Anaircraft is avehicle that is able tofly by gaining support from theair. It counters the force of gravity by using eitherstatic lift or thedynamic lift of anairfoil,[1] or, in a few cases, directdownward thrust from its engines. Common examples of aircraft includeairplanes, drones,rotorcraft (includinghelicopters),airships (includingblimps),gliders,paramotors, andhot air balloons.[2] Part 1[3] (Definitions and Abbreviations) of Subchapter A of Chapter I of Title 14 of the U. S. Code of Federal Regulations states that aircraft "means a device that is used or intended to be used for flight in the air."
The human activity that surrounds aircraft is calledaviation. The science of aviation, including designing and building aircraft, is calledaeronautics.Crewed aircraft are flown by an onboardpilot, whereasunmanned aerial vehicles may be remotely controlled or self-controlled by onboardcomputers. Aircraft may be classified by different criteria, such as lift type,aircraft propulsion (if any), usage and others.
The history of aviation spans over two millennia, from the earliest innovations likekites and attempts at tower jumping tosupersonic andhypersonic flight in powered,heavier-than-airjet aircraft. Kite flying in China, dating back several hundred years BC, is considered the earliest example of man-made flight.[4] In the 15th century,Leonardo da Vinci created flying machine designs incorporating aeronautical concepts, but they were unworkable due to the limitations of contemporary knowledge.[5]
In the 19th century, especially the second half, experiments with gliders provided the basis for learning the dynamics of winged aircraft; most notably by Cayley,Otto Lilienthal, andOctave Chanute. By the early 20th century, advances in engine technology and aerodynamics made controlled, powered, manned heavier-than-air flight possible for the first time. In 1903, following their pioneering research and experiments with wing design and aircraft control, theWright brothers successfully incorporated all of the required elements to create and fly the first airplane.[8] In 1906Charles Frederick Page was granted the first U.S. patent for an aircraft.[9] The basic configuration with its characteristiccruciform tail was established by 1909, followed by rapid design and performance improvements aided by the development of more powerful engines.
The first vessels of the air were the rigid steerable balloons pioneered byFerdinand von Zeppelin that became synonymous withairships and dominated long-distance flight until the 1930s, when largeflying boats became popular for trans-oceanic routes. AfterWorld War II, the flying boats were in turn replaced by airplanes operating from land, made far more capable first by improvedpropeller engines, then byjet engines, which revolutionized both civilian air travel andmilitary aviation.
In the latter half of the 20th century, the development ofdigital electronics led to major advances in flight instrumentation and "fly-by-wire" systems. The 21st century has seen the widespread use ofpilotless drones for military, commercial, and recreational purposes. With computerized controls, inherently unstable aircraft designs, such asflying wings, have also become practical.
Lighter-than-air aircraft oraerostats usebuoyancy 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 alifting gas such ashelium,hydrogen orhot air, which is lessdense than the surrounding air. Other gases lighter than air also theoretically work, however, such gases also needs to be safe for human use (non-flammable, non-toxic).[10]
Small hot-air balloons, calledsky lanterns, were first invented in ancient China prior to the 3rd century BC and used primarily in cultural celebrations, although they also had military purposes.[11] They, along withkites, were two forms ofunmanned aircraft that originated from China.[12] Kites were also used in the military, but unlike sky lanterns, their flight is caused by the differences of air pressure beneath and above the kite.[13]
Aballoon was originally any aerostat, while the termairship was used for large, powered aircraft designs — usually fixed-wing.[14][15][16][17][18][19] In 1919,Frederick Handley Page was reported as referring to "ships of the air," with smaller passenger types as "Air yachts."[20] In the 1930s, large intercontinental flying boats were also sometimes referred to as "ships of the air" or "flying-ships".[21][22]
Lighter-than-air aircraft don't typically require a pilot's license in the United States.[23] In most countries in Europe, standards for flying Lighter-than-air aircraft tend to be stricter compared to the United States.[24]
