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[[File:Air Berlin B737-700 Dreamliner D-ABBN.jpg|thumb|[[Air Berlin]] [[Boeing 737]]-700, showing blended winglets available on the Next Generation 737 models]] An '''airplane''' (also known as an '''aeroplane''' in [[British English]] or simply a '''plane''') is a [[powered]] [[fixed-wing aircraft]] that is propelled forward by [[thrust]] from a [[jet engine]] or [[Propeller (aircraft)|propeller]]. Planes come in a variety of sizes, shapes, and wing configurations. The broad spectrum of uses for planes includes recreation, transportation of goods and people, military, and research. |
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#REDIRECT [[Fixed-wing aircraft]] |
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==Etymology and usage== |
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{{This is a redirect|from alternative name|printworthy}} |
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First attested in English in late 19th century, the word ''aeroplane'' derives from the French ''aéroplane'', which comes from the Greek ἀήρ (''aēr''), "air"<ref>[http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0057%3Aentry%3Da%29h%2Fr ἀήρ], Henry George Liddell, Robert Scott, ''A Greek-English Lexicon'', on Perseus</ref> + either Latin ''planus'', "level",<ref>[http://www.merriam-webster.com/dictionary/aeroplane "aeroplane"], Merriam-Webster Online Dictionary.</ref> or Greek πλάνος (''planos''), "wandering".<ref>[http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0057%3Aentry%3Dpla%2Fnos πλάνος], Henry George Liddell, Robert Scott, ''A Greek-English Lexicon'', on Perseus</ref><ref>[http://oxforddictionaries.com/view/entry/m_en_gb0011110#m_en_gb0011110 aeroplane], Oxford Dictionaries</ref> "Aeroplane" originally referred just to the wing, as it is a plane moving through the air.<ref>[http://www.oed.com/view/Entry/3196#eid9528640 "aeroplane], Oxford English Dictionary online.</ref> In an example of [[synecdoche]], the word for the wing came to refer to the entire aircraft. |
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In the [[United Kingdom]] and most of the [[Commonwealth of Nations|Commonwealth]], the term 'aeroplane' is used for powered fixed-wing aircraft. In the United States and Canada, the term 'airplane' is usually applied to these aircraft. |
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==Propulsion== |
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{{See also|Powered aircraft|Aircraft engine}} |
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===Propeller engines=== |
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[[Image:Antonov An-2 in Vitebsk.jpg|right|thumb|An [[Antonov An-2]] [[biplane]]]] |
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Smaller and older propeller planes make use of [[reciprocating engine]]s (or piston engines) to turn a [[Propeller (aircraft)|propeller]] to create thrust. The amount of thrust a propeller creates is determined by its disk area - the area in which the blades rotate. If the area is too small, efficiency is poor, and if the area is large, the propeller must rotate at a very low speed to avoid going supersonic and creating a lot of noise, and not much thrust. Because of this limitation, propellers are favoured for planes which travel at below mach .5, while jets are a better choice above that speed. Propeller engines may be quieter than jet engines (though not always) and may cost less to purchase maintain and so remain common on light general aviation aircraft such as the [[Cessna 172]]. Larger modern propeller planes such as the [[Bombardier Dash 8|Dash 8]] use a jet engine to turn the propeller, primarily because an equivalent piston engine in power output would be much larger and more complex. |
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===Jet engines=== |
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[[File:Июль 1997 года Ту-144ЛЛ взлетает с аэродрома ЛИИ им.Громовав в Жуковском.jpg|thumb|The [[Tupolev Tu-144]] world's first supersonic transport aircraft]] |
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[[File:British Airways Concorde G-BOAC 03.jpg|right|thumb|The [[Concorde]] supersonic transport aircraft]] |
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[[Jet aircraft]] are propelled by [[jet engine]]s, which are used because the aerodynamic limitations of propellers do not apply to jet propulsion. These engines are much more powerful than a reciprocating engine for a given size or weight and are comparatively quiet and work well at higher altitude. Most modern jet planes use [[turbofan]] jet engines which balance the advantages of a propeller, while retaining the exhaust speed and power of a jet. This is essentially a ducted propeller attached to a jet engine, much like a turboprop, but with a smaller diameter. When installed on an airliner, it is efficient so long as it remains below the [[speed of sound]] (or subsonic). Jet fighters and other [[supersonic aircraft]] that do not spend a great deal of time supersonic also often use turbofans, but to function, air intake ducting is needed to slow the air down so that when it arrives at the front of the turbofan, it is subsonic. When passing through the engine, it is then re-accelerated back to supersonic speeds. To further boost the power output, fuel is dumped into the exhaust stream, where it ignites. This is called an [[afterburner]] and has been used on both pure jet aircraft and [[turbojet]] aircraft although it is only normally used on combat aircraft due to the amount of fuel consumed, and even then may only be used for short periods of time. [[Supersonic transport|Supersonic airliners]] (e.g. [[Concorde]]) are no longer in use largely because flight at supersonic speed creates a [[sonic boom]] which is prohibited in most heavily populated areas, and because of the much higher consumption of fuel supersonic flight requires. |
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Jet aircraft possess high cruising speeds ({{convert|700|to|900|km/h|abbr=on}}) and high speeds for [[takeoff]] and [[landing]] ({{convert|150|to|250|km/h|abbr=on}}). Due to the speed needed for takeoff and landing, jet aircraft use [[Flap (aircraft)|flaps]] and [[Leading edge slats|leading edge devices]] to control of lift and speed. Many also use [[thrust reverser]]s to slow down the aircraft upon landing. |
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===Electric engines=== |
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An [[electric aircraft]] runs on [[electric motor]]s rather than [[internal combustion engine]]s, with [[electricity]] coming from [[fuel cell]]s, [[solar cell]]s, [[ultracapacitors]], [[power beaming]],<ref>[http://www.dfrc.nasa.gov/gallery/Photo/Power-Beaming/index.html Power Beaming]. Dfrc.nasa.gov.</ref> or [[battery (electricity)|batteries]]. Currently, flying electric aircraft are mostly experimental demonstrators, including manned and [[unmanned aerial vehicle]]s. |
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===Rocket engines=== |
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[[Image:X-1-1 In Flight - GPN-2000-000134.jpg|thumb|right|[[Bell X-1]] in flight, 1947]] |
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In [[World War II]], the Germans deployed the [[Messerschmitt Me 163|Me 163 Komet]] [[rocket-powered aircraft]]. The first plane to break the [[sound barrier]] in level flight was a rocket plane – the [[Bell X-1]]. The later [[North American X-15]] broke many speed and [[Flight altitude record|altitude records]] and laid much of the groundwork for later aircraft and spacecraft design. Rocket aircraft are not in common usage today, although [[rocket-assisted take off]]s are used for some military aircraft. Recent rocket aircraft include the [[Scaled Composites SpaceShipOne|SpaceShipOne]] and the [[XCOR EZ-Rocket]]. |
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===Ramjet and scramjet engines=== |
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[[Image:X43a2 nasa scramjet.jpg|thumb|left|Artist's concept of X-43A with [[scramjet]] attached to the underside]] |
