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Airport

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). The terms airfield and airstrip may also be used to refer to a facility that has nothing more than a runway. The term aerodrome refers to any surface used for take off or landing. The term airport refers to an aerodrome that is licensed by the responsible government organization (ie FAA, Transport Canada). Airports have to be maintained to higher safety standards. There is usually no minimum standards for a basic aerodrome.

Attributes

Airports vary in size, with smaller or less-developed airports often having only a single runway shorter than 1,000 m (3,300 ft). Larger airports for international flights generally have paved runways 2,000 m (6,600 ft) 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 takeoff. Typically heavier aircraft require longer runways. The longest public-use runway in the world is at Ulyanovsk-Vostochny International Airport, in Ulyanovsk, Russia. It has a length of 16,404ft. As of 2005, there were approximately 50,000 airports around the world, including 19,815 in the United States alone.

Airport structures

Russia 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 most 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 air traffic density and available funds. 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

mass transits.]] Most international airports have shops and food courts. These services usually provide the passengers food and drinks before they board their flight. Many recognizable chain food restaurants have opened branches in large airports to serve often hungry passengers. London's Heathrow Airport, for example, is home to both a Harrods and a Hamleys Toy Shop, providing Duty Free for international passangers. 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". captive audience

Cargo and freight services

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 are most often performed by a fixed base operator (FBO). At major airports, particularly those used as hubs, airlines may operate their own support facilities.

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 airplanes, 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 [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 Königsberg, 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 an aircraft's position on the glideslope. 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, Illinois retains the IATA code ORD, from its former name of Orchard Field. In many countries airports are often named after a prominent national celebrity, commonly a politician, e.g. John F. Kennedy International Airport, Indira Gandhi International Airport or Charles de Gaulle 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.

Airport operations

Outside the terminal, there is a large team of people who work in concert to ensure aircraft can land, take off, 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 (or ATC) is system whereby ground-based controllers direct aircraft movements, usually via radio. This coordinated oversight facilitates safety and speed in complex operations where traffic moves in all three dimensions. Air traffic control responsibilities at airports are usually divided into two main areas: ground and tower. radio.]] Ground Control is responsible for directing all ground traffic in designated "movement areas," except the traffic on 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 depart 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 identify and accurately locate an aircraft's position in three-dimensional space. 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

radar 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 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

approach slope 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.
- Other - Many airports use conventional traffic signs such as stop and yield signs throughout the airport.

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.
- Runway signs - White on a red. These signs simply identify a runway intersection ahead.
- Frequency Change signs - Usually a stop sign and an instruction to change to another frequency. These signs are used at airports with different areas of ground control.
- Holding Position signs - A single solid yellow bar across a taxiway indicates a position where ground control may require a stop. If a two solid yellow bars and two dashed yellow bars are encountered, this indicates a holding position for a runway intersection ahead; runway holding lines must never be crossed without permission. At some airports, a line of red lights across a taxiway is used during low visibility operations to indicate holding positions.

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. Low-traffic airports may use Pilot Controlled Lighting to save electricity and staffing costs. Along taxiways, blue lights indicate the taxiway's edge, and some airports have embedded green lights that indicate the centerline.

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. Movies such as Airplane!, Airport, Die Hard II, Jackie Brown, and Get Shorty also revolve around the unique culture of the major city airports.

Airport Directories

Each national aviation authority has its own system for pilots to be able to keep track of information about airports in their country.
- The United States uses the Airport/Facility Directory (A/FD), seven volumes that contain information such as elevation, airport lighting, runway information, communications, hours of operation, nearby NAVAIDs and much more.
- In Canada, a single publication, the Canada Flight Supplement (CFS) provides equivalent information.

External links

- [http://www.airnav.com/airports/ AirNav.com] - complete list of U.S. airports, with detailed airport information
- [http://www.pspda.com/efad.html eFAD] - the most powerful electronic airport directory (A/FD) on earth!
- [http://www.fly.faa.gov/flyfaa/usmap.jsp ATCSCC Real-time Airport Status page] - shows airport delay times for major U.S. airports
- [http://www.africaspotter.at.tt AFRICASPOTTER.at.tt] - Airports in Southern Africa
- [http://www.fortliberty.org/american-politics/airport-security.shtml U.S. airport security]
- [http://www.dft.gov.uk Department for Transport] (United Kingdom)
- [http://www.centennialofflight.gov/essay/Government_Role/landing_nav/POL14.htm History of Aircraft Landing Aids]
- [http://www.numlink.com Airport satellite images] Category:Aviation Category:Transport infrastructure Category:Buildings and structures ko:공항 ms:Lapangan terbang ja:空港 simple:Airport th:สนามบิน

Aircraft

An aircraft is any machine capable of atmospheric flight. flight. This is a wide-bodied long-haul aircraft]]

Categories and classification

Aircraft fall into two broad categories:

Heavier than air

- Heavier than air aerodynes, including autogyros, helicopters and variants, and conventional fixed-wing aircraft: aeroplanes in Commonwealth English (excluding Canada), airplanes in North American English. Fixed-wing aircraft generally use an internal-combustion engine in the form of a piston engine (with a propeller) or a turbine engine (jet or turboprop), to provide thrust that moves the craft forward through the air. The movement of air over the airfoil produces lift that causes the aircraft to fly. Exceptions are gliders which have no engines and gain their thrust, initially, from winches or tugs and then from gravity and thermal currents. For a glider to maintain its forward speed it must descend in relation to the air (but not necessarily in relation to the ground). Helicopters and autogyros use a spinning rotor (a rotary wing) to provide lift; helicopters also use the rotor to provide thrust. The abbreviation VTOL is applied to aircraft other than helicopters that can take off or land vertically. STOL stands for Short Take Off and Landing. Mainly used internationally.

Lighter than air

STOL
- Lighter than air aerostats: hot air balloons and airships. Aerostats use buoyancy to float in the air in much the same manner as ships float on the water. In particular, these aircraft use a relatively low density gas such as helium, hydrogen or heated air, to displace the air around the craft. The distinction between a balloon and an airship is that an airship has some means of controlling both its forward motion and steering itself, while balloons are carried along with the wind.

Types of aircraft

:See also: List of aircraft There are several ways to classify aircraft. Below, we describe classifications by design, propulsion and usage.

