Air traffic control

Air Traffic Control (FRP, English Air Traffic Control ATC) is a part of air traffic control and refers to the ground-based service of air traffic controllers, manage the aircraft on the ground and in the air. The primary purpose of air traffic control is the graduation of aircraft to prevent collisions, to organize and expedite the flow of traffic, and the provision of information and support for pilots. In some countries, air traffic control is also partly consistent security and defense tasks ( as in the United States) or is entirely carried out by the military (as in Brazil ).

The collision avoidance is achieved by graduation. This is compliance with the minimum vertical and horizontal distances between aircraft in the foreground. Many planes now have a collision warning system, which exists as an additional tool in addition to the primary air traffic control. In addition to their main tasks the air traffic control offers other services, such as information to pilots, weather, navigation information and NOTAMs.

In many countries, air traffic control is carried out in a large part of the air space and available to all airspace users available (private, commercial and military ). When air traffic controllers are responsible for the differentiation of some or all aircraft, such airspace is called the controlled airspace. Depending on the airspace class and the type of flight are air traffic control instructions to be followed by the pilot, or only information that will help the pilot. In all cases, however, the ultimate responsibility for the safe flight rests with the pilot in command, which may differ in case of emergencies, from the instructions of air traffic control.

  • 5.1 General
  • 5.2 Radar cover
  • 6.1 traffic
  • 6.2 Weather

History in Germany

In 1910, the pilot's warning service was created to provide pilots by telegraph with meteorological and bearing information. The stations were located mainly at the airports.

As of 1945, the entire air traffic control was subject to air navigation services of the victorious powers. In 1953, the BFS ( BFS) was founded in Frankfurt am Main and was responsible for civilian air traffic control. 1959 laid the Federal Ministry of Transport and the Ministry of Defense civil-military division of labor formally.

The controls in the airspace of the GDR were perceived by the Inter flight or by the Department of XIX ( Transportation ) of the Ministry for State Security ( Stasi).

The Allies controlled to 3 October 1990 air corridor to Berlin.

The headquarters of the air traffic control in accordance with the respective territory divided into " ACC" ( Area Control Center ) and "UAC " ( Upper Area Control Center). The duties of an ACC are located in the lower part of the air spaces in the altitude range from ground to about 8 km.

History in the U.S.

In 1919, the International Commission for Air Navigation ( ICAN ) was created to develop general rules for air transport. Their rules and procedures were in most states where wrong aircraft used. The United States did not join the ICAN convention, but developed from 1926 's air traffic rules. First simple arrangements have been made, for example, the instruction to pilots not to start until there is no risk of collision with other aircraft landing or just started was more. With increasing traffic numbers it became clear that such general rules are not sufficient to avoid collisions. Aerodrome operator, began with the establishment of a kind of air traffic control, which was based on visual signs. Early " air traffic controllers " were on the airfield and made ​​use of various flags to communicate with the pilot.

As the equipment of the aircraft with radios displaced radio-based towers the flag signals. In 1930, in the USA the first tower with radio operations on Cleveland Municipal Airport on. By 1935, operated about 20 towers with radio.

A further increase in traffic figures led to the need for a competent and outside the airports air traffic control. 1935 agreed the airlines, the airports Chicago, Cleveland and Newark most used to coordinate the handling of air traffic between these cities. In December opened the first air traffic control center in Newark, New Jersey. Other centers in Chicago and Cleveland followed in 1936.

The first air traffic controllers tracked the position of the aircraft on the basis of marks on maps and flight plan data on tablets. They had no direct radio contact with the aircraft, but stood with the use planners of the airlines and the pilots of the airfields in telephonic communication.

In July 1936, the Air Traffic Control went to the U.S. on the responsibility of the federal government and the first budget items, was $ 175,000 ( $ 2,665,960 today ). The government provided air traffic control on the air lanes ready, but local authorities remained responsible for the operation of the towers. By 1944 there were 115 towers in the United States. After the Second World War, the air traffic control went to many airfields permanently on the responsibility of the federal government. The Civil Aeronautics Administration ( CAA) extended the same time as the track system of air traffic control.

With the introduction of radar set from the mid 1940's a revolutionary development. Air traffic controllers were able to see the current position of aircraft on display devices and track for the first time. The first experimental radar-based civilian control tower took in 1946 on its operation. 1952 was initiated by the CAA with the routine use of radar for approach and departure control. Four years later, a contract for procurement of long -range radar equipment was issued to the track control.

