The wing configuration or planform of a fixed-wing aircraft (including both gliders and powered aeroplanes) is its arrangement of lifting and related surfaces.
Aircraft designs are often classified by their wing configuration. For example, the Supermarine Spitfire is a conventional low wing cantilever monoplane of straight elliptical planform with moderate aspect ratio and slight dihedral.
Many variations have been tried. Sometimes the distinction between them is blurred, for example the wings of many modern combat aircraft may be described either as cropped compound deltas with (forwards or backwards) swept trailing edge, or as sharply tapered swept wings with large leading edge root extensions (or LERX). Some are therefore duplicated here under more than one heading. This is particularly so for variable geometry and combined (closed) wing types.
Most of the configurations described here have flown (if only very briefly) on full-size aircraft. A few theoretical designs are also notable.
Note on terminology: Most fixed-wing aircraft have left hand and right hand wings in a symmetrical arrangement. Strictly, such a pair of wings is called a wing plane or just plane. However, in certain situations it is common to refer to a plane as a wing, as in "a biplane has two wings", or alternatively to refer to the whole thing as a wing, as in "a biplane wing has two planes". Where the meaning is clear, this article follows common usage, only being more precise where needed to avoid real ambiguity or incorrectness.
Number and position of main planes
Fixed-wing aircraft can have different numbers of wings:
Monoplane: one wing plane. Since the 1930s most aeroplanes have been monoplanes. The wing may be mounted at various positions relative to the fuselage: Low wing: mounted near or below the bottom of the fuselage. Mid wing: mounted approximately halfway up the fuselage. Shoulder wing: mounted on the upper part or "shoulder" of the fuselage, slightly below the top of the fuselage. A shoulder wing is sometimes considered a subtype of high wing.Taylor, J. (Ed.), Jayne's all the world's aircraft 1980–81, Jane's (1980)Green, W.; Warplanes of the second world war, Vol. 5, Flying boats, Macdonald (1962), p.131 High wing: mounted on the upper fuselage. When contrasted to the shoulder wing, applies to a wing mounted on a projection (such as the cabin roof) above the top of the main fuselage. Parasol wing: raised clear above the top of the fuselage, typically by cabane struts, pylon(s) or pedestal(s).
A fixed-wing aircraft may have more than one wing plane, stacked one above another: Biplane: two wing planes of similar size, stacked one above the other. The biplane is inherently lighter and stronger than a monoplane and was the most common configuration until the 1930s. The very first Wright Flyer I was a biplane. Unequal-span biplane: a biplane in which one wing (usually the lower) is shorter than the other, as on the Curtiss JN-4 Jenny of the First World War. Sesquiplane: literally "one-and-a-half planes" is a type of biplane in which the lower wing is significantly smaller than the upper wing, either in span or chord or both. The Nieuport 17 of World War I was notably successful. Inverted sesquiplane: has a significantly smaller upper wing. The Fiat CR.1 was in production for many years. Busemann biplane: a theoretical supersonic wing configuration, in which shock waves between the wing planes interfere to reduce their energy and wave drag.
Triplane: three planes stacked one above another. Triplanes such as the Fokker Dr.I enjoyed a brief period of popularity during the First World War due to their manoeuvrability, but were soon replaced by improved biplanes. Quadruplane: four planes stacked one above another. A small number of the Armstrong Whitworth F.K.10 were built in the First World War but never saw service. Multiplane: many planes, sometimes used to mean more than one or more than some arbitrary number. The term is occasionally applied to arrangements stacked in tandem as well as vertically. The 1907 Multiplane of Horatio Frederick Phillips flew successfully with two hundred wing foils. See also the tandem wing, below.
A staggered design has the upper wing slightly forward of the lower. Long thought to reduce the interference caused by the low pressure air over the lower wing mixing with the high pressure air under the upper wing; however the improvement is minimal and its primary benefit is to improve access to the fuselage. It is common on many successful biplanes and triplanes. Backwards stagger is also seen in a few examples such as the Beechcraft Staggerwing.
A tandem wing design has two wings, one behind the other: see Tailplanes and foreplanes below. Some early types had tandem stacks of multiple planes, such as the nine-wing Caproni Ca.60 flying boat with three triplane stacks in tandem.
A cruciform wing is a set of four individual wings arranged in the shape of a cross. The cross may take either of two forms: Wings equally spaced around the cross-section of the fuselage, lying in two planes at right angles, as on a typical missile. Wings lying together in a single horizontal plane about a vertical axis, as in the cruciform rotor wing or X-wing.
Support To support itself a wing has to be rigid and strong and consequently may be heavy. By adding external bracing, the weight can be greatly reduced. Originally such bracing was always present, but it causes a large amount of drag at higher speeds and has not been used for faster designs since the early 1930s.
The types are: Cantilevered: self-supporting. All the structure is buried under the aerodynamic skin, giving a clean appearance with low drag. Braced: the wings are supported by external structural members. Nearly all multi-plane designs are braced. Some monoplanes, especially early designs such as the Fokker Eindecker, are also braced to save weight. Braced wings are of two types: Strut-braced: one or more stiff struts help to support the wing, as on the Fokker D.VII. A strut may act in compression or tension at different points in the flight regime. Wire-braced: alone (as on the Boeing P-26 Peashooter) or, more usually, in addition to struts, tension wires also help to support the wing. Unlike a strut, a wire can act only in tension.
