Air traffic control
Air traffic control, also known as ATC (from English Air Traffic Control), is a service provided by controllers located in ground, which guide aircraft in controlled airspaces and provide information and support to pilots in uncontrolled airspaces. Its objective is to provide security, order and efficiency to air traffic.
Depending on the type of flight and the class of airspace, the controller can offer mandatory instructions or advice that pilots can ignore at their discretion. In either case, the pilot is the ultimate authority in the operation of the aircraft and may, in an emergency, deviate from ATC instructions to maintain flight safety.
History
In 1920, Croydon Airport, London, was the first airport in the world to introduce air traffic control.
In the United States, air traffic control developed into three divisions. The first of the airmail radio stations (AMRS) was created in 1922 after World War I when the US Post Office began using techniques developed by the military to direct and track the movements of aircraft. of recognition. Over time, the AMRS were transformed into flight service stations.
Today's flight service stations do not issue control instructions, but rather provide pilots with many other flight-related informational services. These are in charge of transmitting ATC control instructions in areas where the flight service is the only facility with radio or telephone coverage.
In October 1929, the position notification service was established for aircraft flying on the so-called federal routes.
The first airport traffic control tower, regulating arrivals, departures, and surface movement of aircraft at a specific airport, opened in Cleveland in 1930. Approach/departure control facilities were created after the adoption of radar in the 1950s to monitor and control airport airspace.
The first air route traffic control center, directing the movement of aircraft between departure and destination, opened in Newark, NJ in 1935, followed in 1936 by Chicago and Cleveland.
In April 1935, the first air route control center was installed at the Newark (New Jersey) aerodrome, followed in 1936 by Chicago and Cleveland. This makes it possible to provide information to pilots about the proximity of other aircraft in the aerodrome environment during the existence of meteorological conditions that required it.
In May 1958, the CAB established through special regulation 424 the "route segments with positive control" and VFR flights were prohibited, allowing only operations subject to IFR.
In April 1970, as part of the ATM, the "Central Flow Control Facility" that made it possible to restrict the number of aircraft that coexist in the airspace. Their goal is to get them free and reduce air traffic congested areas.
General information
The airspace is divided into flight information regions, known as FIRs (from the English Flight Information Region), and each country is responsible for the service in those included in its area of responsibility. In many cases, this area of responsibility exceeds the territorial waters of a country, so that the airspace covered by international waters has an information service. The airspace in which the air control service is provided is called controlled airspace and the unit in charge of providing it is called the area control center. Due to the vast airspace they manage, they are divided into control sectors, each responsible for a part of the total space. When an aircraft is about to leave a sector, it is transferred to the next, and so on until landing at its destination. Currently, most of the air routes are covered by radars, which allows permanent monitoring of flights.
In the flight information regions are the terminal areas of major airports and between them run the airways, corridors through which aircraft circulate. Other elements are prohibited, restricted or dangerous areas, which are areas where the flight of aircraft is restricted to different extents and for various reasons.
The rules that regulate air circulation in controlled airspace are included in the Air Circulation Regulations.
Language
In accordance with International Civil Aviation Organization (ICAO) requirements, ATC operations are conducted in English or the language used by the ground station. In practice, the native language of a region is normally used; however, the English language must be used upon request.
Air traffic control tower
The main method of controlling the airport environment immediately is visual observation from the airport control tower. The control tower is a tall, windowed structure located on the airport grounds. Air traffic controllers are responsible for the separation and efficient movement of aircraft and vehicles operating on airport taxiways and runways, and aircraft in the air near the airport, generally 5 to 10 nautical miles (9 to 18 km) depending on airport procedures.
Surveillance screens are also available to controllers at larger airports to help control air traffic. Controllers can use a radar system called secondary surveillance radar for approaching and departing air traffic. These displays include a map of the area, the position of various aircraft, and data labels that include aircraft identification, speed, altitude, and other information described in local procedures. In inclement weather, tower controllers may also use surface movement radar (SMR), surface movement direction and control systems (SMGCS), or advanced SMGCS to control traffic on the maneuvering area (roads of taxiway and runway lane).
