wing to operate at a higher angle of attack. A higher coefficient of lift is produced as a result of angle of attack and speed, so by deploying slats an aircraft can fly at slower speeds, or take off and land in shorter distances. They are used during takeoff and landing or while performing low speed maneuvers which may take the aircraft close to a stall, they are retracted in normal flight to minimize drag. Slats are one
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 a fixed component, or a movable mechanism which is deplo ...
used on high speed turbojet aircraft, trailing edge
flap Flap may refer to: Arts, entertainment, and media * ''Flap'' (film), a 1970 American film * Flap, a boss character in the arcade game ''Gaiapolis'' * Flap, a minor character in the film '' Little Nemo: Adventures in Slumberland'' Biology and he ...
systems running along the trailing edge of the wing are common on all aircraft.


Types

Types include: ;Automatic: The spring-loaded slat lies flush with the wing leading edge, held in place by the force of the air acting on them. As the aircraft slows down, the aerodynamic force is reduced and the springs extend the slats. Sometimes referred to as Handley-Page slats. ;Fixed: The slat is permanently extended. This is sometimes used on specialist low-speed aircraft (these are referred to as slots) or when simplicity takes precedence over speed. ;Powered: The slat extension can be controlled by the pilot. This is commonly used on airliners.


Operation

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 The leading edge of an airfoil surface such as a wing is its foremost edge and is therefore the part which first meets the oncoming air.Crane, Dale: ''Dictionary of Aeronautical Terms, third edition'', page 305. Aviation Supplies & Academics, ...
. Many early aerodynamicists, including
Ludwig Prandtl Ludwig Prandtl (4 February 1875 – 15 August 1953) was a German fluid dynamicist, physicist and aerospace scientist. He was a pioneer in the development of rigorous systematic mathematical analyses which he used for underlying the science of ...
, believed that slats work by inducing a high energy stream to the flow of the main airfoil, thus re-energizing its
boundary layer In physics and fluid mechanics, a boundary layer is the thin layer of fluid in the immediate vicinity of a bounding surface formed by the fluid flowing along the surface. The fluid's interaction with the wall induces a no-slip boundary cond ...
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:High-Lift Aerodynamics, by A. M. O. Smith, McDonnell Douglas Corporation, Long Beach, June 1975
;The slat effect: The velocities at the leading edge of the downstream element (main airfoil) are reduced due to the circulation of the upstream element (slat) thus reducing the pressure peaks of the downstream element. ;The circulation effect: The circulation of the downstream element increases the circulation of the upstream element thus improving its aerodynamic performance. ;The dumping effect: The discharge velocity at the trailing edge of the slat is increased due to the circulation of the main airfoil thus alleviating separation problems or increasing lift. ;Off the surface pressure recovery: The deceleration of the slat wake occurs in an efficient manner, out of contact with a wall. ;Fresh boundary layer effect: Each new element starts out with a fresh
boundary layer In physics and fluid mechanics, a boundary layer is the thin layer of fluid in the immediate vicinity of a bounding surface formed by the fluid flowing along the surface. The fluid's interaction with the wall induces a no-slip boundary cond ...
at its
leading edge The leading edge of an airfoil surface such as a wing is its foremost edge and is therefore the part which first meets the oncoming air.Crane, Dale: ''Dictionary of Aeronautical Terms, third edition'', page 305. Aviation Supplies & Academics, ...
. Thin boundary layers can withstand stronger adverse
gradient In vector calculus, the gradient of a scalar-valued differentiable function of several variables is the vector field (or vector-valued function) \nabla f whose value at a point p is the "direction and rate of fastest increase". If the gr ...
s than thick ones. The slat has a counterpart found in the wings of some birds, the
alula The alula , or bastard wing, (plural ''alulae'') is a small projection on the anterior edge of the wing of modern birds and a few non-avian dinosaurs. The word is Latin and means "winglet"; it is the diminutive of ''ala'', meaning "wing". The al ...
, a feather or group of feathers which the bird can extend under control of its "thumb".


