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118-530: Although the media in the United States frequently refers to them as air controllers , or flight controllers , most air traffic professionals use the term air traffic controllers , ATCOs , or controllers . For a more detailed article on the job itself, see air traffic control . Air traffic controllers are generally individuals who possess superior situational awareness , spatial awareness , and are well organized. Other skills that are essential include

236-521: A Minnesota Multiphasic Personality Inventory before being hired by the Federal Aviation Administration . Conditions such as hypertension , while not disqualifying, are taken seriously and must be monitored with medical examinations by certified doctors. Controllers must take precautions to remain healthy and avoid certain medications that are banned for them; all medications, even over-the-counter drugs , must be reported to

354-477: A ' Flight Information Service ', which is similar to flight following. In the United Kingdom, it is known as a 'basic service'. En-route air traffic controllers issue clearances and instructions for airborne aircraft, and pilots are required to comply with these instructions. En-route controllers also provide air traffic control services to many smaller airports around the country, including clearance off

472-451: A 'Single European Sky', hoping to boost efficiency and gain economies of scale. The primary method of controlling the immediate airport environment is visual observation from the airport control tower. The tower is typically a tall, windowed structure, located within the airport grounds. The air traffic controllers , usually abbreviated 'controller', are responsible for separation and efficient movement of aircraft and vehicles operating on

590-504: A 30-minute break. Except at quieter airports, air traffic control is a 24-hour, 365-day-a-year job where controllers usually work rotating shifts, including nights, weekends, and public holidays. These are usually set 28 days in advance. In many countries, the structure of controllers' shift patterns is regulated to allow for adequate time off. In the UK, the most common pattern is two mornings, two late afternoons, and two evenings/nights followed by

708-400: A bordering terminal or approach control). Terminal control is responsible for ensuring that aircraft are at an appropriate altitude when they are handed off, and that aircraft arrive at a suitable rate for landing. Not all airports have a radar approach or terminal control available. In this case, the en-route centre or a neighbouring terminal or approach control may co-ordinate directly with

826-433: A certain airport or airspace becomes a factor, there may be ground 'stops' (or 'slot delays'), or re-routes may be necessary to ensure the system does not get overloaded. The primary responsibility of clearance delivery is to ensure that the aircraft has the correct aerodrome information, such as weather and airport conditions, the correct route after departure, and time restrictions relating to that flight. This information

944-410: A control service for all aircraft at the airport, and all inbound and outbound flights within its terminal airspace. Because most aircraft fly to/or from the same place (i.e. an airport runway) within this airspace, procedural controllers use a variety of separation standards to achieve a safe and expeditious flow of air traffic to and/or from the airport. One commonly used separation in these locations

1062-416: A controller can review the last radar returns from the aircraft to determine its likely position. For an example, see the crash report in the following citation. RAS is also useful to technicians who are maintaining radar systems. The mapping of flights in real-time is based on the air traffic control system, and volunteer ADS-B receivers. In 1991, data on the location of aircraft was made available by

1180-455: A cruising altitude, such as in trans-oceanic sectors. Each aircraft's strip is placed in a "bay" (labeled section of the strip rack) depending on its altitude. Because aircraft cruising at different altitudes will never conflict regardless of route of flight or estimated times, they don't need to be checked against each other. Only aircraft at the same altitude (i.e. in the same bay) need to be further evaluated. If an aircraft needs to transition to

1298-453: A cumulative nine months on strike between 2004 and 2016. Procedural control Procedural control is a method of providing air traffic control services without the use of radar . It is used in regions of the world, specifically sparsely populated land areas and oceans, where radar coverage is either prohibitively expensive or is simply not feasible. It also may be used at very low-traffic airports, or at other airports at night when

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1416-413: A degree of situational awareness that is significantly better than the population average. In 'games' involving short-term memory, peer-induced stresses, and real-time risk analysis, air traffic control specialists scored better than the control group in every experiment . Excellent hearing and speaking skills are a requirement, and trainees undergo rigorous physical and psychological testing. Moreover,

1534-400: A distance of 100 nautical miles (185 kilometres; 115 miles). Terminal controllers are responsible for providing all ATC services within their airspace. Traffic flow is broadly divided into departures, arrivals, and overflights. As aircraft move in and out of the terminal airspace, they are 'handed off' to the next appropriate control facility (a control tower, an en-route control facility, or

1652-415: A fast processing of numeric computations and mathematics, assertive and firm decision-making skills, the ability to maintain their composure under pressure, and an excellent short-term memory . Through numerous studies throughout the decades, it has been demonstrated that traffic controllers usually have a superior visual memory , and in addition, studies have shown that air traffic controllers generally have

1770-401: A four-day break. Many countries regulate work hours to ensure that controllers are able to remain focused and effective. Research has shown that when controllers remain "on position" for more than two hours without a break, performance can deteriorate rapidly, even at low traffic levels. Many national regulations, therefore, require breaks at least every two hours. Sylvia Noble Tesh documented