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A [[ramjet]] is a form of jet engine that contains no major moving parts and can be particularly useful in applications requiring a small and simple engine for high-speed use, such as with missiles. Ramjets require forward motion before they can generate thrust and so are often used in conjunction with other forms of propulsion, or with and external means of achieving sufficient speed such as a parent aircraft or catapult. The [[Lockheed D-21]] was a Mach 3+ reconnaissance drone that was powered with a ramjet which was launched from a parent aircraft such as the [[Lockheed A-12]]. A ramjet works by using the forward motion of the vehicle to force air through the ramjet without resorting to turbines or vanes. Fuel is added and ignited, which heats and expands the air to provides thrust. |
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[[Scramjet]] aircraft are still in the experimental stage. A scramjet is a supersonic ramjet and aside from differences with dealing with internal supersonic airflow works like a conventional ramjet. This type engine requires very high initial speed in order to work. The [[NASA X-43]] is an experimental unmanned scramjet that set a world speed record in 2004 for a jet-powered aircraft with a speed of Mach 9.7, nearly {{convert|12000|km/h}} at an altitude of about {{convert|36000|m}}. |
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==Design and manufacture== |
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{{main|Aerospace manufacturer}} |
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Most airplanes are constructed by companies with the objective of producing them in quantity for customers. The design and planning process, including safety tests, can last up to four years for small turboprops or longer for larger planes. |
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During this process, the objectives and design specifications of the aircraft are established. First the construction company uses drawings and equations, simulations, wind tunnel tests and experience to predict the behavior of the aircraft. Computers are used by companies to draw, plan and do initial simulations of the aircraft. Small models and mockups of all or certain parts of the plane are then tested in wind tunnels to verify its aerodynamics. |
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When the design has passed through these processes, the company constructs a limited number of prototypes for testing on the ground. Representatives from an aviation governing agency often make a first flight. The flight tests continue until the aircraft has fulfilled all the requirements. Then, the governing public agency of aviation of the country authorizes the company to begin production. |
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In the United States, this agency is the [[Federal Aviation Administration]] (FAA), and in the European Union, [[Joint Aviation Authorities]] (JAA). In Canada, the public agency in charge and authorizing the mass production of aircraft is [[Transport Canada]]. |
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In the case of international sales, a license from the public agency of aviation or transport of the country where the aircraft is to be used is also necessary. For example, airplanes made by the French company, [[Airbus]], need to be certified by the FAA to be flown in the United States, and airplanes made by U.S.-based [[Boeing]] need to be approved by the JAA to be flown in the European Union. |
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Quieter planes are becoming more and more needed due to the increase in air traffic, particularly over urban areas, as [[aircraft noise]] pollution is a major concern. |
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Small planes can be designed and constructed by amateurs as homebuilts. Other [[homebuilt aircraft]] can be assembled using pre-manufactured kits of parts that can be assembled into a basic plane and must then be completed by the builder. |
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There are few companies that produce planes on a large scale. However, the production of a plane for one company is a process that actually involves dozens, or even hundreds, of other companies and plants, that produce the parts that go into the plane. For example, one company can be responsible for the production of the landing gear, while another one is responsible for the radar. The production of such parts is not limited to the same city or country; in the case of large plane manufacturing companies, such parts can come from all over the world. |
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The parts are sent to the main plant of the plane company, where the production line is located. In the case of large planes, production lines dedicated to the assembly of certain parts of the plane can exist, especially the wings and the fuselage. |
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When complete, a plane is rigorously inspected to search for imperfections and defects. After approval by inspectors, the plane is put through a series of [[flight test]]s to assure that all systems are working correctly and that the plane handles properly. Upon passing these tests, the plane is ready to receive the "final touchups" (internal configuration, painting, etc.), and is then ready for the customer. |
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==Characteristics== |
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[[Image:IAI Heron 1 in flight 2.JPEG|thumb|right|An [[IAI Heron]] - an [[unmanned aerial vehicle]] with a [[twin boom]] configuration]] |
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===Airframe=== |
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The structural parts of a fixed-wing aircraft are called the airframe. The parts present can vary according to the aircraft's type and purpose. Early types were usually made of wood with fabric wing surfaces, When engines became available for powered flight around a hundred years ago, their mounts were made of metal. Then as speeds increased more and more parts became metal until by the end of WWII all-metal aircraft were common. In modern times, increasing use of [[composite material]]s has been made. |
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Typical structural parts include: |
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* One or more large horizontal ''wings'', often with an [[airfoil]] cross-section shape. The wing deflects air downward as the aircraft moves forward, generating [[Lift (force)|lifting force]] to support it in flight. The wing also provides stability in [[Flight dynamics (aircraft)|roll]] to stop the aircraft from rolling to the left or right in steady flight. |
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[[Image:Antonov 225 (2010).jpg|thumb|right|The [[An-225 Mriya]], which can carry a 250-tonne payload, has two vertical stabilisers.]] |
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* A ''[[fuselage]]'', a long, thin body, usually with tapered or rounded ends to make its shape [[aerodynamically]] smooth. The fuselage joins the other parts of the airframe and usually contains important things such as the pilot, payload and flight systems. |
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* A ''[[vertical stabiliser]]'' or fin is a vertical wing-like surface mounted at the rear of the plane and typically protruding above it. The fin stabilises the plane's [[Flight dynamics (aircraft)|yaw]] (turn left or right) and mounts the [[rudder]] which controls its rotation along that axis. |
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* A ''[[horizontal stabiliser]]'', usually mounted at the tail near the vertical stabilizer. The horizontal stabilizer is used to stabilise the plane's [[Flight dynamics (aircraft)|pitch]] (tilt up or down) and mounts the [[Elevator (aircraft)|elevators]] which provide pitch control. |
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* ''[[Landing gear]],'' a set of wheels, skids, or floats that support the plane while it is on the surface. On seaplanes the bottom of the fuselage or floats (pontoons) support it while on the water. On some planes the landing gear retracts during flight to reduce drag. |
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===Wings=== |
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The wings of a fixed-wing aircraft are static planes extending either side of the aircraft. When the aircraft travels forwards, |
