| Thursday, January 24, 2008 |
| Flight Definition |
Flight is the process by which an object achieves sustained movement either through the air (or movement beyond earth's atmosphere, in the case of spaceflight) by aerodynamically generating lift, propulsive thrust or aerostatically using buoyancy.
Forces for flight
Main article: Aerodynamics
Forces relevant to flight are
* Propulsive thrust: (except in gliders)
* Lift: created by the deflection of the airflow (usually by wings)
* Drag: created by airflow
* Weight: (created by gravity)
* Buoyancy: for lighter than air flight
These forces must be balanced successfully for stable flight to occur.
Stabilization of flight angles (roll, yaw and pitch) and the rates of change of these can involve horizontal stabilizers (i.e. 'a tail'), ailerons and other movable aerodynamic devices which control angular stability i.e. flight attitude (which in turn affects altitude, heading).
Animal flight
Main article: Flying and gliding animals
The most successful groups of living things that fly are insects, birds, and bats. Each of these groups' wings evolved separately from different structures. See also Bird flight. Also successful were the extinct Pterosaurs, an order of reptiles contemporaneous with the dinosaurs.
Bats are the only mammals capable of true flight. However, there are several gliding mammals which are able to glide from tree to tree using fleshy membranes between their limbs; some can travel hundreds of meters in this way with very little loss in height. Flying tree frogs use greatly enlarged webbed feet for a similar purpose, and there are flying lizards which employ their unusually wide, flattened rib-cages to the same end. Certain snakes also use a flattened rib-cage to fly, with a back and forth motion much the same as they use on the ground.
Flying fish can glide using enlarged wing-like fins, and have been observed soaring for hundreds of meters using the updraft on the leading edges of waves. It is thought that this ability was chosen by natural selection because it was an effective means of escape from underwater predators.
Most birds fly (see bird flight), with some exceptions. The largest birds, the ostrich and the emu, are earthbound, as were the now-extinct dodos, while the non-flying penguins have adapted their wings for use under water. Most small flightless birds are native to small islands, and lead a lifestyle where flight would confer little advantage. The Peregrine Falcon is the fastest animal in the world; its terminal velocity exceeds 370 km/h (199 mph) in a dive.
Among living animals that fly, the wandering albatross has the greatest wingspan, up to 3.5 meters (11.5 ft); the great bustard has the greatest weight, topping at 21 kilograms (46 pounds)[1].
Among the many species of insects, some fly and others do not (See insect flight).
Mechanical flight
Main article: Aviation
Mechanical flight is the use of a machine to fly. These machines include airplanes, kites, helicopters, autogyros, airships, balloons, ornithopters, and spacecraft. Gliders provide unpowered flight. Another form of mechanical flight is parasailing where a parachute-like object is pulled by a boat.
Religion, mythology and fiction
In religion, mythology and fiction, human or anthropomorphic characters sometimes have the ability to fly independently. Well-known examples include angels in the Hebrew Bible, Daedalus in Greek mythology, and Superman in comics. Other non-human legendary creatures, such as some dragons and the Pegasus, are also depicted with an ability to fly.
The ability to fly may come from wings or other visible means of propulsion, from superhuman or godlike powers, or may simply be left unexplained.
source : http://en.wikipedia.org/wiki/FlightLabels: Definition of Flight |
posted by Gelloooo @ 7:35 PM  |
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