Heavier-than-air aircraft oraerodynes are denser than air and thus must find some way to obtain enoughlift that can overcome the aircraft's weight. There are two ways to produce dynamic upthrust —aerodynamic lift by having air flowing past anaerofoil (such dynamic interaction of aerofoils with air is the origin of the term "aerodyne"), orpowered lift in the form ofreactional lift from downward enginethrust.[25][26]
Gliders were one of the first forms of a fixed wing aircraft. They are a special type of aircraft that doesn't require an engine.[28] The first person to successfully build a human-carrying glider wasGeorge Cayley, who also was the first to discover the four major aerodynamic forces.[29] The first powered aircraft (Airplane) was invented byWilbur and Orville Wright.[30]
Arotary-wing aircraft,rotorwing aircraft orrotorcraft is a heavier-than-air aircraft withrotary wings that spin around a vertical mast to generatelift. The assembly of several rotor blades mounted on a single mast is referred to as arotor. TheInternational Civil Aviation Organization (ICAO) defines a rotorcraft as "supported in flight by the reactions of the air on one or more rotors".[31]
Rotorcraft generally include aircraft where one or more rotors provide lift throughout the entire flight, such ashelicopters,gyroplanes,autogyros, andgyrodynes Compound rotorcraft augment the rotor with additional thrust engines, propellers, or static lifting surfaces. Some types, such as helicopters, are capable ofvertical takeoff and landing. An aircraft which uses rotor lift for vertical flight but changes to solely fixed-wing lift in horizontal flight is not a rotorcraft but aconvertiplane.
Alifting body is an aircraft which produces lift through the shape of its body, rather than its wings or rotors, like conventional aircraft. Lifting bodies were first experimented by NASA in the 1960s-70s, but the idea was already conceived in the 1950s.[32]
Apowered lift aircraft is one which has the capability of verticaltakeoff andlanding. These aircraft must transition from vertical to lateral movement, which is considered the most dangerous phases of a flight.[33] Classes of powered lift types includeVTOL jet aircraft (such as theHarrier jump jet) andtiltrotors, such as theBell Boeing V-22 Osprey, among others.[34][35]
Anornithopter is an aircraft that produces lift through the movement of its wings, akin to how a bird flies.[36]
The largest aircraft by dimensions and volume (as of 2016) is the 302 ft (92 m) long BritishAirlander 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).[37][38][39]
The largest aircraft by weight and largest regular fixed-wing aircraft ever built, as of 2016[update], was theAntonov An-225Mriya. That Soviet-built (Ukrainian SSR) six-engine transport of the 1980s was 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 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 was also the heaviest aircraft built to date. It could cruise at 500 mph (800 km/h; 430 kn).[40][41][42][43][44] The aircraft was destroyed during theRusso-Ukrainian War.[45]
The largest military airplanes are the UkrainianAntonov An-124Ruslan (world's second-largest airplane, also used as a civilian transport),[46] and AmericanLockheed C-5 Galaxy transport, weighing, loaded, over 380 t (840,000 lb).[44][47] The 8-engine, piston/propellerHughes H-4Hercules "Spruce Goose" — an AmericanWorld War II wooden flying boat transport with a greater wingspan (94m/260 ft) than any current aircraft and a tail height equal to the tallest (Airbus A380-800 at 24.1m/78 ft) — flew only one short hop in the late 1940s and never flew out ofground effect.[44]
The largest civilian airplanes, apart from the above-noted An-225 and An-124, are theAirbus Beluga cargo transport derivative of theAirbus A300 jet airliner, theBoeing Dreamlifter cargo transport derivative of theBoeing 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)),[47] and the double-deckerAirbus A380 "super-jumbo" jet airliner (the world's largest passenger airliner).[44][48]
The fastest fixed-wing aircraft and fastest glider, is theSpace Shuttle, which re-entered the atmosphere at nearly Mach 25 or 17,500 mph (28,200 km/h)[49]
The fastest recorded powered aircraft flight and fastest recorded aircraft flight of an air-breathing powered aircraft was of theNASA X-43APegasus, ascramjet-powered,hypersonic,lifting body experimental research aircraft, atMach 9.68 or 6,755 mph (10,870 km/h) on 16 November 2004.[50]
Prior to the X-43A, the fastest recorded powered airplane flight, and still the record for the fastest manned powered airplane, was theNorth American X-15, rocket-powered airplane at Mach 6.7 or 7,274 km/h (4,520 mph) on 3 October 1967.[51]
