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sustained, self-powered motion through the air, as accomplished by an animal, aircraft, or rocket.

Animal Flight

Adaptation for flight is highly developed in birdsbird,
warm-blooded, egg-laying, vertebrate animal having its body covered with feathers and its forelimbs modified into wings, which are used by most birds for flight. Birds compose the class Aves (see Chordata). There are an estimated 9,000 living species.
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 and insectsinsect,
invertebrate animal of the class Insecta of the phylum Arthropoda. Like other arthropods, an insect has a hard outer covering, or exoskeleton, a segmented body, and jointed legs. Adult insects typically have wings and are the only flying invertebrates.
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. The batbat,
winged mammal of the order Chiroptera, which includes 900–1,000 species classified in about 200 genera and 17 families. Bats range in size from a wingspread of over 5 ft (150 cm) to a wingspread of less than 2 in. (5 cm).
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 is the only mammal that accomplishes true flight. Flying squirrelsflying squirrel,
name for certain nocturnal tree squirrels adapted for gliding; they do not actually fly. Most are found in Asia, but one species of the genus Pteromys extends into SE Europe and the two species of Glaucomys are found in North America.
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 glide rather than fly, as do flying fishflying fish,
common name for members of the Exocoetidae, a family of carnivorous or herbivorous fish of warmer seas. Flying fishes usually swim in schools. They average 7 to 12 in. (17.
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 and flying lizards. The extinct flying reptiles known as pterosaurspterosaur
[Gr., = winged lizard], extinct flying reptile (commonly called pterodactyl [Gr., = wing finger]) of the order Pterosauria, common in the late Triassic and Cretaceous periods, from approximately 228 to 65 million years ago.
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 are believed to have been the largest known animals capable of true flight.

Birds fly by means of the predominantly up-and-down motion of their wings. The flapping motion is not, however, straight up and down but semicircular, the wings generally moving backward on the upstroke and forward on the downstroke. That motion pushes air downward and to the rear, creating a lift and forward thrust. The leading edge of the slightly concave wings is rather sharp, and the feathers are small and close-fitting, so that a streamlined surface meets the air. On the trailing edge of each wing the interlocking of the larger feathers forms a surface that acts somewhat like the ailerons, or movable airfoils, of an airplane. In wing motion, the leading edge is twisted so as to be lower than the trailing edge in the downward stroke and above the trailing edge in the upward stroke.

Besides flapping, some birds also use gliding and soaring techniques in flight. In gliding, a bird holds its outstretched wings relatively still and relies on its momentum to keep it aloft for short distances. In soaring, a bird uses rising warm air currents to give it lift.

The form and size of wings vary in different birds. In woodland birds the wings are somewhat rounded and have a relatively broad surface area. Birds with well-developed gliding ability, such as gannets and gulls, usually have narrow, pointed wings. Especially noted for their soaring power are eagles, vultures, crows, and some hawks. In soaring flight the feathers on the wings of these birds separate at the tips, resembling opened fingers against the sky. It is thought that this movement diverts the airstream over the wing and aids the bird in turning, banking, and wheeling. There is disagreement as to the maximum speeds achieved by birds in flight. While the flight speeds of most birds range from 10 to 60 mi (16–100 km) per hr, some have been recorded at speeds reaching 70 mi (110 km) per hr, for long distances and near 100 mi (160 km) per hr, for short flights. In a stoop, falcons can reach faster speeds.

Aircraft and Rocket Flight

Humanity's first attempts at flight were made with flapping wings strapped to the arms in imitation of birds, but these had no success. Machines designed to fly in this way, called ornithopters, date to antiquity (c.400 B.C.) and models that are capable of flight have been known for more than 100 years. However, there are no practical aircraft based on ornithopter designs, even though an ornithopter—which has no theoretical top speed limit—should be capable at least of efficient low-speed flight. In the 1930s an Italian model weighing approximately 50 lb (110 kg) and powered by a 0.5-hp motor was successfully flown.