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air flows over the wings which are shaped to create lift. |
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====Wing structure==== |
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Airplanes have flexible wing surfaces which are stretched across a frame and made rigid by the lift forces exerted by the airflow over them. Larger aircraft have rigid wing surfaces which provide additional strength. |
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Whether flexible or rigid, most wings, have a strong frame to give them their shape and to transfer lift from the wing surface to the rest of the aircraft. The main structural elements are one or more spars running from root to tip, and many ribs running from the leading (front) to the trailing (rear) edge. |
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Early airplane engines had little power and light weight was very important. Also, early airfoil sections were very thin, and could not have strong frame installed within. So until the 1930s most wings were too light weight to have enough strength and external bracing struts and wires were added. When the available engine power increased during the 1920s and 30s, wings could be made heavy and strong enough that bracing was not needed any more. This type of unbraced wing is called a cantilever wing. |
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====Wing configuration==== |
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{{main|Wing configuration}} |
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{{main|Wing}} |
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[[File:Morane-Saulnier Type L - Captured with german insigna.jpg|thumb|Captured [[Morane-Saulnier L]] wire-braced parasol monoplane]] |
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The number and shape of the wings varies widely on different types. A given wing plane may be full-span or divided by a central [[fuselage]] into port (left) and starboard (right) wings. Occasionally even more wings have been used, with the three-winged [[triplane]] achieving some fame in WWI. The four-winged [[quadruplane]] and other [[multiplane]] designs have had little success. |
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A [[monoplane]] has a single wing plane, a [[biplane]] has two stacked one above the other, a [[tandem wing]] has two placed one behind the other. When the available engine power increased during the 1920s and 30s and bracing was no longer needed, the unbraced or cantilever monoplane became the most common form of powered type. |
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The wing [[planform]] is the shape when seen from above. To be aerodynamically efficient, a wing should be straight with a long span from side to side but have a short chord (high [[aspect ratio]]). But to be structurally efficient, and hence light weight, a wing must have a short span but still enough area to provide lift (low aspect ratio). |
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At transonic speeds, near the [[speed of sound]]), it helps to sweep the wing backwards or forwards to reduce drag from supersonic shock waves as they begin to form. The [[swept wing]] is just a straight wing swept backwards or forwards. |
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[[Image:Dassault Mirage G8.jpg|thumb|Two [[Dassault Mirage G]] prototypes, one with wings swept]] |
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The [[delta wing]] is a triangle shape which may be used for a number of reasons. As a flexible [[Rogallo wing]] it allows a stable shape under aerodynamic forces, and so is often used for ultralight aircraft and even [[kites]]. As a supersonic wing it combines high strength with low drag and so is often used for fast jets. |
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A variable geometry wing can be changed in flight to a different shape. The [[variable sweep wing|variable-sweep wing]] transforms between an efficient straight configuration for takeoff and landing, to a low-drag sewpt configuration for high-speed flight. Other forms of variable planform have been flown, but none have gone beyond the research stage. |
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===Fuselage=== |
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{{Main|fuselage}} |
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A ''[[fuselage]]'' is a long, thin body, usually with tapered or rounded ends to make its shape [[aerodynamically]] smooth. The fuselage may contain the [[flight crew]], passengers, cargo or [[payload (air and space craft)|payload]], fuel and engines. The pilots of manned aircraft operate them from a ''[[Cockpit (aviation)|cockpit]]'' located at the front or top of the fuselage and equipped with controls and usually windows and instruments. A plane may have more than one fuselage, or it may be fitted with booms with the tail located between the booms to allow the extreme rear of the fuselage to be useful for a variety of purposes. |
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===Wings vs. bodies=== |
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====Flying wing==== |
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{{main|Flying wing}} |
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[[Image:USAF B-2 Spirit.jpg|thumb|right|The US-produced [[B-2 Spirit]], a [[strategic bomber]] using a flying wing configuration which is capable of intercontinental missions]] |
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A flying wing is a [[tailless aircraft|tailless]] aircraft which has no definite [[fuselage]], with most of the crew, payload and equipment being housed inside the main wing structure.<ref name="Crane">Crane, Dale: ''Dictionary of Aeronautical Terms, third edition'', page 224. Aviation Supplies & Academics, 1997. ISBN 1-56027-287-2</ref> |
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The flying wing configuration was studied extensively in the 1930s and 1940s, notably by [[Jack Northrop]] and [[Cheston L. Eshelman]] in the United States, and [[Alexander Lippisch]] and the [[Horten brothers]] in Germany. |
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After the war, a number of experimental designs were based on the flying wing concept, but the known difficulties remained intractable. Some general interest continued until the early 1950s but designs did not necessarily offer a great advantage in range and presented a number of technical problems, leading to the adoption of "conventional" solutions like the [[Convair B-36]] and the [[B-52 Stratofortress]]. Due to the practical need for a deep wing, the flying wing concept is most practical for designs in the slow-to-medium speed range, and there has been continual interest in using it as a tactical [[airlift]]er design. |
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Interest in flying wings was renewed in the 1980s due to their potentially low [[radar]] reflection cross-sections. [[Stealth technology]] relies on shapes which only reflect radar waves in certain directions, thus making the aircraft hard to detect unless the radar receiver is at a specific position relative to the aircraft - a position that changes continuously as the aircraft moves. This approach eventually led to the Northrop [[B-2 Spirit]] [[Stealth aircraft|stealth]] bomber. In this case the aerodynamic advantages of the flying wing are not the primary needs. However, modern computer-controlled [[fly-by-wire]] systems allowed for many of the aerodynamic drawbacks of the flying wing to be minimized, making for an efficient and stable long-range bomber. |
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====Blended wing body==== |
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{{main|Blended wing}} |
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[[Image:NASA BWB.jpg|thumb|right|300px|Computer-generated model of the [[Boeing X-48]]]] |
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Blended wing body aircraft have a flattened and airfoil shaped body, which produces most of the lift to keep itself aloft, and distinct and separate wing structures, though the wings are smoothly blended in with the body. |
