Airport

For other uses, see Airport (disambiguation).

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An aerial view of a medium-sized airport.

An airport is a facility where aircraft can take off and land. At the very minimum, an airport consists of one runway (or helipad), but other common components are hangars and terminal buildings. Apart from these, an airport may have a variety of facilities and infrastructure, including fixed base operator services, air traffic control, passenger facilities such as restaurants and lounges, and emergency services. A military airport is known as an airbase in North American terminology (other countries may use the term airfield or air station in current parlance or aerodrome in 1930s parlance). The term 'airfield' may also be used (especially in the UK) to refer to a facility that has nothing more than a landing strip.

Attributes

Airports vary in size, with smaller or less-developed airports often having only a single runway shorter than 2000 m. Larger airports for international flights generally have paved runways 3000 m or longer. Many small airports have dirt, grass, or gravel runways, rather than asphalt or concrete.

In the United States, the minimum dimensions for dry, hard landing fields are defined by the FAR Landing And Takeoff Field Lengths. These include considerations for safety margins during landing and take-off. Typically heavier aircraft need longer fields.

One of the largest landing fields in the world is at the Kennedy Space Center, which is used for landings of the Space Shuttle. The field is 4,572 m in length and 91.4 m wide. There are an additional 305m of paved overruns at the end, and the paving thickness is 406 mm at the center.

Airport structures

Airports are divided into landside and airside areas. Landside areas include parking lots, tank farms and access roads. Airside areas include all areas accessible to aircraft, including runways, taxiways and ramps. Access from landside areas to airside areas is tightly controlled at major airports. Passengers on commercial flights access airside areas through terminals, where they can purchase tickets, clear security, check or claim luggage and board aircraft. The waiting areas which provide passenger access to aircraft are typically called concourses, although this term is often used interchangeably with terminal.

The area where aircraft park next to a terminal to load passengers and baggage is known as a ramp. Parking areas for aircraft away from terminals are generally called aprons.

Both large and small airports can be towered or uncontrolled, depending on funds and traffic. Due to their high capacity and busy airspace, most international airports have air traffic control located on site.

International airports

Customs facilities for international flights define an international airport, and often require a more conspicuous level of physical security. International airports generally have a complex of buildings where passengers can embark on airliners, and where cargo can be stored and loaded.

The largest international airports are often located next to freeways or are served by their own freeways. Often, traffic is fed into two access roads, designed as loops, one sitting on top of the other. One level is for departing passengers and the other is for arrivals. Many airports also have light rail lines or other mass transit systems directly connected to the main terminals.

Shops and food services

Most International Airports have shops and food courts. These services usually provide the passengers food and drinks before they get on to their flight. Many recognizable chain food restaurants have opened branches in large airports to serve often hungry passengers.

International areas usually have a duty-free shop where travellers are not required to pay the usual duty fees on items. Larger airlines often operate member-only lounges for premium passengers.

Airports have a captive audience, and consequently the prices charged for food is generally higher than are available elsewhere in the region. However some airports now regulate food costs to keep them comparable to so-called "street prices".

Cargo and freight services

Loading luggage

In addition to people, airports are responsible for moving large volumes of cargo around the clock. Cargo airlines often have their own on-site and adjecent infrastructure to rapidly transfer parcels between ground and air modes of transportation.

Support services

Aircraft maintenance, pilot services, aircraft rental, and hangar rental is most often performed by a fixed base operator (FBO). At major airports, particularly those used as hubs, airlines may operate their own facilities, e.g. British Airways at Heathrow.

History and development

The earliest airplane landing sites were simply open, grassy fields. The plane could approach at any angle that provided a favorable wind direction. Early airfields were often built for the purpose of entertainment. These aerodromes consisted of a grassy field, with hangar for storage and servicing of airplaines, and observation stands for the visitors.

Increased aircraft traffic during World War I led to the construction of regular landing fields. Airplanes had to approach these from certain directions. This led to the development of aids for directing the approach and landing slope.

Following the war, some of these military airfields added commercial facilities for handling passenger traffic. One of the earliest such fields was Le Bourget, near Paris. The first international airport to open was the Croydon Airport, in South London [1] (http://www.sutton.gov.uk/leisure/heritage/croydon+airport.htm). In 1922, the first permanent airport and commercial terminal solely for commercial aviation was built at Königsburg, Germany. The airports of this era used a paved "apron", which permitted night flying as well as landing heavier airplanes.

The first lighting used on an airport was during the later part of the 1920s; in the 1930s approach lighting came into use. These indicated the proper direction and angle of descent. The colors and flash intervals of these lights became standardized under the ICAO. In the 1940s, the slope-line approach system was introduced. This consisted of two rows of lights that formed a funnel indicating the direction of the airfield. Additional lights indicated incorrect altitude and direction.

Following World War II, airport design began to become more sophisticated. Passenger buildings were being grouped together in an island, with runways arranged in groups about the terminal. This arrangement permitted expansion of the facilities. But it also meant that passengers had to travel further to reach their plane.

