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| Trousers'" are an item of clothing worn on the lower part of the body from the waist to the ankles, covering both legs separately (rather than with cloth stretching across both as in skirts and dresses). Such items of clothing are often referred to as "'pants'" in countries such as Canada, South Africa and The United States. Additional synonyms include "'slacks'", "'kegs'" or "'kex'", "'breeches'" (sometimes) or "'breeks'". Historically, as for the West, trousers have been the standard lower-body clothing item for males since the 16th century; by the late 20th century, they had become prevalent for females as well. Trousers are worn at the hips or waist, and may be held up by their own fastenings, a belt, or suspenders (braces). Leggings are form-fitting trousers of a clingy material, often knitted cotton and lycra. Terminology. In North America, "pants" is the general category term, and "trousers" refers, often more formally, specifically to tailored garments with a waistband and (typically) belt-loops and a fly-front. For instance, informal elastic-waist knitted garments would never be called "trousers" in the U.S. Undergarments are called "underwear", "underpants", or "panties" (the last are women's garments specifically) to distinguish them from other pants that are worn on the outside. The term "drawers" normally refers to undergarments, but in some dialects, may be found as a synonym for "breeches", that is, trousers. In these dialects, the term "underdrawers" is used for undergarments. In Australia the terms "pants" and "trousers" are synonymous. In most parts of the United Kingdom, "trousers" is the general category term, and "pants" refers to underwear. In some parts of Scotland, trousers are known as "trews"; taken from the early Middle English "trouse", its plural developed into "trousers". Various people in the contemporary fashion industry use the word "pant" instead of "pants". This is grammatically incorrect. The word pants is a "plurale tantum", always in plural form much like the words scissors and tongs. The origin of pants is due to the use of two pieces of cloth in making it. Pant would actually mean just a single leg being covered with clothing. History. Nomadic Eurasian horsemen such as the Iranian Scythians, along with Achaemenid Persians, were among the first to wear trousers. In ancient China, trousers were only worn by soldiers. The first european appearance of trousers was in Hungary in the IX century. Men's clothes in Hungary in the 15th century consisted of a shirt and trousers as underwear, and a dolman worn over them, as well as a short fur-lined or sheepskin coat. At special occasions people wore gowns made of expensive materials, and these preferred by Pipo of Ozora too. Hungarian people had unique hair styles and wore high (fur) caps. Their trousers were simple in general, only their colour being unusual, but the dolman covered the greater part of the trousers. Trousers were introduced into Western European culture at several points in history, but gained their current predominance only in the 16th century, from a Commedia dell'Arte character named "Pantalone" (Italian word for Trousers). In England in the Twelfth century, the rustic were often seen in long garments to the ankle, rather like trousers, which are really glorified braies. Strangely enough, trouserlike garments, which became rare again in the thirteenth century, vanished during the fourteenth century and scarcely reappeared for six hundred years. The word itself is of Gaelic or Scots Gaelic origin, from the Middle Irish word "triubhas" (close-fitting shorts), however it is important to note that trews of the Early Industrial Period were in not trousers. Men's trousers. Trousers trace their ancestry to the individual hose worn by men in the 15th century (which is why trousers are plural and not singular). The hose were easy to make and fastened to a doublet at the top with ties called "points". It is important that at this point in time, these were not trousers, but trews, as can be seen in the 1746 painting by David Morier.. As time went by, the two hose were joined, first in the back then across the front, but still leaving a large opening for sanitary functions. Originally, doublets came almost to the knees, effectively covering the private parts, but as fashions changed and doublets became shorter, it became necessary for men to cover their genitals with a codpiece. By the end of the 16th century, the codpiece had been incorporated into the hose, now usually called breeches, which were roughly knee-length and featured a "fly" or "fall front" opening. During the French Revolution, the male citizens of France adopted a working-class costume including ankle-length trousers or pantaloons in place of the aristocratic knee-breeches. This