In 1960 the Federal Aviation Administration (FAA ), which contested the 1958 successor to the CAA, in defined airspace with successful tests of secondary radar systems and on-board transponders bound. This helped determine the position of aircraft and to improve the radar display. Pilots in these airspaces also had to fly by instruments only - regardless of the weather - and with the air traffic controllers stay in touch. Under these conditions, the air traffic controllers were able to halve the separation between the aircraft.

From 1965 to 1975, the FAA developed complex computer systems, the presentation and analysis of the radar data automated and improved and thereby enabling the air traffic controllers, to focus more on the management of air traffic.

In April 1970, a Central Flow Control Facility was established, which should reduce air traffic delays by avoiding selective overloading of air traffic control units.

With the introduction of the National Airspace System ( NAS) in January 1982, a comprehensive modernization of air traffic control units and communication and surveillance systems took place.

A further stage of modernization began in 1999, when the Standard Terminal Automation Replacement System was introduced with new display devices and more efficient workplaces.

Current developments are aimed at the improvement of communication, navigation and surveillance and mainly use the advanced transponder, the Global Positioning System and more precise radars. At the same time to offer pilots more and more accurate information about other traffic, weather and possible dangers ready to improve the cockpit displays.


Pursuant to the requirements of the International Civil Aviation Organization (ICAO ) air traffic control services are performed either in English or in the language used by the ground station. In practice, the local language is often used, but must be used to request the English language.

Aerodrome control

The primary method for monitoring the direct airport environment is visual observation from the control tower. Tower controllers are responsible for the differentiation and efficient traffic control of aircraft and vehicles operating on the taxiways and start and runways and in the air in close proximity to the airport (control zones, usually within 2-5 nautical miles, or 3, 7 to 9.2 kilometers ).

Radar displays are also available at some airports for pilots. The pilots can get displayed on a digital map with information about call sign, speed, direction and altitude by secondary radar arriving and departing traffic.

The tasks of the pilots at the airfield can be basically divided into three categories: space control, floor control and release / clearance delivery. Other services, such as Apron Control and marshaler are available depending on the traffic at the airport, but are not affected by the air traffic control, but by the aerodrome operator. In each tower different local practices are regulated, the following sections provide an overview of the fundamental tasks within the Tower.

Roll control

The roll control (English ground control ) is responsible for the runway of the airfield and other operational areas. This usually includes taxiways, abandoned take-off and landing runways, as well as some waiting areas. Exact limitations of the scope should be clearly defined in local regulations. Every aircraft, every other vehicle and any working or passing person shall obtain a release of the roll control within this range. Normally this is done via wireless connection, but there are also different procedures. Most aircraft and vehicles are equipped with radios. If no wireless connection is possible, they have to make contact by light signal or must be accompanied by radio -equipped vehicles. For most people are ready portable radios or mobile phones. The roll control is essential to ensure smooth operation sequence at the airport, since the order of departures and the threading of incoming aircraft must be harmonized.

At larger airports, the roll control is often a ground radar available, which represents the current position of the aircraft on the ground. In this way, especially at night and in poor visibility to avoid risk and a speedy operation can be maintained.

Place control

The space control, called the tower (English tower ), is responsible for the active start and runways as well as the traffic in the control zone. The space control granted approvals for take off and landing on the condition that specified minimum distances are maintained. In uncertain situations approaching aircraft can durchzustarten be instructed and to be newly included in the approach.

Inside the tower close coordination between roll control and space control is necessary. The roll control must obtain a permit if they want an active start and runway crossing by aircraft or vehicles. Other hand, the space control must ensure that the roll control is informed of any operations that could affect the operation on the taxiways. Furthermore, it shall coordinate with the pilot approach control to take advantage of gaps in the approaching traffic for planes taking off or intersecting traffic. Crew Resource Management (CRM ) training is used extensively to make these communication processes more efficient and safer.

Enable / Flight Data

The release (german clearance delivery ) is the position, transmitted which route clearances to aircraft, typically before they begin the rolling process. The route clearances contain details of the route to fly the aircraft after take-off. The release coordinated this with the non-local area control centers. Often, the approval process is automated or generally governed by local agreements. If weather conditions or high traffic density for an aerodrome or a specified airspace are critical, it may be necessary to cause the aircraft on other routes or to have them wait at the bottom and move the slot to avoid overloading. The main purpose of the release is to ensure that all aircraft receive the proper route and slot time. In cooperation with the roll control must ensure that the aircraft at the required time to reach the runway and are ready for takeoff. The release is also responsible for the authorization of pushback and engine start to prevent congestion on taxiways and apron at some airports.