1888-432: A large airspace area, they will typically use long-range radar, that has the capability, at higher altitudes, to see aircraft within 200 nautical miles (370 kilometres; 230 miles) of the radar antenna. They may also use 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, at higher altitudes, over 90% of

2006-414: 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. Centres also exercise control over traffic travelling over

2124-417: A map of the area, the position of various aircraft, and data tags that include aircraft identification, speed, altitude, and other information described in local procedures. In adverse weather conditions, the tower controllers may also use surface movement radar (SMR), surface movement guidance and control system (SMGCS), or advanced surface movement guidance and control system (ASMGCS) to control traffic on

2242-424: A new altitude (whether changing cruising level, or descending to or climbing from an airport), it only needs to be checked against others in the bays between the current altitude and destination altitude. The fix posting area method is easier however when there are a lot of altitude changes because of numerous departures and arrivals within the sector. This is a more obscure method today because most airports around

2360-746: A new area control centre into service at the London Area Control Centre (LACC) 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 the London Area Control Centre. However, the centre was initially troubled by software and communications problems causing delays and occasional shutdowns. Some tools are available in different domains to help

2478-472: A number of airlines, particularly in Europe, have started using alphanumeric call signs that are not based on flight numbers (e.g. DLH23LG, spoken as Lufthansa -two-three-lima-golf , to prevent confusion between incoming DLH23 and outgoing DLH24 in the same frequency). Additionally, it is the right of the air traffic controller to change the 'audio' call sign for the period the flight is in his sector if there

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2596-510: A radar control facility that is associated with that specific airport. In most countries, this is referred to as terminal control and abbreviated to TMC; in the U.S., it is referred to as a 'terminal radar approach control' or TRACON. While every airport varies, terminal controllers usually handle traffic in a 30-to-50-nautical-mile (56 to 93 km; 35 to 58 mi) radius from the airport. Where there are many busy airports close together, one consolidated terminal control centre may service all

2714-428: A seamless manner; in other cases, local agreements may allow 'silent handovers', such that the receiving centre does not require any co-ordination if traffic is presented in an agreed manner. After the hand-off, the aircraft is given a frequency change, and its pilot begins talking to the next controller. This process continues until the aircraft is handed off to a terminal controller ('approach'). Since centres control

2832-520: 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 ACCs, 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

2950-484: A single misunderstanding about altitude levels or runway numbers can have tragic consequences. Controllers communicate with the pilots of aircraft using a push-to-talk radiotelephony system which has many attendant issues, such as the fact that only one transmission can be made on a frequency at a time and can either merge or block each other and become unintelligible. Although local languages are used in ATC communications,

3068-480: A study that compared stress in the general population and this kind of system markedly showed more stress level for controllers. This variation can be explained, at least in part, by the characteristics of the job. Surveillance displays are also available to controllers at larger airports to assist with controlling air traffic. Controllers may use a radar system called secondary surveillance radar for airborne traffic approaching and departing. These displays include

3186-451: A target by interrogating the transponder, the ADS-B equipped aircraft 'broadcasts' a position report as determined by the navigation equipment on board the aircraft. ADS-C is another mode of automatic dependent surveillance, however ADS-C operates in the 'contract' mode, where the aircraft reports a position, automatically or initiated by the pilot, based on a predetermined time interval. It

3304-415: A two or three letter combination followed by the flight number such as AAL872 or VLG1011. As such, they appear on flight plans and ATC radar labels. There are also the audio or radio-telephony call signs used on the radio contact between pilots and air traffic control. These are not always identical to their written counterparts. An example of an audio call sign would be 'Speedbird 832', instead of

3422-419: 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. Usually, a flight data processing system manages all the flight plan related data, incorporating, in a low or high degree,

3540-403: Is a conflict. Aircraft on the same route however (in either direction) must be checked for conflict regardless of time over the intersection. As new altitudes are issued, all of the strips for that aircraft must be annotated with the new data and separation checked again at all of the intersections it passes through. This is more laborious than the altitude method of grouping where only one strip

3658-446: Is a form of air traffic control that can be provided to aircraft in regions without radar, by providing horizontal separation based upon time, the geography of predetermined routes, or aircraft position reports based upon ground-based navigation aids, for those aircraft that are not vertically separated. The central rule of procedural control is that each aircraft is cleared onto a predetermined route (airway), and no aircraft traveling on

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3776-541: Is a risk of confusion, usually choosing the aircraft registration identifier instead. Many technologies are used in air traffic control systems. Primary and secondary radars are used to enhance a controller's situational awareness within their 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

3894-416: Is a wide range of capabilities on these systems as they are being modernised. Older systems will display a map of the airport and the target. Newer systems include the capability to display higher-quality mapping, radar targets, data blocks, and safety alerts, and to interface with other systems, such as digital flight strips. Air control (known to pilots as tower or tower control ) is responsible for