Tower controller areas of responsibility fall into three general operational disciplines; local control or air control, ground control and data delivery/flight dispatch; other categories, such as apron control or earth movement planner, may exist in extremely busy airports. While each tower may have unique procedures specific to the airport, such as multiple teams of controllers ('crews') at major airports or complexes with multiple runways, the following provides a general concept of the delegation of responsibilities within the tower environment.
Remote Virtual Tower (RVT) is a system based on air traffic controllers who are located somewhere other than the local airport tower and can still provide air traffic control services. Displays for air traffic controllers can be live video, synthetic images based on surveillance sensor data, or both.
Surface Control
Surface control (sometimes known as ground movement control) is responsible for "maneuvering" from the airport, as well as from areas not released to airlines or other users. This generally includes all taxiways, idle runways, holding areas, and some transition intersections where aircraft arrive after having vacated the runway or exit gate. Control responsibilities are clearly defined in local documents and agreements at each airport. Any aircraft, vehicle or person walking or working in these areas must be cleared by 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 must be driven by 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 mobile phone. Ground control is vital for the proper functioning of the airport, since this position affects the sequence of departure aircraft, which affects the safety and efficiency of the airport operation.
Some busier airports have a surface movement radar (SMR), such as ASDE-3, AMASS, or ASDE-X, designed to show 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 in these systems as they are modernized. Older systems will display a map of the airport and the target. Newer systems include the ability to display higher quality mapping, radar targets, data blocks and safety alerts, and to interface with other systems such as digital flight legs. to
Air control or local control
Air control (known to pilots as the "control tower") is responsible for the active runway surfaces. Air control clears aircraft to take off or land, ensuring that prescribed aerodrome separation will exist at all times. If the air controller detects any unsafe conditions, a landing aircraft may be instructed to perform "missed or missed approach" and return to the sequence to land. This new sequence will depend on the type of flight and can be handled by the air controller, approach or terminal area controller.
Inside the control tower, a highly disciplined communication process between air control and ground control is an absolute necessity. Air control must ensure that ground control is aware of any operations that impact taxiways, and work with approach radar controllers to create "loopholes" in arriving traffic to allow traffic to cross the runways and allow take off. Ground control needs to keep air controllers aware of the flow of traffic to their runways in order to maximize runway utilization through effective approach spacing. Crew Resource Management (CRM) procedures are often used to ensure that this communication process is efficient and clear. Within ATC it is generally known as TRM (Team Resource Management) and the level of focus on TRM varies within different ATC organizations.
Terminal and approach control
Many airports have a radar monitoring facility that is associated with the airport. In most countries, this is known as terminal control; in the US, it is known as TRACON (terminal radar approach control). While each airport varies, terminal controllers generally handle traffic within a 30 to 50 nautical mile (56 to 93 km) radius of the airport. Where there are many busy airports, a consolidated terminal control center can service all airports. The airspace boundaries and altitudes assigned to a terminal control center, which vary widely from airport to airport, are based on factors such as traffic flows, neighboring airports, and terrain. A large and complex example is the “London Terminal Control Center”, which controls traffic for five major London airports up to 20,000 feet (6,100 m) and up to 100 nautical miles (190 km).
Terminal controllers are responsible for providing all ATC services within their airspace. Traffic flow is broadly divided into departures, arrivals, and overflights. As aircraft enter and exit terminal airspace, they are transferred to the next appropriate control facility (a control tower, en-route control facility, or nearby terminal or approach control). Terminal control is responsible for ensuring that aircraft are at a proper altitude, and that aircraft arrive at a proper speed for landing.
