The wingspan (or just span) of an airplane or a bird, is the distance from one wingtip to the other wingtip. For example, the Boeing 777 has a wingspan of about 60 metres (197 ft); and a Wandering Albatross (Diomedea exulans) caught in 1965 had a wingspan of 3.63 metres (11 ft 11 in), the official record for a living bird.
The term wingspan, more technically extent, is also used for other winged animals such as pterosaurs, bats, insects, etc, and other winged aircraft such as ornithopters.
Wingspan of aircraft
The wingspan of an aircraft is always measured in a straight line, from wingtip to wingtip, independently of wing shape or sweep.
Implications for aircraft design and animal evolution
The lift from wings is proportional to their area, so the heavier the animal or aircraft the bigger that area must be. The area is the product of the span times the width (mean chord) of the wing, so either a long, narrow wing or a shorter, broader wing will support the same mass. For efficient steady flight the ratio of span to chord, the aspect ratio, should be as high as possible (the constraints are usually structural) because this lowers the lift-induced drag associated with the inevitable wingtip vortices. Long-ranging birds, like albatrosses, and most commercial aircraft maximize aspect ratio. Alternatively, animals and aircraft which depend on maneuverability (fighters, predators, the predated and those who live amongst trees and bushes, insect catchers, etc.) need to be able to roll fast to turn, and the high moment of inertia of long narrow wings produces lower roll rates. For them, short-span, broad wings are preferred.
The highest aspect ratio man-made wings are aircraft propellers, in their most extreme form as helicopter rotors.
Wingspan of flying animals
To measure the wingspan of a bird, a live or freshly dead specimen is placed flat on its back, the wings are grasped at the wrist joints,ankles and the distance is measured between the tips of the longest primary feathers on each wing.
Wingspan in sports
In basketball, a fingertip to fingertip measurement is used to determine the player's armspan. This is called reach in boxing terminology.
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