4012-545: Is also common for ATC to provide services to all private , military , and commercial aircraft operating within its airspace; not just civilian aircraft. Depending on the type of flight and the class of airspace, ATC may issue instructions that pilots are required to obey, or advisories (known as flight information in some countries) that pilots may, at their discretion, disregard. The pilot in command of an aircraft always retains final authority for its safe operation, and may, in an emergency, deviate from ATC instructions to

4130-510: Is also coordinated with the relevant radar centre or flow control unit and ground control, to ensure that the aircraft reaches the runway in time to meet the time restriction provided by the relevant unit. At some airports, clearance delivery also plans aircraft push-backs and engine starts, in which case it is known as the ground movement planner (GMP): this position is particularly important at heavily congested airports to prevent taxiway and aircraft parking area gridlock. Flight data (which

4248-464: Is also possible for controllers to request more frequent reports to more quickly establish aircraft position for specific reasons. However, since the cost for each report is charged by the ADS service providers to the company operating the aircraft, more frequent reports are not commonly requested, except in emergency situations. ADS-C is significant, because it can be used where it is not possible to locate

4366-402: Is brought in, more and more sites are upgrading away from paper flight strips. Constrained control capacity and growing traffic lead to flight cancellation and delays : By then the market for air-traffic services was worth $ 14bn. More efficient ATC could save 5-10% of aviation fuel by avoiding holding patterns and indirect airways . The military takes 80% of Chinese airspace, congesting

4484-522: Is compared against all other aircraft in the sector to determine if there are any conflicts. For aircraft that conflict, the controller issues an altitude, speed or routing change that both separates the conflicting aircraft from each other, while still remaining separated from all others. After all conflicts have been resolved in this way, the sector is considered "separated" and the controller only needs to check again for conflicts when new aircraft are added, or if an aircraft needs to change its altitude, or if

4602-462: Is due to an FAA requirement that trainees begin their training at the Academy no later than their 31st birthday, and face mandatory retirement at age 56. However, retired military air traffic controllers may qualify for appointment after reaching 31 years of age. Communication is a vital part of the job: controllers are trained to focus on the exact words that pilots and other controllers speak, because

4720-417: Is needed, but possible conflicts between multiple aircraft climbing and descending are easier to discern or discard this way since all intersection points and times are pre-calculated and laid out separately. With the altitude grouping method, if two aircraft are determined to conflict based on altitude, the controller must then manually determine the intersection points and times to further determine or rule out

4838-556: Is posted to a new unit or starts work on a new sector within a particular unit, they must undergo a period of training regarding the procedures peculiar to that particular unit and/or sector. The majority of this training is done in a live position controlling real aircraft and is termed On the Job Training (OJT), with a fully qualified and trained mentor or On the Job Training Instructor (OJTI) also 'plugged into'

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4956-518: Is required to have clearance from ground control. This is normally done via VHF / UHF radio, but there may be special cases where other procedures are used. Aircraft or vehicles without radios must respond to ATC instructions via aviation light signals , or else be led by official airport vehicles with radios. People working on the airport surface normally have a communications link through which they can communicate with ground control, commonly either by handheld radio or even cell phone . Ground control

5074-480: Is responsible for the airport movement areas, as well as areas not released to the airlines or other users. This generally includes all taxiways, inactive runways, holding areas, and some transitional aprons or intersections where aircraft arrive, having vacated the runway or departure gate. 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

5192-438: Is routinely combined with clearance delivery) is the position that is responsible for ensuring that both controllers and pilots have the most current information: pertinent weather changes, outages, airport ground delays / ground stops, runway closures, etc. Flight data may inform the pilots using a recorded continuous loop on a specific frequency known as the automatic terminal information service (ATIS). Many airports have

5310-546: Is the only facility with radio or phone coverage. The first airport traffic control tower, regulating arrivals, departures, and surface movement of aircraft in the US at a specific airport, opened in Cleveland in 1930. Approach / departure control facilities were created after adoption of radar in the 1950s to monitor and control the busy airspace around larger airports. The first air route traffic control center (ARTCC), which directs

5428-606: Is the position that issues route clearances to aircraft, typically before they commence taxiing. These clearances contain details of the route that the aircraft is expected to fly after departure. Clearance delivery, or, at busy airports, ground movement planner (GMP) or traffic management coordinator (TMC) will, if necessary, coordinate with the relevant radar centre or flow control unit to obtain releases for aircraft. At busy airports, these releases are often automatic, and are controlled by local agreements allowing 'free-flow' departures. When weather or extremely high demand for

5546-443: Is to prevent collisions, organize and expedite the flow of traffic in the air, and provide information and other support for pilots. Personnel of air traffic control monitor aircraft location in their assigned airspace by radar , and communicate with the pilots by radio . To prevent collisions, ATC enforces traffic separation rules, which ensure each aircraft maintains a minimum amount of 'empty space' around it at all times. It