Not all airports have an approach radar or terminal control available. In this case, the en-route center or a neighboring terminal or approach control can coordinate directly with the airport tower and vector incoming aircraft to a position from where they can visually land. At some of these airports, the tower may provide a non-radar procedure approach service to arriving aircraft delivered from a radar unit before they are visual to land. Some units also have a dedicated approach unit that can provide procedural approach service all the time or for any period of radar outage for any reason.
En route, center or control area
Air traffic control also provides services to aircraft in flight between airports. Pilots fly under one of two sets of rules: Visual Flight Rules (VFR) or Instrument Flight Rules (IFR). Air traffic controllers have different responsibilities for aircraft operating under different sets of rules. While IFR flights are under positive control, in the US VFR pilots can request flight tracking, which provides traffic advisory services in the time allowed and can also provide assistance in avoiding weather areas and traffic restrictions. flight. Throughout Europe, pilots can request a 'Flight Information Service', which is similar to the following flight. In the UK it is known as a 'traffic service'.
Enroute air traffic controllers issue clearances and instructions to aircraft in the air, and pilots must comply with these instructions. En route controllers also provide air traffic control services to many smaller airports across the country, including ground clearance and airport approach clearance. 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 to provide ATC services.
General characteristics
Enroute air traffic controllers work in facilities called air traffic control centers, each of which is commonly referred to as a "hub.". The United States uses the equivalent of the Air Route Traffic Control Center (ARTCC). Each center is responsible for many thousands of square miles of airspace (known as a flight information region) and for the airports within that airspace. The centers control IFR aircraft from the time they leave the airspace of one airport or terminal area until the time they arrive in the airspace of another airport or terminal area. Centers can also "pick up" VFR aircraft that are already airborne and integrate them into the IFR system. These aircraft must, however, remain VFR until clearance is provided by the center.
Center controllers are responsible for issuing instructions for pilots to bring their aircraft up to their assigned altitude while, at the same time, ensuring that the aircraft is adequately separated from all other aircraft in the immediate area. Additionally, the aircraft must be positioned in a flow consistent with the aircraft's flight path. This effort is complicated by cross traffic, severe weather, special missions requiring large airspace allocations, and traffic density. As aircraft near their destination, the center is responsible for issuing instructions to pilots to comply with point-specific altitude restrictions, as well as providing many destination airports with a traffic flow that prohibits all arrivals from being "clustered" these "flow restrictions" they often start in the middle of the route, as controllers will position the plane landing at the same destination, so when the plane is close to its destination, they are sequenced.
When an aircraft reaches the boundary of a center's area of control, it is "transferred" or "delivers" to the next Area Control Center. In some cases, this "delivery" involves a transfer of identification and details between controllers so that air traffic control services can be provided in a transparent manner; in other cases, local agreements may allow "silent handovers" so that the receiving center does not require any coordination if the traffic is presented in the agreed manner. After the transfer, the plane receives a frequency change and starts talking to the next controller. This process continues until the aircraft is transferred to a terminal controller ("approach").
Radar coverage
Because the centers control a large area of airspace, they will typically use long-range radar that has the ability, at higher altitudes, to see aircraft within 200 nautical miles (370 km) of the radar antenna. They can also use the TRACON radar data to monitor when it provides a better 'picture' of the target. traffic or when it may fill a part of the area not covered by long-range radar.
A center 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 radar coverage floor. This results in a large amount of data available to the controller. To address this, automation systems have been designed that consolidate the radar data for the controller. This consolidation includes deduplication of radar returns, ensuring that the best radar for each geographic area is providing the data and displaying the data in an effective format.
Precision approach radars are commonly used by military controllers in the air forces of various countries to assist the pilot in the final stages of landing at locations where the instrument landing system and other airborne equipment Sophisticated systems are not available to assist pilots in marginal or near zero visibility conditions. This procedure is also called talkdowns.
A radar archiving system (RAS) keeps an electronic record of all radar information, and keeps it for a few weeks. This information can be useful for search and rescue. When an aircraft has "disappeared" From the radar displays, a controller can review the aircraft's latest radar returns to determine its probable position.