CantileverStrut-bracedWire-braced
A braced multiplane may have one or more "bays", which are the compartments created by adding interplane struts; the number of bays refers to one side of the aircraft's wing panels only. For example, the de Havilland Tiger Moth is a single-bay biplane where the Bristol F.2 Fighter is a two-bay biplane.Taylor, 1990. p. 76
Single-bay biplaneTwo-bay biplane
Closed wing: two wing planes are merged or joined structurally at or near the tips in some way. This stiffens the structure and can reduce aerodynamic losses at the tips. Variants include: Box wing: upper and lower planes are joined by a vertical fin between their tips. The first officially witnessed plane to take off and fly, the Santos-Dumont 14-bis, used this configuration. Tandem box wings have also been studied (see Joined wing description below). Annular box wing: A type of box wing whose vertical fins curve continuously, blending smoothly into the wing tips. An early example was the Blériot III, which featured two annular wings in tandem. Annular (cylindrical): the wing is shaped like a cylinder. The Coléoptère had concentric wing and fuselage. It took off and landed vertically, but never achieved transition to horizontal flight. Examples with the wing mounted on top of the fuselage have been proposed but never built. Annular (planar): the wing is shaped like a disc with a hole in it. A number of Lee-Richards annular monoplanes flew shortly before the First World War.Airliners.net, Lee Richards Annular, 2012, retrieved 31 March 2012 Joined wing: a tandem-wing layout in which the front low wing sweeps back and/or the rear high wing sweeps forwards such that they join at or near the tips to form a continuous surface in a hollow diamond or triangle shape.Henderson, William P. and Huffman, Jarrett K.; Aerodynamic characteristics of a tandem wing configuration of a Mach number of 0.30, NASA, October 1975. The Ligeti Stratos is a rare example.Marcel, Arthur; The Ligeti Stratos, ultralightaircraftaustralia.com, 2024. (retrieved 13 May 2022). Rhomboidal wing: a joined wing consisting of four surfaces in a diamond arrangement. The Edwards Rhomboidal biplane of 1911 had both wings in the same plane but failed to fly.Angelucco, E. and Matrciardi, P.; World Aircraft Origins-World War 1, Sampson Low, 1977
Box wingAnnular box wingCylindrical wingJoined wing
Flat annular wingRhomboidal wing
Wings can also be characterised as: Rigid: stiff enough to maintain the aerofoil profile in varying conditions of airflow. A rigid wing may have external bracing and/or a fabric covering. Flexible: The surface may be flexible, typically a thin membrane. Requires external bracing and/or wind pressure to maintain the aerofoil shape. Common types include the Rogallo wing, parafoil and most kites. An otherwise rigid structure may be designed to flex, either because it is inherently aeroelastic as in the aeroisoclinic wing, or because shape changes are actively introduced.
Rigid delta wingFlexible Rogallo wing
Planform The wing planform is the silhouette of the wing when viewed from above or below.
See also variable geometry types which vary the wing planform during flight.
Aspect ratio
The aspect ratio is the span divided by the mean or average chord.Kermode (1972), Chapter 3, p. 103. It is a measure of how long and slender the wing appears when seen from above or below.
Low aspect ratio: short and stubby wing. Structurally efficient, high instantaneous roll rate, low supersonic drag. They tend to be used on fighter aircraft, such as the Lockheed F-104 Starfighter, and on very high-speed aircraft including the North American X-15. Moderate aspect ratio: general-purpose wing, very widely used, for example on the Douglas DC-3 transport. High aspect ratio: long and slender wing. More efficient aerodynamically, having less induced drag at subsonic speeds. They tend to be used by high-altitude subsonic aircraft such as the Lockheed U-2 spy plane and by high-performance sailplanes such as the Glaser-Dirks DG-500.
Low aspect ratioModerate aspect ratioHigh aspect ratio
Most variable-geometry configurations vary the aspect ratio in some way, either deliberately or as a side effect.
Chord variation along span The wing chord may be varied along the span of the wing, for both structural and aerodynamic reasons.
Constant chord: parallel leading & trailing edges. Simplest to make, and common where low cost is important, such as on the Piper J-3 Cub but inefficient as the outer section generates little lift while adding both weight and drag. Sometimes known in North America as the Hershey Bar wing due to its similarity in shape to a popular chocolate bar.
Tapered: wing narrows towards the tip. Structurally and aerodynamically more efficient than a constant chord wing, and easier to make than the elliptical type. Trapezoidal: a tapered wing with straight leading and trailing edges: may be unswept or swept.Tom Benson; Wing Area, NASAIlan Kroo. AA241 Aircraft Design: Synthesis and Analysis Wing Geometry Definitions, , Stanford University.G. Dimitriadis; Aircraft Design Lecture 2: Aerodynamics, Université de Liège. The straight tapered wing is one of the most common wing planforms, as seen on the Messerschmitt Bf 109. Inverse or reverse tapered: wing is widest near the tip. Structurally inefficient, leading to high weight. Flown experimentally on the XF-91 Thunderceptor in an attempt to overcome the stall problems of swept wings.