History

Slats were first developed by
Gustav Lachmann Gustav Victor Lachmann (3 February 1896 – 30 May 1966) was a German aeronautical engineer who spent most of his professional life working for the British aircraft company Handley Page. He was, with Frederick Handley Page, the co-inventor of the ...
in 1918. The stall-related crash in August 1917 of a
Rumpler Rumpler-Luftfahrzeugbau GmbH, Rumpler-Werke, usually known simply as Rumpler was a German aircraft and automobile manufacturer founded in Berlin by Austrian engineer Edmund Rumpler in 1909 as Rumpler Luftfahrzeugbau.Gunston 1993, p.259 The fir ...
C aeroplane prompted Lachmann to develop the idea and a small wooden model was built in 1917 in
Cologne Cologne ( ; german: Köln ; ksh, Kölle ) is the largest city of the German western state of North Rhine-Westphalia (NRW) and the fourth-most populous city of Germany with 1.1 million inhabitants in the city proper and 3.6 millio ...
. In Germany in 1918 Lachmann presented a patent for leading-edge slats. However, 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 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 The Airco DH.9A was a British single-engined light bomber designed and first used shortly before the end of the First World War. It was a development of the unsuccessful Airco DH.9 bomber, featuring a strengthened structure and, crucially, repla ...
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 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 The Handley Page HP.52 Hampden is a British twin-engine medium bomber that was operated by the Royal Air Force (RAF). It was part of the trio of large twin-engine bombers procured for the RAF, joining the Armstrong Whitworth Whitley and Vickers ...
. 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 the wing, a design that was used on a number of
STOL A short takeoff and landing (STOL) aircraft is a conventional fixed-wing aircraft that has short runway requirements for takeoff and landing. Many STOL-designed aircraft also feature various arrangements for use on airstrips with harsh conditio ...
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 Atmospheric pressure, also known as barometric pressure (after the barometer), is the pressure within the atmosphere of Earth. The standard atmosphere (symbol: atm) is a unit of pressure defined as , which is equivalent to 1013.25 millibars ...
, popping out when the angle of attack increased to a critical angle. Notable slats of that time belonged to the German
Fieseler Fi 156 The Fieseler Fi 156 ''Storch'' (, "stork") was a German liaison aircraft built by Fieseler before and during World War II. Production continued in other countries into the 1950s for the private market. It was notable for its excellent short fie ...
''Storch''. These were similar in design to retractable slats, but were fixed and non-retractable. This design feature allowed the aircraft to take-off 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, the wing panel's outer leading edges. Post-World War II, slats have also been used on larger aircraft and generally operated by
hydraulics Hydraulics (from Greek: Υδραυλική) is a technology and applied science using engineering, chemistry, and other sciences involving the mechanical properties and use of liquids. At a very basic level, hydraulics is the liquid counte ...
or
electricity Electricity is the set of physical phenomena associated with the presence and motion of matter that has a property of electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as describ ...
.


Research

Several technology research and development efforts exist to integrate the functions of flight control systems such as ailerons,
elevators An elevator or lift is a cable-assisted, hydraulic cylinder-assisted, or roller-track assisted machine that vertically transports people or freight between floors, levels, or decks of a building, vessel, or other structure. They are ...
,
elevon Elevons or tailerons are aircraft control surfaces that combine the functions of the elevator (used for pitch control) and the aileron (used for roll control), hence the name. They are frequently used on tailless aircraft such as flying wings. A ...
s,
flap Flap may refer to: Arts, entertainment, and media * ''Flap'' (film), a 1970 American film * Flap, a boss character in the arcade game ''Gaiapolis'' * Flap, a minor character in the film '' Little Nemo: Adventures in Slumberland'' Biology and he ...
s, and
flaperon A flaperon (a portmanteau of flap and aileron) on an aircraft's wing is a type of control surface that combines the functions of both flaps and ailerons. Some smaller kitplanes have flaperons for reasons of simplicity of manufacture, while ...
s into wings to perform the aerodynamic purpose with the advantages of less: mass, cost, drag,
inertia Inertia is the idea that an object will continue its current motion until some force causes its speed or direction to change. The term is properly understood as shorthand for "the principle of inertia" as described by Newton in his first law ...
(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 vehicle An unmanned aerial vehicle (UAV), commonly known as a drone, is an aircraft without any human pilot, crew, or passengers on board. UAVs are a component of an unmanned aircraft system (UAS), which includes adding a ground-based controll ...
s (UAVs) and 6th generation fighter aircraft. One promising approach that could rival slats are flexible wings. 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 The X-53 Active Aeroelastic Wing (AAW) development program is a completed American research project that was undertaken jointly by the Air Force Research Laboratory (AFRL), Boeing Phantom Works and NASA's Dryden Flight Research Center, where t ...
is a
NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeeding t ...
effort. The
adaptive compliant wing An adaptive compliant wing is a wing which is flexible enough for aspects of its shape to be changed in flight. Flexible wings have a number of benefits. Conventional flight control mechanisms operate using hinges, resulting in disruptions to the ...
is a military and commercial effort.


See also

*
Leading-edge droop flap The leading-edge droop flap is a device on the leading edge of aircraft wings designed to improve airflow at high pitch angles (high angle of attack). The droop flap is similar to the leading-edge slat and the Krueger flap, but with the differen ...
* Flap (aeronautics) *
Flight control surfaces Aircraft flight control surfaces are aerodynamic devices allowing a pilot to adjust and control the aircraft's flight attitude. Development of an effective set of flight control surfaces was a critical advance in the development of aircraft. Ea ...
* Krueger flap *
Leading-edge slot A leading-edge slot is a fixed aerodynamic feature of the wing of some aircraft to reduce the stall speed and promote good low-speed handling qualities. A leading-edge slot is a spanwise gap in each wing, allowing air to flow from below the wing ...


References


External links

{{Aircraft components Aircraft wing design Aircraft controls