Controller
The air traffic controller is the person professionally in charge of directing the traffic of aircraft in the airspace and at airports, in a safe, orderly and fast way, authorizing the pilots with the necessary instructions and information, within the airspace of their jurisdiction, in order to prevent collisions, mainly between aircraft and obstacles in the maneuvering area. He is the most important person in charge of air traffic control.
Their work is complicated due to the heavy traffic of planes, possible weather changes and other unforeseen events. Air traffic controllers are selected from among people with great perception and spatial projection, receiving, in turn, intensive training, both in control tower simulators, approach control, area control and radar, as well as pilots, in flight simulators, to deepen their knowledge of instrument flight, in basic and intermediate air traffic control courses.
To maintain safety in terms of separation between aircraft, ATCs apply standards set forth and recommendations issued by the International Civil Aviation Organization (ICAO), Federal Aviation Administration (FAA) and other aeronautical authorities of each country. The shift controller is responsible for aircraft flying in a three-dimensional area of airspace known as the control area, terminal control area, airway, etc. Each controller must coordinate with the controllers of adjacent sectors to plan the conditions in which an aircraft will enter their area of responsibility, delivering said flight without any type of conflict regarding other traffic, meteorological conditions, geographical position or altitude (level of flight), this being valid for both national and international flights.
Controllers work in the area control centers (ACC), in the control tower (TWR) or the approach control office (APP), where they have various electronic and computer systems that help them in the traffic control and management, such as radar (RDR), (Radio Detection and Ranging), which is a transmitting/ very high frequency wave receiver, which detects objects flying within its airspace and, through computer programs, presents them on radar screens, which facilitates the management and progress of flights in their control positions. There are other assistance programs, such as those that adjust the runways available, both for taking off and landing aircraft and the order in which the flights have to take off and land to optimize the number of controllable flights.
Normally, the control tower group is made up of a large number of individuals, specialized in a specific task; for example, the person in charge of the radar, the runway and take-off controller (Local Control), the controller in charge of issuing clearances to aircraft departing under instrument flight rules (Clearance Delivery), the controller in charge of street clearances taxiway (TWY) and apron, (Ground Control) or the general supervisor.
Types of air traffic controllers
Authorization controller (DELIVERY/CLEARANCE). It is in charge of giving all flight plan authorizations to outgoing aircraft.
Ground Controller (GND). He is in charge of guiding the aircraft "on the ground" along the taxiways (TWY-Taxiway), both from the boarding gates to the active runway, as well as to other platforms at the airport and from the runway to the parking lot.
Tower Controller (TWR). Has command of the runway or landing strips and intersections; authorizes the aircraft to land or take off, and controls visual flight rules (VFR). It operates in space known as ATZ with a range of 5 nautical miles, which is equivalent to 9,260 meters; You must provide information on adverse weather, work that affects the runway and others such as flocks of birds.
Approach Controller (APP). Controls the airspace; CTR gives priorities to IFR flights or instrument flight rules, around 5 miles to the limit of its own space, which can be 10, 20 or 40 miles depending on the case and FL 195, depending on the airport. Handles the traffic that leaves and arrives at one or more airports. On departures, it transfers them to the center controller (ACC) before reaching the limit of its airspace both in extension and in height. On arrivals, the APP controller transfers aircraft to TWR when they are about to approach for landing. You can work either with radar, or through estimated hours and flight progress sheets, known as procedural control.
Area Route Controller (ACC). Controls the rest of the airspace. The limits between approach and route are established between the control centers through letters of agreement. In general terms, the route or area controller controls the traffic established at a flight level and the approach controller the traffic in evolution, both ascending to the ideal flight level and descending to land at the destination airport.
Departures Controller (DEP). Controls aircraft from the moment they take off from the airport to a designated altitude, depending on the aerodrome. Not all aerodromes have a departure controller, only those where there is too much traffic for the approach controller (APP) to do so.
