Responsibilities of approach control
Larger airports have a radar control facility that is associated with the control tower. In most countries, this is referred to as ‘terminal area control’ or ‘approach control’. Approach controllers are responsible for providing all air traffic control (ATC) services within their airspace. Traffic flow is broadly divided into departures, arrivals, overflights, and VFR aircraft.
As aircraft move in and out of the approach airspace, approach control hands them off to the next appropriate control facility (tower control, area control). Approach control is responsible for ensuring that aircraft are at an appropriate altitude when they are handed off, and that aircraft arrive at a slow enough rate to permit safe landing.
Varying demands per airport
Approach controllers usually handle traffic in a 30 to 50 nautical mile (56 to 93 km) radius from the airport and from the surface of anything from 2,500 feet to 24,500 feet. Because every airport is unique, the actual airspace boundaries and altitudes assigned to Approach controllers are based on factors such as traffic flows and terrain, and vary widely from airport to airport.
Not all airports have approach control available. In this case, the area control centre will coordinate directly with the tower and provide this type of service where radar coverage permits. Under these circumstances, the separation minimums between aircraft are usually increased.