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Thus blended wing bodied aircraft incorporate design features from both a futuristic fuselage and flying wing design. The purported advantages of the blended wing body approach are efficient high-lift wings and a wide [[airfoil]]-shaped body. This enables the entire craft to contribute to [[lift (force)|lift]] generation with the result of potentially increased fuel economy. |
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====Lifting body==== |
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[[Image:X24.jpg|thumb|left|The Martin Aircraft Company [[Martin-Marietta X-24|X-24]] was built as part of a 1963 to 1975 experimental US military program.]] |
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{{main|Lifting body}} |
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A lifting body is a configuration in which the body itself produces [[lift (force)|lift]]. In contrast to a [[flying wing]], which is a wing with minimal or no conventional [[fuselage]], a lifting body can be thought of as a fuselage with little or no conventional wing. Whereas a flying wing seeks to maximize cruise efficiency at [[Subsonic flight|subsonic]] speeds by eliminating non-lifting surfaces, lifting bodies generally minimize the drag and structure of a wing for subsonic, [[supersonic]], and [[hypersonic]] flight, or, [[spacecraft]] [[re-entry]]. All of these flight regimes pose challenges for proper flight stability. |
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Lifting bodies were a major area of research in the 1960s and 70s as a means to build a small and lightweight manned spacecraft. The US built a number of famous lifting body rocket planes to test the concept, as well as several rocket-launched re-entry vehicles that were tested over the Pacific. Interest waned as the [[US Air Force]] lost interest in the manned mission, and major development ended during the [[Space Shuttle design process]] when it became clear that the highly shaped fuselages made it difficult to fit fuel tankage. |
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{{clear}} |
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===Empennage and foreplane=== |
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The classic [[airfoil]] section wing is unstable in flight and difficult to control. Flexible-wing types often rely on an anchor line or the weight of a pilot hanging beneath to maintain the correct attitude. Some free-flying types use an adapted airfoil that is stable, or other ingenious mechanisms including, most recently, electronic artificial stability. |
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But in order to achieve trim, stability and control, most fixed wing types have an [[empennage]] comprising a fin and rudder which act horizontally and a tailplane and elevator which act vertically. This is so common that it is known as the conventional layout. Sometimes there may be two or more fins, spaced out along the tailplane. |
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[[File:SaabViggen Canards.jpg|thumb|Canards on the [[Saab Viggen]]]] |
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Some types have a horizontal "[[Canard (aeronautics)|canard]]" foreplane ahead of the main wing, instead of behind it.<ref name="Crane">Crane, Dale: ''Dictionary of Aeronautical Terms, third edition'', page 86. Aviation Supplies & Academics, 1997. ISBN 1-56027-287-2</ref><ref name="GroundUp">Aviation Publishers Co. Limited, ''From the Ground Up'', page 10 (27th revised edition) ISBN 0-9690054-9-0</ref><ref name="FAR1.1">{{cite web|url = http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr&sid=49436e70336dc8d8f1ab7b3d789254af&rgn=div8&view=text&node=14:1.0.1.1.1.0.1.1&idno=14|title = Title 14: Aeronautics and Space - PART 1—DEFINITIONS AND ABBREVIATIONS|accessdate =5 August 2008|last = [[Federal Aviation Administration]]|authorlink = |year = 2008|month = August}}</ref> This foreplane may contribute to the trim, stability or control of the aircraft, or to several of these. |
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===Airplane controls=== |
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{{Main|Aircraft flight control system}}[[File:Pilotska kabina zrakoplova.JPG|thumb|Typical light aircraft ([[Cessna 150]]M) cockpit with control yokes]] |
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Airplanes have complex control systems. The main controls allow the pilot to direct the aircraft in the air. Typically these are: |
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*The ''[[yoke (aircraft)|yoke]]'' or ''[[joystick]]'' controls rotation of the plane about the pitch and roll axes. A [[yoke (aircraft)|yoke]] resembles a steering wheel, and a control stick is a joystick. The pilot can pitch the plane down by pushing on the yoke or stick, and pitch the plane up by pulling on it. Rolling the plane is accomplished by turning the yoke in the direction of the desired roll, or by tilting the control stick in that direction. |
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*''[[Rudder]] pedals'' control rotation of the plane about the yaw axis. There are two pedals that pivot so that when one is pressed forward the other moves backward, and vice versa. The pilot presses on the right rudder pedal to make the plane yaw to the right, and pushes on the left pedal to make it yaw to the left. The rudder is used mainly to balance the plane in turns, or to compensate for winds or other effects that tend to turn the plane about the yaw axis. |
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*On powered types, an engine stop control ("fuel cutoff", for example) and, usually, a ''[[Throttle]]'' or ''[[thrust lever]]'' and other controls, such as a fuel-mixture control (to compensate for air density changes with altitude change). |
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Other common controls include: |
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*''[[Flap (aircraft)|Flap]] levers,'' which are used to control the deflection position of flaps on the wings. |
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*''[[Spoiler (aeronautics)|Spoiler]] levers,'' which are used to control the position of spoilers on the wings, and to arm their automatic deployment in planes designed to deploy them upon landing. The spoilers reduce lift for landing. |
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*''[[Trim tab|Trim]] controls,'' which usually take the form of knobs or wheels and are used to adjust pitch, roll, or yaw trim. These are often connected to small airfoils on the trail edge of the control surfaces called 'trim tabs'. Trim is used to reduce the amount of pressure on the control forces needed to maintain a steady course. |
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*On wheeled types, ''[[Brake]]s'' are used to slow and stop the plane on the ground, and sometimes for turns on the ground. |
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A craft may have two pilots' seats with dual controls, allowing two pilots to take turns. This is often used for training or for longer flights. |
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The control system may allow full or partial automation of flight, such as an [[autopilot]], a wing leveler, or a [[flight management system]]. An [[Unmanned aerial vehicle|unmanned aircraft]] has no pilot but is controlled remotely or via means such as gyroscopes or other forms of autonomous control. |
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===Cockpit instrumentation=== |
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[[File:Six flight instruments.JPG|thumb|Six basic flight instruments]] |
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[[Cockpit]] instruments provide information to the pilots, including [[Flight instruments|flight data]], [[Aircraft engine|engine output]], navigation, communications and other aircraft systems that may be installed. |
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The six basic instruments (sometimes referred to as the six pack) include:<ref name=6pack>{{cite web|title=Six Pack - The Primary Flight Instruments|url=http://www.learntofly.ca/six-pack-primary-flight-instruments/|publisher=LearnToFly.ca|accessdate=31 January 2011}}</ref> |
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* An ''[[airspeed indicator]],'' which indicates the speed at which the plane is moving through the surrounding air. |