Flight Data is a task that is routinely adopted by the release. Here, both air traffic controllers and pilots are constantly supplied with current information like weather changes, system failures, delays on the ground, closures start and runways etc. Flight Data informs pilots also by means of a broadcast on a separate frequency loop, known as the Automatic Terminal Information Service ( ATIS).

Approach control

Many airports have a radar control center, which is associated with the airfield. In most countries it is referred to as Terminal Control, in the United States as a TRACON (Terminal Radar Approach Control ). Although the conditions at each airport differ, the pilots take over the traffic usually within 30-50 nautical miles ( 56-93 kilometers ) around the airfield. If more busy airfields are close together, an approach control unit takes over the services for all airports. The boundaries of the airspace for approach control vary greatly depending on local traffic flow, neighboring airports and terrain. A large and complex example of this was the London Terminal Control Centre, which controlled the traffic for five London airports up to 20,000 feet in height and 100 nautical miles.

Approach pilots are responsible for the provision of all air navigation services within their airspace. The traffic flow can be roughly divided into departures, approaches and overflights. If aircraft in the airspace of the approach control fly in and out, they are the next inspection body handed over (eg Tower, area control center or adjacent approach control units ). The approach control is responsible for compliance with specified altitudes when passed to adjacent sites and that aircraft ansetzten in a suitable rate for landing.

Not all airports have an approach control unit. In this case, the area control center or an adjacent approach control unit takes care of the traffic and coordinates directly to the tower. Some of these airfields the Tower can offer an approach procedures without radar assistance if the aircraft can not land on sight.

Route control

→ For more information, see the Area Control Center.

Air traffic control is aircraft between airfields by the area control centers also available. Pilots fly either to Visual Flight Rules ( VFR) or Instrument Flight Rules (IFR ). Air traffic controllers are responsible for the aircraft according to flight control in different ways. During IFR traffic is under positive control, VFR traffic can receive traffic information and navigation instructions, as far as the capacity of the air traffic control permits.

The pilots of the track control issue clearances and instructions for aircraft in the air and pilots have to follow these arrangements. The pilots also smaller airports air traffic control services, by issuing approvals for arrivals and departures. Note a number of fixed minimum distances for the differentiation of airplanes, which can vary depending on the equipment and procedures used.


Controllers, the route control work in ACC ( Area Control Centre ), commonly referred to only as the center. In the United States there is also the name ARTCC (Air Route Traffic Control Center). Each center is responsible for an air space of many thousands of square miles ( known as Flight Information Region) and for airfields therein. Center conduct IFR flights from the time they were flying or leaving the sector approach until they arrive at another airfield or approach sector. Center can also accept VFR flights which are already underway and include them in the IFR traffic. However, these flights must VFR rules do until they get a share of Center.

Center controllers are responsible to send up aircraft to their requested altitude while they need, while ensuring that this staggering to other aircraft is maintained. In addition, the aircraft must be integrated according to their route into the traffic flow. These efforts are complicated by crossing traffic, bad weather and traffic density. When an aircraft approaches its destination, the Center are responsible for complying with restrictions on the flying height above specified trace points and to have staggered the approaches that there will be no shortages. This traffic flow management starts already during the haul flight, as the aircraft pilot position with the same goal so that they do not arrive at the same time.

Once an aircraft reaches the boundary of the airspace of a center, it is passed to the next center. In some cases, only the details of the flight are exchanged between the air traffic controller in order to allow a smooth transition, in other cases, by complying with agreed transfer criteria, no separate coordination necessary. With the delivery of the aircraft will be assigned a new frequency and makes contact with the new sector. This process is repeated until the aircraft reaches the approach sector of its target airfield.

Radar coverage

Since center control a large airspace, they mostly use long range radar devices that have the ability to airplanes at higher altitudes up to 200 miles ( 370 kilometers) to detect distance. You can also use the radar approach control facilities, if this a better " picture" deliver or if they represent a portion of the airspace that is not covered by the long- range radar.

In the United States there is at higher altitudes to 90% of a radar coverage of the airspace, often by multiple radar systems. Nevertheless, gaps at lower altitudes can be caused by high terrain or long distances to the nearest radar station. A center may take several radars to monitor its allotted space may or must even rely on position information of the pilots. In order to process the wealth of data available for the pilot, automated systems are available that produce a single clear picture of all radar data and display data in a clear format.

The Center also monitor the air traffic across the oceans, as these regions to the North Atlantic Tracks are also part of a Flight Information Region. For the oceans no radars are available, thus the air traffic controllers and pilots depend exclusively on established flight procedures. These procedures use aircraft position reports, time, altitude, distance and speed to ensure graduation. Pilot draw on the available information on the control strips and in specially developed oceanic regions for computer systems. In applying this method Aircraft must be staggered at a greater distance, which reduces the total capacity of the individual routes.