5664-685: Is track separation, which states that two aircraft on different tracks to/from a navigational aid must be separated from each other provided at least one is a minimum distance from the navaid. The distance required varies dependent upon how far apart the tracks are. For example, two aircraft on tracks that are 60° apart do not have to be far from the navaid to be clear of each other in comparison to two aircraft whose tracks are 13° apart. En-route jet aircraft tend to fly at roughly 8NM per minute: therefore 10–15 minutes' flying time separation using procedural control equates to around 80 to 120 NM (150 to 220 km; 92 to 138 mi) distance between aircraft at

5782-466: Is vital to the smooth operation of the airport because this position impacts the sequencing of departure aircraft, affecting the safety and efficiency of the airport's operation. Some busier airports have surface movement radar (SMR), such as ASDE-3, AMASS, or ASDE-X , designed to display aircraft and vehicles on the ground. These are used by ground control as an additional tool to control ground traffic, particularly at night or in poor visibility. There

5900-817: The Federal Aviation Administration to the airline industry. The National Business Aviation Association (NBAA), the General Aviation Manufacturers Association, the Aircraft Owners and Pilots Association, the Helicopter Association International, and the National Air Transportation Association, petitioned the FAA to make ASDI information available on a 'need-to-know' basis. Subsequently, NBAA advocated

6018-531: The EU called for a 'Digital European Sky', focusing on cutting costs by including a common digitisation standard, and allowing controllers to move to where they are needed instead of merging national ATCs, as it would not solve all problems. Single air-traffic control services in continent-sized America and China does not alleviate congestion. Eurocontrol tries to reduce delays by diverting flights to less busy routes: flight paths across Europe were redesigned to accommodate

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6136-727: The R-side Area controller. This can be done with or without the use of radar: radar allows a sector to handle much more traffic; however, procedural control is used in many areas where traffic levels do not justify radar or the installation of radar is not feasible, such as over oceans. In the United States, en-route controllers work at air route traffic control centers or ARTCCs. In other countries, area controllers work in area control centers , controlling high-level en-route aircraft, or terminal control centers , which control aircraft climbing from or descending to major groups of airports. Aerodrome or Tower controllers control aircraft within

6254-407: The U.S. airspace is covered by radar, and often by multiple radar systems; however, coverage may be inconsistent at lower altitudes used by aircraft, due to high terrain or distance from radar facilities. A centre may require numerous radar systems to cover the airspace assigned to them, and may also rely on pilot position reports from aircraft flying below the floor of radar coverage. This results in

6372-492: The U.S., TRACONs are additionally designated by a three-digit alphanumeric code. For example, the Chicago TRACON is designated C90. Air traffic control also provides services to aircraft in flight between airports. 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

6490-413: The US, "center" controllers. Area controllers are responsible for specific sectors of 3D blocks of airspace with defined dimensions. Each sector is managed by at least one area controller, known as an "R-side" (Radar) controller that handles radio communications. During busier times of traffic, there may also be a second area controller, known as a "D-side" (Data), assigned to the same area in order to assist

6608-562: The United States, with some speculating it was due to too many white males being hired over minorities. The FAA says it "is blind on the issue of diversity". At the same time, the FAA also stopped giving preference to applicants who were military veterans with aviation experience. In addition, group of external experts appointed by the Federal Aviation Administration emphasized the need for immediate action on Wednesday, November 15, 2023, to address safety concerns in

6726-465: The active runway surfaces. Air control gives clearance for aircraft takeoff or landing, whilst ensuring that prescribed runway separation will exist at all times. If the air controller detects any unsafe conditions, a landing aircraft may be instructed to ' go-around ', and be re-sequenced into the landing pattern. This re-sequencing will depend on the type of flight, and may be handled by the air controller, approach, or terminal area controller. Within

6844-471: The air by holding over specified locations until they may be safely sequenced to the runway. Up until the 1990s, holding, which has significant environmental and cost implications, was a routine occurrence at many airports. Advances in computers now allow the sequencing of aircraft hours in advance. Thus, aircraft may be delayed before they even take off (by being given a 'slot'), or may reduce speed in flight and proceed more slowly thus significantly reducing

6962-419: The air controllers aware of the traffic flow towards their runways to maximise runway utilisation through effective approach spacing. Crew resource management (CRM) procedures are often used to ensure this communication process is efficient and clear. Within ATC, it is usually known as 'team resource management' (TRM), and the level of focus on TRM varies within different ATC organisations. Clearance delivery

7080-900: 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 aircraft crosses the approach end of the runway. This process requires at least one, and up to four minutes for each aircraft. Allowing for departures between arrivals, each runway can thus handle about 30 aircraft arrivals per hour. A large airport with two arrival runways can handle about 60 arrivals per hour in good weather. Problems arise 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

7198-454: The air, a ground delay programme may be established, delaying aircraft on the ground before departure due to conditions at the arrival airport. In Area Control Centres, a major weather problem is thunderstorms , which present a variety of hazards to aircraft. Airborne 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