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* An ''[[altimeter]],'' which indicates the altitude or height of the plane above mean sea level. |
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* A ''[[heading indicator]],'' (sometimes referred to as a "directional gyro (DG)"), which indicates the magnetic compass heading that the plane's fuselage is pointing towards. The actual direction the plane is flying towards is affected by the wind conditions. |
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* An ''[[attitude indicator]],'' sometimes called an ''artificial horizon,'' which indicates the exact orientation of the plane about its pitch and roll axes. |
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* A ''[[vertical speed indicator]],'' which shows the rate at which the plane is climbing or descending. |
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* A ''[[turn coordinator]],'' or ''turn and bank indicator'' which helps the pilot maintain the plane in a coordinated attitude while turning. |
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Other instruments might include: |
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* A ''[[two-way radio]]'' to enable communications with other planes and [[air traffic control]]. Planes built before [[World War II]] may not have been equipped with a radio but they are nearly essential now. |
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* A ''[[horizontal situation indicator]],'' shows the position and movement of the plane as seen from above with respect to the ground, including course/heading and other information. |
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* Instruments showing the status of each engine in the plane (operating speed, thrust, temperature, RPM, and other variables). |
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* Combined display systems such as ''[[primary flight display]]s'' or ''navigation displays.'' |
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* Information displays such as on-board ''[[weather radar]]'' displays. |
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* A ''[[radio direction finder]]'' which indicates the direction to one or more radio beacons and which can be used to determine the plane's position. |
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* A ''[[satellite navigation]]'' system to provide an accurate position. |
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==Safety== |
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{{Main|Air safety}} |
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When risk is measured by deaths per passenger kilometer, air travel is approximately 10 times safer than travel by bus or rail. However, when using the deaths per journey statistic, air travel is significantly more dangerous than car, rail, or bus travel.<ref>[http://www.numberwatch.co.uk/risks_of_travel.htm The risks of travel]. Numberwatch.co.uk.</ref> Air travel insurance is relatively expensive for this reason- insurers generally use the deaths per journey statistic.<ref>[http://space.newscientist.com/article/mg16321985.200-flight-into-danger.html Flight into danger - 7 August 1999 - New Scientist Space]. Space.newscientist.com (7 August 1999).</ref> There is a significant difference between the safety of airliners and that of smaller private planes, with the per-mile statistic indicating that airliners are 8.3 times safer than smaller planes.<ref>{{citation|title=Is GA Flying Safer Than Driving?|url=http://www.meretrix.com/~harry/flying/notes/safetyvsdriving.html|first=Harry|last=Mantakos|accessdate=13 May 2012}}</ref> |
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==See also== |
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* [[Aircraft flight mechanics]] |
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* [[Airliner]] |
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* [[Aviation]] |
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* [[Aviation and the environment]] |
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* [[Aviation history]] |
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* [[Fuel efficiency]] |
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* [[List of altitude records reached by different aircraft types]] |
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* [[Maneuvering speed]] |
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* [[Metaplane]] |
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* [[Rotorcraft]] |
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==Reflist== |
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{{reflist}} |
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[[Category:American inventions]] |
[[Category:American inventions]] |
Revision as of 19:13, 2 March 2013
An airplane (also known as an aeroplane in British English or simply a plane) is a powered fixed-wing aircraft that is propelled forward by thrust from a jet engine or propeller. Planes come in a variety of sizes, shapes, and wing configurations. The broad spectrum of uses for planes includes recreation, transportation of goods and people, military, and research.
Etymology and usage
First attested in English in late 19th century, the word aeroplane derives from the French aéroplane, which comes from the Greek ἀήρ (aēr), "air"[1] + either Latin planus, "level",[2] or Greek πλάνος (planos), "wandering".[3][4] "Aeroplane" originally referred just to the wing, as it is a plane moving through the air.[5] In an example of synecdoche, the word for the wing came to refer to the entire aircraft.
In the United Kingdom and most of the Commonwealth, the term 'aeroplane' is used for powered fixed-wing aircraft. In the United States and Canada, the term 'airplane' is usually applied to these aircraft.
Propulsion
Propeller engines
Smaller and older propeller planes make use of reciprocating engines (or piston engines) to turn a propeller to create thrust. The amount of thrust a propeller creates is determined by its disk area - the area in which the blades rotate. If the area is too small, efficiency is poor, and if the area is large, the propeller must rotate at a very low speed to avoid going supersonic and creating a lot of noise, and not much thrust. Because of this limitation, propellers are favoured for planes which travel at below mach .5, while jets are a better choice above that speed. Propeller engines may be quieter than jet engines (though not always) and may cost less to purchase maintain and so remain common on light general aviation aircraft such as the Cessna 172. Larger modern propeller planes such as the Dash 8 use a jet engine to turn the propeller, primarily because an equivalent piston engine in power output would be much larger and more complex.
Jet engines
Jet aircraft are propelled by jet engines, which are used because the aerodynamic limitations of propellers do not apply to jet propulsion. These engines are much more powerful than a reciprocating engine for a given size or weight and are comparatively quiet and work well at higher altitude. Most modern jet planes use turbofan jet engines which balance the advantages of a propeller, while retaining the exhaust speed and power of a jet. This is essentially a ducted propeller attached to a jet engine, much like a turboprop, but with a smaller diameter. When installed on an airliner, it is efficient so long as it remains below the speed of sound (or subsonic). Jet fighters and other supersonic aircraft that do not spend a great deal of time supersonic also often use turbofans, but to function, air intake ducting is needed to slow the air down so that when it arrives at the front of the turbofan, it is subsonic. When passing through the engine, it is then re-accelerated back to supersonic speeds. To further boost the power output, fuel is dumped into the exhaust stream, where it ignites. This is called an afterburner and has been used on both pure jet aircraft and turbojet aircraft although it is only normally used on combat aircraft due to the amount of fuel consumed, and even then may only be used for short periods of time. Supersonic airliners (e.g. Concorde) are no longer in use largely because flight at supersonic speed creates a sonic boom which is prohibited in most heavily populated areas, and because of the much higher consumption of fuel supersonic flight requires.