style was introduced to England in the early 19th century, possibly by Beau Brummell, and supplanted breeches as fashionable street wear by mid-century. Breeches survived into the 1940s as the plus-fours or knickers worn for active sports and by young school-boys. Types of breeches are still worn today by baseball and American football players. Sailors may have played a role in the dissemination of trousers as a fashion around the world. In the 17th and 18th centuries, sailors wore baggy trousers known as "galligaskins". Sailors were also the first to wear jeans, trousers made of denim. These became more popular in the late 19th century in the American West, because of their ruggedness and durability. Women's trousers. Although trousers for women in western countries did not become fashion items until the later 20th century, women began wearing men's trousers (suitably altered) for outdoor work a hundred years earlier. Starting around the mid 19th Century, Wigan "pit brow girls" scandalized Victorian society by wearing trousers for their work at the local coal mines. They wore skirts over their trousers and rolled them up to their waist to keep them out of the way. Although "pit brow lassies" worked above-ground at the pit-head, the task of sorting and shovelling coal was hard manual labour, so wearing the usual long skirts of the time would have greatly hindered their movements. Women working the ranches of the 19th century American West also wore trousers for riding, and in the early 20th century aviatrices and other working women often wore trousers. Actresses Marlene Dietrich and Katharine Hepburn were often photographed in trousers from the 1930s and helped make trousers acceptable for women. During World War II, women working in factories and doing other forms of "men's work" on war service wore trousers when the work demanded it, and in the post-war era trousers became acceptable casual wear for gardening, the beach, and other leisure pursuits. In Britain during the Second World War, because of the rationing of clothing, many women took to wearing their husbands' civilian clothes, including their trousers, to work while their husbands were away in the armed forces. This was partly because they were seen as practical garments of workwear, and partly to allow women to keep their clothing allowance for other uses. As this practice of wearing trousers became more widespread and as the men's clothes wore out, replacements were needed, so that by the summer of 1944 it was reported that sales of women's trousers were five times more than in the previous year. In the 1960s, André Courrèges introduced long trousers for women as a fashion item, leading to the era of the pantsuit and designer jeans and the gradual eroding of the prohibitions against girls and women wearing trousers in schools, the workplace, and fine restaurants. Pleats. Pleats just below the waistband on the front are typical of many styles of formal and casual trousers including suit trousers and khakis. There may be one, two, three, or no pleats, which may face either direction. When the pleats open towards the pockets they are called reverse pleats (typical of khakis and corduroy trousers) and when they open toward the zipper, they are known as forward pleats. Utilitarian or very casual styles such as jeans and cargo pants are flat-front (without pleats at the waistband) but may have bellows pockets. Cuffs. Most trouser legs are finished by hemming the bottom to prevent fraying. Trousers with cuffs ("turn-ups" in British English), after hemming, are rolled outward and sometimes pressed or stitched into place. The main reason for the cuffs is to add weight to the bottom of the leg, to help the drape of the trousers. Fly. A fly on clothing is a covering over an opening join concealing the mechanism, such as a zip, velcro or buttons used to join the opening. The term is most frequently applied to a short opening in trousers, shorts and other garments covering the groin, and to allow garments to be taken on and off with greater ease. Trousers have varied historically in whether or not they have flies. Originally, hose did not cover between the legs, which was hidden by a codpiece, and when breeches were worn, for example in the Regency period, they were fall-fronted (or broad fall). After trousers (pantaloons) were later invented later the fly-front (split fall) emerged. Later the panelled front returned as a sporting option, such as in riding breeches, but is now hardly used, flies being by far the most common fastening. Most flies now use a zip, though enthusiasts continue to wear button flies. Society. It is customary in the western world for men to wear trousers and not skirts or dresses. However, there are exceptions, such as the Scottish kilt and the Greek foustanella, worn on ceremonial occasions, as