The basics of bird flight

Press, 28 February 1984, Page 18

The basics of bird flight

Except in the matter of speed, a bird is better at flying than any man-made aircraft.

Wing joints and flight feathers give precise control. allowing twists and turns, soaring and hovering. Even so. birds and aeroplanes achieve flight basically in the same way. As a wing moves through the air. the curve of the upper surface causes air to move faster over its top. This effect reduces the air pressure above the wing, creating lift.

Vast amounts of study have been done on the aerodynamics of bird flight, but the many flexible parts of a bird's wing defy the sort of analysis that can be applied to the fixed wings of an aircraft. Gliding is the simplest form of flight, but skilful soaring, making use of upward air currents, also requires little energy. More complex, flapping

flight involves the bird being pulled forward by the propeller-type wing-tip feathers which increasingly twist and bite into the air in front of the bird’s body during the powerful downstroke. The unusual hovering flight of a humming-bird is made possible by modifica-

As a bird makes its downward stroke, the wing feathers are tightly closed and the tip feathers increasingly twist forwards (2,3).

tions that make it resemble a helicopter rather than a fixed-wing aircraft. However, the bird's wings scull backwards and forwards at great speed, not round and round.

As the wing is lifted (1,4), the feathers part to allow air through.

On landing, the wing and tail feathers are spread to form brakes.