Jet aircraft possess high cruising speeds (700 to 900 km/h (430 to 560 mph)) and high speeds for takeoff and landing (150 to 250 km/h (93 to 155 mph)). Due to the speed needed for takeoff and landing, jet aircraft use flaps and leading edge devices to control of lift and speed. Many also use thrust reversers to slow down the aircraft upon landing.
Electric engines
An electric aircraft runs on electric motors rather than internal combustion engines, with electricity coming from fuel cells, solar cells, ultracapacitors, power beaming,[6] or batteries. Currently, flying electric aircraft are mostly experimental demonstrators, including manned and unmanned aerial vehicles.
Rocket engines
In World War II, the Germans deployed the Me 163 Komet rocket-powered aircraft. The first plane to break the sound barrier in level flight was a rocket plane – the Bell X-1. The later North American X-15 broke many speed and altitude records and laid much of the groundwork for later aircraft and spacecraft design. Rocket aircraft are not in common usage today, although rocket-assisted take offs are used for some military aircraft. Recent rocket aircraft include the SpaceShipOne and the XCOR EZ-Rocket.
Ramjet and scramjet engines
A ramjet is a form of jet engine that contains no major moving parts and can be particularly useful in applications requiring a small and simple engine for high-speed use, such as with missiles. Ramjets require forward motion before they can generate thrust and so are often used in conjunction with other forms of propulsion, or with and external means of achieving sufficient speed such as a parent aircraft or catapult. The Lockheed D-21 was a Mach 3+ reconnaissance drone that was powered with a ramjet which was launched from a parent aircraft such as the Lockheed A-12. A ramjet works by using the forward motion of the vehicle to force air through the ramjet without resorting to turbines or vanes. Fuel is added and ignited, which heats and expands the air to provides thrust.
Scramjet aircraft are still in the experimental stage. A scramjet is a supersonic ramjet and aside from differences with dealing with internal supersonic airflow works like a conventional ramjet. This type engine requires very high initial speed in order to work. The NASA X-43 is an experimental unmanned scramjet that set a world speed record in 2004 for a jet-powered aircraft with a speed of Mach 9.7, nearly 12,000 kilometres per hour (7,500 mph) at an altitude of about 36,000 metres (118,000 ft).
Design and manufacture
Most airplanes are constructed by companies with the objective of producing them in quantity for customers. The design and planning process, including safety tests, can last up to four years for small turboprops or longer for larger planes.
During this process, the objectives and design specifications of the aircraft are established. First the construction company uses drawings and equations, simulations, wind tunnel tests and experience to predict the behavior of the aircraft. Computers are used by companies to draw, plan and do initial simulations of the aircraft. Small models and mockups of all or certain parts of the plane are then tested in wind tunnels to verify its aerodynamics.
When the design has passed through these processes, the company constructs a limited number of prototypes for testing on the ground. Representatives from an aviation governing agency often make a first flight. The flight tests continue until the aircraft has fulfilled all the requirements. Then, the governing public agency of aviation of the country authorizes the company to begin production.
In the United States, this agency is the Federal Aviation Administration (FAA), and in the European Union, Joint Aviation Authorities (JAA). In Canada, the public agency in charge and authorizing the mass production of aircraft is Transport Canada.
In the case of international sales, a license from the public agency of aviation or transport of the country where the aircraft is to be used is also necessary. For example, airplanes made by the French company, Airbus, need to be certified by the FAA to be flown in the United States, and airplanes made by U.S.-based Boeing need to be approved by the JAA to be flown in the European Union.
Quieter planes are becoming more and more needed due to the increase in air traffic, particularly over urban areas, as aircraft noise pollution is a major concern.
Small planes can be designed and constructed by amateurs as homebuilts. Other homebuilt aircraft can be assembled using pre-manufactured kits of parts that can be assembled into a basic plane and must then be completed by the builder.
There are few companies that produce planes on a large scale. However, the production of a plane for one company is a process that actually involves dozens, or even hundreds, of other companies and plants, that produce the parts that go into the plane. For example, one company can be responsible for the production of the landing gear, while another one is responsible for the radar. The production of such parts is not limited to the same city or country; in the case of large plane manufacturing companies, such parts can come from all over the world.
The parts are sent to the main plant of the plane company, where the production line is located. In the case of large planes, production lines dedicated to the assembly of certain parts of the plane can exist, especially the wings and the fuselage.
When complete, a plane is rigorously inspected to search for imperfections and defects. After approval by inspectors, the plane is put through a series of flight tests to assure that all systems are working correctly and that the plane handles properly. Upon passing these tests, the plane is ready to receive the "final touchups" (internal configuration, painting, etc.), and is then ready for the customer.
Characteristics
Airframe
The structural parts of a fixed-wing aircraft are called the airframe. The parts present can vary according to the aircraft's type and purpose. Early types were usually made of wood with fabric wing surfaces, When engines became available for powered flight around a hundred years ago, their mounts were made of metal. Then as speeds increased more and more parts became metal until by the end of WWII all-metal aircraft were common. In modern times, increasing use of composite materials has been made.
Typical structural parts include:
- One or more large horizontal wings, often with an airfoil cross-section shape. The wing deflects air downward as the aircraft moves forward, generating lifting force to support it in flight. The wing also provides stability in roll to stop the aircraft from rolling to the left or right in steady flight.
- A fuselage, a long, thin body, usually with tapered or rounded ends to make its shape aerodynamically smooth. The fuselage joins the other parts of the airframe and usually contains important things such as the pilot, payload and flight systems.
- A vertical stabiliser or fin is a vertical wing-like surface mounted at the rear of the plane and typically protruding above it. The fin stabilises the plane's yaw (turn left or right) and mounts the rudder which controls its rotation along that axis.