Airships and balloons owe their ability to ascend and remain aloft to their inflation with a gas lighter than air; this is an application of Archimedes' principle of flotation, i.e., that a body immersed in a fluid (liquid or gas) is buoyed up by a force equal to the weight of the fluid that it displaces. Aircraft, which are heavier than air, are able to remain aloft because of forces developed by the movement of the craft through the air. Propulsion of most aircraft derives from the rearward acceleration of the air. It is an application of Newton's third law, i.e., that for every action there is an equal and opposite reaction. In propeller aircraft the forward motion is obtained through conversion of engine power to thrust by means of acceleration of air to the rear by the propeller. Lift is obtained largely from the upward pressure of the air against the airfoils (e.g., wings, tail fins, and ailerons), on whose upper surface the pressure becomes lower than that of the atmosphere. In jet-propelled aircraft, propulsion is achieved by heating air that passes through the engine and accelerating the resultant hot exhaust gases rearward at high velocities. Rockets are propelled by the rapid expulsion of gas through vents at the rear of the craft. The high speeds that are produced by jet and rocket engines have brought about substantial changes in the science of flight.

See aerodynamicsaerodynamics,
study of gases in motion. As the principal application of aerodynamics is the design of aircraft, air is the gas with which the science is most concerned. Although aerodynamics is primarily concerned with flight, its principles are also used in designing automobile
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; airplaneairplane,
or aircraft,
heavier-than-air vehicle, mechanically driven and fitted with fixed wings that support it in flight through the dynamic action of the air.
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; jet propulsionjet propulsion,
propulsion of a body by a force developed in reaction to the ejection of a high-speed jet of gas. Jet Propulsion Engines

The four basic parts of a jet engine are the compressor, turbine, combustion chamber, and propelling nozzles.
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; rocketrocket,
any vehicle propelled by ejection of the gases produced by combustion of self-contained propellants. Rockets are used in fireworks, as military weapons, and in scientific applications such as space exploration.
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See H. Tennekes, The Simple Science of Flight (1996, repr. 2009); see also bibliography under aviationaviation,
operation of heavier-than-air aircraft and related activities. Aviation can be conveniently divided into military aviation, air transport, and general aviation.
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a tactical and fire subunit composed of three or four aircraft, of different arms of aviation. Several flights make up a squadron. A flight may carry out its combat mission as part of the squadron or independently.


(aerospace engineering)
The movement of an object through the atmosphere or through space, sustained by aerodynamic reaction or other forces.
(civil engineering)
A series of stairs between landings or floors.
(mechanical engineering)
Plain or shaped plates that are attached to the propelling mechanism of a flight conveyor.


A continuous series of steps with no intermediate landings.


i. A single aircraft airborne on a nonoperational mission.
ii. The basic tactical unit in the air force, consisting of four or more aircraft in two or more elements.
iii. One of the elements of the squadron (e.g., A flight, B flight, etc.).
iv. The art or the act of flying with wings or in an airplane or other vehicle.
v. The movement of an object through the atmosphere or space sustained by aerodynamic, aerostatic, or reaction forces or by orbital speed. The movement of a human-operated or humancontrolled device, such as a rocket, a space probe, a space vehicle, or an aircraft. Also, an instance of such a movement.
vi. A regular air journey, numbered and at a fixed time, made by an aircraft.


a. a scheduled airline journey
b. an aircraft flying on such a journey
2. the basic tactical unit of a military air force
3. a journey through space, esp of a spacecraft
4. Athletics
a. a single line of hurdles across a track in a race
b. a series of such hurdles
5. a bird's wing or tail feather; flight feather
6. a feather or plastic attachment fitted to an arrow or dart to give it stability in flight
7. See flight arrow
8. the distance covered by a flight arrow
9. Sport, esp cricket
a. a flighted movement imparted to a ball, dart, etc.
b. the ability to flight a ball
10. Angling a device on a spinning lure that revolves rapidly
11. a large enclosed area attached to an aviary or pigeon loft where the birds may fly but not escape
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He brought along a scale model of the Angel of the North to explain the principles of flight and to explore whether the Antony Gormley sculpture could actually fly.
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Principles of Flight Simulation is a comprehensive guide to flight simulator design, covering the modelling, algorithms and software which underpin flight simulation.
Contents: Foreword; Preface; The organisation and operation of European airspace, Marc Baumgartner; The principles of flight planning and ATM messaging, Graham Tanner; Understanding en-route sector capacity in Europe, Arnab Majumdar; The management and costs of delay, Andrew Cook; European ATM and the environment, Victoria Williams; The future of European air transport operations, Nigel Dennis; The single European sky - EU reform of ATM, Ben van Houtte; ATM and society - demands and expectations, Nadine Pilon; Conclusions and a look ahead, Andrew Cook; Appendix, Graham Tanner; Glossary; Bibliography; Index.
The gallery will feature AirTran Airways' Aircraft 903's fuselage, cockpit and wing section in interactive displays focusing on the principles of flight and aviation safety.

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