Airport designation and naming

Airports are uniquely represented by their IATA airport code and ICAO airport code. IATA airport codes are often, but not always, abbreviated forms of the common name of the airport, such as PHL for Philadelphia International Airport. Exceptions to this rule often occur when an airport's name is changed. O'Hare International Airport in Chicago retains the IATA code ORD, from its former name of Orchard Field.

In many countries airports are often named after a prominent local celebrity, commonly a politician, e.g. John F. Kennedy International Airport, Indira Gandhi International Airport.

Airport security

Airports are required to have safety precautions in most countries. Rules vary in different countries, but there are common elements worldwide. Airport security normally requires baggage checks, metal screenings of individual persons, and rules against any object that could be used as a weapon. Since the September 11, 2001 attacks, airport security has been dramatically increased worldwide.

See also: Airport security repercussions due to the September 11, 2001 attacks

Airport operations

Outside the terminal, there is a large team of people who work in concert to ensure aircraft can land, takeoff, and move around quickly and safely. These processes are largely invisible to passengers, but they can be extraordinarily complex at large airports.

Air Traffic Control

Air Traffic Control is system whereby ground-based controllers direct aircraft movements, usually via radio. This coordinated oversight facilitates safety and speed in complex operations where traffic can move in all three dimensions. Air Traffic Control is usually divided into two main areas: ground and tower.

Ground Control is responsible for directing all vehicles on the ground inside the airport, except those on the runways. This includes planes, baggage trains, snowplows, grass cutters, fuel trucks, and a wide array of other vehicles. Ground Control will instruct these vehicles on which taxiways to use, which runway they will use (in the case of planes), where they will park, and when it is safe to cross runways. When a plane is ready to take off it will stop short of the runway, at which point it will be turned over to Tower Control. After a plane has landed, it will turn off the runway and be returned to Ground Control.

Tower Control controls aircraft on the runway and in the Controlled airspace immediately surrounding the airport. Tower controllers use radar to visualize an aircrafts' position in three-dimensional space and identify it with Transponder codes. They coordinate the sequencing of aircraft in the traffic pattern and direct aircraft on how to safely join and leave the circuit. Aircraft which are only passing through the airspace must also contact Tower Control in order to be sure that they remain clear of other traffic and do not disrupt operations.

Traffic pattern

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Smaller airports and military airfields use a traffic pattern to assure smooth traffic flow between departing and arriving aircraft. Generally, this pattern is a circuit consisting of five "legs" that form a rectangle (two legs and the runway form one side, with the remaining legs each form another side). Each leg is named (see diagram), and ATC directs pilots on how to join and leave the circuit. Traffic patterns are flown at one specific altitude, usually 1000 ft AGL. Most traffic patterns are left-handed, meaning all turns are made to the left. Right-handed patterns do exist, usually because of obstacles such as a mountain or to reduce noise for local residents. The predetermined circuit helps pilots look for other aircraft, and helps reduce the chance of a mid-air collision.

At extremely large airports, a circuit is not usually used. Rather, ATC schedules aircraft for landing while they are still hours away from the airport. Airplanes can then take the most direct approach to the runway and land without worrying about interference from other aircraft. While this system keeps the airspace free and is simpler for pilots, it requires detailed knowledge of how aircraft are planning to use the airport ahead of time and is therefore only possible with large commercial airliners on pre-scheduled flights. The system has recently become so advanced that controllers can predict whether an aircraft will be delayed on landing before it even takes off; that aircraft can then be delayed on the ground, rather than wasting expensive fuel waiting in the air.

Navigational aids

Before takeoff, pilots usually check an Automatic Terminal Information Service (ATIS) for information about airport conditions where they exist. The ATIS contains information about weather, which runway and traffic patterns are in use, and other information that pilots should be aware of.

When flying, there are a number of aids available to pilots, though not all airports are equipped with them. A VASI, helps pilots fly a perfect approach for landing once they have found the airport. Some airports are equipped with a VOR to help pilots find the direction to the airport, VORs are often accompanied by a DME to determine the distance to the airport. In poor weather, pilots will use an Instrument Landing System to find the runway and fly the correct approach, even if they cannot see the ground.

Larger airports sometimes offer Precision Approach on Radar (PAR). The aircraft's horizontal and vertical movement is tracked via radar, and the controller tells the pilot his position relative to the approach slope. Once the pilots can see the runway lights, they may continue with a visual landing.

Guidance signs

Airport guidance signs provide direction and information to taxiing aircraft and airport vehicles and assist in safe and expedient movement of aircraft. Smaller airports may have few or no signs, relying instead on airport diagrams and charts.

There are two classes of signage at airports, with several types of each:

Operational guidance signs

• Location signs - yellow on black background. Identifies the runway or taxiway currently on or entering.
• Direction/Runway Exit signs - black on yellow. Identifies the intersecting taxiways the aircraft is approaching, with an arrow indicating the direction to turn.
• Destination signs -
• Other -

Mandatory instruction signs

Madatory instruction signs are white on red. They show entrances to runways or critical areas. Vehicles and aircraft are required to stop at these signs until the control tower gives clearance to proceed.