well as robes or robe-like clothing such as the cassocks, etc. of clergy and academic robes (both rarely worn in daily use today). (See also Men's skirts.) Based on Deuteronomy 22:5 in the Bible, some groups believe that women should not wear trousers, but only skirts and dresses. Among certain groups, low-rise, baggy trousers exposing underwear are in fashion, e.g. among skaters and in 1990s hip hop fashion despite its prison-based origins. This fashion is called sagging. "Cut-offs" are homemade shorts made by cutting the legs off trousers, usually after holes have been worn in fabric around the knees. This extends the useful life of the trousers. The remaining leg fabric may be hemmed or left to fray after being cut. Removing one's trousers in public is considered taboo. Law. In May 2004 in Louisiana, state legislator Derrick Shepherd proposed a bill that would make it a crime to appear in public wearing trousers below the waist and thereby exposing one's skin or "intimate clothing". The Louisiana bill was retracted after negative public reaction. In February 2005, Virginia legislators tried to pass a similar law that would have made punishable by a $50 fine: "any person who, while in a public place, intentionally wears and displays his below-waist undergarments, intended to cover a person's intimate parts, in a lewd or indecent manner". It is not clear whether, with the same coverage by the trousers, exposing underwear was considered worse than exposing bare skin, or that the latter was already covered by another law. It passed in the Virginia House of Delegates. However, various criticisms to it arose. For example, newspaper columnists and radio talk show hosts consistently said that since most people that would be penalized under the law would be young African-American men, the law would thus be a form of discrimination against them. Virginia's state senators voted against passing the law. Carol Broussard, mayor of Delcambre, said that he will sign the proposal unanimously passed by town councillors, so that wearing trousers that reveal one's underwear will lead to a $500 penalty and the risk of six months in jail. "If you expose your private parts, you'll get a fine," said Mr Broussard. He told the Associated Press that people wearing low-slung trousers are "better off taking the pants off and wearing a dress." Ted Ayo, town attorney, said that the new legislation would expand on existing indecent exposure laws in Louisiana: "This is a new ordinance that deals specifically with sagging pants. It's about showing off your underwear in public". Mr. Broussard has received local criticism for the ordinance, with some Delcambre residents claiming that the proposal is racially motivated, due to the popularity of "sagging pants" among black hip-hop fans. However, he responded: "White people wear sagging pants, too." | A fixed-wing aircraft'" is an aircraft capable of heavier-than-air flight whose lift is generated not by wing motion relative to the aircraft, but by forward motion through the air. The term is used to distinguish from rotary-wing aircraft or ornithopters, where the movement of the wing surfaces relative to the aircraft generates lift. In the United States and Canada, the term "'airplane'" is used; the term "'aeroplane'" is more common in the rest of the English-speaking countries, including Great Britain, the rest of the Commonwealth countries (excluding Canada), and the Republic of Ireland. These terms refer to any fixed wing aircraft powered by propellers or jet engines. The word derives from the Greek "αέρας" (aéras-) ("air") and "-plane". The spelling "aeroplane" is the older of the two, dating back to the mid-late 19th century. Some fixed-wing aircraft may be remotely or robot controlled. Overview. Fixed-wing aircraft range from small training and recreational aircraft to wide-body aircraft and military cargo aircraft. The word also embraces aircraft with folding or removable wings that are intended to fold when on the ground. This is usually to ease storage or facilitate transport on, for example, a vehicle trailer or the powered lift connecting the hangar deck of an aircraft carrier to its flight deck. It also embraces aircraft with "variable-sweep wings", such as the General Dynamics F-111, Grumman F-14 Tomcat and the Panavia Tornado, which can vary the sweep angle of their wings during flight. There are also rare examples of aircraft which can vary the angle of incidence of their wings in flight, such the F-8 Crusader, which are also considered to be "fixed-wing". The two necessities for fixed-wing aircraft are air flow over the wings for lifting of the aircraft, and an area for landing. The majority of aircraft, however, also need an airport with the infrastructure to receive maintenance, restocking, refueling and for the loading and unloading of