biplane

Reproduction of a Sopwith Camel biplane flown by Lt. George A. Vaughn Jr., 17th Aero Squadron

A biplane is a fixed-wing aircraft with two main wings. 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.

The term is also occasionally used in biology, to describe the wings of some flying animals.

Aviation

Rutan Quickie tandem wing biplane

In a biplane aircraft, two wings are placed one above the other. Both provide lift. Very often there is a fuselage to which the lower wing is attached, while the upper wing is raised above, although other combinations have occurred. Almost all biplanes also have a third horizontal surface, the tailplane, to control the pitch, or angle of attack of the aircraft (although there have been a few exceptions). Either or both of the main wings can support flaps or ailerons to assist lateral and speed control, although the upper wing has tended historically to be more important in this regard. Often there is bracing in the form of wires and slender struts positioned symmetrically on either side of the fuselage.

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. Sometimes the lower wing is 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 (e.g. a wing in the nose and a wing in the tail).

Advantages and drawbacks to biplane designs

RAF BE2c biplane of 1915.

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. The struts and wire bracing of a typical biplane form a box girder that permits a light but very strong wing structure.

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.

Boeing Stearman E75 (PT-13D) biplane of 1944

Antonov An-2 is one of heaviest biplanes.

History

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.

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

See also

Wikimedia Commons has media related to:

Biplanes

• 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

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