The fastest manned, air-breathing powered airplane is theLockheed SR-71 Blackbird, a U.S.reconnaissance jet fixed-wing aircraft, having reached 3,530 km/h (2,193 mph) on 28 July 1976.[52]
The main feature of unpowered aircraft is the inability to directly provide thrust through its engines. This means that all unpowered aircraft rely on theenvironment for sustained flight. Gliders, for example, take advantage of their aerodynamic properties to enable them to travel long distances. Techniques such as thermal circling, where gliders fly into warm air which allows them to rise, prolongs flight time.[53]Due to the lack of an engine, initial propulsion assistance is usually necessary to ensure flight. A common glider launching method is aerotowing, where another aircraft tows the glider to an altitude from which sustained flight is possible.[54] Steering for a glider is also rudimentary, while more complex gliders like sailplanes usually have joysticks for steering, more basic aircraft likehang gliders rely on the pilot's physical coordination to change the centre of gravity.[55]
A powered aircraft is an aircraft with a source of mechanical power, used to produce thrust. Such sources are generallyengines, as is the case with airplanes, but can be human-powered in more extreme cases.[56][57]
Compared to engines using propellers, jet engines can provide much higher thrust, higher speeds and, above about 40,000 ft (12,000 m), greater efficiency.[58]
Although some rotorcraft, such asrotor kites, can be unpowered, most rotorcraft are powered by eitherpiston engines orturboprops. Some rotorcraft, including autogyros andgyrodynes, are propelled by a conventional propeller or jet engine, with the rotor unpowered, but most modern rotorcraft have a powered rotor, allowing them to hover in place. Autogyros and gyrodynes are steered using arudder, similarly to propeller and jet aircraft, and rotorcraft with powered rotors, such as helicopters, turn by adjusting the pitch of the rotor cylically, so that the rotors on one side produce more lift than the other.[59] Rotorcraft with powered rotors typically need atail rotor to counter the rotational thrust produced by the rotor, which can cause the helicopter to spin.[59]
Anaerostat orlighter-than-air aircraft relies onbuoyancy to maintainflight. Aerostats include unpoweredballoons (free-flying ortethered) andpoweredairships. Therelative density of an aerostat as a whole is lower than that of the surroundingatmosphericair (hence the name "lighter-than-air"). Its main component is one or more gas capsules made of lightweightskins, containing alifting gas (hot air, or any gas with lower density than air, typicallyhydrogen orhelium) thatdisplaces a large volume of air to generate enough buoyancy to overcome its ownweight.Payload (passengers and cargo) can then be carried on attached components such as abasket, agondola, acabin or varioushardpoints.[66][67] With airships, which need to be able to fly against wind, the lifting gas capsules are often protected by a more rigid outer envelope or anairframe, with other gasbags such asballonets to help modulate buoyancy.
Aerostats are so named because they useaerostatic buoyant force that does not require any forward movement through the surrounding air mass, resulting in the inherent ability tolevitate and performvertical takeoff and landing. This contrasts with the heavier-than-airaerodynes that primarily useaerodynamiclift, which must have consistent airflow over anaerofoil (wing) surface to stay airborne. The term has also been used in a narrower sense, to refer to the staticallytethered balloon in contrast to the free-flying airship.[68] This article uses the term in its broader sense.
Anaerodyne is a heavier-than-air aircraft that relies onaerodynamic lift, or upthrust produced by the airflow, to fly. Aerodynes includerotorcraft,airplanes,gliders, and several other varieties of aircraft. Airplanes use wings, or airfoils, to direct the airflow to produce lift. Wings are usually constructed with a wooden or metal inner framework, and askin stretched over it.[69] Rotorcraft use arotor which acts like a rotating wing, allowing them to hover in place. When aerodynes carry a payload, it is usually carried inside the aircraft's fuselage, or central structure, but aerodynes can also carry loads attached outside the aircraft or inside the wing. Unlike aerostats, which control their altitude by changing their weight, aerodynes use control surfaces to control their altitude, or raise or lower the lift on their wing by adjusting their speed.[70] As they typically travel at higher speeds than aerostats, most aerodynes have a rigid structure consisting of a frame covered by a skin.
