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(ôr`nəthŏp'tər): see flightflight,
sustained, self-powered motion through the air, as accomplished by an animal, aircraft, or rocket. Animal Flight

Adaptation for flight is highly developed in birds and insects. The bat is the only mammal that accomplishes true flight.
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a heavier-than-air craft with flapping wings. A flapping motion of wings is used in flight by various living beings, such as birds.

Studies show that the ratio of a bird’s weight to the power of its muscles is about the same as in humans—(1,350 ± 675) newtons per kilowatt, or (100 ± 50) kilograms-force per horsepower—but the considerable additional weight of the ornithopter structure itself makes takeoff in this type of aircraft virtually impossible for humans. However, if a muscle-powered ornithopter is first accelerated or is launched from an elevated position, it can take off and fly a distance of 1–2 km. Experimental flights in the simplest type of ornithopter (called an orthopter) were made as early as the early 20th century (in 1921 by the Soviet aircraft designer B. I. Cheranovskii and in 1929 by the German aircraft designer H. Krause). The design and construction of ornithopters equipped with an engine and with a complex transmission for the flapping wings are of interest mainly from the viewpoint of developing a theory of the dynamics of a flapping wing.


Tikhonravov, M. K. Polet ptits i mashiny s mashushchimi kryl’iami, 2nd ed. Moscow, 1949.
Alexander, R. Biomekhanika. Moscow, 1970. (Translated from English.)
Shestakova, G. S. Stroenie kryl’ev i mekhanika poleta ptits. Moscow, 1971.



An aircraft that derives its lift by the flapping of wings or oscillating about any axis but not by rotating.