NOTE: There are states where a single air traffic controller performs more than one function. For example, the DEP can in turn perform GND.
Visual Flight Meteorological Conditions (VMC) and Instrument Flight Meteorological Conditions (IMC)
Air traffic moves following the VFR visual flight rules or the IFR instrument flight rules, depending on the equipment that the aircraft possesses, the qualifications of the crew and weather conditions, among others. In general, VFR operations are flown when weather conditions are good around the aircraft to be operated under a visual condition to the ground and to other aircraft, and when air traffic density is low enough for the pilot to be able to rely more on your radius of vision than on instrumental reading. For this the conditions have to be only VMC; that is, you cannot fly with VFR in IMC. Unlike VFR, IFR is engaged when visibility or cloud cover falls below prescribed VFR conditions, or when air traffic density requires instrument control, but these rules can be applied for both VMC and VMC conditions. as BMI. Each aerodrome determines and reports the conditions under which it is operating.
Technologies
CNS/ATM (Communication Navigation Surveillance / Air Traffic Management, communication, navigation, surveillance / air traffic management) are communication, navigation and surveillance systems that use digital technologies, including satellite systems along with various levels of automation, applied as support for an imperceptible global air traffic management system. It was born as a solution to be adopted in all countries and airlines in the world, which would have the same satellite navigation and communication systems (communication, navigation, surveillance and air traffic management).
The system was conceived by the International Civil Aeronautics Organization (ICAO), which in 1983 created the FANS (Future Air Navigation Systems Committee) which studied the avionics and air traffic management conditions necessary to operate in the new demand.
There are many technologies used in air traffic control systems, for example primary and secondary radars (intended to improve situational awareness for a controller in their assigned area). As for these radars, they are used by all aircraft, sending these primary echoes of various sizes to the controllers' screens as the radar energy is emitted, and aircraft equipped with transponders responding to the secondary radar. Some weather situations may also register on the radar screen.
On radar tracks, some basic processing occurs, such as computation of ground speed and magnetic headings. Generally, a flight data processing is in charge of managing all the data related to the flight plan, acquiring the information referring to the runway once the correlation between them is established (flight plan and follow-up). All this information is sent to modern operational display systems, so it can be accessed by controllers.
Certain tools are available to controllers in different domains to help them further:
- Flight data processing systems: one is usually available by centre and is responsible for processing flight-related information (flight plan). This information uses it to activate other tools related to the flight plan and is distributed to all interested parties (air traffic controllers, guarantee centers, airports, etc.).
- Short-term conflict alert (STCA) that checks possible trajectories that could be conflictive on a temporary horizon of 2 or 3 minutes. The algorithms you use allow in some systems a vector solution is possible.
- Secure minimum altitude warning (MSAW): is a tool whose function is to alert the controller if an aircraft flies too close to the ground or if it will impact the terrain depending on its altitude and course.
Problems
Physical space
Currently, the main problem is space at airports, since once aircraft land, they must use parking platforms or aircraft access walkways. This generates delays in the air and on the ground.
Traffic
One of the main problems of air traffic control is related to the large amount of existing traffic. Airports need to have all the necessary data to be able to make a landing. On many occasions, landing delays have had to be carried out due to calculation errors, or a high number of landing requests, as well as weather conditions that also affect landing or takeoff.
These problems are mainly related to the volume of air traffic demand in the system and the weather. Several factors determine the amount of traffic that can land at an airport in a given period of time. Each landing aircraft must land, slow down, 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 handle approximately 30 arrivals per hour. A large airport with two runways can handle around 60 arrivals per hour in good weather. Problems start when airlines schedule more arrivals at an airport than can be physically handled, or when delays elsewhere cause groups of aircraft, otherwise separated in time, to arrive simultaneously. The aircraft must be held in the air by holding holding specific locations until they can be safely sequenced to the runway. Until the 1990s, exploitation, which has significant environmental and cost implications, was a routine occurrence at many airports. Advances in computers now allow aircraft to be sequenced hours in advance. Therefore, planes can be delayed even before they take off (by being 'slotted'), or they can slow down in flight and proceed more slowly, significantly reducing the amount of cargo.
