aviation

aviation

[ey-vee-ey-shuhn, av-ee-]
aviation, operation of heavier-than-air aircraft and related activities. Aviation can be conveniently divided into military aviation, air transport, and general aviation. Military aviation includes all aviation activity by the armed services, such as combat, reconnaissance, and military air transport. Air transport consists mainly of the operation of commercial airlines, which handle both freight and passengers. General aviation consists of agricultural, business, charter, instructional, and pleasure flying; it includes such activities as the operation of air taxis, as well as aerial surveying and mapping.

See also air, law of the; air navigation; airplane; airship.

Early Interest in Human Flight

Interest in aviation can be traced back as far as Leonardo da Vinci; a human-powered aircraft based in part on his designs, Daedalus 88, flew 72 mi (115 km) in 1988. However, real progress toward achieving flight in heavier-than-air machines only began in the middle of the 19th cent. In 1842 the Englishman W. S. Henson patented a design for a machine that closely foreshadowed the modern monoplane; another Englishman, John Stringfellow, developed a model plane said to be the first power-driven machine to fly; and a third Englishman, F. H. Wenham, devised the first wind-tunnel experiments. In France, Alphonse Penaud made successful flying models of airplanes, while Clément Ader actually achieved flight (over a distance of about 150 ft/45 m in 1890 and about 300 yd/280 m in 1897) in a power-driven monoplane fashioned after a bat. In 1894 a plane built in England by Sir Hiram S. Maxim, operated by steam engines and carrying a crew of three, rose into the air from the track on which it was being tested. In the United States, S. P. Langley, Octave Chanute, and Otto Lilienthal made notable contributions to the early development of the airplane.

The Birth and Development of the Airplane

Finally, on Dec. 17, 1903, Orville and Wilbur Wright flew the first piloted airplane off the beach near Kitty Hawk, N. C. Henri Blériot and Glenn H. Curtiss made significant improvements in airplane design and, as more powerful engines became available, flew successively longer distances. In 1909 Blériot flew across the English Channel; ten years later a Curtiss-designed flying boat crossed the Atlantic Ocean. At first aviation development was motivated by the large prizes put up by publicity-seeking newspapers; but the outbreak of World War I in 1914 provided far greater motivation for aviation research and development (see air forces. The cessation of hostilities made available a large number of aircraft that could be bought cheaply, and the result was a great deal of aviation activity; barnstorming and stunt-flying kept aviation before the eyes of the public for a time, but the real stimulus was the initiation of airmail service in the mid-1920s. The intrepid airmail pilots caught the fancy of the public, and out of this group came the famous solo fliers Lindbergh, St-Exupéry, and others.

During the 1930s aviation continued to expand. Technological improvements in wind-tunnel testing, engine and airframe design, and maintenance equipment combined to provide faster, larger, and more durable airplanes. The transportation of passengers became profitable, and routes were extended to include several foreign countries. TransPacific airmail service, begun by Pan American Airways (later Pan American World Airways) in 1934, was followed by the first transoceanic aviation service for passengers, on the China Clipper, from San Francisco to Manila (to Hong Kong in 1937). In 1939 the first transatlantic service carrying both mail and passengers was inaugurated.

The Era of Mass Commercial Aviation

The outbreak of World War II interrupted commercial air service, but by 1947 all the basic technology essential to contemporary aviation had been developed: jet propulsion, streamlining, radar, and metallurgy. Perhaps the greatest example of this transition from military technology to commercial applications is the Boeing Company, a minor military contractor which became the largest aircraft manufacturer in the world. Commercial jet transportation began in 1952, when the British Overseas Airways Comet first flew from London to Johannesburg. Though this service was short-lived, by 1960 several commercial jet aircraft were in service; today virtually all commercial air routes are flown by jet or turboprop aircraft. The latest significant development in aviation has been the introduction of fly-by-wire control systems, which rely on computers and electronics rather than cables to operate aircraft control surfaces.

The result has been the explosive growth of commercial aviation, from jumbo and superjumbo jetliners to overnight package services, while general aviation has lagged behind. This growth has not been without some major problems. Jet aircraft use more fuel and require longer runways and more durable construction materials, and their sheer numbers create special problems for air-traffic control. In addition, the takeoff and landing of jet aircraft over populated areas create locally dangerous levels of noise pollution.

Bibliography

See A. de Saint-Exupéry, Wind, Sand, and Stars (tr. 1939); B. Markham, West with the Night (1942, repr. 1987); W. Green and G. Pollinger, The Aircraft of the World (1979); L. K. Loftin, The Evolution of Modern Aircraft (1985); D. Todd and J. Simpson, The World Aircraft Industry (1986).

Branch of medicine, pioneered by Paul Bert, dealing with atmospheric flight (aviation medicine) and space flight (space medicine). Intensive preflight simulator training and attention to design of equipment and spacecraft promote the safety and effectiveness of humans exposed to the stresses of flight and can prevent some problems. The world's first unit for space research was established in the U.S. in 1948. Physicians trained in aerospace medicine are known as flight surgeons.

