Диспетчерская служба управления воздушным движением

Service to direct pilots of aircraft

Air traffic control (ATC) is a service provided by ground based air traffic controllers (people) 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 worldwide is to prevent collisions, organise 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 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 their aircraft always retain final authority for its safe operation, and may, in an emergency, deviate from ATC instructions to the extent required to maintain safe operation of their 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. The 'aerodrome control tower' was a wooden hut 15 feet (5 m) 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 of America, air traffic control developed three divisions. The first of several air mail radio stations (AMRS) 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 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 USA 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 the movement of aircraft between departure and destination, was opened in Newark in 1935, followed in 1936 by Chicago and Cleveland. Currently in the U. S., 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 over the United States in 1958, and this 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 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 the taxiways and runways of the airport itself, and aircraft in the air near the airport, generally , 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 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 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 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, 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) is responsible for the airport movement areas, 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 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 the active runway surfaces.

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 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 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 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 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 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 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 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 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 a large airspace area, they will typically use long range radar, that has the capability, at higher altitudes, to see aircraft within 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 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 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 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 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' 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 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 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 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, 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 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 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 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 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 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 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 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 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 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 is brought in, more and more sites are upgrading away from paper flight strips.

The United States airspace is divided into 21 zones (centres), and each zone is divided into sectors. Also within each zone are portions of airspace, about 50 mile (80 km) in diameter, called TRACON (Terminal Radar Approach Control) airspaces. Within each TRACON airspace are a number of airports, each of which has its own airspace with a 5 mile (8 km) radius. FAA control tower operators (CTO) / air traffic controllers use FAA Order 7110.65 as the authority for all procedures regarding air traffic.