crew, cargo and passengers. Some aircraft are capable of take off and landing on ice, aircraft carriers, snow, or calm water. The aircraft is the second fastest method of transport, after the rocket. Commercial jet aircraft can reach up to 1000 km h. Certified single-engined, piston-driven aircraft are capable of reaching up to 435 km h, while Experimental (modified WW II fighters) piston singles reach over 815 km h at the Reno Air Races. Supersonic aircraft (military, research and a few private aircraft) can reach speeds faster than sound. The speed record for a plane powered by an air-breathing engine is held by the experimental NASA X-43, which reached nearly ten times the speed of sound. The biggest aircraft built is the Antonov An-225, while the fastest still in production is the Mikoyan MiG-31. The biggest supersonic jet ever produced is the Tupolev Tu-160. Structure. The structure of a fixed-wing aircraft consists of the following major parts: Some varieties of aircraft, such as flying wing aircraft, may lack a discernible fuselage structure and horizontal or vertical stabilizers. Controls. A number of controls allow pilots to direct aircraft in the air. The controls found in a typical fixed-wing aircraft are as follows: The controls may allow full or partial automation of flight, such as an autopilot, a wing leveler, or a flight management system. Pilots adjust these controls to select a specific attitude or mode of flight, and then the associated automation maintains that attitude or mode until the pilot disables the automation or changes the settings. In general, the larger and or more complex the aircraft, the greater the amount of automation available to pilots. Control duplication. On an aircraft with a pilot and copilot, or instructor and trainee, the aircraft is made capable of control without the crew changing seats. The most common arrangement is two complete sets of controls, one for each of two pilots sitting side by side, but in some aircraft (military fighter aircraft, some taildraggers and aerobatic aircraft) the dual sets of controls are arranged one in front of the other. A few of the less important controls may not be present in both positions, and one position is usually intended for the pilot in command ("e.g.," the left "captain's seat" in jet airliners). Some small aircraft use controls that can be moved from one position to another, such as a single yoke that can be swung into position in front of either the left-seat pilot or the right-seat pilot (i.e. Beechcraft Bonanza). Aircraft that require more than one pilot usually have controls intended to suit each pilot position, but still with sufficient duplication so that all pilots can fly the aircraft alone in an emergency. For example, in jet airliners, the controls on the left (captain's) side include both the basic controls and those normally manipulated by the pilot in command, such as the tiller, whereas those of the right (first officer's) side include the basic controls again and those normally manipulated by the copilot, such as flap levers. The unduplicated controls that are required for flight are positioned so that they can be reached by either pilot, but they are often designed to be more convenient to the pilot who manipulates them under normal condition. Aircraft instruments. "Instruments" provide information to the pilot. "Flight instruments" provide information about the aircraft's speed, direction, altitude, and orientation. "Powerplant instruments" provide information about the the status of the aircraft's engines and APU. "Systems instruments" provide information about the aircraft's other systems, such as fuel delivery, electrical, and pressurization. "Navigation and communication instruments" include all the aircraft's radios. Instruments may operate mechanically or electrically, requiring 12VDC, 24VDC, or 400 Hz power systems. An aircraft that uses computerized CRT or LCD displays almost exclusively is said to have a "glass cockpit." Propulsion. Fixed-wing aircraft can be sub-divided according to the means of propulsion they use. Unpowered aircraft. Aircraft that primarily intended for unpowered flight include gliders (sometimes called sailplanes), hang gliders and paragliders. These are mainly used for recreation. After launch, the energy for sustained gliding flight is obtained through the skilful exploitation of rising air in the atmosphere. Gliders that are used for the sport of gliding have high aerodynamic efficiency. The highest lift-to-drag ratio is 70:1, though 50:1 is more common. Glider flights of thousands of kilometers at average speeds over 200 km h have been achieved. The glider is most commonly launched by a tow-plane or by a winch. Some gliders, called motor gliders, are equipped with engines (often retractable) and some are capable of self-launching. The most