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A laughing gull with its wingsextended in the gull wing profile

Several aircraft wing planform shapes:a swept wing KC-10 Extender (top)refuels a trapezoidal-wing F-22 Raptorfighter plane

The wing of a landing BMI AirbusA319-100. The slats at its leading edgeand the flaps at its trailing edge areextended.

WingFrom Wikipedia, the free encyclopedia

A wing is a type of fin with a surface that produces aerodynamic forcefor flight or propulsion through the atmosphere, or through anothergaseous or liquid fluid. As such, wings have an airfoil shape, astreamlined cross-sectional shape producing a useful lift to drag ratio.

The word "wing" from the Old Norse vængr[1] for many centuriesreferred mainly to the foremost limbs of birds (in addition to thearchitectural aisle.) But in recent centuries the word's meaning hasextended to include lift producing appendages of insects, bats,pterosaurs, boomerangs, some sail boats and aircraft, or the invertedairfoil on a race car that generates a downward force to increasetraction.

Various species of penguins and other flighted or flightless water birdssuch as auks, cormorants, guillemots, shearwaters, eider and scoterducks and diving petrels are avid swimmers, and use their wings topropel through water.[2]

A wing's aerodynamic quality is expressed as its lift-to-drag ratio. Thelift a wing generates at a given speed and angle of attack can be one totwo orders of magnitude greater than the total drag on the wing. A highlift-to-drag ratio requires a significantly smaller thrust to propel the wingsthrough the air at sufficient lift.

Contents

1 Aerodynamics of wings1.1 Devices to change the shape of a wing1.2 A common misconception1.3 Other examples

2 Design features3 See also4 References5 External links

Aerodynamics of wings

The design and analysis of the wings of aircraft is one of the principalapplications of the science of aerodynamics, which is a branch of fluidmechanics. The properties of the airflow around any moving object can -in principle - be found by solving the Navier-Stokes equations of fluiddynamics. However, except for simple geometries these equations arenotoriously difficult to solve.[3] Fortunately, simpler explanations can bedescribed.

For a wing to produce "lift", it must be oriented at a suitable angle ofattack relative to the flow of air past the wing. When this occurs thewing deflects the airflow downwards, "turning" the air as it passes thewing. Since the wing exerts a force on the air to change its direction, the air must exert a force on the wing,equal in size but opposite in direction. This force manifests itself as differing air pressures at different points onthe surface of the wing.[4][5][6]

A region of lower-than-normal air pressure is generated over the top surface of the wing, with a higher pressureexisting on the bottom of the wing. (See: airfoil) These air pressure differences can be either measured directlyusing instrumentation, or they can be calculated from the airspeed distribution using basic physical principles,including Bernoulli's Principle which relates changes in air speed to changes in air pressure.

The lower air pressure on the top of the wing generates a smaller downward force on the top of the wing than

Wing - Wikipedia, the free encyclopedia http://en.wikipedia.org/wiki/Wing

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The low pressure region over the wingof this A340 is clearly shown by thecondensation it causes in the humid air

Flaps (green) are used in variousconfigurations to increase the wingarea and to increase the lift. Inconjunction with spoilers (red), flapsmaximize drag and minimize liftduring the landing roll.

Internal mechanical construction of ageneric monospar wing. Black = solid,red = tube used for the spar, green =foam, wood, honeycomb, or sheetmetal used for the ribs. The leadingedge gives torsional stiffness. Thetrailing edge can either have a flexibleskin, which does not break under wingbending (birdlike,) or have a stiff skin(made of carbon fiber, aluminum alloy,or titanium, aircraft-like), which isprevented from buckling by span-wise"stringers."

the upward force generated by the higher air pressure on the bottom ofthe wing. Hence, a net upward force acts on the wing. This force iscalled the "lift" generated by the wing.