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Development and operation of aircraft. In 1783 the balloon became the first aircraft to carry humans. Production of a successful glider in 1891 and refinement of the internal-combustion engine led to the first successful engine-powered airplane flight by Wilbur and Orville Wright in 1903. World War I accelerated the expansion of aviation, and in the 1920s the first small airlines began carrying mail and passengers. World War II was another period of innovation in aircraft size, speed, and range. In the late 1940s the jet engine made possible the subsequent development of commercial airlines throughout the world. Seealso airship; helicopter; seaplane.

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Aviation refers to activities involving man-made flying devices (aircraft), including the people, organizations, and regulatory bodies involved with them.

History

Many cultures have built devices that travel through the air, from the earliest projectiles such as stones and spears, to more sophisticated buoyant or aerodynamic devices such as the mechanical pigeon of Archytas in Ancient Greece, the boomerang in Australia, the hot air Kongming lantern, and kites. There are early legends of human flight such as the story of Icarus, and later, more credible claims of short-distance human flights including a kite flight by Yuan Huangtou in China, and the parachute flight and controlled glider flight of Abbas Ibn Firnas (Armen Firman).

The modern age of aviation began with the first untethered human lighter-than-air flight on November 21 1783, in a hot air balloon designed by the Montgolfier brothers.

The practicality of balloons was limited because they could only travel downwind. It was immediately recognized that a steerable, or dirigible, balloon was required. Jean-Pierre Blanchard flew the first human-powered dirigible in 1784 and crossed the English Channel in one in 1785. Subsequent early dirigible developments included machine-powered propulsion (Henri Giffard, 1852), rigid frames (David Schwarz, 1896), and improved speed and maneuverability (Alberto Santos-Dumont, 1901).

While there are many competing claims for the earliest powered, heavier-than-air flight, the most widely-accepted date is December 17 1903 by the Wright brothers, though their 1903 aircraft was impractical to fly for more than a short distance because of control problems. The widespread adoption of ailerons made aircraft much easier to manage, and only a decade later, at the start of World War I, heavier-than-air powered aircraft had become practical for reconnaissance, artillery spotting, and even attacks against ground positions.

Aircraft began to transport people and cargo as designs grew larger and more reliable. In contrast to small non-rigid blimps, giant rigid airships became the first aircraft to transport passengers and cargo over great distances. The best known aircraft of this type were manufactured by the German Zeppelin company.

The most successful Zeppelin was the Graf Zeppelin. It flew over one million miles, including an around-the-world flight in August 1929. However, the dominance of the Zeppelins over the airplanes of the that period, which had a range of only a few hundred miles, was diminishing as airplane design advanced. The "Golden Age" of the airships ended on June 6, 1937 when the Hindenburg caught fire killing 36 people. Although there have been periodic initiatives to revive their use, airships have seen only niche application since that time.

Great progress was made in the field of aviation during the 1920s and 1930s, such as Charles Lindbergh's transatlantic flight in 1927, and Charles Kingsford Smith's transpacific flight the following year. One of the most successful designs of this period was the Douglas DC-3 which became the first airliner that was profitable carrying passengers exclusively, starting the modern era of passenger airline service. By the beginning of World War II, many towns and cities had built airports, and there were numerous qualified pilots available. The war brought many innovations to aviation, including the first jet aircraft and the first liquid-fueled rockets.

After WWII, especially in North America, there was a boom in general aviation, both private and commercial, as thousands of pilots were released from military service and many inexpensive war-surplus transport and training aircraft became available. Manufacturers such as Cessna, Piper, and Beechcraft expanded production to provide light aircraft for the new middle class market.

By the 1950s, the development of civil jets grew, beginning with the de Havilland Comet, though the first widely-used passenger jet was the Boeing 707, because it was much more economical than other planes at the time. At the same time, turboprop propulsion began to appear for smaller commuter planes, making it possible to serve small-volume routes in a much wider range of weather conditions.

Yuri Gagarin was the first human to travel to space on April 12, 1961, while Neil Armstrong was the first to set foot on the moon on July 21, 1969.

Since the 1960s, composite airframes and quieter, more efficient engines have become available, and the Concorde provided supersonic passenger service for a time, but the most important lasting innovations have taken place in instrumentation and control. The arrival of solid-state electronics, the Global Positioning System, satellite communications, and increasingly small and powerful computers and LED displays, have dramatically changed the cockpits of airliners and, increasingly, of smaller aircraft as well. Pilots can navigate much more accurately and view terrain, obstructions, and other nearby aircraft on a map or through synthetic vision, even at night or in low visibility.