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7316-412: The aircraft approaches its destination, the centre is responsible for issuing instructions to pilots so that they will meet altitude restrictions by specific points, as well as providing many destination airports with a traffic flow, which prohibits all of the arrivals being 'bunched together'. These 'flow restrictions' often begin in the middle of the route, as controllers will position aircraft landing in

7434-481: The aircraft operator, and identical call sign might 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 east-bound, and odd if west-bound. In order to reduce the possibility of two call signs on one frequency at any time sounding too similar,

7552-426: The aircraft reaches a reporting point significantly earlier or later than previously estimated. There are two main techniques controllers use to organize flight progress strips in order to best detect conflicts: grouped together by altitude , or grouped together by route intersection points ( fix posting area ). Altitude grouping is the easiest and most common method when most aircraft in the sector tend to be level at

7670-418: The airport aligned with the runway to make an approach (becoming 'inbound track established' or just 'established'). In procedural approach control, separation is maintained by allowing only one aircraft to be making an approach at any one time; the proceeding aircraft must either be in visual contact by the airport's control tower, or have reported that it has landed before the next aircraft is allowed to leave

7788-543: The airports. The airspace boundaries and altitudes assigned to a terminal control centre, which vary widely from airport to airport, are based on factors such as traffic flows, neighbouring airports, and terrain. A large and complex example was the London Terminal Control Centre (LTCC), which controlled traffic for five main London airports up to an altitude of 20,000 feet (6,096 metres) and out to

7906-578: The amount of holding. Air traffic control errors occur when the separation (either vertical or horizontal) between airborne aircraft falls below the minimum prescribed separation set (for the domestic United States) by the US Federal Aviation Administration. Separation minimums for terminal control areas (TCAs) around airports are lower than en-route standards. Errors generally occur during periods following times of intense activity, when controllers tend to relax and overlook

8024-470: The broad-scale dissemination of air traffic data. The Aircraft Situational Display to Industry ( ASDI ) system now conveys up-to-date flight information to the airline industry and the public. Some companies that distribute ASDI information are Flightradar24 , FlightExplorer, FlightView, and FlyteComm. Each company maintains a website that provides free updated information to the public on flight status. Stand-alone programmes are also available for displaying

8142-528: The centre provides a clearance. Centre controllers are responsible for issuing instructions to pilots to climb their aircraft to their assigned altitude, while, at the same time, ensuring that the aircraft is properly separated from all other aircraft in its immediate area. Additionally, the aircraft must be placed in a flow consistent with the aircraft's route of flight. This effort is complicated by crossing traffic, severe weather, special missions that require large airspace allocations, and traffic density. When

8260-683: The completion of academic training, the graduating student will be granted an Air Traffic Control license, which will include one or more Ratings. These are sub-qualifications denoting the air traffic control discipline or disciplines in which the person has been trained. ICAO defines five such ratings: Area (procedural), Area Radar, Approach (procedural), Approach Radar, and Aerodrome. In the United States, controllers may train in several similar specialties: Tower, Ground-Controlled Approach (GCA), Terminal Radar Control, or En route Control (both radar and non-radar). This phase of training takes between six months and several years. Whenever an air traffic controller

8378-408: The computers, rather than being automated out of existence altogether. However, there are problems envisaged with technology that normally takes the controller out of the decision loop but requires the controller to step back in to control exceptional situations: air traffic control is a skill that has to be kept current by regular practice. This in itself may prove to be the largest stumbling block to

8496-424: The conflict. Every runway used by IFR aircraft normally has a procedural approach defined and published. This generally involves the aircraft flying over a fix (navaid or 'beacon') on or close to the airport (where the aircraft can hold if necessary), flying away from the airport on a set track while descending (going 'beacon outbound'), then at some point (perhaps ten miles) from the airport turning back towards

8614-603: The controller further: In the United States, some alterations to traffic control procedures are being examined: In Europe, the Single European Sky ATM Research (SESAR) programme plans to develop new methods, technologies, procedures, and systems to accommodate future (2020 and beyond) air traffic needs. In October 2018, European controller unions dismissed setting targets to improve ATC as "a waste of time and effort", as new technology could cut costs for users but threaten their jobs. In April 2019,

8732-595: The default language of aviation worldwide is Aviation English . Controllers who do not speak English as a first language are generally expected to show a certain minimum level of competency. Area controllers are responsible for the safety of aircraft at higher altitudes, in the en-route phase of their flight surrounding busier airports and airspace. Area controllers may also handle aircraft at lower altitudes as well as air traffic around small airports that do not have their own towers or approach controllers. In most nations, they are known as "area", "en route", or, colloquially in

8850-472: The different sets of rules. While IFR flights are under positive control, in the US and Canada, VFR pilots can request 'flight following' (radar advisories), which provides traffic advisory services on a time permitting basis, and may also provide assistance in avoiding areas of weather and flight restrictions, as well as allowing pilots into the air traffic control system prior to the need to a clearance into certain airspace. Throughout Europe, pilots may request

