Saturday, August 30, 2008
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.
Safety
Comparisons
There are three main statistics which may be used to compare the safety of various forms of travel:[12]:
| Deaths per billion journeys |
|---|
| Bus: 4.3 |
| Rail: 20 |
| Van: 20 |
| Car: 40 |
| Foot: 40 |
| Water: 90 |
| Air: 117 |
| Bicycle: 170 |
| Motorcycle: 1640 |
| Deaths per billion hours |
|---|
| Bus: 11.1 |
| Rail: 30 |
| Air: 30.8 |
| Water: 50 |
| Van: 60 |
| Car: 130 |
| Foot: 220 |
| Bicycle: 550 |
| Motorcycle: 4840 |
| Deaths per billion kilometres |
|---|
| Air: 0.05 |
| Bus: 0.4 |
| Rail: 0.6 |
| Van: 1.2 |
| Water: 2.6 |
| Car: 3.1 |
| Bicycle: 44.6 |
| Foot: 54.2 |
| Motorcycle: 108.9 |
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.[13]
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.
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.[3]
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.[4][5] This machine, which its inventor called The Pigeon (Greek: Περιστέρα "Peristera"), may have been suspended on a wire or pivot for its flight.[6][7] Amongst the first recorded attempts at aviation were the attempts made by Yuan Huangtou and Abbas Ibn Firnas. Leonardo da Vinci researched the wing design of birds and designed a man-powered aircraft in the 15th 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 inventor 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.[8] 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.[citation needed]
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".[9] By 1905, the Wright Flyer III was capable of fully controllable, stable flight for substantial periods. Strictly speaking, the Flyer's wings were not completely fixed, as it depended for stability on a flexing mechanism named wing warping. This was later superseded by the development of ailerons, devices which performed a similar function but were attached to an otherwise rigid wing.
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 in Europe, the 14-bis, which was of his and Gabriel Voisin's design. It was the first aircraft to take off, fly and land without the use of catapults, high winds, or other external assistance.[10] A later design of his, the Demoiselle, introduced ailerons and brought all around pilot control during a flight.[11]
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 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.
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 9.6, 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.
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.
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