How Air Traffic Control Works
How Air Traffic Control Works
This article serves as a repository of the content related to various aspects of air traffic control (ATC) that is available on SKYbrary. While some of the content can be of interest to air traffic controllers, the main purpose of this article is to provide a structured view on how ATC works to other professionals and aviation enthusiasts as well as to trainee air traffic controllers.
Communication Aspects
Air-ground communication is one of the most important aspects of air traffic control.
- ATS Unit Callsigns
- Callsign Change by ATC
- Light and Pyrotechnic Signals
- Multi-language ATC Operations
- Urgency Instructions and Clearances
- Unauthorised Use of ATC Frequency
The Place of Air Traffic Control
Air Traffic Management (ATM) comprises the following:
- Air Traffic Service. This is a general term encompassing:
- Air Traffic Control (ATC). This is the main service provided by air traffic controllers and is divided into:
- Aerodrome control service. This is focused on aircraft on the ground (the manoeuvring area of the aerodrome) or in the vicinity of the aerodrome (mostly the Aerodrome Traffic Circuit)
- Approach control service. This service links the aerodrome control and the area control and is focused on the climb, descent and approach phases of the flight.
- Area control service. This service is focused on the cruising part of the flight.
- Flight Information Service (FIS). This service is performed in uncontrolled airspace
- Alerting Service. This service is provided in order to inform the Search and Rescue (SAR) facilities of aircraft in distress.
- Air Traffic Control (ATC). This is the main service provided by air traffic controllers and is divided into:
- Air Traffic Flow Management (ATFM) is intended to arrange traffic flows in such a way as to avoid congestion and reduce the risk of controller overload.
- Airspace Management (ASM) is intended to organize the airspace so that it meets the needs of the users in the most optimal way.
Controller Positions
Air Traffic Controllers
There are three main types (ratings) of air traffic controllers. Within each type, different roles may be defined to address specific aspects of traffic demand or the airspace served.
- Tower Controller is a person that provides air traffic control service at and in the vicinity of an aerodrome.
- Approach Controller is a person that provides air traffic control for departing and arriving flights. They are the link between the tower controllers and the area controllers.
- Area Controller (sometimes called en-route controller) is a person that normally serves the flights during the cruise phase.
Other Similar Positions
These positions do not provide ATC service but there are many similarities between them and air traffic controllers.
- FIS Officer is a person that provides flight information service.
- Assistant is a person that assists air traffic controllers by performing some routine tasks (e.g. certain coordinations or flight data exchange).
- Supervisor is a person who is operationally responsible for the management of an ATS unit during a shift.
Working Position Organization
The information in these articles is relevant to all controller positions.
- Single Person Operations in ATC
- Executive and Planner Controller
- The Handover-Takeover Process (Operational ATC Positions)
Controller Training and Competency
Before a person starts to provide ATC service, they must be properly trained and qualified.
- Controller Training
- Controller Refresher Training
- Minimum Hours in Position
- English Language Proficiency Requirements
Tools
Surveillance
The surveillance tools greatly enhance the controllers' situational awareness and allow them to handle more traffic without compromising safety.
- Primary Surveillance Radar (PSR)
- Secondary Surveillance Radar (SSR)
- Multilateration
- Automated Dependent Surveillance-Broadcast (ADS-B)
- Surface Movement Radar
- A-SMGCS
- Precision Approach Radar (PAR)
ATM Systems and Support Tools
The automated systems combine data from different sources thus further enhancing the controllers' situational awareness. This leads to a great increase of capacity (i.e. the ability to safely handle multiple flights).
- Automation and ATM
- Plots, Tracks and Labels
- Correlation
- Integrated Tower Working Position (ITWP)
- Medium Term Conflict Detection (MTCD)
- Tactical Controller Tool (TCT)
- Probe (what-if)
- Safety Nets
- OLDI
- Lost Track Tool
Procedures
ATC Clearances
Air traffic controllers issue clearances and instruction to aircraft in order to separate them and to create and maintain an expeditious traffic flow.
- ATC Clearance
- North Atlantic Operations - ATC Clearance
- Immediate Тakeoff Clearances
- Conditional Clearance
Separation
One of the most important tasks of air traffic controllers is to provide separation, i.e. make sure that there is enough spacing between aircraft so that there is no risk of collision.
- Separation Standards
- Own Separation
- Strategic Lateral Offset
- Composite Separation
- Reduced Vertical Separation Minima (RVSM)
Conflict Detection and Solving
Prevention of collisions between aircraft is normally done by providing adequate separation. This is a two step process. First, the controller detects potential conflicting aircraft pairs. Then, appropriate measures are taken to resolve the conflicts.
- Controller Detection of Manoeuvring Area Conflicts
- Blind Spot – Inefficient conflict detection with closest aircraft
- Conflict Detection with Adjacent Sectors
- Conflict Detection
- Conflict Solving
Basic Controller Techniques
This subsection contains information on the basic techniques used by controllers in order to achieve the objectives of air traffic control.
- Identification
- Basic Controller Techniques - Vectoring
- Basic Controller Techniques - Speed Control
- Basic Controller Techniques - Vertical Speed
- Basic Controller Techniques - Level Change
- Parallel Offset
Coordination
Coordination with neighbouring ATC sectors and units is an integral part of air traffic control.
- ATC Unit Coordination
- ATC Team Coordination
- GND-TWR Coordination
- Civil-Military Interaction in ATM
- Release Procedure
- Transfer of Communication
- Transfer of Control
- Approval Requests
Articles Related to ATFM
Air traffic flow management aims to adjust traffic demand with the available capacity.
Articles Related to ASM
The main objective of airspace management is to ensure optimal use of the available airspace.