- A horizontal stabiliser, usually mounted at the tail near the vertical stabilizer. The horizontal stabilizer is used to stabilise the plane's pitch (tilt up or down) and mounts the elevators which provide pitch control.
- Landing gear, a set of wheels, skids, or floats that support the plane while it is on the surface. On seaplanes the bottom of the fuselage or floats (pontoons) support it while on the water. On some planes the landing gear retracts during flight to reduce drag.
Wings
The wings of a fixed-wing aircraft are static planes extending either side of the aircraft. When the aircraft travels forwards, air flows over the wings which are shaped to create lift.
Wing structure
Airplanes have flexible wing surfaces which are stretched across a frame and made rigid by the lift forces exerted by the airflow over them. Larger aircraft have rigid wing surfaces which provide additional strength.
Whether flexible or rigid, most wings, have a strong frame to give them their shape and to transfer lift from the wing surface to the rest of the aircraft. The main structural elements are one or more spars running from root to tip, and many ribs running from the leading (front) to the trailing (rear) edge.
Early airplane engines had little power and light weight was very important. Also, early airfoil sections were very thin, and could not have strong frame installed within. So until the 1930s most wings were too light weight to have enough strength and external bracing struts and wires were added. When the available engine power increased during the 1920s and 30s, wings could be made heavy and strong enough that bracing was not needed any more. This type of unbraced wing is called a cantilever wing.
Wing configuration
The number and shape of the wings varies widely on different types. A given wing plane may be full-span or divided by a central fuselage into port (left) and starboard (right) wings. Occasionally even more wings have been used, with the three-winged triplane achieving some fame in WWI. The four-winged quadruplane and other multiplane designs have had little success.
A monoplane has a single wing plane, a biplane has two stacked one above the other, a tandem wing has two placed one behind the other. When the available engine power increased during the 1920s and 30s and bracing was no longer needed, the unbraced or cantilever monoplane became the most common form of powered type.
The wing planform is the shape when seen from above. To be aerodynamically efficient, a wing should be straight with a long span from side to side but have a short chord (high aspect ratio). But to be structurally efficient, and hence light weight, a wing must have a short span but still enough area to provide lift (low aspect ratio).
At transonic speeds, near the speed of sound), it helps to sweep the wing backwards or forwards to reduce drag from supersonic shock waves as they begin to form. The swept wing is just a straight wing swept backwards or forwards.
The delta wing is a triangle shape which may be used for a number of reasons. As a flexible Rogallo wing it allows a stable shape under aerodynamic forces, and so is often used for ultralight aircraft and even kites. As a supersonic wing it combines high strength with low drag and so is often used for fast jets.
A variable geometry wing can be changed in flight to a different shape. The variable-sweep wing transforms between an efficient straight configuration for takeoff and landing, to a low-drag sewpt configuration for high-speed flight. Other forms of variable planform have been flown, but none have gone beyond the research stage.
Fuselage
A fuselage is a long, thin body, usually with tapered or rounded ends to make its shape aerodynamically smooth. The fuselage may contain the flight crew, passengers, cargo or payload, fuel and engines. The pilots of manned aircraft operate them from a cockpit located at the front or top of the fuselage and equipped with controls and usually windows and instruments. A plane may have more than one fuselage, or it may be fitted with booms with the tail located between the booms to allow the extreme rear of the fuselage to be useful for a variety of purposes.
Wings vs. bodies
Flying wing
A flying wing is a tailless aircraft which has no definite fuselage, with most of the crew, payload and equipment being housed inside the main wing structure.[7]
The flying wing configuration was studied extensively in the 1930s and 1940s, notably by Jack Northrop and Cheston L. Eshelman in the United States, and Alexander Lippisch and the Horten brothers in Germany. After the war, a number of experimental designs were based on the flying wing concept, but the known difficulties remained intractable. Some general interest continued until the early 1950s but designs did not necessarily offer a great advantage in range and presented a number of technical problems, leading to the adoption of "conventional" solutions like the Convair B-36 and the B-52 Stratofortress. Due to the practical need for a deep wing, the flying wing concept is most practical for designs in the slow-to-medium speed range, and there has been continual interest in using it as a tactical airlifter design.
Interest in flying wings was renewed in the 1980s due to their potentially low radar reflection cross-sections. Stealth technology relies on shapes which only reflect radar waves in certain directions, thus making the aircraft hard to detect unless the radar receiver is at a specific position relative to the aircraft - a position that changes continuously as the aircraft moves. This approach eventually led to the Northrop B-2 Spirit stealth bomber. In this case the aerodynamic advantages of the flying wing are not the primary needs. However, modern computer-controlled fly-by-wire systems allowed for many of the aerodynamic drawbacks of the flying wing to be minimized, making for an efficient and stable long-range bomber.
Blended wing body
Blended wing body aircraft have a flattened and airfoil shaped body, which produces most of the lift to keep itself aloft, and distinct and separate wing structures, though the wings are smoothly blended in with the body.
Thus blended wing bodied aircraft incorporate design features from both a futuristic fuselage and flying wing design. The purported advantages of the blended wing body approach are efficient high-lift wings and a wide airfoil-shaped body. This enables the entire craft to contribute to lift generation with the result of potentially increased fuel economy.
Lifting body
A lifting body is a configuration in which the body itself produces lift. In contrast to a flying wing, which is a wing with minimal or no conventional fuselage, a lifting body can be thought of as a fuselage with little or no conventional wing. Whereas a flying wing seeks to maximize cruise efficiency at subsonic speeds by eliminating non-lifting surfaces, lifting bodies generally minimize the drag and structure of a wing for subsonic, supersonic, and hypersonic flight, or, spacecraft re-entry. All of these flight regimes pose challenges for proper flight stability.
Lifting bodies were a major area of research in the 1960s and 70s as a means to build a small and lightweight manned spacecraft. The US built a number of famous lifting body rocket planes to test the concept, as well as several rocket-launched re-entry vehicles that were tested over the Pacific. Interest waned as the US Air Force lost interest in the manned mission, and major development ended during the Space Shuttle design process when it became clear that the highly shaped fuselages made it difficult to fit fuel tankage.