TheBoeing 777-200LR is one of the longest-range airliners, capable of flights of more than halfway around the world.
The maximal totalrange is the maximum distance an aircraft can fly betweentakeoff andlanding.Powered aircraft range is limited by theaviation fuel energy storage capacity (chemical or electrical) considering both weight and volume limits.[78]Unpowered aircraft range depends on factors such as cross-country speed and environmental conditions. The range can be seen as the cross-countryground speed multiplied by the maximum time in the air. The fuel time limit for powered aircraft is fixed by the available fuel (considering reserve fuel requirements) and rate of consumption. TheAirbus A350-900ULR is among the longest range airliners.[79]
Some aircraft can gain energy while airborne through the environment (e.g. collecting solar energy or through rising air currents from mechanical or thermal lifting) or from in-flight refueling. These aircraft could theoretically have an infinite range.
Ferry range means the maximum range that an aircraft engaged inferry flying can achieve. This usually means maximumfuel load, optionally with extra fuel tanks and minimum equipment. It refers to the transport of aircraft without any passengers or cargo.Combat radius is a related measure based on the maximum distance a warplane can travel from its base of operations, accomplish some objective, and return to its original airfield with minimal reserves.
Flight dynamics is the science of air vehicle orientation and control in three dimensions. The three critical flight dynamics parameters are theangles of rotation in threedimensions about the vehicle'scenter of gravity (cg), known aspitch,roll andyaw. These are collectively known asaircraft attitude, often principally relative to the atmospheric frame in normal flight, but also relative to terrain during takeoff or landing, or when operating at low elevation. The concept of attitude is not specific to fixed-wing aircraft, but also extends torotary aircraft such as helicopters, anddirigibles, where the flight dynamics involved in establishing and controlling attitude are entirely different.
Control systems adjust the orientation of a vehicle about its cg. A control system includes control surfaces which, when deflected, generate a moment (or couple from ailerons) about the cg which rotates the aircraft in pitch, roll, and yaw. For example, apitching moment comes from a force applied at a distance forward or aft of the cg, causing the aircraft to pitch up or down.
Afixed-wing aircraft increases or decreases the lift generated by the wings when it pitches nose up or down by increasing or decreasing theangle of attack (AOA). The roll angle is also known as bank angle on a fixed-wing aircraft, which usually "banks" to change the horizontal direction of flight. An aircraft is streamlined from nose to tail to reducedrag making it advantageous to keep thesideslip angle near zero, though an aircraft may be deliberately "sideslipped" to increase drag and descent rate during landing, to keep aircraft heading same as runway heading during cross-wind landings and during flight with asymmetric power.[80]
A fixed wing is typically unstable in pitch, roll, and yaw. Pitch and yaw stabilities of conventional fixed wing designs requirehorizontal and vertical stabilisers,[81][82] which act similarly to the feathers on an arrow.[83] These stabilizing surfaces allow equilibrium of aerodynamic forces and to stabilise theflight dynamics of pitch and yaw.[81][82]
Infixed-wing aircraft, multiplecontrol surfaces are used to adjust the aircraft's roll, pitch, and yaw.Ailerons, hinged surfaces normally located on the rear edge of the wing, can raise or lower the lift produced by one side of the wing, causing the aircraft to bank to one side.Elevators, usually located in thehorizontal stabilizer, are used to increase or decrease the lift produced by thetail, causing the aircraft to pitch upwards or downwards, which in turn affects the lift of the wing.[84] However, when the ailerons are used to turn an aircraft to the left, the right aileron must be tilted downwards, producing moredrag than the left aileron and causing the aircraft toyaw right. To counteract this force, most fixed-wing aircraft have arudder mounted on thevertical stabilizer which can deflect the airflow to the tail left or right to control the aircraft's yaw.[84] In rotorcraft, control is mainly accomplished through the cyclical tilting of the rotor's blades, increasing theangle of attack of the blades on one side and decreasing the angle of attack on the other.[85] Similarly to the rudder on fixed-wing aircraft, rotorcraft with powered rotors have atail rotor, which counters the rotational thrust produced by the rotor and allows the aircraft to turn in forward flight.[85] Rotorcraft with unpowered rotors, such asautogyros, use a rudder for yaw.