By design

A first division by design among aircraft is between lighter-than-air, aerostat, and heavier-than-air aircraft, aerodyne. Examples of lighter-than-air aircraft include non-steerable balloons, such as hot air balloons and gas balloons, and airships (sometimes called dirigible balloons) such as blimps (that have non-rigid construction) and rigid airships that have a rigid frame. The most successful type of rigid airship was the Zeppelin, although there were some accidents such as the Hindenburg Zeppelin which was destroyed in a fire at Lakehurst, NJ, in 1937. In heavier-than-air aircraft, there are two ways to produce lift: aerodynamic lift and engine lift. In the case of aerodynamic lift, the aircraft is kept in the air by wings or rotors (see aerodynamics). With engine lift, the aircraft defeats gravity by use of vertical thrust greater than its weight. Examples of engine lift aircraft are rockets, and VTOL aircraft such as the Hawker-Siddeley Harrier. Among aerodynamically lifted aircraft, most fall in the category of fixed-wing aircraft, where horizontal airfoils produce lift, by profiting from airflow patterns determined by Bernoulli's equation and, to some extent, the Coanda effect. The forerunner of these type of aircraft is the kite. Kites depend upon the tension between the cord which anchors it to the ground and the force of the wind currents. Much aerodynamic work was done with kites until test aircraft, wind tunnels and now computer modelling programs became available. In a "conventional" configuration, the lift surfaces are placed in front of a control surface or tailplane. The other configuration is the canard where small horizontal control surfaces are placed forward of the wings, near the nose of the aircraft. Canards are becoming more common as supersonic aerodynamics grows more mature and because the forward surface contributes lift during straight-and-level flight. The number of lift surfaces varied in the pre-1950 period, as biplanes (two wings) and triplanes (three wings) were numerous in the early days of aviation. Subsequently most aircraft are monoplanes. This is principally an improvement in structures and not aerodynamics. Other possibilities include the delta-wing, where lift and horizontal control surfaces are often combined, and the flying wing, where there is no separate vertical control surface (e.g. the B-2 Spirit). A variable geometry ('swing-wing') has also been employed in a few examples of combat aircraft (the F-111, Panavia Tornado, F-14 Tomcat and B-1 Lancer, among others). The lifting body configuration is where the body itself produce lift. So far the only significant practical application of the lifting body is in the Space Shuttle, but many aircraft generate lift from nothing other than wings alone. A second category of aerodynamically lifted aircraft are the rotary-wing aircraft. Here, the lift is provided by rotating aerofoils or rotors. The best-known examples are the helicopter, the autogyro and the tiltrotor aircraft (such as the V-22 Osprey). Some craft have reaction-powered rotors with gas jets at the tips but most have one or more lift rotors powered from engine-driven shafts. A further category might encompass the wing-in-ground-effect types, for example the Russian ekranoplan also nicknamed the "Caspian Sea Monster" and hovercraft; most of the latter employing a skirt and achieving limited ground or water clearance to reduce friction and achieve speeds above those achieved by boats of similar weight. A recent innovation is a completely new class of aircraft, the fan wing. This uses a fixed wing with a forced airflow produced by cylindrical fans mounted above. It is (2005) in development in the United Kingdom. And finally the flapping-wing ornithopter is a category of its own. These designs may have potential but are not yet practical.

By propulsion

ornithopter adapted as a floatplane]] Some types of aircraft, such as the balloon or glider, do not have any propulsion. Balloons drift with the wind, though normally the pilot can control the altitude either by heating the air or by releasing ballast, giving some directional control (since the wind direction changes with altitude). For gliders, takeoff takes place from a high location, or the aircraft is pulled into the air by a ground-based winch or vehicle, or towed aloft by a powered "tug" aircraft. Airships combine a balloon's buoyancy with some kind of propulsion, usually propeller driven. Until World War II, the internal combustion piston engine was virtually the only type of propulsion used for powered aircraft. (See also: Aircraft engine.) The piston engine is still used in the majority of aircraft produced, since it is efficient at the lower altitudes used by small aircraft, but the radial engine (with the cylinders arranged in a circle around the crankshaft) has largely given way to the horizontally-opposed engine (with the cylinders lined up on two sides of the crankshaft). Water cooled V engines, as used in automobiles, were common in high speed aircraft, until they were replaced by jet and turbine power. Piston engines typically operate using avgas or regular gasoline, though some new ones are being designed to operate on diesel or jet fuel. Piston engines normally become less efficient above 7,000-8,000 ft (2100-2400 m) above sea level because there is less oxygen available for combustion; to solve that problem, some piston engines have mechanically powered compressors (blowers) or turbine-powered turbochargers or turbonormalizers that compress the air before feeding it into the engine; these piston engines can often operate efficiently at 20,000 ft (6100 m) above sea level or higher, altitudes that require the use of supplemental oxygen or cabin pressurisation. During the forties and especially following the 1973 energy crisis, development work was done on propellers with swept tips or even scimitar-shaped blades for use in high-speed commercial and military transports. Pressurised aircraft, however, are more likely to use the turbine engine, since it is naturally efficient at higher altitudes and can operate above 40,000 ft. Helicopters also typically use turbine engines. In addition to turbine engines like the turboprop and turbojet, other types of high-altitude, high-performance engines have included the ramjet and the pulse jet. Rocket aircrafts have occasionally been experimented with. They are restricted to rather specialised niches, such as spaceflight, where no oxygen is available for combustion (rockets carry their own oxygen).

By usage

The major distinction in aircraft usage is between military aviation, which includes all uses of aircraft for military purposes (such as combat, patrolling, search and rescue, reconnaissance, transport, and training), and civil aviation, which includes all uses of aircraft for non-military purposes.

Military aircraft

Combat aircraft like fighters or bombers represent only a minority of the category. Many civil aircraft have been produced in separate models for military use, such as the civil Douglas DC-3 airliner, which became the military C-47/C-53/R4D transport in the U.S. military and the Dakota in Britain and the Commonwealth. Even the little fabric-covered two-seater Piper J3 Cub had a military version, the L-4 liaison, observation and trainer aircraft. In the past, gliders and balloons have also been used as military aircraft; for example, balloons were used for observation during the American Civil War and World War I, and cargo gliders were used during World War II to land intruding German troops in many European countries in the 1940/42 period, while Allied troops used them in Europe after D-Day . Combat aircraft themselves, though used a handful of times for reconnaissance and surveillance during the Italo-Turkish War, did not come into widespread use until the Balkan War when first air-dropped bomb was invented and widely used by Bulgarian air force against Turkey. During World War I many types of aircraft were adapted for attacking the ground or enemy vehicles/ships/guns/aircraft, and the first aircraft designed as bombers were born. In order to prevent the enemy from bombing, fighter aircraft were developed to intercept and shoot down enemy aircraft. Tankers were developed after World War II to refuel other aircraft in mid-air, thus increasing their operational range. By the time of the Vietnam War, helicopters had come into widespread military use, especially for transporting and supporting ground troops.

Civil aviation

helicopter]] Civil aviation includes both scheduled airline flights and general aviation, a catch-all covering other kinds of private and commercial use. The vast majority of flights flown around the world each day belong to the general aviation category, ranging from recreational balloon flying to civilian flight training to business trips to firefighting to medevac flights to cargo transportation on freight aircraft. Within general aviation, the major distinction is between private flights (where the pilot is not paid for time or expenses) and commercial flights (where the pilot is paid by a customer or employer). Private pilots use aircraft primarily for personal travel, business travel, or recreation. Usually these private pilots own their own aircraft and take out loans from banks or specialized lenders to purchase them. Commercial general aviation pilots use aircraft for a wide range of tasks, such as flight training, pipeline surveying, passenger and freight transport, policing, crop dusting, and medical transport (medevac). Piston-powered propeller aircraft (single-engine or twin-engine) are especially common for both private and commercial general aviation, but even private pilots occasionally own and operate helicopters like the Bell JetRanger or turboprops like the Beechcraft King Air. Business jets are typically flown by commercial pilots, although there is a new generation of small jets arriving soon for private pilots.