On June 21 2004, SpaceShipOne became the first privately funded aircraft to make a spaceflight, opening the possibility of an aviation market outside the earth's atmosphere. Meanwhile, flying prototypes of aircraft powered by alternative fuels, such as ethanol, electricity, and even solar energy, are becoming more common and may soon enter the mainstream, at least for light aircraft.

Civil aviation

Civil aviation includes all non-military flying, both general aviation and scheduled air transport.

Air transport

There are five major manufacturers of civil transport aircraft (in alphabetical order):

Boeing, Airbus, and Tupolev concentrate on wide-body and narrow-body jet airliners, while Bombardier and Embraer concentrate on regional airliners. Large networks of specialized parts suppliers from around the world support these manufacturers, who sometimes provide only the initial design and final assembly in their own plants. The Chinese ACAC consortium will also soon enter the civil transport market with its ACAC ARJ21 regional jet.

Until the 1970s, most major airlines were flag carriers, sponsored by their governments and heavily protected from competition. Since then, open skies agreements have resulted in increased competition and choice for consumers, coupled with falling prices for airlines. The combination of high fuel prices, low fares, high salaries, and crises such as the September 11, 2001 attacks and the SARS epidemic have driven many older airlines to government-bailouts, bankruptcy or mergers. At the same time, low-cost carriers such as Ryanair and Southwest have flourished.

General aviation

General aviation includes all non-scheduled civil flying, both private and commercial. General aviation may include business flights, air charter, private aviation, flight training, ballooning, parachuting, gliding, hang gliding, aerial photography, foot-launched powered hang gliders, air ambulance, crop dusting, charter flights, traffic reporting, police air patrols and forest fire fighting.

Each country regulates aviation differently, but general aviation usually falls under different regulations depending on whether it is private or commercial and on the type of equipment involved.

Many small aircraft manufacturers, including Cessna, Piper, Diamond, Mooney, Cirrus Design, Raytheon and others serve the general aviation market, with a focus on private aviation and flight training.

The most important recent developments for small aircraft (which form the bulk of the GA fleet) have been the introduction of advanced avionics (including GPS) that were formerly found only in large airliners, and the introduction of composite materials to make small aircraft lighter and faster. Ultralight and homebuilt aircraft have also become increasingly popular for recreational use, since in most countries that allow private aviation, they are much less expensive and less heavily regulated than certified aircraft.

Military aviation

Simple balloons were used as surveillance aircraft as early as the 18th century. Over the years, military aircraft have been built to meet ever increasing capability requirements. Manufacturers of military aircraft compete for contracts to supply their government's arsenal. Aircraft are selected based on factors like cost, performance, and the speed of production.

Types of military aircraft

Air Traffic Control (ATC)

Air traffic control (ATC) involves communication with aircraft to help maintain separation — that is, they ensure that aircraft are sufficiently far enough apart horizontally or vertically for no risk of collision. Controllers may co-ordinate position reports provided by pilots, or in high traffic areas (such as the United States) they may use RADAR to see aircraft positions.

There are generally four different types of ATC:

  • centre controllers, who control aircraft enroute between airports
  • control towers (including tower, ground control, clearance delivery, and other services), which control aircraft within a small distance (typically 10-15 km horizontal, and 1,000 m vertical) of an airport.
  • oceanic controllers, who control aircraft over international waters between continents, generally without radar service.
  • terminal controllers, who control aircraft in a wider area (typically 50-80 km) around busy airports.

ATC is especially important for aircraft flying under Instrument flight rules (IFR), where they may be in weather conditions that do not allow the pilots to see other aircraft. However, in very high-traffic areas, especially near major airports, aircraft flying under Visual flight rules (VFR) are also required to follow instructions from ATC.

In addition to separation from other aircraft, ATC may provide weather advisories, terrain separation, navigation assistance, and other services to pilots, depending on their workload.

ATC do not control all flights. The majority of VFR flights in North America are not required to talk to ATC (unless they are passing through a busy terminal area or using a major airport), and in many areas, such as northern Canada, ATC services are not available even for IFR flights at lower altitudes.

Environmental impact

Like all activities involving combustion, operating powered aircraft (from airliners to hot air balloons) releases greenhouse gases such as carbon dioxide (CO2), soot, and other pollutants into the atmosphere. In addition, there are environmental impacts specific to aviation:

  • Aircraft operating at high altitudes near the tropopause (mainly large jet airliners) emit aerosols and leave contrails, both of which can increase cirrus cloud formation — cloud cover may have increased by up to 0.2% since the birth of aviation.
  • Aircraft operating at high altitudes near the tropopause can also release chemicals that interact with greenhouse gases at those altitudes, particularly nitrogen compounds, which interact with ozone, increasing ozone concentrations.
  • Most light piston aircraft burn avgas, which contains tetra-ethyl lead (TEL), a highly-toxic substance that can cause soil contamination at airports. Some lower-compression piston engines can operate on unleaded mogas, and turbine engines and diesel engines — neither of which requires lead — are appearing on some newer light aircraft.

Notes

See also

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