Air traffic control errors occur when the separation (vertical or horizontal) between aircraft in the air falls below the separation minimum prescribed (for the United States) by the US Federal Aviation Administration In the US, separation minima for terminal control areas (TCAs) around airports are lower than en-route standards. Errors generally occur during periods following busy times, when controllers tend to relax and overlook the presence of traffic and conditions that lead to loss of minimum separation.
Weather
Another serious problem in air traffic control is the weather: rain, snow, or ice on the runways can make landings difficult.
In control centers, storms are a serious problem, since electrical discharges can harm the systems and reduce the range of the signal.
Beyond runway capacity issues, weather is a major factor in traffic capacity. Rain, ice, snow or hail on the runway causes the landing aircraft to take longer to slow down and depart, reducing the safe arrival rate and requiring more space between landing the aircraft. Fog also requires a drop in landing rate. These, in turn, increase the delay in the air to sustain aircraft. If more aircraft are scheduled than can be safely and efficiently kept in the air, a ground delay schedule may be established, delaying the aircraft on the ground prior to departure due to conditions at the arrival airport.
In Area Control Centers, a major weather issue is thunderstorms, which present a variety of hazards to aircraft. Aircraft will reroute around storms, reducing en-route system capacity by requiring more space per aircraft or causing congestion as many aircraft attempt to move through a single hole in a thunderstorm line. Occasionally weather conditions cause aircraft delays prior to departure as routes are closed due to thunderstorms.
A lot of money was spent creating software to streamline this process. However, in some ACCs, air traffic controllers still record each flight's data on slips of paper and personally coordinate their routes. At newer sites, these flight progress strips have been replaced by electronic data presented on computer screens. As new equipment comes on board, more and more sites are upgrading away from paper flight lists.
Proposed changes
The Next Generation Air Transportation System examines how to overhaul America's national airspace system.
Free flight is a method of air traffic control that is under development and does not use centralized control (for example, air traffic controllers). However, part of the space is reserved to guarantee the required separation between aircraft, (among others), using computer communication.
In Europe, the SESAR (Single European SKY ATM Research) program aims to develop methods, technologies, procedures and systems to adapt to future air traffic needs (as of 2020).
Privatization
Many countries have privatized or incorporated their air navigation service providers.
The Canadian system is the one most used as a model by proponents of privatization. This privatization was successful in Canada with the birth of Nav Canada, which has allowed new technologies to be developed more quickly, resulting in shorter flights and less fuel use, with added security thanks to these advances. Nav Canada is funded by fees collected from airlines based on aircraft weight and distance flown.
In Spain
In 2022, ENAIRE managed traffic control at 21 airports in the AENA network in Spain, six of them the Air Force, while private operators managed traffic at 14.
ENAIRE complies with both the national regulatory framework and the Community Single European Sky (the regulations and directives on the Single European Sky are applicable to all Member States of the European Union, and upon entry into force, its provisions are automatically mandatory).
In general, ATC in Spain is mainly in charge of:
- Prevent collisions and accelerate and maintain the air traffic movement in an orderly manner.
- Providing advice and useful information for the safe and effective operation of flights.
- Notify and assist relevant agencies with respect to aircraft in need of assistance and rescue.
It is in charge of granting the highest priority to safety in the provision of air navigation services, evaluating and minimizing, with a proactive and systematic approach, the risks for aviation that may lead to accidents or incidents. In addition, the level of weighted safety incidents of 1 per 100,000 flight hours has been reduced by 15% over the three-year period; The quality of the provision of the ATS service has been improved, reducing the delay associated with our service.
Finally, it should be noted that at least 90% of the flights are expected to meet their scheduled takeoff time window (ETOT/CTOT) and to exceed the average delay of 0.3 minutes per IFR flight en route.