thumb|A group of [[Military of Norway|Norwegian Bell 412 helicopters take part in a military exercise.]]
Aviation is the activity involving man-made air-borne
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, somewhat more credible claims of short-distance human flights appear, such as the winged flights of
Abbas Ibn Firnas (810–887),
Eilmer of Malmesbury (11th century), and the hot-air
Passarola of
Bartolomeu Lourenço de Gusmão (1685-1724).
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.
In 1799
Sir George Cayley set forth the concept of the modern airplane as a fixed-wing flying machine with separate systems for lift, propulsion, and control. Early dirigible developments included machine-powered propulsion (
Henri Giffard, 1852), rigid frames (
David Schwarz, 1896), and improved speed and maneuverability (
Alberto Santos-Dumont, 1901)
thumb|left|First flight by the Wright Brothers, December 17, 1903
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, who had solved the age old problem of controlling a craft in flight. 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 May 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
WW II, 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.
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 capable of leaving 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,
Southwest and
Westjet 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:
- center controllers, who control aircraft en route 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 and low altitude in northern
Scotland, 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 (CO
2),
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.
See also