8968-598: The equivalent term air route traffic control center. Each centre is responsible for a given flight information region (FIR). Each flight information region typically covers many thousands of square miles of airspace, and the airports within that airspace. Centres control IFR aircraft from the time they depart from an airport or terminal area's airspace, to the time they arrive at another airport or terminal area's airspace. Centres may also 'pick up' VFR aircraft that are already airborne, and integrate them into their system. These aircraft must continue under VFR flight rules until

9086-575: The extent required to maintain safe operation of the aircraft. Pursuant to requirements of the International Civil Aviation Organization (ICAO), ATC operations are conducted either in the English language, or the local language used by the station on the ground. In practice, the native language for a region is used; however, English must be used upon request. In 1920, Croydon Airport near London, England,

9204-523: The following provides a general concept of the delegation of responsibilities within the air traffic control tower environment. Remote and virtual tower (RVT) is a system based on air traffic controllers being located somewhere other than at the local airport tower, and still able to provide air traffic control services. Displays for the air traffic controllers may be live video, synthetic images based on surveillance sensor data, or both. Ground control (sometimes known as ground movement control , GMC)

9322-432: The geographic location of airborne instrument flight rules (IFR) air traffic anywhere in the FAA air traffic system. Positions are reported for both commercial and general aviation traffic. The programmes can overlay air traffic with a wide selection of maps such as, geo-political boundaries, air traffic control centre boundaries, high altitude jet routes, satellite cloud and radar imagery. The day-to-day problems faced by

9440-427: The ground and clearance for approach to an airport. 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. En-route air traffic controllers work in facilities called air traffic control centres, each of which is commonly referred to as a 'centre'. The United States uses

9558-436: The hold and commence the approach. At airports equipped with radar, procedural approaches normally are used only in the event of an aircraft suffering a radio failure, or for training purposes. At non-radar airports or when radar is not available, these are the only means of IFR flights making approaches to the airport. At some non-radar airports, the procedural approach may be combined with aerodrome control, thus providing

9676-428: The immediate vicinity of the airport and use visual observation from the airport tower. The tower's airspace is often a 5-nautical-mile (9.3 km) radius around the airport, but can vary greatly in size and shape depending on traffic configuration and volume. The tower positions are typically split into many different positions such as Flight Data/Clearance Delivery, Ground Control, and Local Control (known as Tower by

9794-408: The information of the track once the correlation between them (flight plan and track) is established. All this information is distributed to modern operational display systems , making it available to controllers. The Federal Aviation Administration (FAA) has spent over US$ 3 billion on software, but a fully automated system is still yet to be achieved. In 2002, the United Kingdom commissioned

9912-571: The infrastructure for a radar system (e.g., over water). Computerised radar displays are now being designed to accept ADS-C inputs as part of their display. This technology is currently used in portions of the North Atlantic and the Pacific by a variety of states who share responsibility for the control of this airspace. 'Precision approach radars' (PAR) are commonly used by military controllers of air forces of several countries, to assist

10030-435: The introduction of highly automated air traffic control systems. User acceptance or willingness to use such technology is another important consideration air service providers need to consider prior to implementing any new technology. In a recent study with over 500 air traffic controllers from around the world, Bekier and colleagues found that once the focus of decision-making shifts from the air traffic controller, support for

10148-476: The job. Despite years of effort and billions of dollars spent on computer software designed to assist air traffic control, success has been largely limited to improving the tools at the disposal of the controllers, such as computer-enhanced radar. It is likely that in the next few decades, future technology will make the controller more of a systems manager overseeing decisions made by automated systems and manually intervening to resolve situations not handled well by

10266-424: The last three numbers (e.g. three-four-five for N12345). In the United States, the prefix may be an aircraft type, model, or manufacturer in place of the first registration character, for example, 'N11842' could become 'Cessna 842'. This abbreviation is only allowed after communications have been established in each sector. Before around 1980, International Air Transport Association (IATA) and ICAO were using

10384-517: The manoeuvring area (taxiways and runways). The areas of responsibility for tower controllers fall into three general operational disciplines: local control or air control, ground control, and flight data / clearance delivery. Other categories, such as airport apron control, or ground movement planner, may also exist at extremely busy airports. While each tower may have unique airport-specific procedures, such as multiple teams of controllers ( crews ) at major or complex airports with multiple runways,

10502-463: The means of determining horizontal separation is by a controller observing the radar returns of the aircraft to be at least a minimum horizontal distance apart. This is the essence of radar control and is probably the form of air traffic control most familiar to lay people. However, in times gone by radar was not very common, and in certain parts of the world today it still is not common, on grounds of cost or technical feasibility. Procedural control

10620-477: The medical authority, and failure to do so can result in a revocation of medical certification. Numerous drugs approved by the U.S. Food and Drug Administration (FDA) are either banned or would require an air traffic controller to apply for a Special Consideration Medical Certificate and undergo stringent and continuous monitoring of the underlying medical condition. Almost universally, trainee controllers begin work in their twenties and retire in their fifties. This

