Air Traffic Control Introduction
Air Traffic Control (ATC) is a service provided to direct and organise the flow of aircraft traffic while ensuring safe separation between aircraft. The ATC task involves monitoring and issuing instructions to aircraft with the goal of safe, orderly, and efficient use of an airspace. A person who provides this service is referred to as an Air Traffic Controller or Air Traffic Control Officer (ATCO).
Separation minima
The minimum safety standard in ATC is judged using lateral and vertical distances. The lateral distance is measured in nautical miles (NM), while the vertical distance is in feet or flight levels.
The separation minima is defined as the separation of aircraft by at least 5NM laterally or 1000 feet (10 flight level) vertically at any given time.
Any aircraft that does not meet the defined requirement at a given time is regarded to have lost separation.
Transfer of communication
An aircraft usually monitors the single frequency (apart from guard) of the sector responsible for their ATC service. As aircraft fly through the airspace, this communication will be transferred between sectors.
Units
ATC has a long history and therefore uses some non standard units.
Flight levels
A flight level is used to define an altitude above mean sea level, used at high altitudes to have a common vertical reference system.
Flight levels will commonly be prefixed by "FL", such that FL100 is flight level 100, which corresponds to 10,000ft above mean sea level.
Knots
Refers to the unit of measure of indicated airspeed, calibrated airspeed, true airspeed, and ground speed of an aircraft. Knots stands for "Nautical Miles per Hour".