External links

History
- [http://www.nasm.si.edu/ Smithsonian Air and Space Museum] - Excellent online collection with a particular focus on history of aircraft and spacecraft
- [http://invention.psychology.msstate.edu/Tale_of_Airplane/taleplane.html Virtual Museum]
- [http://www.centennialofflight.gov/essay/Prehistory/PH-OV.htm Prehistory of Powered Flight]
- [http://www.hq.nasa.gov/office/pao/History/SP-468/contents.htm The Evolution of Modern Aircraft (NASA)]
- [http://www.check-six.com Check-Six] - Information on historic aircraft crashes including the X-15 and Flying Wing
- [http://www.anythingplanes.net Aircraft community ] Information
- [http://www.aircraft-info.net Aircraft-Info.net]
- [http://www.airliners.net/info/ Airliners.net]
- [http://www.HomebuiltAircraft.com HomebuiltAircraft.com]- Information Portal about Homebuilt Aircraft
- [http://www.DefenceTalk.com Airforces ]
- [http://www.challoner.com/aviation/index.html Series of Photo Essays on British Aviation]
- [http://www.usenet-replayer.com/webrings/aviation.html Pictures of Aircraft] published on Usenet
- [http://www.sulman4paf.tk PAF Procedures and Information, Wallpapers, Picture Gallery, Updated News] Patents
- US[http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=/netahtml/srchnum.htm&r=1&f=G&l=50&s1=821393.WKU.&OS=PN/821393&RS=PN/821393 821393] -- Flying machine -- O. & W. Wright Category:Aircraft Category:Aviation zh-min-nan:Hui-hêng-ki ko:항공기 ms:Pesawat udara ja:航空機 simple:Aircraft

Take off

Take off is the phase of flight where an aircraft transitions from moving along the ground (taxiing) to flying in the air (see flight), usually from a runway. For a balloon, helicopter and some specialized fixed wing aircraft (VTOLs) vertical take off aircraft, no taxi is needed. Take off is the opposite of landing. For light aircraft, full power is normally used during take off. Large transport category (airliner) aircraft will usually use a derated power take-off, where less than full power is used. The aircraft is permitted to accelerate to rotation speed (often referred to as V_r) and then rotated off the ground gently. The term rotation is used, because the aircraft pivots or rotates about the axle of its main landing gear when the flight controls are used to change the aircraft attitude. Usually the rotation is approximately 10 to 15 degrees nose up compared to the position of the nose while on the ground. Autorotation is where an aircraft will do this by itself when it reaches some speed. aircraft attitude Larger planes (such as commercial jet aircraft) have difficulty generating enough lift at the (comparatively) low speeds encountered during take off. These are therefore fitted with high-lift devices, such as flaps or slats, which increase the lift of the wing at low speed. These are deployed from the front and rear edges of the wing before take off, and retracted during climb. The speeds needed for take off are relative to the motion of the air (air speed). A headwind will reduce the ground speed needed for take off. Typical take-off air speeds for jetliners are in the 130 to 155 knot range (150 to 180 miles/hour, 250 - 290 km/hour.) Light aircraft, such as a Cessna 150, take off at around 55 knots (63 miles/hour, 100 km/hour). Ultralights have even lower take-off speeds. The speed required varies according to many factors, including airport altitude, outside temperature, aircraft gross weight, power setting, and flap position. Pilots of multi-engine aircraft calculate a decision speed (V₁) for each take off that dictates action to be taken in case an engine fails. Below V₁ the take off is aborted; above V₁ the pilot should continue to take off. If an obstacle needs to be cleared, the pilot lowers the nose just until the speed for maximum climb angle is achieved, V_x. If no obstacle needs to be cleared, or once an obstacle is cleared, the pilot further lowers the nose to accelerate to V_y, the speed at which climb is the most rapid. At this point the climb phase of flight begins. Gliders take off using a variety of methods (see article on gliding), but most commonly they use winching-launching and towing behind a light aircraft. Category:Aviation

Landing

Landing is the last part of a flight, where a flying animal or aircraft returns to the ground. A similar process is correctly called alighting when returning to water. Hitting the ground too hard is prevented by wings (including rotor wings), a parachute or rockets or a vertically directed jet engine; in the case of a balloon the buoyancy is slightly decreased for a soft landing. Aircraft usually land at an airport on a runway or helicopter landing pad. helicopter landing pad For aircraft or birds, landing is generally accomplished by trading airspeed for lift. The first phase is the flare, where the rate of descent will be reduced by transitioning to a stall attitude. After slowing down, the plane changes pitch into the landing attitude shortly before touching down. In a perfect touchdown, assuming there is no crosswind, contact with the ground is made just as the forward speed is reduced to the point where there is no longer sufficient lift to remain aloft. If there is a crosswind, techniques such as a crab landing or a slip landing are used to land the plane safely. During landing, the ground effect becomes significant for aircraft. This tends to make the aircraft "keep flying" when it ordinarly would not (at higher altitudes) and therefore to extend the distance required to land. ground effect and flaps.]] Large jet transport aircraft land differently than described above. If the pilot waited for the aircraft to stall too much runway length would be used so the flare just reduces the rate of descent at touchdown and the aircraft is flown onto the runway. Usually spoilers (Sometimes called "Lift Dumpers") are immediately deployed to dramatically reduce the lift and transfer the aircraft's weight to its wheels, where mechanical braking can take effect. To land on an aircraft carrier, an aircraft (moving at, perhaps, 150 mph (240 km/h)) is equipped with tailhooks to engage one of up to four arresting cables stretched across the deck, stopping the aircraft within 320 feet (100 m) after engaging one of the cables. To assist safe landings, the carrier will usually steam directly into wind at full speed, thus reducing aircraft's speed relative to the carrier deck, and eliminating any crosswind.

Runway

A runway is a strip of land on an airport, on which aircraft can take off and land. Runways may be a prepared surface, (often asphalt or concrete) or an unprepared surface (grass, dirt, gravel).

Description

Large airports may have several runways. They are identified by the magnetic direction in which they point, rounding to the nearest ten degrees. So, for example, a runway identified with "36" would stand for a 360 degrees direction (i.e. North), "09" for 94 degrees, and "17" for 168 degrees. Each runway can be used in two directions, and hence has two numbers. Since the directions are necessarily opposite, the number of a runway can always be found by adding or subtracting 18 from the opposite runway number (whichever yields a positive number less than 37). For example runway 10 is called runway 28 when used in the opposite direction. If in an airport there is more than one runway pointing in the same direction, the runways are identified by the letters L, C and R, for Left, Center and Right, behind the number. Such an example would be runways "15L", "15C" and "15R". In speech runways are always referred to by saying each digit of the number, followed by 'Left', 'Right' or 'Center' if necessary. The first example above would be referred to as "Runway One Five Left". In many cases, at large airports where there are more than three parallel runways, one or more of the runway numbers is arbitrarily altered by 10 degrees, so as to avoid the need for potentially confusing terms such as "15 left center." For fixed wing aircraft it as advantageous to perform take-offs and landings into the wind to achieve the maximum lift. Airports usually have several runways, running in different directions, so that this can be done for different wind directions.

