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A 'biplane' is a fixed-wing aircraft with two main wings of similar spans, normally one mounted above, and the other level with the underside of the fuselage. The first powered heavier-than-air aircraft, the Wright brothers' Wright Flyer, used a biplane design, as did most airplanes in the early years of aviation. While a biplane wing structure has several advantages it inevitably produces much more drag than a similar monoplane wing. Improved structural techniques and materials, and the need for greater speed, effectively made the biplane configuration obsolete for most purposes by the late 1930s.

Contents

Aviation

The biplane in avian evolution

References

See also

Trivia

External links

Aviation

In a biplane aircraft, two wings are placed one above the other. Both provide lift. Almost all biplanes also have a third horizontal surface, the tailplane, to control the pitch, or angle of attack of the aircraft. Either or both of the main wings can support flaps or ailerons to assist lateral and speed control. Often there is bracing in the form of wires and slender struts positioned symmetrically on either side of the fuselage. These connect the upper and lower wings into a strong box structure, which is inherently stronger and lighter in weight than an equivalent monoplane. Aircraft built with two main wings (or three in a triplane) can usually lift more than can a similarly sized monoplane of similar wing-span. Another advantage of biplane wings is that a given wing area requires a shorter wing span, which tends to afford greater maneuverability.
On the other hand there are many disadvantages to the configuration. Each wing negatively interferes with the aerodynamics of the other. For a given wing area the biplane produces more drag and less lift than a monoplane, but this effect can be reduced by placing one wing forward of the other. Placing one wing forward of the other is known as stagger. Forward stagger (where the upper wing is further forward) is most common, but backward stagger has also been used, notably in Beechcraft Staggerwing. Excessive amounts of stagger distort the box girder effect of the wing - and this tends to reduce the structural benefits of the biplane layout.
Biplanes were most successful in the early days of aviation when the all wing structures (including those of monoplanes) needed to be strengthened by external bracing wires and struts. The inherent strength of the biplane configuration in this situation was decisive, as early monoplanes tended to suffer from overly flexible wings, resulting in poor lateral control, and a greater risk of wing failure. Once the need for external bracing was removed by the widespread adoption of improved structural materials and techniques monoplanes quickly superseded biplanes in aviation. Modern biplane designs now exist only in specialist niche roles and markets such as aerobatics and agricultural aircraft.


Variations on the biplane include the 'sesquiplane', where one wing (usually the lower) is significantly smaller than the other, either in span, chord, or both. On occasion, the lower wing was only large enough to support the bracing struts for the upper wing. The name means "one-and-a-half wings". Another (aerodynamically quite distinct) variation is the 'tandem wing biplane', which is an aircraft with one wing in front of the other (i.e. a wing in the nose and a wing in the tail).
The vast majority of biplane designs have been fitted with reciprocating engines of comparatively low power; exceptions include the Antonov An-3 and WSK-Mielec M-15 Belphegor, fitted with turboprop and turbofan engines, respectively. Some older biplane designs, such as the Grumman Ag Cat and the aforementioned An-2 (in the form of the An-3) are available in upgraded versions with turboprop engines.
Famous biplanes include the Sopwith Camel, Avro Tutor, Antonov An-2, Beechcraft Staggerwing, Boeing Stearman, Bristol Bulldog, Curtiss JN-4, de Havilland Tiger Moth, Fairey Swordfish, Hawker Hart, Pitts Special and the Wright Flyer. The Stearman is particularly associated with stunt flying with wing-walkers. Famous sesquiplanes include the Nieuport 17 and Albatros D.III.

The biplane in avian evolution

In an interesting parallel to the role of the biplane in human aviation, some researchers have suggested that the feathered dinosaur ''Microraptor'' glided, and perhaps even flew, on four wings which were held in a biplane-like arrangement. This was made possible by the presence of flight feathers on both the forelimbs and hindlimbs of ''Microraptor'', and it has been suggested that the earliest flying ancestors of birds may have possessed this morphology, with the monoplane arrangement of modern birds evolving later.^[1]

References

1. Biplane wing planform and flight performance of the feathered dinosaur Microraptor gui, Chatterjee S, Templin RJ, , , Proc Natl Acad Sci U S A, 2007

See also

★ Monoplane

★ Triplane

★ Tandem wing

Trivia

★ Moonlander, an experimental electric guitar inspired on a biplane

External links

★ Historical Collection of Biplane Pictures

★ Jacqui Hayes: Bird wings evolved from biplane dinosaurs COSMOS magazine