The different velocities of the air passing by the wing, the air pressuredifferences, the change in direction of the airflow, and the lift on thewing are intrinsically one phenomenon. It is, therefore, possible tocalculate lift from any of the other three. For example, the lift can becalculated from the pressure differences, or from different velocities ofthe air above and below the wing, or from the total momentum change ofthe deflected air. There are other approaches in fluid dynamics to solvingthese problems. All of these approaches will result in the same answers ifdone correctly. Given a particular wing and its velocity through the air,debates over which mathematical approach is the most convenient to usecan be misperceived by novices as differences of opinion about the basicprinciples of flight.

For a more detailed coverage see lift (force).

Devices to change the shape of a wing

Usually, aircraft wings have various devices, such as flaps or slats thatthe pilot uses to modify the shape and surface area of the wing to changeits operating characteristics in flight. In 1948, Francis Rogallo inventedthe fully limp flexible wing, which ushered new possibilities for aircraft.Near in time, Domina Jalbert invented flexible un-sparred ram-airairfoiled thick wings. These two new branches of wings have been sinceextensively studied and applied in new branches of aircraft, especiallyaltering the personal recreational aviation landscape.

A common misconception

A common misconception is that in order to generate lift it is essentialfor the wing to have a longer path on the topside compared with theunderside.[7] Wings with this shape are the norm in subsonic flight, butsymmetrically shaped wings (above and below) can generate lift by usinga positive angle of attack to deflect air downward. Symmetrical airfoilshave higher stalling speeds than cambered airfoils of the same wingarea[8] but are used in aerobatic aircraft as they provide practicalperformance whether the aircraft is upright or inverted. Another examplecomes from sailboats, where the sail is a thin membrane with nopath-length difference between one side and the other.[9]

For flight speeds near the speed of sound (transonic flight), airfoils withcomplex asymmetrical shapes are used to minimize the drastic increasein drag associated with airflow near the speed of sound.[10] Such airfoils,called supercritical airfoils, are flat on top and curved on the bottom.[11]

Other examples

The science of wings applies in other areas beyond conventionalfixed-wing aircraft, including:

Hang gliders, which use wings from fully flexible (paragliders,gliding parachutes) wings, flexible wings (framed sail wings), torigid wingsKites, which use a vast variety of wings.Flying model airplanesHelicopters, which use a rotating wing with a variable pitch angleto provide directional forcesThe NASA Space Shuttle, which uses its wings only to glide duringits descent to a runway. These types of aircraft are called spaceplanes.Some racing cars, especially Formula One cars, which use upside-down wings (or airfoils) to providegreater traction at high speeds


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Various trees such as maples havewinged seeds that enable them todisperse, some autorotating as theyfall, often catching the autumn wind asthey do so.

Sailboats, which use sails as vertical wings with variable fullnessand direction to move across water

Structures with the same purpose as wings, but designed for use in liquidmedia, are generally called fins or hydroplanes, with hydrodynamics asthe governing science, rather than aerodynamics. Applications of thesearise in craft such as hydrofoils and submarines. Sailboats and sailingships use both fins and wings.

Design features

Aircraft wings may feature some of the following:

A rounded leading edge cross-sectionA sharp trailing edge cross-sectionLeading-edge devices such as slats, slots, or extensionsTrailing-edge devices such as flaps or flaperons (combination offlaps and ailerons)Ailerons (usually near the wingtips) to roll the aircraft clockwiseor counterclockwise about its long axisSpoilers on the upper surface to disrupt the lift and to provideadditional traction to an aircraft that has just landed but is stillmoving.Vortex generators to help prevent flow separation in transonic flowWing fences to keep flow attached to the wing by stopping boundary layer separation from spreadingWinglets to keep wingtip vortices from increasing drag and decreasing liftDihedral, or a positive wing angle to the horizontal. This gives inherent stability in the roll direction.Anhedral, or a negative wing angle to the horizontal, has a destabilizing effectFolding wings allow more aircraft storage in the confined space of the hangar deck of an aircraft carrierVariable-sweep wing or "swing wings" that allow outstretched wings during low-speed flight (i.e., take-offand landing) and swept back wings for high-speed flight (including supersonic flight), such as in the F-111Aardvark, the F-14 Tomcat, the Panavia Tornado, the MiG-23, the MiG-27 and the B-1B Lancerwarplanes