• Holding Position signs -
• Runway signs -

Lighting

Many airports have lighting that help guide planes using the runways and taxiways at night or in rain or fog.

On runways, green lights indicate the beginning of the runway for landing, while red lights indicate the end of the runway. Runway edge lighting is white lights spaced out on both sides of the runway, indicating the edge. Some airports have more complicated lighting on the runways including lights that run down the centerline of the runway and lights that help indicate the approach. At little-used airports Pilot Controlled Lighting may be used to save electricity and staffing costs.

Along taxiways, some airports have blue lights that indicate the taxiway's edge, and embedded green lights indicate the centerline of the taxiway.

Wind indicators

Planes take-off and land into the wind in order to achieve maximum performance. Wind speed and direction information is available through the ATIS or ATC, but pilots need instantaneous information during landing. For this purpose, a windsock is kept in view of the runway.

Safety management

Air safety is an important concern in the operation of an airport, and almost every airfield includes equipment and procedures for handling emergency situations. Commercial airfields include one or more emergency vehicles and their crew that are specially equipped for dealing with airfield accidents, crew and passenger extractions, and the hazards of highly flammable airplane fuel. The crews are also trained to deal with situations such as bomb threats, hijacking, and terrorist activities.

Potential airfield hazards to aircraft include debris, nesting birds, and environmental conditions such as ice or snow. The fields must be kept clear of debris using cleaning equipment so that loose material doesn't become a projectile and enter an engine duct. Similar concerns apply to birds nesting near an airfield, and crews often need to discourage birds from taking up residence. In adverse weather conditions, ice and snow clearing equipment can be used to improve traction on the landing strip. For waiting aircraft, equipment is used to spray special deicing fluids on the wings.

During the 1980s, a phenomenon known as microburst became a growing concern due to accidents caused by microburst wind shear. (For example, see Delta Air Lines Flight 191.) Microburst radar was developed as an aid to safety during landing, giving two to five minutes warning to aircraft in the vicinity of the field of an microburst event.

Environmental concerns

The traffic generated by airports both in the air and on the surface can be a major source of aviation noise and air pollution which may interrupt nearby residents' sleep or, in extreme cases, be harmful to their health . The construction of new airports, or addition of runways to existing airports, is often resisted by local residents because of the effect on the countryside, historical sites, local flora and fauna. As well, due to the risk of collision between birds and airplanes, large airports undertake population control programs where they frighten or shoot birds to ensure the safety of air travellers.

The construction of airports has been known to change local weather patterns. For example, because they often flatten out large areas, they can be succeptible to fog in areas where fog rarely forms. In addition, because they generally replace trees and grass with pavement, they often change drainage patterns in agricultural areas, leading to more flooding, run-off and erosion in the surrounding land.

Military Airbase

An Airbase, sometimes referred to as a military airport or airfield, provides basing and support of military aircraft. Some airbases provide facilites similar to their civilian counterparts. For example, RAF Brize Norton in Oxfordshire, England has a terminal which caters to passengers for the Royal Air Force's scheduled Tristar flights to the Falkland Islands. A special military airfield is an Aircraft Carrier.

Aircraft Carriers

An aircraft carrier is a warship that functions as a floating airport for military aircraft. Aircraft carriers allow a naval force to project air power great distances without having to depend on local bases for land-based aircraft. After their development in World War II, aircraft carriers rapidly replaced the battleship as the centrepiece of a modern fleet. Unescorted carriers are considered vulnerable to missile or submarine attacks and therefore travel as part of a carrier battle group that includes a wide array of other ships with specific functions.

Airports in Entertainment

Airports have occasionally played major roles in motion pictures and television shows due to being transportation hubs, but also because of their unique characteristics. One such example of this is the movie The Terminal, a film about a man who becomes permanently grounded in an airport terminal and must survive only on the food and shelter provided by the airport. If nothing else, this movie demonstrates the sustaining properties of airport terminals.

See also

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• List of airports
• Heliport
• World's Busiest Airport
• List of Aviation Topics
• NIMBY
• Aircraft Carrier

External links

• ATCSCC Real-time Airport Status page (http://www.fly.faa.gov/flyfaa/usmap.jsp) - shows airport delay times for major U.S. airports
• AFRICASPOTTER.at.tt (http://www.africaspotter.at.tt) - Airports in Southern Africa
• U.S. airport security (http://www.fortliberty.org/american-politics/airport-security.shtml)
• Department for Transport (http://www.dft.gov.uk) (United Kingdom)
• History of Aircraft Landing Aids (http://www.centennialofflight.gov/essay/Government_Role/landing_nav/POL14.htm)
• World airports (http://www.gofox.com/flights/popCodes.php?field=pickup_city)id:Bandar Udara

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