Jet airliners contribute toclimate change by emittingcarbon dioxide (CO2), the best understoodgreenhouse gas, and, with lessscientific understanding,nitrogen oxides,contrails and particulates. Theirradiative forcing is estimated at 1.4 that of CO2 alone, excluding inducedcirrus cloud with a very low level of scientific understanding.In 2018, global commercial operations generated 2.4% of CO2 emissions.[87] Jet airliners have become more fuel efficient and CO2 emissions per revenueton-kilometer (RTK) in 2018 were 47% of those in 1990. In 2018, CO2 emissions averaged 88 grams of CO2 per revenue passenger per km. While theaviation industry is morefuel efficient, overall emissions have risen as the volume ofair travel has increased. By 2020, aviation emissions were 70% higher than in 2005 and they could grow by 300% by 2050.[88]
A military aircraft is any aircraft that is operated by a legal or insurrectionary armed service of any type.[89] Military aircraft can be either combat or non-combat:
Combat aircraft are aircraft designed to destroy enemy equipment using its own armament.[89] Combat aircraft are typically developed and procured only by military forces.
Non-combat aircraft, such astransports andtankers, are not designed for combat as their primary function but may carry weapons for self-defense. These mainly operate in support roles, and may be developed by either military forces or civilian organizations.
Civil aviation is one of two major categories of flying, representing all non-military and non-stateaviation, which can be both private and commercial. Most countries in the world are members of theInternational Civil Aviation Organization and work together to establish commonStandards and Recommended Practices for civil aviation through that agency.
Aerial work, in which an aircraft is used for specialized services such as agriculture, photography, surveying, search and rescue, etc.
General aviation (GA), including all other civil flights, private or commercial[90]
Although scheduled air transport is the larger operation in terms of passenger numbers, GA is larger in the number of flights (and flight hours, in the U.S.[91]) In the U.S., GA carries 166 million passengers each year,[92] more than any individual airline, though less than all the airlines combined. Since 2004, the U.S. airlines combined have carried over 600 million passengers each year, and in 2014, they carried a combined 662,819,232 passengers.[93]
Some countries also make a regulatory distinction based on whether aircraft are flown for hire, like:
Commercial aviation includes most or all flying done for hire, particularly scheduled service onairlines; and
Private aviation includes pilots flying for their own purposes (recreation, business meetings, etc.) without receiving any kind of remuneration.
All scheduled air transport is commercial, but general aviation can be either commercial or private. Normally, the pilot, aircraft, and operator must all be authorized to perform commercial operations through separate commercial licensing, registration, and operation certificates.
Anexperimental aircraft is an aircraft intended for testing newaerospace technologies and design concepts.
The termresearch aircraft ortestbed aircraft, by contrast, generally denotes aircraft modified to perform scientific studies, such as weather research or geophysical surveying, similar to aresearch vessel.[94]
The term "experimental aircraft" also has specific legal meaning in Australia, the United States and some other countries; usually used to refer to aircraft flown with anexperimental certificate.[95] In theUnited States, this also includes mosthomebuilt aircraft, many of which are based on conventional designs and hence are experimental only in name because of certain restrictions in operation.[96]
Model aircraft are typically small-scale replicas of flying aircraft, or new designs built smaller than mostpassenger aircraft. Static model aircraft, which cannot fly, are usually not considered to be aircraft, but they can be used to test aspects of a flying aircraft, such as its aerodynamics. Flying models are commonly propelled byelectric motors,combustion engines, or aregliders, but there are many alternate methods of propulsion, such as wound rubber bands and smalljet engines. Most flying model aircraft are eitherradio-controlled aircraft, fly freely, or are controlled by wires held by the pilot.
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Note 1:Atiltwing ortiltrotor aircraft functions as an aeroplane during normal (horizontal) flight and as a helicopter during low-speed flight.
Note 2:For full-size aircraft with powered rotors the rotor is normally tilted to achieve thrust (e.g. in a helicopter). Some toys (e.g.balloon helicopter) do have a powered rotor with no means to tilt the rotor to produce horizontal thrust.
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