numerous unpowered aircraft are hang gliders and paragliders. These are foot-launched and are generally slower, less massive, and less expensive than sailplanes. Hang gliders most often have flexible wings which are given shape by a frame, though some have rigid wings. This is in contrast to paragliders which have no frames in their wings. Military gliders have been used in war to deliver assault troops, and specialized gliders have been used in atmospheric and aerodynamic research. Experimental aircraft and winged spacecraft have also made unpowered landings. Propeller aircraft. Smaller and older propeller aircraft make use of reciprocating internal combustion engines that turns a propeller to create thrust. They are quieter than jet aircraft, but they fly at lower speeds, and have lower load capacity compared to similar sized jet powered aircraft. However, they are significantly cheaper and much more economical than jets, and are generally the best option for people who need to transport a few passengers and or small amounts of cargo. They are also the aircraft of choice for pilots who wish to own an aircraft. Turboprop aircraft are a halfway point between propeller and jet: they use a turbine engine similar to a jet to turn propellers. These aircraft are popular with commuter and regional airlines, as they tend to be more economical on shorter journeys. Jet aircraft. Jet aircraft make use of turbines for the creation of thrust. These engines are much more powerful than a reciprocating engine. As a consequence, they have greater weight capacity and fly faster than propeller driven aircraft. One drawback, however, is that they are noisy; this makes jet aircraft a source of noise pollution. However, turbofan jet engines are quieter, and they have seen widespread usage partly for that reason. The jet aircraft was developed in Germany in 1931. The first jet was the Heinkel He 178, which was tested at Germany's Marienehe Airfield in 1939. In 1943 the Messerschmitt Me 262, the first jet fighter aircraft, went into service in the German Luftwaffe. In the early 1950s, only a few years after the first jet was produced in large numbers, the De Havilland Comet became the world's first jet airliner. However, the early Comets were beset by structural problems discovered after numerous pressurization and depressurization cycles, leading to extensive redesigns. Most wide-body aircraft can carry hundreds of passengers and several tons of cargo, and are able to travel for distances up to 17,000 km. Aircraft in this category are the Boeing 747, Boeing 767, Boeing 777, the upcoming Boeing 787 and Airbus A380, Airbus A300 A310, Airbus A330, Airbus A340, Airbus A380, Lockheed L-1011 TriStar, McDonnell Douglas DC-10, McDonnell Douglas MD-11, Ilyushin Il-86, and Ilyushin Il-96. Jet aircraft possess high cruising speeds (700 to 900 km h, or 400 to 550 mph) and high speeds for take-off and landing (150 to 250 km h). Due to the speed needed for takeoff and landing, jet aircraft make use of flaps and leading edge devices for the control of lift and speed, as well as thrust reversers to direct the airflow forward, slowing down the aircraft upon landing. Supersonic jet aircraft. Supersonic aircraft, such as military fighters and bombers, Concorde, and others, make use of special turbines (often utilizing afterburners), that generate the huge amounts of power for flight faster than the speed of the sound. Flight at supersonic speed creates more noise than flight at subsonic speeds, due to the phenomenon of sonic booms. This limits supersonic flights to areas of low population density or open ocean. When approaching an area of heavier population density, supersonic aircraft are obliged to fly at subsonic speed. Due to the high costs, limited areas of use and low demand there are no longer any supersonic aircraft in use by any major airline. The last Concorde flight was on 26 November 2003. Unmanned Aircraft. An aircraft is said to be 'unmanned' when there is no person in the cockpit of the plane. The aircraft is controlled only by remote controls or other electronic devices. Rocket-powered aircraft. Experimental rocket powered aircraft were developed by the Germans as early as World War II (see Me 163 Komet), and about 29 were manufactured and deployed. The first fixed wing aircraft to break the sound barrier in level flight was a rocket plane- the Bell X-1. The later North American X-15 was another important rocket plane that 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 takeoffs are used for some military aircraft. SpaceShipOne is the most famous current rocket aircraft, being the testbed for developing a commercial sub-orbital passenger service; another rocket plane is the XCOR EZ-Rocket; and there is of course the Space Shuttle. Ramjet aircraft. 