Wing Configuration - Wing Support

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. 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.

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.

• Non planar wing or closed wing - two wings in different planes are joined structurally at or near the tips in some way. This may stiffen 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. Some Dunne biplanes were of this type. 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.
  • Joined wing - a tandem 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. The design has recently seen a revival of interest where it is referred to as a joined wing. The Ligeti Stratos is a rare example.

• Annular wing (planar)
  • Rhomboidal wing - an annular wing consisting of four surfaces in a diamond arrangement. The wing planform looks similar to the joined wing, however here the two wings are in the same plane. The Edwards Rhomboidal biplane of 1911 failed to fly. The Small Diameter Bomb, a smart guided bomb, has a rhomboidal wing.
  • Flat - the wing is shaped like a circular disc with a hole in it. A Lee-Richards type flew shortly before the First World War.

Wings can also be characterised as:

• Rigid - stiff enough to maintain the aerofoil profile in varying conditions of airflow.
• Flexible - usually a thin membrane. Requires external bracing or wind pressure to maintain the aerofoil shape. Common types include Rogallo wings and kites.