A wing is a type of fin that produces lift, while moving through air
or some other fluid. As such, wings have streamlined cross-sections
that are subject to aerodynamic forces and act as an 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.
Lifting structures used in water, include various foils, including
Hydrodynamics is the governing science, rather than
aerodynamics. Applications of underwater foils occur in hydroplanes,
sailboats and submarines.
1 Etymology and usage
2 In nature
3.1 Cross-sectional shape
4 Design features
6 Tensile structures
7 See also
9 External links
Etymology and usage
The word "wing" from the Old Norse vængr for many centuries
referred mainly to the foremost limbs of birds (in addition to the
architectural aisle). But in recent centuries the word's meaning has
extended to include lift producing appendages of insects, bats,
pterosaurs, boomerangs, some sail boats and aircraft, or the inverted
airfoil on a race car that generates a downward force to increase
In nature wings have evolved in dinosaurs, birds, mammals, fish,
reptiles and plants as means of locomotion. Various
species of penguins and other flighted or flightless water birds such
as auks, cormorants, guillemots, shearwaters, eider and scoter ducks
and diving petrels are avid swimmers, and use their wings to propel
Wing forms in nature
Winged tree seeds that cause autorotation in descent
A laughing gull, exhibiting the "gull wing" outline.
Bat in flight
Condensation in the low pressure region over the wing of an Airbus
A340, passing through humid air
Flaps (green) are used in various configurations to increase the wing
area and to increase the lift. In conjunction with spoilers (red),
flaps maximize drag and minimize lift during the landing roll.
Main article: Lift (force)
The design and analysis of the wings of aircraft is one of the
principal applications of the science of aerodynamics, which is a
branch of fluid mechanics. The properties of the airflow around any
moving object can – in principle – be found by solving the
Navier-Stokes equations of fluid dynamics. However, except for simple
geometries these equations are notoriously difficult to solve.
Fortunately, simpler explanations can be described.
For a wing to produce "lift", it must be oriented at a suitable angle
of attack relative to the flow of air past the wing. When this occurs
the wing deflects the airflow downwards, "turning" the air as it
passes the wing. 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 on the surface of the wing.
A region of lower-than-normal air pressure is generated over the top
surface of the wing, with a higher pressure on the bottom of the wing.
(See: airfoil) These air pressure differences can be either measured
directly using instrumentation, or 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
The lower air pressure on the top of the wing generates a smaller
downward force on the top of the wing than the upward force generated
by the higher air pressure on the bottom of the wing. Hence, a net
upward force acts on the wing. This force is called the "lift"
generated by the wing.
The different velocities of the air passing by the wing, the air
pressure differences, the change in direction of the airflow, and the
lift on the wing are intrinsically one phenomenon. It is, therefore,
possible to calculate lift from any of the other three. For example,
the lift can be calculated from the pressure differences, or from
different velocities of the air above and below the wing, or from the
total momentum change of the deflected air.
Fluid dynamics offers
other approaches to solving these problems—and all produce the same
answers if done correctly. Given a particular wing and its velocity
through the air, debates over which mathematical approach is the most
convenient to use can be mistaken by novices as differences of opinion
about the basic principles of flight.
Wings with an asymmetrical cross section are the norm in subsonic
flight. Wings with a symmetrical cross section can also generate lift
by using a positive angle of attack to deflect air downward.
Symmetrical airfoils have higher stalling speeds than cambered
airfoils of the same wing area but are used in aerobatic
aircraft as they provide practical performance
whether the aircraft is upright or inverted. Another example comes
from sailboats, where the sail is a thin membrane with no path-length
difference between one side and the other.
For flight speeds near the speed of sound (transonic flight), airfoils
with complex asymmetrical shapes are used to minimize the drastic
increase in drag associated with airflow near the speed of sound.
Such airfoils, called supercritical airfoils, are flat on top and
curved on the bottom.
The wing of a landing BMI
Airbus A319-100. The slats at its leading
edge and the flaps at its trailing edge are extended.
Aircraft wings may feature some of the following:
A rounded leading edge cross-section
A sharp trailing edge cross-section
Leading-edge devices such as slats, slots, or extensions
Trailing-edge devices such as flaps or flaperons (combination of flaps
Winglets to keep wingtip vortices from increasing drag and decreasing
Dihedral, or a positive wing angle to the horizontal, increases spiral
stability around the roll axis, whereas anhedral, or a negative wing
angle to the horizontal, decreases spiral stability.