10738-465: The movement of aircraft between departure and destination, was opened in Newark in 1935, followed in 1936 by Chicago and Cleveland. Currently in the US, the Federal Aviation Administration (FAA) operates 22 Air Route Traffic Control Centers . After the 1956 Grand Canyon mid-air collision , killing all 128 on board, the FAA was given the air-traffic responsibility in the United States in 1958, and this

10856-491: The nation's aviation system. The two primary issues they highlighted were inadequate staffing levels among air traffic controllers and the existence of outdated technology. Air traffic control Air traffic control ( ATC ) is a service provided by ground-based air traffic controllers who direct aircraft on the ground and through a given section of controlled airspace , and can provide advisory services to aircraft in non-controlled airspace. The primary purpose of ATC

10974-530: The new airport in Istanbul, which opened in April, but the extra capacity will be absorbed by rising demand for air travel. Well-paid jobs in western Europe could move east with cheaper labour. The average Spanish controller earn over €200,000 a year, over seven times the country average salary, more than pilots, and at least ten controllers were paid over €810,000 ($ 1.1m) a year in 2010. French controllers spent

11092-438: The overall capacity for any given route. The North Atlantic Track system is a notable example of this method. Some air navigation service providers (e.g., Airservices Australia, the U.S. Federal Aviation Administration, Nav Canada , etc.) have implemented automatic dependent surveillance – broadcast (ADS-B) as part of their surveillance capability. This newer technology reverses the radar concept. Instead of radar 'finding'

11210-418: The overseeing aviation authority without explicit testing and waivers signed by the overseeing medical authority, demonstrating that the disorder does not impact the individuals ability to do the job. Almost universally, controllers are subjected to rigid medical and mental exams to ensure safety in the air traffic system. In the United States, for example, all air traffic controllers are required to take and pass

11328-482: The pilot in final phases of landing in places where instrument landing system and other sophisticated airborne equipment are unavailable to assist the pilots in marginal or near zero visibility conditions. This procedure is also called a 'talk-down'. A radar archive system (RAS) keeps an electronic record of all radar information, preserving it for a few weeks. This information can be useful for search and rescue . When an aircraft has 'disappeared' from radar screens,

11446-620: The pilots); at busier facilities, a limited radar approach control position may be needed. The roles of the positions are: Most countries' armed forces employ air traffic controllers, often in most if not all branches of the forces. Although actual terms vary from country to country, controllers are usually enlisted. In some countries, all air traffic control is performed by the military. In other countries, military controllers are responsible solely for military airspace and airbases; civilian controllers maintain airspace for civilian traffic and civilian airports. Historically, in most countries, this

11564-440: The position of the air traffic controller requires some of the strictest physical and mental health requirements for any profession in the world; conditions such as diabetes , epilepsy , heart disease , and many psychiatric disorders (e.g., clinical depression , ADHD , bipolar disorder , personality disorders , a history of drug abuse , among many others) almost always disqualify people from obtaining medical certification from

11682-399: The position to give guidance and ready to immediately take over should it become necessary. The length of this phase of training varies from a matter of months to years, depending on the complexity of the sector. Only once a person has passed all these training stages they will be allowed to control a position alone. Typically, controllers work "on position" for 90 to 120 minutes followed by

11800-544: The presence of traffic and conditions that lead to loss of minimum separation. Beyond runway capacity issues, the weather is a major factor in traffic capacity. Rain, ice , snow, or hail 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. Fog also requires a decrease in the landing rate. These, in turn, increase airborne delay for holding aircraft. If more aircraft are scheduled than can be safely and efficiently held in

11918-400: The same destination so that when the aircraft are close to their destination they are sequenced. As an aircraft reaches the boundary of a centre's control area, it is 'handed off' or 'handed over' to the next area control centre . In some cases, this 'hand-off' process involves a transfer of identification and details between controllers so that air traffic control services can be provided in

12036-447: The same or intersecting routes at the same level shall come within 10 minutes' flying time of another (or sometimes 15 minutes depending on the accuracy of the available radio navigation beacons). Using procedural control, the controller must maintain a mental picture of the location of aircraft based on each aircraft's flight progress strip , which contains its route, altitude and estimated times over reporting points. That information

12154-472: The same route. Each intersection point ("fix posting area") in the sector is made into a separate bay on the strip rack, and multiple strips are printed for each aircraft, one per bay. The controller then sorts strips within each bay by the estimated time the aircraft is expected over that point. Only aircraft estimated to cross within 10 minutes of each other are considered possible conflicts, at which point altitudes are then compared to determine if there actually

12272-550: The same two-letter call signs. Due to the larger number of new airlines after deregulation, the ICAO established the three-letter call signs as mentioned above. The IATA call signs are currently used in aerodromes on the announcement tables, but are no longer used in air traffic control. For example, AA is the IATA call sign for American Airlines ; the ATC equivalent is AAL. Flight numbers in regular commercial flights are designated by