Runway Lighting

At bigger airports, runways use a standard lighting system to allow night landings. Seen from a landing plane, the runway starts with a strip of green lights at the near end and stops with a strip of red lights at the far end. The runway itself is framed with white elevated edge lights, as opposed to the blue elevated edge lights of a taxiway. The centerline is often indicated by white lights, which may be coded alternately white and yellow and then purely yellow nearing the far end of the runway. Furthermore, many runways equipped with instrument landing systems feature touchdown zone lighting. This consists of rows of white light bars on either side of the centerline over the first 30 feet of the runway. The sides of the runway are marked by lines of bright white lights. Larger runways may have another line of dimmer white lights running down the centerline. According to Transport Canada's regulations, the runway-edge lights must be visible for at least 2 miles.
- The lights must be arranged such that:
- the minimum distance between lines is 75 feet, and maximum is 200 feet;
- the maximum distance between lights within each line is 200 feet;
- the minimum length of parallel lines is 1400 feet;
- the minimum number of lights in the line is 8.

Runway markings

There are various runway markings and signs on any given runway. Larger runways have a distance remaining sign (black box with white numbers). This sign uses a single number to indicate the thousands of feet remaining, so 7 will indicate 7,000 feet remaining. The runway threshold is marked by a line of green lights. Image:Runway diagram.jpg Some airports/airfields (particularly uncontrolled ones) are equipped with Pilot Controlled Lighting, so that pilots can temporarily turn on the lights when they need them. This avoids the need for automatic systems or staff to turn the lights on at night or in other low visibility situations. This also avoids the costs of having hundreds of lights on for extended periods.

Active runway

An active runway is the runway at an airport that is in current use for all takeoffs and landings. Since takeoffs and landings are always done as close as "into the wind" as possible, wind direction determines the active runway (or just the active in aviation slang). Barring elevation constraints, runways are bidirectional. For example, a west-east runway will be both "Runway 27" and "Runway 9" (derived from the compass heading divided by ten) depending on direction. If the wind is blowing from the west, the active runway will be Runway 27, as 270° points west.

Longest runways

Some of the longest runways include:
- Edwards Air Force Base, California, USA () - 11,905 m (39,060 ft) dirt
- Nellis Air Force Base (Clark County, Nevada) () - 5506 m (18,067 ft)¹ asphalt/concrete
- Zhukovsky Aerodrome, Moscow, Russia () - 5403 m (17,726 ft) concrete
- Jih Ko Tse, China () - 5000 m (16,404 ft) concrete
- Embraer Gaviao Peixoto, Brazil () - 4967 m (16,295 ft) asphalt
- Upington, South Africa () - 4900 m (16,076 ft) asphalt
- Denver International Airport, Colorado, USA () - 4877 m (16,000 ft) concrete
- Edwards Air Force Base, California, USA () - 4576 m (15,013 ft) concrete
- Qamdo Bangda, China (Tibet) () - 4200 m (13,779 ft) concrete² ¹ Marked as "abandoned" on satellite imagery. Total pavement length including overruns is 24,085 ft. The facility's sole active runway has a length of 3651 m (11,980 ft). ² Listed here as Chinese sources have contributed to misperceptions that it is the world's longest runway. It is billed as the world's highest airport at 4300 m (14,707 ft).

Helipad

A helipad or helicopter landing pad is a landing area for helicopters. Though helicopters can usually land anywhere flat, a fabricated helipad provides a clearly marked hard surface away from obstacles where a helicopter can land. Helipads are usually constructed out of concrete and are marked with a circle, so as to be visible from the air. They may be located at a heliport or airport where fuel, air traffic control, and service facilities for aircraft are available. Conversely, a helipad may also be located away from such facilities; for example, helipads are commonly placed on the roof of hospitals to facilitate MEDEVACs. Large ships sometimes have a helipad onboard, and some buisinesses maintain a helipad on the roof of their office tower. Helipads are not always constructed out of concrete; sometimes forest fire fighters will construct a temporary helipad out of wood to receive supplies in remote areas. Category:Airfields

Hangar

A hangar is a metal, wooden, or concrete structure designed to hold one or many aircraft in protective storage. Hangars may be used to protect aircraft from weather or enemy attack (if in a wartime environment), when undergoing repairs, or are simply not in use. Any type of aircraft can be housed in a hangar—some very large ones were constructed to house dirigibles during refueling and boarding. The word hangar comes from a northern French dialect, and literally means "cattle pen." French (helicopters), and lighter-than-air ships.]]

History

lighter-than-air ships lighter-than-air ships In 1909, Louis Bleriot crash-landed on a northern French farm in Les Baraques (between Sangatte and Calais) and rolled his monoplane into the farmer's cattle pen. At the time, Bleriot was in a race to be the first man to cross the English Channel in a heavier-than-air aircraft, so he set up headquarters in the unused shed. After returning home, Bleriot called REIDsteel, the maker of the cattle pen, and ordered three "hangars" for personal use. REIDsteel continues to make hangars and hangar parts to this day. The Wright brothers were the first to store and repair a functional airplane in a protective structure. They constructed a wooden hangar in 1902 on Kill Devil Hill in North Carolina for their glider. After completing design and construction of the Wright Flyer in Ohio, the brothers returned to Kill Devil Hill only to find their hangar damaged. They repaired the structure and constructed a new workshop while they waited for the Flyer to be shipped. After every disappointing run they returned to the hangar to carry out any repairs.

Airship hangars

Ohio Air Station in Tustin, California. The structures appear in the [http://www.nationalregisterofhistoricplaces.com/CA/Orange/state2.html National Register of Historic Places] as #NPS-#75000451.]] Airship hangars are generally larger than conventional airplane hangars (particularly in terms of their overall height), which subjects them to different design constraints. Many early airships used hydrogen gas to provide them with sufficient buoyancy for flight, so their hangars therefore had to provide protection from stray sparks in order to to prevent the flammable gas from exploding. Hangars that held multiple craft of this type were at risk from chain-reaction explosions. For this reason, most hangars for hydrogen-based airships were sized to house only 1 or 2 such craft. With World War I on the horizon, hangar design had to keep pace with advances in aviation technology. Airships were becoming a standard for transoceanic travel. The Germans used Zeppelins to bomb Paris and London, while the British used blimps (non-rigid airships) to patrol their coasts. The US Navy established two "lighter-than-air" bases on the West Coast during World War II as part of the coastal defense plan, which required the construction of some of the world's largest freestanding wood structures.