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 missiles. The D-21 Tagboard was an unmanned Mach 3+ reconnaissance drone that was put into production in 1969 for spying, but due to the development of better spy satellites, it was cancelled in 1971. The SR-71's Pratt & Whitney J58 engines ran 80% as ramjets at high speeds (Mach 3.2). The SR-71 was dropped at the end of the Cold War, then brought back during the 1990s. They were used also in the Gulf War. The last SR-71 flight was in October 2001. Scramjet aircraft. Scramjet aircraft are in the experimental stage. The Boeing X-43 is an experimental scramjet with a world speed record for a jet-powered aircraft Mach 9.7, nearly 12,000 km h (≈ 7,000 mph) at an altitude of about 36,000 meters (≈ 110,000 ft). The X-43A set the flight speed record on 16 November 2004. History. The dream of flight goes back to the days of pre-history. Many stories from antiquity involve flight, such as the Greek legend of Icarus and Daedalus, and the Vimana in ancient Indian epics. Around 400 BC, Archytas, the Ancient Greek philosopher, mathematician, astronomer, statesman, and strategist, was reputed to have designed and built the first artificial, self-propelled flying device, a bird-shaped model propelled by a jet of what was probably steam, said to have actually flown some 200 meters. This machine, which its inventor called "The Pigeon" (Greek: "Περιστέρα" "Peristera"), may have been suspended on a wire or pivot for its flight. Amongst the first recorded attempts at aviation were the attempts made by Yuan Huangtou in the 6th century and by Abbas Ibn Firnas in the 9th century. Leonardo da Vinci researched the wing design of birds and designed a man-powered aircraft in his "Codex on the Flight of Birds" (1502). In the 1630s, Lagari Hasan Çelebi flew in a rocket artificially powered by gunpowder. In the 18th century, Francois Pilatre de Rozier and Francois d'Arlandes flew in an aircraft lighter than air, a balloon. The biggest challenge became to create other craft, capable of controlled flight. Sir George Cayley, the founder of the science of aerodynamics, was building and flying models of fixed-wing aircraft as early as 1803, and he built a successful passenger-carrying glider in 1853. In 1856, Frenchman Jean-Marie Le Bris made the first powered flight, by having his glider "L'Albatros artificiel" pulled by a horse on a beach. On 28 August 1883, the American John J. Montgomery made a controlled flight in a glider. Other aviators who had made similar flights at that time were Otto Lilienthal, Percy Pilcher and Octave Chanute. The first self-powered aircraft was created by an Englishman by the name of John Stringfellow of Chard in Somerset, who created a self-powered model aircraft that had its first successful flight in 1848. Clément Ader constructed and designed a self-powered aircraft. On October 9, 1890, Ader attempted to fly the Éole, which succeeded in taking off and flying uncontrolled a distance of approximately 50 meters before witnesses. In August 1892 the Avion II flew for a distance of 200 meters, and on October 14, 1897, Avion III flew a distance of more than 300 meters. Richard Pearse made a poorly documented uncontrolled flight on March 31, 1903 in Waitohi, New Zealand, and on August 28, 1903 in Hanover, the German Karl Jatho made his first flight. Alberto Santos-Dumont, a Brazilian living in France, built the first practical dirigible balloons at the end of the nineteenth century. In 1906 he flew the first fixed wing aircraft, the "14-bis", which was of his and Gabriel Voisin's design. A later design of his, the "Demoiselle", introduced ailerons and brought all around pilot control during a flight. The Wright Brothers made their first successful test flights on December 17, 1903. This flight is recognized by the Fédération Aéronautique Internationale (FAI), the standard setting and record-keeping body for aeronautics and astronautics, as "the first sustained and controlled heavier-than-air powered flight". By 1905, the Wright Flyer III was capable of fully controllable, stable flight for substantial periods. World War I served as a testbed for the use of the aircraft as a weapon. Initially seen by the generals as a "toy", aircraft demonstrated their potential as mobile observation platforms, then proved themselves to be machines of war capable of causing casualties to the enemy. "Fighter aces" appeared, described as "knights of the air"; the greatest (by number of air victories) was the German Manfred von Richthofen, the "Red Baron". On the side of the allies, the ace with the highest number of downed aircraft was René Fonck, of France. Following the war, aircraft technology continued to develop. Alcock and Brown crossed the Atlantic non-stop for the first time in 1919, a feat first performed solo by Charles Lindbergh in 1927. The first commercial flights took place between the