Aircraft wings may have various devices, such as flaps or slats that
the pilot uses to modify the shape and surface area of the wing to
change its operating characteristics in flight.
Ailerons (usually near the wingtips) to roll the aircraft clockwise or
counterclockwise about its long axis
Spoilers on the upper surface to disrupt the lift and to provide
additional traction to an aircraft that has just landed but is still
Vortex generators to help prevent flow separation in transonic flow
Wing fences to keep flow attached to the wing by stopping boundary
layer separation from spreading roll direction.
Folding wings allow more aircraft storage in the confined space of the
hangar deck of an aircraft carrier
Variable-sweep wing or "swing wings" that allow outstretched wings
during low-speed flight (i.e., take-off and landing) and swept back
wings for high-speed flight (including supersonic flight), such as in
the F-111 Aardvark, the F-14 Tomcat, the Panavia Tornado, the MiG-23,
the MiG-27, the
Tu-160 and the
B-1B Lancer warplanes
Besides fixed-wing aircraft, applications for wing shapes
Hang gliders, which use wings ranging from fully flexible
(paragliders, gliding parachutes), flexible (framed sail wings), to
Kites, which use a variety of lifting surfaces
Flying model airplanes
Helicopters, which use a rotating wing with a variable pitch angle to
provide directional forces
Propellers, whose blades generate lift for propulsion.
NASA Space Shuttle, which uses its wings only to glide during its
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 provide greater traction at high speeds
Sailboats, which use sails as vertical wings with variable fullness
and direction to move across water
Francis Rogallo invented the fully limp flexible wing, which
ushered in new possibilities for aircraft. Near in time, Domina
Jalbert invented flexible un-sparred ram-air airfoiled thick wings.
These two new branches of wings have been since extensively studied
and applied in new branches of aircraft, especially altering the
personal recreational aviation landscape.
Flying and gliding animals
List of soaring birds
Samara (winged seeds of trees)
Flettner airplane (experimental wing types)
Flight dynamics (fixed-wing aircraft)
Ornithopter – Flapping-wing aircraft (research prototypes, simple
toys and models)
Forces on sails
^ "Online Etymology Dictionary". Etymonline.com. Retrieved
^ "Swimming". Stanford.edu. Retrieved 2012-04-25.
^ "Navier-Stokes Equations". Grc.nasa.gov. 2012-04-16. Retrieved
^ "...the effect of the wing is to give the air stream a downward
velocity component. The reaction force of the deflected 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
^ "If the body is shaped, moved, or inclined in such a way as to
produce a net deflection or turning of the flow, the local velocity is
changed in magnitude, direction, or both. Changing the velocity
creates a net force on the body" "Lift from Flow Turning".
Research Center. Retrieved 2011-06-29.
^ "The cause of the aerodynamic lifting force is the downward
acceleration of air by the airfoil..." Weltner, Klaus;
Flight – reviewed, archived
from the original on 2011-07-19
^ E. V. Laitone, Wind tunnel tests of wings at Reynolds numbers below
70 000, Experiments in Fluids 23, 405 (1997).
^ "...consider a sail that is nothing but a vertical wing (generating
side-force to propel a yacht). ...it is obvious that the distance
between the stagnation point and the trailing edge is more or less the
same on both sides. This becomes exactly true in the absence of a
mast—and clearly the presence of the mast is of no consequence in
the generation of 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
^ John D. Anderson, Jr. Introduction to
Flight 4th ed page 271.
^ 'Supercritical wings have a flat-on-top "upside down" look.' NASA
Flight Research Center
Wikimedia Commons has media related to Wings.
How Wings Work - Holger Babinsky
Physics Education 2003
How Airplanes Fly: A Physical Description of Lift
Demystifying the Science of
Flight – Audio segment on NPR's
the Nation Science Friday
NASA's explanations and simulations
Flight of the StyroHawk wing
See How It Flies
Fins, limbs and wings
Fin and flipper locomotion
Flying and gliding animals
Evolution of fish
Evolution of tetrapods
Evolution of birds
Origin of birds
Origin of avian flight
Evolution of cetaceans
Tradeoffs for locomotion in air and water