An aircraft is a vehicle or machine that is able to fly by gaining support from the air. It counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines. Common examples of aircraft include airplanes, helicopters, airships (including blimps), gliders, paramotors, and hot air balloons.
The human activity that surrounds aircraft is called aviation. The science of aviation, including designing and building aircraft, is called aeronautics. Crewed aircraft are flown by an onboard pilot, but unmanned aerial vehicles may be remotely controlled or self-controlled by onboard computers. Aircraft may be classified by different criteria, such as lift type, aircraft propulsion, usage and others.
Flying model craft and stories of manned flight go back many centuries; however, the first manned ascent and safe descent in modern times took place by larger hot-air balloons developed in the 18th century. Each of the two World Wars led to great technical advances. Consequently, the history of aircraft can be divided into five eras:
* Pioneers of flight, from the earliest experiments to 1914.
* First World War, 1914 to 1918.
Aviation between the World Wars, 1918 to 1939.
* Second World War, 1939 to 1945.
* Postwar era, also called the Jet Age, 1945 to the present day.
Methods of lift
Lighter than air – aerostats
Aerostats use buoyancy to float in the air in much the same way that ships float on the water. They are characterized by one or more large cells or canopies, filled with a relatively low-density gas such as helium, hydrogen, or hot air, which is less dense than the surrounding air. When the weight of this is added to the weight of the aircraft structure, it adds up to the same weight as the air that the craft displaces.
Small hot-air balloons, called sky lanterns, were first invented in ancient China prior to the 3rd century BC and used primarily in cultural celebrations, and were only the second type of aircraft to fly, the first being kites, which were first invented in ancient China over two thousand years ago.
During World War II, this shape was widely adopted for tethered balloons; in windy weather, this both reduces the strain on the tether and stabilizes the balloon. The nickname blimp was adopted along with the shape. In modern times, any small dirigible or airship is called a blimp, though a blimp may be unpowered as well as powered.
Heavier-than-air – aerodynes :
Heavier-than-air aircraft, such as airplanes, must find some way to push air or gas downwards so that a reaction occurs (by Newton’s laws of motion) to push the aircraft upwards. This dynamic movement through the air is the origin of the term. There are two ways to produce dynamic upthrust aerodynamic lift, and powered lift in the form of engine thrust.
Aerodynamic lift involving wings is the most common, with fixed-wing aircraft being kept in the air by the forward movement of wings, and rotorcraft by spinning wing-shaped rotors sometimes called rotary wings. A wing is a flat, horizontal surface, usually shaped in cross-section as an aerofoil. To fly, air must flow over the wing and generate lift. A flexible wing is a wing made of fabric or thin sheet material, often stretched over a rigid frame. A kite is tethered to the ground and relies on the speed of the wind over its wings, which may be flexible or rigid, fixed, or rotary.
The forerunner of the fixed-wing aircraft is the kite. Whereas a fixed-wing aircraft relies on its forward speed to create airflow over the wings, a kite is tethered to the ground and relies on the wind blowing over its wings to provide lift. Kites were the first kind of aircraft to fly and were invented in China around 500 BC. Much aerodynamic research was done with kites before test aircraft, wind tunnels, and computer modelling programs became available.
The first heavier-than-air craft capable of controlled free-flight were gliders. A glider designed by George Cayley carried out the first true manned, controlled flight in 1853.
The practical, powered, fixed-wing aircraft (the airplane or aeroplane) was invented by Wilbur and Orville Wright
Rotorcraft, or rotary-wing aircraft, use a spinning rotor with aerofoil section blades (a rotary wing) to provide lift. Types include helicopters, autogyros, and various hybrids such as gyrodynes and compound rotorcraft.
Helicopters have a rotor turned by an engine-driven shaft. The rotor pushes air downward to create lift. By tilting the rotor forward, the downward flow is tilted backward, producing thrust for forward flight. Some helicopters have more than one rotor and a few have rotors turned by gas jets at the tips.
Autogyros have unpowered rotors, with a separate power plant to provide thrust. The rotor is tilted backward. As the autogyro moves forward, air blows upward across the rotor, making it spin. This spinning increases the speed of airflow over the rotor, to provide lift. Rotor kites are unpowered autogyros, which are towed to give them forward speed or tethered to a static anchor in high-wind for kited flight.
Other methods of lift:
A lifting body is an aircraft body shaped to produce lift. If there are any wings, they are too small to provide significant lift and are used only for stability and control. Lifting bodies are not efficient: they suffer from high drag, and must also travel at high speed to generate enough lift to fly. Many of the research prototypes, such as the Martin Marietta X-24, which led up to the Space Shuttle, were lifting bodies, though the Space Shuttle is not, and some supersonic missiles obtain lift from the airflow over a tubular body.
Powered lift types rely on engine-derived lift for vertical takeoff and landing (VTOL). Most types transition to fixed-wing lift for horizontal flight. Classes of powered lift types include VTOL jet aircraft (such as the Harrier Jump Jet) and tiltrotors, such as the Bell Boeing V-22 Osprey, among others.
The smallest aircraft are toys/recreational items, and nano aircraft.