Some air traffic control (such as Airservices Australia, The Federal Aviation Administration, NAVCANADA, etc.) have ADS-B (Automatic Dependent Surveillance - Broadcast ) was introduced as part of their monitoring capabilities. This new technology reverses the radar concept. Instead of a radar, the need to find a target, and detect, send ADS- equipped aircraft independently determined by means of their own navigational position reports. ADS-B is important because it can be used where radar devices are not available. With the development of computer-based radar displays ADS-B information can be brought to display it. This technology is currently used in the North Atlantic and the Pacific, where several countries share the responsibility for the control of air space.



The everyday problems faced by air traffic control, mainly based on the volume of traffic and the weather. Various factors determine the number of landings at an airport in a given period of time. Each landing aircraft must touch down, slow down and leave the runway before the next plane crosses the end of the runway. This process requires at least one to four minutes per aircraft. If still take place departures between the approaches, a runway per hour take about 30 approaches. A large airport with two runways for arrivals can thus handle about 60 approaches in good weather. Problems occur when airlines want to carry more approaches to an airport than it can physically cope or if delays cause groups of aircraft arrive simultaneously, which were originally flying at different times. Aircraft must then fly a holding pattern in the air above a specified point until they can be safely threaded into the approach. Until the 1990s were queues that have significant consequences for the environment and costs, regularly seen at many airports. Advances in computer technology now make it possible by means of Air Traffic Flow Management to sort aircraft time hours earlier. This allows departures before the start delay to be adjusted ( by allocating a new slots) or the speed in flight, to shorten the time considerably in the queues.


In addition to the capacity limits of the take-off and landing runways, the flying weather is a key factor for air transport. Rain, ice or snow on the runway can cause that landing planes take longer to slow down and to leave the path and therefore the time must be set up between two approaches. Fog also leads to a reduction of the approach rates. Thereof on the other results in a increase in the delay in the air. If more are planned approaches can be taken to be safe, it may come because of the weather at the destination airport delays at departure here.

For the Center thunderstorms mean a big problem since they involve a number of risks to aviation with it. Aircraft will be diverted around the thunderstorms, which may lead through greater graduation or overloading a single route between the thunderstorms in a reduction of capacity of the network. Occasionally, thunderstorms result in a delay of departures when routes or locations have been closed due to the storms. Similar problems arise in heavy and / or prolonged snowfalls make the runway closures during the site clearance required. Of approaching traffic must then u.U. are staggered by the holding company.

A lot of money has been invested in the development of software in order to make these processes more efficient. However, data in some centers of the air traffic controllers still for each flight check written on strips of paper and personally coordinate flight paths. In newer plants, these control strips have been replaced by electronic displays and older devices will gradually modernized.


A need for reliable differentiation of the air traffic participants is the allocation and use of call sign. By default, the callsign of flights is the respective aircraft registration mark of the aircraft, such as " N12345 " or "C - GABC ". These marks are usually painted on the tail of the aircraft, but can also be on the engines on the aircraft fuselage or often mounted on the wings.

For airlines, your call will be permanently allocated by ICAO ( and by the air forces for military flights ). It is written by callsign of a combination of three letters like KLM, AAL, SWA, BAW, DLH followed by the flight number as AAL872, BAW018. In this way they are shown in timetables and as a label at radar displays. There are also radio call sign used at the contact between controllers and pilots. They are not always the same as the written call sign. For example BAW stands for British Airways, but in radio communications the word Speedbird used.

The part of the flight number is determined by the operator of the aircraft. In this way, the same call sign can be used every day for the same flight, even if the departure time of day can vary by day. The call sign for the return flight often differs only in the last digit from the outbound flight. In general, flight numbers are just for flights in an easterly direction and odd in a westerly direction. To reduce the possibility of confusion between two similar looking rings, especially European airlines have begun to use alphanumeric callsign. For example DLH23LG, spoken as Lufthansa -two -tree- lima - golf. In addition, an air traffic controller has the right to change the callsign of the flight within its sector in order to avoid confusion, usually by the aircraft registration mark is used instead.

Prior to 1980, the IATA and ICAO used the same call sign consisting of two letters. With the advent of many new airlines, ICAO introduced the above-mentioned three-letter call sign. The IATA callsigns are currently still on billboards in airports, but no longer used in air traffic control. As an example, AA is the IATA callsign for American Airlines, the ICAO call sign is AAL. Other examples include LY / ELY for El Al, DL / DAL for Delta Air Lines and LH / DLH for Lufthansa.