United States and Canada in 1919. The turbine or the jet engine was in development in the 1930s; military jet aircraft began operating in the 1940s. Aircraft played a primary role in the Second World War, having a presence in all the major battles of the war, Pearl Harbor, the battles of the Pacific, the Battle of Britain. They were an essential component of the military strategies of the period, such as the German Blitzkrieg or the American and Japanese aircraft carrier campaigns of the Pacific. In October 1947, Chuck Yeager was the first person to exceed the speed of sound, flying the Bell X-1. Aircraft in a civil military role continued to feed and supply Berlin in 1948, when access to railroads and roads to the city, completely surrounded by Eastern Germany, were blocked, by order of the Soviet Union. The first commercial jet, the de Havilland Comet, was introduced in 1952. A few Boeing 707s, the first widely successful commercial jet, are still in service after nearly 50 years. The Boeing 727 was another widely used passenger aircraft, and the Boeing 747 was the world's biggest commercial aircraft between 1970 and 2005, when it was surpassed by the Airbus A380. Designing and constructing an aircraft. Small aircraft can be designed and constructed by amateurs as homebuilts, such as Chris Neil's Woody Helicopter. Other aviators with less knowledge make their aircraft using pre-manufactured kits, assembling the parts into a complete aircraft. Most aircraft 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, and up to 12 years for aircraft with the capacity of the A380. 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 aircraft are then tested in wind tunnels to verify the aerodynamics of the aircraft. When the design has passed through these processes, the company constructs a limited number of these aircraft 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 of the aircraft. 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 the international sales of aircraft, a license from the public agency of aviation or transports of the country where the aircraft is also to be used is necessary. For example, aircraft from Airbus need to be certified by the FAA to be flown in the United States and vice versa, aircraft of Boeing need to be approved by the JAA to be flown in the European Union. Quieter aircraft are becoming more and more needed due to the increase in air traffic, particularly over urban areas, as noise pollution is a major concern. MIT and Cambridge University have been designing delta-wing aircraft that are 25 times more silent (63 dB) than current craft and can be used for military and commercial purposes. The project is called the Silent Aircraft Initiative, but production models will not be available until around 2030. Industrialized production. There are few companies that produce aircraft on a large scale. However, the production of an aircraft 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 aircraft. 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 aircraft manufacturing companies, such parts can come from all over the world. The parts are sent to the main plant of the aircraft company, where the production line is located. In the case of large aircraft, production lines dedicated to the assembly of certain parts of the aircraft can exist, especially the wings and the fuselage. When complete, an aircraft goes through a set of rigorous inspection, to search for imperfections and defects, and after being approved by the inspectors, the aircraft is tested by a pilot, in a flight test, in order to assure that the controls of the aircraft are working properly. With this final test, the aircraft is ready to receive the "final touchups" (internal configuration, painting, etc), and is then ready for the customer. Comparisons. There are three main statistics which may be used to compare the safety of various forms of travel: It is worth noting that the air industry's insurers base their calculations on the "number of deaths per journey" statistic while the industry itself generally uses the "number of deaths per kilometre" statistic in press releases. Causes. The majority of aircraft accidents are a result of human error on the part of the pilot(s) or controller(s). After human error, mechanical failure is the biggest cause of air accidents, which sometimes also can involve a human component; e.g., negligence of the airline in carrying out proper maintenance. Adverse weather is the third largest cause of accidents. Icing, downbursts, and low visibility are often major contributors to weather related crashes. Birds have been ranked as a major cause for large rotor bursts on commercial turboprop engines, spurring extra safety measures to keep birds away. Technological advances such as ice detectors also help pilots ensure the safety of their aircraft. |