See also

Flight

Natural world:

Bird flightFlight featherFlying and gliding animalsInsect flightList of soaring birdsSamara (winged seeds of trees)

Aviation:

FanWing and Flettner airplane (experimental wing types)Kite typesOrnithopter - Flapping-wing aircraft (research prototypes, simple toys and models)Otto LilienthalPlanformWing configurationWing suit

Sailing:

SailsForces on sails

References^ "Online Etymology Dictionary" (http://www.etymonline.com/index.php?term=wing). Etymonline.com. Retrieved1.


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2012-04-25.^ "Swimming" (http://www.stanford.edu/group/stanfordbirds/text/essays/Swimming.html). Stanford.edu. Retrieved2012-04-25.

2.

^ ">"Navier-Stokes Equations" (http://www.grc.nasa.gov/WWW/K-12/airplane/nseqs.html). Grc.nasa.gov.2012-04-16. Retrieved 2012-04-25.

3.

^ "...the effect of the wing is to give the air stream a downward velocity component. The reaction force of thedeflected air mass must then act on the wing to give it an equal and opposite upward component." In: Halliday,David; Resnick, Robert, Fundamentals of Physics 3rd Edition, John Wiley & Sons, p. 378

4.

^ "If the body is shaped, moved, or inclined in such a way as to produce a net deflection or turning of the flow, thelocal velocity is changed in magnitude, direction, or both. Changing the velocity creates a net force on the body""Lift from Flow Turning" (http://www.grc.nasa.gov/WWW/K-12/airplane/right2.html). NASA Glenn ResearchCenter. Retrieved 2011-06-29.

5.

^ "The cause of the aerodynamic lifting force is the downward acceleration of air by the airfoil..." Weltner, Klaus;Ingelman-Sundberg, Martin, Physics of Flight - reviewed (http://user.uni-frankfurt.de/~weltner/Flight/PHYSIC4.htm)

6.

^ http://www.grc.nasa.gov/WWW/k-12/airplane/wrong1.html7.^ E. V. Laitone, Wind tunnel tests of wings at Reynolds numbers below 70 000, Experiments in Fluids 23, 405(1997). doi:10.1007/s003480050128 (http://dx.doi.org/10.1007%2Fs003480050128)

8.

^ "...consider a sail that is nothing but a vertical wing (generating side-force to propel a yacht). ...it is obvious thatthe distance between the stagnation point and the trailing edge is more or less the same on both sides. This becomesexactly true in the absence of a mast—and clearly the presence of the mast is of no consequence in the generationof lift. Thus, the generation of lift does not require different distances around the upper and lower surfaces."Holger Babinsky How do Wings Work? Physics Education November 2003, PDF (http://iopscience.iop.org/0031-9120/38/6/001/pdf/pe3_6_001.pdf)

9.

^ John D. Anderson, Jr. Introduction to Flight 4th ed page 271.10.^ 'Supercritical wings have a flat-on-top "upside down" look.' NASA Dryden Flight Research Centerhttp://www.nasa.gov/centers/dryden/about/Organizations/Technology/Facts/TF-2004-13-DFRC.html

11.

External links

How Wings Work - Holger Babinsky Physics Education 2003 (http://www.iop.org/EJ/article/0031-9120/38/6/001/pe3_6_001.pdf)How Airplanes Fly: A Physical Description of Lift (http://www.aviation-history.com/theory/lift.htm)Demystifying the Science of Flight (http://www.npr.org/templates/story/story.php?storyId=3875411) -Audio segment on NPR's Talk of the Nation Science FridayNASA's explanations and simulations (http://www.grc.nasa.gov/WWW/K-12/airplane/short.html)Flight of the StyroHawk wing (https://www.youtube.com/watch?v=O4E6M2VGQyk)See How It Flies (http://www.av8n.com/how/htm/airfoils.html)

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