External links

World War II. The structure measures some 1,000 feet long by 300 feet wide by 18 stories tall, and is said to "create its own weather" due to the large volume of air inside.]]
- [http://www.hangardoorsecrets.com Aircraft Hangar Door Designs]
- [http://www.buildingsguide.com/aircraft-hangars.htm Aircraft Hangars] at [http://www.buildingsguide.com BuildingsGuide.com]
- [http://www.militarymuseum.org/MCASTustin.html Marine Corps Air Station, Tustin] at the [http://www.militarymuseum.org California Military Musem] official website
- [http://www.challoner.com/aviation/hangars/index.html Nick Challoner's photo history of British Hangars]
- [http://www.reidsteel.aero/history.htm REIDsteel] company website Category:Aviation Category:Buildings and structures

Fixed base operator

A Fixed Base Operator (also known as Fixed Base of Operation), or FBO, is a service center at an airport that may be a private enterprise or may be a department of the municipality that the airport serves. The services offered by an FBO may include any of the following:
- Aircraft fueling and oil dispensing
- Aircraft parking, tie-down and hangar storage.
- Airframe, power plant and accessory service.
- Radio, avionics and instrument service.
- Air charter or aircraft rental.
- Flight training.
- Ground services, such as
- Aircraft towing
- Baggage handling
- Glycol deicing
- Power starts
- Air Starts
- Lavatory services
- Potable water
- Aircraft cleaning
- Cabin supplies Additionally the FBO may serve pilots, private airplane owners, travelers and airlines with services such as rental cars, charters, lounges, catering, hotel reservations, weather briefing and flight planning services, and a wide variety of related and non-related services.

External links

- [http://www.airnav.com/airports/ AirNav list of FBOs] - A comprehensive list of FBOs serving U.S. airports, with their contact information and lists of services offered Category:Airports Category:Aviation

Air traffic control

] Air Traffic Control (ATC) is a service provided by ground based controllers who direct aircraft on the ground and in the air to ensure safe, orderly and expeditious traffic flow. In the United States, the Federal Aviation Administration (FAA) provides this service to all aircraft in the National Airspace System (NAS). The FAA is responsible for all aspects of U.S. Air Traffic Control including hiring and training controllers, who are employees of the Federal Government. In many countries, ATC services are provided throughout the majority of airspace, and its services are available to all users (private, military, and commercial). Such airspace is called "controlled airspace" in contrast to "uncontrolled airspace." By law, pilots must obey the directions of air traffic controllers when they are in controlled airspace. Air traffic control services can be divided into two major subspecialties, terminal control and en-route control. Terminal control includes the control of traffic (aircraft and vehicles) on the airport proper and airborne aircraft within the immediate airport environment. Generally, this is approximately a 30 to 50 nautical mile (56 to 93 km) radius of the airport, from the surface to about 10,000 ft (about 3,050 m). Terminal controllers work in facilities called control towers and Terminal Radar Approach Control (TRACON). At some locations, staffs are shared between Tower Control and the TRACON, while at others the tower and the TRACON are completely separate entities. For example, Honolulu International Airport is served by a combined ("up/down") facility, while Chicago's O'Hare Airport is served by a control tower at the airport, and a remote TRACON located at Elgin, Illinois. En-route controllers control the traffic between the terminals. They can also control traffic in and out of airports where the traffic volume does not warrant the establishment of a terminal ATC operation.

Terminal Control

Elgin, Illinois.]] The primary method of controlling the immediate airport environment is visual observation from the control tower. The tower is a tall, windowed structure located on the airport grounds. Tower controllers are responsible for the separation and efficient movement of aircraft and vehicles operating on the taxiways and runways of the airport itself, and aircraft in the air near the airport, generally 2 to 5 nautical miles (4 to 9 km) depending on the airport procedures. Radar displays are also available to controllers at some airports. Controllers may use a radar system called Secondary Surveillance Radar for airborne traffic approaching and departing. These displays include a map of the area, the position of various aircraft, and data tags that include aircraft identification, speed, heading, and other information described in local procedures. The areas of responsibility for tower controllers fall into three general operational disciplines; Ground Control, Local Control, and Clearance Delivery. While each tower's procedures will vary and while there may be multiple teams in larger towers that control multiple runways, the following provides a general concept of the delegation of responsibilities within the tower environment.

Ground Control

Ground Control is responsible for the airport "movement" areas, or areas not released to the airlines or other users. This generally includes all taxiways, holding areas, and some transitional aprons or intersections where aircraft arrive having vacated the runway and departure gates. Exact areas and control responsibilities are clearly defined in local documents and agreements at each airport. Any aircraft, vehicle, or person walking or working in these areas is required to have clearance from the ground controller. This is normally done via VHF radio, but there may be special cases where other processes are used. Most aircraft and airside vehicles have radios. Aircraft or vehicles without radios will communicate with the tower via aviation light signals or will be led by vehicles with radios. People working on the airport surface normally have a communications link through which they can reach or be reached by ground control, commonly either by handheld radio or even cell phone. Ground control is vital to the smooth operation of the airport because this position might constrain the order in which the aircraft will be sequenced to depart, which can affect the safety and efficiency of the airport's operation. Some busier airports have systems, such as the ASDE-X, designed to display aircraft and vehicles on the ground. These are used by the ground controller as an additional tool to control ground traffic, particularly at night or in poor visibility. There are a wide range of capabilities on these systems as they are being modernized. Older systems will display a map of the airport and the target. Newer systems include the capability to display higher quality mapping, radar target, data blocks, and safety alerts.

Local Control

Local Control (most often referred to as the generic "Tower" control, although Tower control can also refer to a combination of the local, ground and clearance delivery positions) is responsible for the active runway surfaces. Local control clears aircraft for take off or landing and ensures the runway is clear for these aircraft. To accomplish this, local control controllers are normally given 2 to 5 nautical miles (4 to 9 km) of airspace around the airport, allowing them to give the clearances necessary for airport safety. If the local controller detects any unsafe condition, a landing aircraft will be told to "go around" and will be re-sequenced into the landing pattern by the TRACON controller. Within the tower, a highly disciplined communications process between local and ground control is an absolute necessity. Ground control must request and gain approval from local control to cross any runway with any aircraft or vehicle. Likewise, local control must ensure ground control is aware of any operations that impact the taxiways and must work with the arrival radar controllers to ensure "holes" in the arrival traffic are created (where necessary) to allow taxiing traffic to cross runways and to allow departures aircraft to take off. Crew resource management procedures are often used to ensure this communication process is efficient and clear.

Clearance Delivery

Clearance delivery is the position that coordinates with the national command center and the en-route center to obtain releases for aircraft. Under normal conditions, this is more or less automatic. When weather or extremely high demand for a certain airport become a factor, there may be ground "stops" (or delays), or re-routes to ensure the system does not get overloaded. The primary responsibility of the clearance delivery position is to ensure that the aircraft have the proper route and release time. This information is also coordinated with the en-route center and the ground controller in order to ensure the aircraft reaches the runway in time to meet the release time provided by the command center.

TRACON Control

Crew resource management Larger airports have a radar control facility that is associated with the control tower. In the U.S., this is referred to as a TRACON or Terminal Radar Approach CONtrol facility (sometimes referred to as Approach or Departure control). While every airport varies, TRACONs usually control traffic in a 30 to 50 nautical mile (56 to 93 km) radius from the airport and from the surface up to 10,000 feet. The actual airspace boundaries and altitudes assigned to a TRACON are based on factors such as traffic flows and terrain, and vary widely from airport to airport. TRACONs are responsible for providing all ATC services within their airspace. Traffic flow is broadly divided into departures, arrivals, overflights, and VFR aircraft. As aircraft move in and out of the TRACON airspace, they are handed off to the next appropriate control facility (a control tower, an en-route control facility, or a bordering TRACON). TRACON is responsible for ensuring that aircraft are at an appropriate altitude when they are handed off, and that aircraft arrive at a slow enough rate to permit safe landing times. Not all airports have a TRACON available. In this case, the en-route center will coordinate directly with the tower and provide this type of service where radar coverage permits. Under these circumstances, the separation minimums are usually increased.

