Wing
- For some other uses of the word "wing" please see Wing (disambiguation).
A wing is a surface used to produce an aerodynamic force normal to the direction of motion by travelling in air or another gaseous medium. The first use of the word was for the foremost limbs of birds, but has been extended to include other animal limbs and man-made devices.
Use
The commonest use of wings is to fly by deflecting air downwards to produce lift, but upside-down wings are also commonly used as a way to produce downforce and hold objects to the ground (for example racing cars).
Artificial Wings
Terms used to describe aeroplane wings
- Leading edge: the front edge of the wing
- Trailing edge: the back edge of the wing
- Span: distance from wing tip to wing tip
- Chord: distance from wing leading edge to wing trailing edge, usually measured parallel to the long axis of the fuselage
- aspect ratio: ratio of span to standard mean chord
Design Features
Aeroplane 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 or slots
- Trailing-edge devices such as flaps
- Ailerons (usually near the wingtips) to provide roll control
- Spoilers on the upper surface to disrupt lift
Wing Types
- Dihedral wings, which have an angle between them, have inherent stability in roll. As the aircraft rolls, one wing generates more lift, rolling the aircraft back into position.
- Swept wings are good for fast aircraft. They present the wing at an angle to the airflow, so that the wing "sees" a slower airflow.
- Elliptical wings are theoretically optimum for efficiency at subsonic speeds.
- Delta wings have reasonable performance at subsonic and supersonic speeds.
- Waveriders are efficient supersonic wings.
- Rogallo wings are two hollow half-cones of fabric, one of the simplest wings to construct.
- Swing-wings (or variable geometry wings) are able to move in flight to give the benefits of dihedral and delta wing. Although they were originally proposed for the unbuilt Boeing 2707, they are currently only found on some military fighter aircraft such as the Panavia Tornado and General Dynamics F-111.
Science of Wings
At the simplest level, a wing produces lift by deflecting air downward, which propels the flying body upward with an equal and opposite force (see Newton's Third Law). Bernoulli's principle has traditionally been used to explain the functioning of a wing in terms of differing pressure above and below the wing, but this model can often be misleading or depend on false assumptions. See Coanda effect for an alternative explanation of how a wing produces lift.
The amount of lift produced by a wing increases with the angle of attack (the angle between the onset flow and the chord line) but this relationship ends once the stall angle is reached. At this angle the airflow starts to separate from the upper surface, and any further increase in angle of attack gives no more lift (it will in fact dramatically reduce) and gives a large increase in drag.
Wing design can be complex and is one of the principal applications of the science of aerodynamics.
- A helicopter uses a rotating wing with a varible pitch or angle to provide a directional force.
- The space shuttle uses its wings only for lift during its descent.
Structures with the same purpose as wings, but designed to operate in liquid media, are generally called fins, with hydrodynamics as the governing science.
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