Terminal Control Center

A Terminal Radar Approach Control (or FAA TRACON in the United States) is an Air Traffic Control facility usually located within the vicinity of a large airport. Typically, the TRACON controls aircraft within a 30-50 nautical mile (56 to 93 km) radius of the airport between the surface and 10,000 to 15,000 feet. A TRACON is sometimes called Approach Control or Departure Control in radio transmissions. In The US Air Force it is known as RAPCON (Radar Approach Control), and in the US Navy as a "RATCF" (Radar Air Traffic Control Facility) In Canada, Approach Control may be called Arrival or Terminal.

TRACON radar facilities

TRACONs normally have their own radar system that allow air traffic controllers to track aircraft. This is typically based on one or more Airport Surveillance Radar(s) (ASR), sweeping once every 4-5 seconds. The largest TRACON in the world (Southern California Consolidated TRACON - SCT, Callsign "SoCal Approach") services 62 airports and is located in San Diego, California. This huge facility utilizes 10 radar sites and is soon to expand to 11. Most US terminal Radar Approach Control (TRACON) facilities utilize an ASR-9 with a range of 63 7/8 miles and a scan rate (rotation) of approximately 4.25 seconds.

These frequent updates help controllers see the result of direction changes quickly. Larger U.S. TRACONs are able to directly incorporate en route long range Air Route Surveillance Radar(s) (ARSR) into their automated tracking systems as a backup. Smaller U.S. TRACONs also have the capability to make use of CENRAP (CENter RAdar Presentation) as a backup if their primary system fails. This makes use of en-route surveillance radar used by Air Route Traffic Control Centers (ARTCCs). Expanded separation minimums (5 nautical miles versus 3 nautical miles) are required when in this mode.

Equipment

Most of the United States FAA TRACONs are currently using Common ARTS equipment. Most of ARTS IIIA and some ARTS IIE sites have been updated to Raytheon's Standard Terminal Automation Replacement System (STARS) equipment. The program to manage the updates is now called Terminal Automation Modernization/Replacement ( [http://www.faa.gov/about/office_org/headquarters_offices/ato/publications/oep/version1/reference/tamr/ TAMR] ).

TRACON Control positions

TRACON control positions usually include a radar controller and a coordinator who generally stands behind the radar position.

Approach/Departure/Arrival/or Sector Radar controller

The radar controller is responsible for ensuring appropriate separation, and issuing traffic and other local aviation information for aircraft under its control. Additionally, the radar controller is responsible for ensuring all required coordination with other controllers in the tower, TRACON, or en-route center is completed, making required computer entries, and updating the flight progress strips.

Coordinator

The coordinator provides coordination support for the radar controller. He/she will provide inter/intra facility coordination when required for the radar controller and make computer entries.

Assistant / "D Side" Controller

Some TRACONs have the ability to staff a second position at the radar console, referred to as a "Assistant" or "D Side" (FAA)controller. This position is responsible for providing direct support by coordinating for the radar controller, managing flight progress strips, and making computer entries. When this position is staffed, the coordinator duties are greatly reduced, allowing him/her to provide support for a number of positions. The support controller may make transmissions on the radio along with the main controller: the support controller focuses on the more procedural aspects of controlling (e.g. holding aircraft) while the main controller focuses on accurately radar-vectoring the approach sequence.

TRACON traffic responsibilities

TRACONs are responsible for providing all ATC services within their airspace. Generally, there are four types of traffic flows controlled by TRACON controllers. These are departures, arrivals, overflights, and aircraft operating under Visual Flight Rules (VFR).

Departure aircraft

Departure aircraft are received from the tower and are generally 1,000 feet to 2,000 feet high, climbing to a pre-determined altitude. The TRACON controller working this traffic is responsible for clearing all other TRACON traffic and, based on the route of flight, placing the departing aircraft on a track and in a geographical location (sometimes referred to as a "gate" or "exit") that is pre-determined through agreements for the en-route center controller. This positioning is designed to allow the en-route center to integrate the aircraft into its traffic flow easily.

Arrival aircraft

Arrival aircraft are received from the en-route center in compliance with pre-determined agreements on routing, altitude, speed, spacing, etc. The TRACON controller working this traffic will take control of the aircraft and blend it with other aircraft entering the center airspace from other areas or "gates" into a single, parallel or perpendicular final for the runway. The spacing is critical to ensure the aircraft can land and clear the runway prior to the next aircraft touching down on the runway. The tower may also request expanded spacing between aircraft to allow aircraft to depart or to cross the runway in use.

Overflight aircraft

Overflight aircraft are aircraft that enter the TRACON airspace at one point and exit the airspace at another without landing at an airport. They must be controlled in a manner that ensures they remain separated from the climbing and descending traffic that is moving in and out of the airport. Their route may be altered to ensure this is possible. When they are returned to the en-route center, they must be on the original routing unless a change has been coordinated.

VFR aircraft

If the class of airspace allows flight under VFR, such aircraft are handled as traffic permits. Controllers will provide traffic information to ensure safety with other aircraft, and may even positively separate VFR aircraft from other aircraft, depending on the class of airspace. Controllers lack the level of control over these aircraft that they have over aircraft operating under IFR as they will not want to vector VFR aircraft into IMC. Controllers usually provide information for the pilot about traffic in the immediate vicinity and weather reports if applicable. This ensures that separation from Instrument Flight Plan (IFR) aircraft is maintained in the critical flight areas around the airports.

TRACON availability

Not all airports have a TRACON available. In this case, the en-route center will coordinate directly with the tower and provide this type of service where radar coverage permits. Generally, however, the separation minimums are greatly increased. In many countries, mid-sized airports without a TRACON have a dedicated Approach Radar Controller based upon the airport itself to sequence inbounds and to provide radar services to aircraft in the vicinity of the airport.