En-route Control

ATC provides services to aircraft in flight between airports as well. The level of service is dependant on the type of flight the aircraft falls under (IFR or VFR), the type of airspace the aircraft is in and the services requested by the pilots. En-route Air Traffic Controllers issue clearances and instructions for airborne aircraft, and pilots are required to comply with these instructions. Controllers adhere to a set of separation standards that define the minimum distance allowed between aircraft. These distances vary depending on the equipment and procedures used in providing ATC services. Pilots fly under one of two sets of rules for separation; Visual flight rules (VFR) or Instrument flight rules (IFR). Air Traffic Controllers have different responsibilities to aircraft operating under the different sets of rules.

Visual flight rules (VFR)

Pilots flying under VFR assume responsibility for their separation from all other aircraft and are not assigned routes or altitudes by ATC (outside of positive control airspace). They fly on their own using a "see and be seen" separation criteria. In busier controlled airspace, VFR aircraft are required to have a transponder. This amplifies the radar signal (as well broadcasting altitude level and a transponder code), and is used to allow controllers to warn IFR aircraft of any potential conflict. Governing agencies establish strict VFR "weather minima" for visibility, distance from clouds, and altitude to ensure that VFR pilots can see far enough. VFR pilots can request, and ATC can elect to provide "VFR Advisory Services," if the controllers' workload permits. This is also referred to as "Flight following." Under this environment, the controllers will radar identify the VFR aircraft and provide traffic information and weather advisory services for the VFR pilot. Controllers do not provide any instructions concerning direction of flight, altitude, or speed to the VFR pilot receiving advisory services, and they do not provide separation services. This is an optional service and may be discontinued by ATC or the pilot at any time.

Instrument Flight Rules (IFR)

Pilots flying under IFR must file a flight plan with ATC and accept any revisions ATC requests to their route or altitude. In return, controllers will ensure that pilots flying IFR are separated from all other IFR aircraft and terrain by the appropriate minimum separation. The IFR pilot, however, must maintain a close watch for VFR aircraft since ATC has no control over these aircraft. For this reason, VFR aircraft are restricted to altitudes below 18,000 ft and must have an operating transponder in congested airspace. Once IFR aircraft are above 18,000 ft (Flight Level 180) the aircraft is considered in "Positive Control Airspace," meaning that ATC controls all aircraft in the airspace.

General Characteristics

En-route air traffic controllers work in facilities called Air Route Traffic Control Centers (ARTCCs), commonly referred to as "Center." Each center is responsible for many thousands of square miles of airspace (known as a Flight Information Region) and for the airports within that airspace. Centers control IFR aircraft from the time the aircraft departs an airport or leaves the TRACON's airspace or until the aircraft approaches the airspace controlled by a TRACON or if the airport does not have a TRACON, until the aircraft lands. Centers may also "pick up" aircraft that are airborne and integrate them into the IFR system. These aircraft must, however, remain VFR until the Center provides a clearance. Center controllers are responsible for climbing the aircraft to their requested altitude while, at the same time, ensuring that the aircraft is properly separated from all other aircraft in the immediate area. Additionally, the aircraft must be placed in a flow consistent with the aircraft's route of flight. This effort is complicated by cross traffic, severe weather, special missions that require large airspace allocations, and traffic density. As an aircraft reaches the boundary of a Center's control area it is "handed off" to the next Area Control Center. This "hand-off" process is simply a transfer of identification between controllers so that air traffic control services can be provided in a seamless manner. Once the hand-off is complete, the aircraft is given a frequency change and begins talking to the next controller. This process continues until the aircraft is handed off to a TRACON.

Radar Coverage

Since centers control a large airspace area, they will typically use long range radar that has the capability to see aircraft within 200 nautical miles (370 km) of the radar antenna. They may also use TRACON radar data to control when it provides a better "picture" of the traffic or when it can fill in a portion of the area not covered by the long range radar. In the U.S. system, over 90% of the U.S. airspace is covered by radar and often by multiple radar systems. A center may require numerous radar systems to cover the airspace assigned to them. This results in a large amount of data being available to the controller. To address this, automation systems have been designed that consolidate the radar data for the controller. This consolidation includes eliminating duplicate radar returns, ensuring the best radar for each geographical area is providing the data, and displaying the data in an effective format. Centers also exercise control over traffic travelling over the world's ocean areas. These areas are also FIRs. Due to the fact that there are no radar systems available for oceanic control, oceanic controllers provide ATC services using "non-radar" procedures. These procedures use aircraft position reports, time, altitude, distance, and speed to ensure separation. Controllers record information on flight progress strips and in specially developed oceanic computer systems as aircraft report positions. This process requires that aircraft be separated by greater distances, which reduces the overall capacity for any given route. Some Air Navigation Service Providers (e.g Airservices Australia, Alaska Center, etc.) are implementing Automatic Dependant Surveillance - Broadcast (ADS-B) as part of their surveillance capability. This new technology reverses the radar concept. Instead of radar "finding" a target by interrogating the transponder, ADS transmits the aircraft's position several times a second. ADS also has other modes such as the "contract" mode where the aircraft reports a position based on a pre-determined time interval. This is significant because it can be used where it is not possible to locate the infrastructure for a radar system (e.g. over water). Computerised radar displays are now being designed to accept ADS inputs as part of the display. As this technology develops, oceanic ATC procedures will be modernised to take advantage of the benefits this technology provides.

Problems

Traffic

The day-to-day problems faced by the air traffic control system are primarily related to the volume of air traffic demand placed on the system, and weather. Several factors dictate the amount of traffic that can land at an airport in a given amount of time. Each landing aircraft must touch down, slow, and exit the runway before the next crosses the end of the runway. This process requires between one and up to four minutes for each aircraft. Allowing for departures between arrivals, each runway can thus handle about 30 arrivals per hour. A typical large airport with two arrival runways can thus handle about 60 arrivals per hour in good weather. Problems begin when airlines schedule more arrivals into an airport than can be physically handled, or when delays elsewhere cause groups of aircraft that would otherwise be separated in time to arrive simultaneously. Aircraft must then be delayed in the air by holding over specified locations until they may be safely sequenced to the runway. Up until the 1990s, holding was a common occurrence at airports. Advances in computers now allow controllers to predict transit times and sequence planes hours in advance. Thus, planes may be delayed before they even take off, or may reduce power in flight and proceed more slowly in order to fit perfectly into a landing sequence without holding.