12390-474: The stresses and challenges faced by air traffic controllers in her 1984 study "The politics of stress: the case of air traffic control." published in the International journal of health services. In a study which compared stress in the general population and in this kind of systems markedly showed more stress level for controllers. This variation can be explained, at least in part, by the characteristics of

12508-418: The taxiways and runways of the airport itself, and aircraft in the air near the airport, generally 5 to 10 nautical miles (9 to 19 kilometres ; 6 to 12 miles ), depending on the airport procedures. A controller must carry out the job using the precise and effective application of rules and procedures; however, they need flexible adjustments according to differing circumstances, often under time pressure. In

12626-428: The technology dramatically decreases. Unsurprisingly, they also found that air traffic controllers enjoy the core tasks of their role: namely, conflict detection and resolution. In 2014, it was reported that in the United States, the Federal Aviation Administration had stopped giving preferential treatment to air-traffic controller applicants who had passed classes from the 36 FAA-approved college aviation programs across

12744-418: The thin corridors open to airliners. The United Kingdom closes its military airspace only during military exercises. A prerequisite to safe air traffic separation is the assignment and use of distinctive call signs . These are permanently allocated by ICAO on request, usually to scheduled flights , and some air forces and other military services for military flights . There are written call signs with

12862-452: The tower on the airport and vector inbound aircraft to a position from where they can land visually. At some of these airports, the tower may provide a non-radar procedural approach service to arriving aircraft handed over from a radar unit before they are visual to land. Some units also have a dedicated approach unit, which can provide the procedural approach service either all the time, or for any periods of radar outage for any reason. In

12980-432: The tower, a highly disciplined communications process between the air control and ground control is an absolute necessity. Air control must ensure that ground control is aware of any operations that will impact the taxiways, and work with the approach radar controllers to create gaps in the arrival traffic; to allow taxiing traffic to cross runways, and to allow departing aircraft to take off. Ground control needs to keep

13098-420: The traffic levels may not justify staffing the radar control positions, or as a back-up system in the case of radar failure. In air traffic control, the risk of aircraft colliding is managed by applying separation rules . These rules require aircraft to be separated by either a minimum vertical distance, or if vertical separation is not feasible, by a minimum horizontal distance defined by various means. One of

13216-650: The world with significant enough traffic to warrant this technique have at least a radar covering the climb out and arrival area, and only need procedural control for points between (in which case altitude grouping is likely more efficient). Nevertheless, the fix posting area method was the main technique used in U.S. en route system prior to the 1960s, for example, when en route radar became more widespread. This method evolved from similar techniques used in railroad dispatch . It simplifies conflict detection because aircraft on different routes can only possibly conflict at intersection points with other routes, or with aircraft on

13334-557: The world's ocean areas. These areas are also flight information regions (FIRs). Because there are no radar systems available for oceanic control, oceanic controllers provide ATC services using procedural control . 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

13452-496: The written 'BAW832'. This is used to reduce the chance of confusion between ATC and the aircraft. By default, the call sign for any other flight is the registration number (or tail number in US parlance) of the aircraft, such as 'N12345', 'C-GABC', or 'EC-IZD'. The short radio-telephony call signs for these tail numbers is the last three letters using the NATO phonetic alphabet (e.g. ABC, spoken alpha-bravo-charlie for C-GABC), or

13570-507: Was created in 1922, after World War I, when the U.S. Post Office began using techniques developed by the U.S. Army to direct and track the movements of reconnaissance aircraft . Over time, the AMRS morphed into flight service stations . Today's flight service stations do not issue control instructions, but provide pilots with many other flight related informational services. They do relay control instructions from ATC in areas where flight service

13688-702: Was followed by other countries. In 1960, Britain, France, Germany, and the Benelux countries set up Eurocontrol , intending to merge their airspaces. The first and only attempt to pool controllers between countries is the Maastricht Upper Area Control Centre (MUAC), founded in 1972 by Eurocontrol, and covering Belgium, Luxembourg, the Netherlands, and north-western Germany. In 2001, the European Union (EU) aimed to create

13806-596: Was part of the government and controllers were civil servants. However, many countries have partly or wholly privatized their air traffic control systems; others are looking to do the same. Civilian Air Traffic Controllers' licensing is standardized by international agreement through ICAO . Many countries have Air Traffic Control schools, academies or colleges, often operated by the incumbent provider of air traffic services in that country, but sometimes privately. These institutions are structured to provide training to individuals without any prior air traffic control experience. At

13924-415: Was the first airport in the world to introduce air traffic control. The 'aerodrome control tower' was a wooden hut 15 feet (5 metres) high with windows on all four sides. It was commissioned on 25 February 1920, and provided basic traffic, weather, and location information to pilots. In the United States, air traffic control developed three divisions. The first of several air mail radio stations (AMRS)

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