The largest aircraft by dimensions and volume (as of 2016) is the 302 ft (92 m) long British Airlander 10, a hybrid blimp, with helicopter and fixed-wing features, and reportedly capable of speeds up to 90 mph (140 km/h; 78 kn), and an airborne endurance of two weeks with a payload of up to 22,050 lb (10,000 kg).
The largest aircraft by weight and largest regular fixed-wing aircraft ever built, as of 2016, is the Antonov An-225 Mriya. That Ukrainian-built six-engine Russian transport of the 1980s is 84 m (276 ft) long, with an 88 m (289 ft) wingspan. It holds the world payload record, after transporting 428,834 lb (194,516 kg) of goods, and has recently flown 100 t (220,000 lb) loads commercially. With a maximum loaded weight of 550–700 t (1,210,000–1,540,000 lb), it is also the heaviest aircraft built to date. It can cruise at 500 mph (800 km/h; 430 kn).
The largest military airplanes are the Ukrainian Antonov An-124 Ruslan (world’s second-largest airplane, also used as a civilian transport), and American Lockheed C-5 Galaxy transport, weighing, loaded, over 380 t (840,000 lb). The 8-engine, piston/propeller Hughes H-4 Hercules “Spruce Goose” an American World War II wooden flying boat transport with a greater wingspan (94m/260ft) than any current aircraft and a tail height equal to the tallest (Airbus A380-800 at 24.1m/78ft) — flew only one short hop in the late 1940s and never flew out of ground effect.
The largest civilian airplanes, apart from the above-noted An-225 and An-124, are the Airbus Beluga cargo transport derivative of the Airbus A300 jet airliner, the Boeing Dreamlifter cargo transport derivative of the Boeing 747 jet airliner/transport (the 747-200B was, at its creation in the 1960s, the heaviest aircraft ever built, with a maximum weight of over 400 t (880,000 lb)),and the double-decker Airbus A380 “super-jumbo” jet airliner
Size and speed extremes:
The fastest recorded powered aircraft flight and fastest recorded aircraft flight of an air-breathing powered aircraft was of the NASA X-43A Pegasus, a scramjet-powered, hypersonic, lifting body experimental research aircraft, at Mach 9.6, exactly 3,292.8 m/s (11,854 km/h; 6,400.7 kn; 7,366 mph). The X-43A set that new mark, and broke its own world record of Mach 6.3, exactly 2,160.9 m/s (7,779 km/h; 4,200.5 kn; 4,834 mph), set in March 2004, on its third and final flight on 16 November 2004.
Prior to the X-43A, the fastest recorded powered airplane flight (and still the record for the fastest manned, powered airplane / fastest manned, non-spacecraft aircraft) was of the North American X-15A-2, rocket-powered airplane at Mach 6.72, or 2,304.96 m/s (8,297.9 km/h; 4,480.48 kn; 5,156.0 mph), on 3 October 1967. On one flight it reached an altitude of 354,300 ft (108,000 m).
The fastest known, production aircraft (other than rockets and missiles) currently or formerly operational (as of 2016) are:
The fastest fixed-wing aircraft, and fastest glider, is the Space Shuttle, a rocket-glider hybrid, which has re-entered the atmosphere as a fixed-wing glider at more than Mach 25, equal to 8,575 m/s (30,870 km/h; 16,668 kn; 19,180 mph).
The fastest military airplane ever built: Lockheed SR-71 Blackbird, a U.S. reconnaissance jet fixed-wing aircraft, known to fly beyond Mach 3.3, equal to 1,131.9 m/s (4,075 km/h; 2,200.2 kn; 2,532 mph). On 28 July 1976, an SR-71 set the record for the fastest and highest-flying operational aircraft with an absolute speed record of 2,193 mph (3,529 km/h; 1,906 kn; 980 m/s) and an absolute altitude record of 85,068 ft (25,929 m).
Uses for aircraft:
Aircraft are produced in several different types optimized for various uses; military aircraft, which includes not just combat types but many types of supporting aircraft, and civil aircraft, which include all non-military types, experimental and model.
A military aircraft is any aircraft that is operated by a legal or insurrectionary armed service of any type.] Military aircraft can be either combat or non-combat:
Combat aircraft are aircraft designed to destroy enemy equipment using its own armament.Combat aircraft divide broadly into fighters and bombers, with several in-between types, such as fighter-bombers and attack aircraft, including attack helicopters.
Non-combat aircraft are not designed for combat as their primary function, but may carry weapons for self-defense. Non-combat roles include search and rescue, reconnaissance, observation, transport, training, and aerial refueling. These aircraft are often variants of civil aircraft.
Civil aircraft divide into commercial and general types, however there are some overlaps.
Commercial aircraft include types designed for scheduled and charter airline flights, carrying passengers, mail and other cargo. The larger passenger-carrying types are the airliners, the largest of which are wide-body aircraft. Some of the smaller types are also used in general aviation, and some of the larger types are used as VIP aircraft.
General aviation is a catch-all covering other kinds of private (where the pilot is not paid for time or expenses) and commercial use, and involving a wide range of aircraft types such as business jets (bizjets), trainers, homebuilt, gliders, warbirds and hot air balloons to name a few. The vast majority of aircraft today are general aviation types.
A model aircraft is a small unmanned type made to fly for fun, for static display, for aerodynamic research or for other purposes. A scale model is a replica of some larger design.
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