Weather

Beyond runway capacity issues, weather is a major factor in traffic capacity. Rain or ice and snow on the runway cause landing aircraft to take longer to slow and exit, thus reducing the safe arrival rate and requiring more space between landing aircraft. This, in turn, increases airborne delay for holding aircraft. If more aircraft are scheduled than can be safely and efficiently held in the air, a ground delay program may be established, delaying aircraft on the ground before departure due to conditions at the arrival airport. In ACCs, a major weather problem is thunderstorms, which present a variety of hazards to aircraft. Aircraft will deviate around storms, reducing the capacity of the en-route system by requiring more space per aircraft, or causing congestion as many aircraft try to move through a single hole in a line of thunderstorms. Occasionally weather considerations cause delays to aircraft prior to their departure as routes are closed by thunderstorms. Much money has been spent on creating software to streamline this process. However, at some Area Control Centers, air traffic controllers still record data for each flight on strips of paper and personally coordinate their paths. In newer sites, these flight progress strips have been replaced by electronic data presented on computer screens. As new equipment is brought in, more and more sites are upgrading away from paper flight strips.

Call signs

A prerequisite to safe air traffic separation is the assignment and use of distinctive airline call signs that usually include up to four digits (the flight number) prefaced by a company-specific airline call sign. In this arrangement, an identical call sign might well be used for the same scheduled journey each day it is operated, even if the departure time varies a little across different days of the week. The call sign of the return flight often differs only by the final digit, from the outbound flight. Generally, airline flight numbers are even if eastbound, and odd if westbound. In air traffic control terminology, a block of airspace of predetermined size assigned to a radar air traffic controller is called a "sector". Depending on various factors (traffic density, etc.), a controller may be responsible for one or more sectors at any given time.

Technology

Many technologies are used in air traffic control systems. Primary and secondary radar are used to enhance a controller's "situational awareness" within his assigned airspace — all types of aircraft send back primary echoes of varying sizes to controllers' screens as radar energy is bounced off their skins, and transponder-equipped aircraft reply to secondary radar interrogations by giving an ID (Mode A), an altitude (Mode C) and/or a unique callsign (Mode S). Certain types of weather may also register on the radar screen. These inputs, added to data from other radars, are correlated to build the air situation. Some basic processing occurs on the radar tracks, such as calculating ground speed and magnetic headings. Other correlations with electronic flight plans are also available to controllers on modern operational display systems. Some tools are available in different domains to help the controller further:
- Conflict Alert (CA): a tool that checks possible conflicting trajectories and alerts the controller.
- Minimum Safe Altitude Warning (MSAW): a tool that alerts the controller if an aircraft appears to be flying too low to the ground or will impact terrain based on its current altitude and heading.
- System Coordination (SYSCO) to enable controller to negotiate the release of flights from one sector to another.
- Area Penetration Warning (APW) to inform a controller that a flight will penetrate a restricted area.
- Arrival and Departure manager to help sequence the takeoff and landing of aircraft.

Major Accidents

Failures in the system have caused delays or even, in rare cases, crashes. On July 1, 2002 a Tupolev Tu-154 and Boeing 757 collided above Überlingen near the boundary between German and Swiss-controlled airspace when a Skyguide-employed controller apparently gave instructions to the southbound Tupolev to descend despite an instruction from the on-board automatic Traffic Collision Avoidance System software to climb. The northbound Boeing, equipped with similar avionics, was already descending due to a software prompt. All passengers and crew died in the resultant collision. Skyguide company publicity had previously acknowledged that the relatively small size of Swiss airspace makes real-time cross-boundary liaison with adjoining authorities particularly important. See Bashkirian Airlines Flight 2937 for more on this accident. It is worth noting, that currently air traffic controllers have no way of knowing if or when the TCAS system is issuing resolution advisories to pilots. They also do not know what the advisory is telling the pilots. Therefore, pilots are supposed to immediately report TCAS resolution advisories and follow them as soon as possible. Consequently, they should ignore ATC instructions until they have reported to the ground that they are clear of the conflict. Other fatal collisions between airliners have occurred over India and Zagreb in Croatia. When a risk of collision is identified by aircrew or ground controllers an "air miss" or "air prox" report can be filed with the air traffic control authority concerned. The worst fatal collision between airliners actually took place on the ground, on March 27, 1977, in what is known as the Tenerife Disaster. The FAA has spent over USD$3 billion on software, but a fully-automated system is still over the horizon. The UK has recently brought a new control centre into service at Swanwick, in Hampshire, relieving a busy suburban centre at West Drayton in Middlesex, north of London Heathrow Airport. Software from Lockheed-Martin predominates at Swanwick. The Swanwick facility, however, has been troubled by software and communications problems causing delays and occasional shutdowns, paralyzing air traffic in the area.

Air Traffic Control Internationally

This article is based upon Air Traffic Control in the US. Although there is much common ground between Air Traffic Control in various countries around the world (since ICAO has many Standards and Recommended Practices in this Area), there are some significant differences in airspace, procedures and terminology. In the UK, Clearance Delivery is referred to as 'Planner', Ground Control is referred to as 'Ground Movement Control' or 'GMC' and Local Control is referred to as 'Air Control'. It is common for airports to have an Approach Radar Control based upon the airport to provide radar services to arriving and departing aircraft. For six London-area airports approach radar control is provided from the London Terminal Control Centre in West Drayton, Middlesex.

Air Navigation Service Providers (ANSPs)

- Australia - Airservices Australia (State Owned Corporation)
- Canada - NAV CANADA
- Europe - Eurocontrol (European Organisation for the Safety of Air Navigation)
- France - DGAC (French ATC)
- Germany - Deutsche Flugsicherung (German ATC)
- Italy - ENAV (Italian ATC)
- Mexico - [http://www.seneam.gob.mx Servicios a la Navegación en el Espacio Aéreo Mexicano]
- Netherlands - LVNL (Dutch ATC)
- New Zealand - Airways Corporation (State Owned Enterprise)
- Spain - AENA (Spanish ATC and Airports)
- Sweden - LFV (Swedish ATC)
- United Kingdom - National Air Traffic Services (49% State Owned Public-Private Partnership)
- United States of America - Federal Aviation Administration (Government Body)

External links

Official Air Traffic Control Organizations and Research Institutes

- [http://www.aena.es/ AENA] - Spanish ATC and Airports (Madrid)
- [http://www.airservicesaustralia.com Airservices Australia]
- [http://www.atcguild.com/ ATC Guild India]
- [http://www.aviation-civile.gouv.fr/ DGAC] - French ATC (Paris)
- [http://www.dfs.de/ Deutsche Flugsicherung] - German ATC (Frankfurt/Langen)
- [http://www.dlr.de/ Deutsches Zentrum für Luft- und Raumfahrt] - German Aerospace Centre (Cologne)
- [http://www.easa.eu.int/ EASA] - European Aviation Safety Agency (Cologne)
- [http://www.egats.org EGATS] - Eurocontrol Guild of Air Traffic Services
- [http://www.enav.it/ ENAV] - Italian ATC (Rome)
- [http://www.eurocontrol.int Eurocontrol] - European Organisation for the Safety of Air Navigation (Brussels)
- [http://www.eurocontrol.int/eec/ Eurocontrol Experimental Centre] - EEC (Paris/Brétigny)
- [http://www.eurocontrol.int/muac/ Eurocontrol Maastricht Upper Area Control Center] - MUAC
- [http://www.faa.gov FAA] - Federal Aviation Administration (Washington)
- [http://www.faa.gov/atpubs/ATC/ Air Traffic Control Manual]
- [http://www.lfv.se/ LFV] - Swedish ATC (Stockholm)
- [http://www.lvnl.nl/ Luchtverkeersleiding Nederland] - Dutch ATC (Amsterdam)
- [http://www.natca.org NATCA] - National Air Traffic Controllers Association (Washington,United States)
- [http://www.nats.co.uk/ NATS] - National Air Traffic Services of the UK (London)
- [http://www.navcanada.ca/ NAV CANADA] - Canadian Air Navigation Services
- [http://www.nlr.nl/ Nationaal Lucht- en Ruimtevaartlaboratorium] - National Aerospace Lab of the Netherlands (Amsterdam)