Empennage and foreplane
The classic airfoil section wing is unstable in flight and difficult to control. Flexible-wing types often rely on an anchor line or the weight of a pilot hanging beneath to maintain the correct attitude. Some free-flying types use an adapted airfoil that is stable, or other ingenious mechanisms including, most recently, electronic artificial stability.
But in order to achieve trim, stability and control, most fixed wing types have an empennage comprising a fin and rudder which act horizontally and a tailplane and elevator which act vertically. This is so common that it is known as the conventional layout. Sometimes there may be two or more fins, spaced out along the tailplane.
Some types have a horizontal "canard" foreplane ahead of the main wing, instead of behind it.[7][8][9] This foreplane may contribute to the trim, stability or control of the aircraft, or to several of these.
Airplane controls
Airplanes have complex control systems. The main controls allow the pilot to direct the aircraft in the air. Typically these are:
- The yoke or joystick controls rotation of the plane about the pitch and roll axes. A yoke resembles a steering wheel, and a control stick is a joystick. The pilot can pitch the plane down by pushing on the yoke or stick, and pitch the plane up by pulling on it. Rolling the plane is accomplished by turning the yoke in the direction of the desired roll, or by tilting the control stick in that direction.
- Rudder pedals control rotation of the plane about the yaw axis. There are two pedals that pivot so that when one is pressed forward the other moves backward, and vice versa. The pilot presses on the right rudder pedal to make the plane yaw to the right, and pushes on the left pedal to make it yaw to the left. The rudder is used mainly to balance the plane in turns, or to compensate for winds or other effects that tend to turn the plane about the yaw axis.
- On powered types, an engine stop control ("fuel cutoff", for example) and, usually, a Throttle or thrust lever and other controls, such as a fuel-mixture control (to compensate for air density changes with altitude change).
Other common controls include:
- Flap levers, which are used to control the deflection position of flaps on the wings.
- Spoiler levers, which are used to control the position of spoilers on the wings, and to arm their automatic deployment in planes designed to deploy them upon landing. The spoilers reduce lift for landing.
- Trim controls, which usually take the form of knobs or wheels and are used to adjust pitch, roll, or yaw trim. These are often connected to small airfoils on the trail edge of the control surfaces called 'trim tabs'. Trim is used to reduce the amount of pressure on the control forces needed to maintain a steady course.
- On wheeled types, Brakes are used to slow and stop the plane on the ground, and sometimes for turns on the ground.
A craft may have two pilots' seats with dual controls, allowing two pilots to take turns. This is often used for training or for longer flights.
The control system may allow full or partial automation of flight, such as an autopilot, a wing leveler, or a flight management system. An unmanned aircraft has no pilot but is controlled remotely or via means such as gyroscopes or other forms of autonomous control.
Cockpit instrumentation
Cockpit instruments provide information to the pilots, including flight data, engine output, navigation, communications and other aircraft systems that may be installed.
The six basic instruments (sometimes referred to as the six pack) include:[10]
- An airspeed indicator, which indicates the speed at which the plane is moving through the surrounding air.
- An altimeter, which indicates the altitude or height of the plane above mean sea level.
- A heading indicator, (sometimes referred to as a "directional gyro (DG)"), which indicates the magnetic compass heading that the plane's fuselage is pointing towards. The actual direction the plane is flying towards is affected by the wind conditions.
- An attitude indicator, sometimes called an artificial horizon, which indicates the exact orientation of the plane about its pitch and roll axes.
- A vertical speed indicator, which shows the rate at which the plane is climbing or descending.
- A turn coordinator, or turn and bank indicator which helps the pilot maintain the plane in a coordinated attitude while turning.
Other instruments might include:
- A two-way radio to enable communications with other planes and air traffic control. Planes built before World War II may not have been equipped with a radio but they are nearly essential now.
- A horizontal situation indicator, shows the position and movement of the plane as seen from above with respect to the ground, including course/heading and other information.
- Instruments showing the status of each engine in the plane (operating speed, thrust, temperature, RPM, and other variables).
- Combined display systems such as primary flight displays or navigation displays.
- Information displays such as on-board weather radar displays.
- A radio direction finder which indicates the direction to one or more radio beacons and which can be used to determine the plane's position.
- A satellite navigation system to provide an accurate position.
Safety
When risk is measured by deaths per passenger kilometer, air travel is approximately 10 times safer than travel by bus or rail. However, when using the deaths per journey statistic, air travel is significantly more dangerous than car, rail, or bus travel.[11] Air travel insurance is relatively expensive for this reason- insurers generally use the deaths per journey statistic.[12] There is a significant difference between the safety of airliners and that of smaller private planes, with the per-mile statistic indicating that airliners are 8.3 times safer than smaller planes.[13]
See also
- Aircraft flight mechanics
- Airliner
- Aviation
- Aviation and the environment
- Aviation history
- Fuel efficiency
- List of altitude records reached by different aircraft types
- Maneuvering speed
- Metaplane
- Rotorcraft
Reflist
- ^ ἀήρ, Henry George Liddell, Robert Scott, A Greek-English Lexicon, on Perseus
- ^ "aeroplane", Merriam-Webster Online Dictionary.
- ^ πλάνος, Henry George Liddell, Robert Scott, A Greek-English Lexicon, on Perseus
- ^ aeroplane, Oxford Dictionaries
- ^ "aeroplane, Oxford English Dictionary online.
- ^ Power Beaming. Dfrc.nasa.gov.
- ^ a b Crane, Dale: Dictionary of Aeronautical Terms, third edition, page 224. Aviation Supplies & Academics, 1997. ISBN 1-56027-287-2 Cite error: The named reference "Crane" was defined multiple times with different content (see the help page).
- ^ Aviation Publishers Co. Limited, From the Ground Up, page 10 (27th revised edition) ISBN 0-9690054-9-0
- ^ Federal Aviation Administration (2008). "Title 14: Aeronautics and Space - PART 1—DEFINITIONS AND ABBREVIATIONS". Retrieved 5 August 2008.
{{cite web}}
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ignored (help) - ^ "Six Pack - The Primary Flight Instruments". LearnToFly.ca. Retrieved 31 January 2011.
- ^ The risks of travel. Numberwatch.co.uk.
- ^ Flight into danger - 7 August 1999 - New Scientist Space. Space.newscientist.com (7 August 1999).
- ^ Mantakos, Harry, Is GA Flying Safer Than Driving?, retrieved 13 May 2012