Next Generation ATC - Research

- [http://www.gisdevelopment.net/technology/gps/ma04082pf.htm Communication Navigation Surveillance / Air Traffic Management ]
- [http://www.intentproject.org/deliverables/INTENT_D3-1_v04_22-05-03_P.pdf Global Air and Ground Collaboration in Air Traffic Separation Assurance]

Internet Services

- [http://www.dxtuners.com Listen to Air Traffic Control radio with live audio]
- [http://www.liveatc.net Live audio Air Traffic Control from over 100 airports worldwide]
- [http://www.futurastudios.com/atc.html Live Air Traffic Control & Live Airport Webcams]
- [http://flightaware.com/live/ Map of airborne flights controlled by US ATC]
- Category:Airports ja:航空交通管制

Military

A military or military force (n., from Latin militarius, miles "soldier") has seen many different incarnations throughout time. Early armies may have been just men with sharpened sticks and rocks, through time they have included advancements such as men mounted on horses, men wielding swords and other metallic weapons, the bow and arrow, siege weapons, to the advance of the musket which form the roots of the armed force of most nations we know today. In modern times people use vehicles and guns. While military can refer to any armed force, it generally refers to a permanent, professional force of soldiers or guerrillas—trained exclusively for the purpose of warfare and should be distinguished from a sanctioned militia or a levy, which are temporary forces— citizen soldiers with less training, who may be 'called up' as a reserve force, when a nation mobilizes for total war, or to defend against invasion. The term military is often used to mean an army. The doctrine that asserts the primacy of a military within a society is called militarism.

Meaning of the word

:Also see: Armed forces As an adjective, "military" is a descriptive property of things related to soldiers and warfare. It also refers to such context dependent terms such as military reserves which may indicate an actual unit deployable on command or the general sense, of a Nation States reserve troops available to or eligible for duty in its armed forces. In formal British English, "military" as an adjective [http://www.opsi.gov.uk/si/si2003/20030636.htm refers] more particularly to matters relating to an army (land forces), as opposed to the naval and air force matters of the other two services. In American English, "military" as an adjective is more widely used for regulations pertaining to and between all the armed forces like military procurement, military transport, military justice, military strength and military force.

Military procurement

Military procurement refers to common regulations and requirements for a ship or a detached unit to requisistion and draw on a base's facilies (housing, pay, and rations for detached personnel), supplies (most commonly food stocks or materials, and vehicles) by the service running a primary base; e.g. Army units detached to or staging through an air base, a vessel calling at a port near an army or air base, an army unit drawing supplies from a naval base.

Military transport

Military transport would pertain to an equipment trans-shipped via a sister service, or an individual detached for a technical school operated by a sister service, or the travel orders and authorization of such an individual to procede via a sister services vehicles, as well as the drawing (loan of) transportation assets (staff cars, Hum-Vees, military trucks) operating from the primary base command.

Military Justice

Military Justice, as in the Uniform Code of Military Justice. Most nations have a separate code of law which regulates both certain activities allowed only in war, as well as provides a code of law applicable only to a soldier in war (or 'in uniform' during in peacetime). The statutory laws set down by the United States Congress to apply to the individual conduct within any military force of the United States— these are the specific articles under which a soldier or sailor would be tried for infractions ranging from minor (Late Return, petty theft; ) to severe (Rape, Murder); this code is usually referred to by the acronym UCMJ.

Military strength

Military strength is a term that describes a quantification or reference to a nation's standing military forces or the capacity for fulfillment of that military's role. For example, the military strength of a given country could be interpreted as the number of individuals in its armed forces, the destructive potential of its arsenal, or both. For example, while China and India maintain the largest armed forces in the world, the US Military is considered to be the world's strongest.

Military Force

Military Force is a term that might refer to a particular unit, a regiment or gunboat deployed in a particular locale, or as an aggregate of such forces (e.g. "In the Gulf War the United States Central Command controled military forces (units) of each of the five military services of the United States.").

Military history

:Main article: Military history Military history is often considered to be the history of all conflicts, not just the history of proper militaries. It differs somewhat from the history of war with military history focusing on the people and institutions of war-making while the history of war focuses on the evolution of war itself in the face of changing technology, governments, and geography. Military history has a number of purposes. One main purpose is to learn from past accomplishments and mistakes so as to more effectively wage war in the future. Another is to create a sense of tradition which is used to create cohesive military forces. Still another may be to learn to prevent wars more effectively.

Military reserve

:Main article: Military reserve Military reserve refers to specific trained pre-organized forces operating as an on call basis from the main military force. In the United States, the Reserves forces such as the qunit mission profile (e.g. Many 'Military Police' trained regular reserve units and ' National Guard units' were mobilized during the Iraq war, as were units specializing in supply, transport, engineering, et al.) These various volunteer manned units are always 'on call' and refered to as the ready reserves but might be augmented by the Inactive Reserves in time of dire emergency or total war under the United States model— the inactive reserve is composed of all former serving members of any of the US Armed Forces of military age. Individuls in this class are former members of the regular and ready reserve forces, that have opted to discontinue service in any of those organized bodys; in general, the inactive reserves are not an organized force, but a resource of trained manpower that can be mobilized similar to calling up a levy but in theory with the training of a militia. Individuals in the inactive reserves with specialized talents are from time to time also recalled into service, albeit rarely, one exception being the ongoing current need for Military Police and Quartermasters in Iraq.

Military science

:Main article: Military science Military science concerns itself with the study and of the diverse technical, psychological, and practical phenomena that encompass the events that make up warfare, especially armed combat. It strives to be an all-encompassing scientific system that if properly employed, will greatly enhance the practitioner's ability to prevail in an armed conflict with any adversary. To this end, it is unconcerned whether that adversary is an opposing military force, guerrillas or other irregulars, or even knows of or utilizes military science in return.

Specific militaries

- British Armed Forces
- Royal Navy
- British Army
- Royal Air Force
- Royal Marines
- Special Air Service
- Special Boat Service
- Canadian Armed Forces
- Canadian Army
- Royal Canadian Air Force
- Royal Canadian Navy
- Military of India
- Indian Army
- Indian Air Force
- Indian Navy
- Indian Coast Guard
-

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Next Generation ATC - Research