- What is a TRACON or Terminal Control?
- When do pilots need to be helped by a TRACON?
- Where is it usually located and what is the difference between TRACON, En Route and Tower?
What is a TRACON (Terminal Radar Approach CONtrol)?
TRACON is a go-between:
- Climbing departing flights received from TOWERs and handing them over to ARTCC.
- Descending cruising flights received from ARTCC and handing them over to airfield TOWERs
Potomac consolidated TRACON, operation room (source)
A TRACON is the name in the US for what is also known in other countries as the Terminal Control Center, the control in charge of operations close to one or more large airports (but not on the airports themselves). TRACON manage arrivals and departures, the related transitions to/from cruise, and also aircraft transiting in their area.
From Nasa's Air Traffic Management System page (with some adjustments):
TRACONs are facilities containing radar operations from which air traffic controllers direct aircraft:
- During departure, descent and approach phases of flight.
- Transitioning from the en route phase through to the approach phase into a destination airport located within the TRACON’s airspace.
- Transitioning after takeoff to the departure phase until the flight is handed off to the Air Route Traffic Control Center (ARTCC) for its en route phase, [...] via a preferential departure route (PDR) leading away from the departure airport.
The TRACON controller directs the movement of aircraft in and out of that airspace by monitoring a radar screen and maintaining voice contact with pilots.
- High altitude descent controller
- Low altitude descent controller
- Approach controller
- Feeder controller
- Departure controller
One TRACON can handle the air traffic for several different airports in its sector.
Although the controller's individual responsibility is only for his or her own sector, all controllers within a TRACON have full radar information on all the aircraft that are under control of the entire TRACON facility. In addition, these controllers are able to communicate with one another instantly- something that contributes significantly to assuring the safety of aircraft passengers.
As emphasized by @TomMcW in his comment, smaller airfields don't have an associated TRACON, the approaches and departures are in this case directly managed by controllers at the airfield tower.
Controllers mostly use the Automated Radar Terminal System (ARTS) or the Standard Terminal Automation Replacement System (STARS) to track aircraft:
Philadelphia TRACON (source)
When do pilots need to be helped by a TRACON?
Pilots are directed to a TRACON center either by the Tower controller (for departures), or the ARTCC controller (for descents and transits).
The aircraft scheduled to land on a given runway are sequenced by the feeder controller, to maximize the landing flow.
Where are TRACON usually located?
TRACON premises by themselves can be located anywhere. Controllers work on radar screens, in the half-light, they don't have a view of the outdoor. Basement rooms are usual.
Depending on the country they may be located close to major airports, within the area they control.
TRACON controlled areas are located around major airports.
- In the US: FAA - Terminal Radar Approach Control Facilities
- In Europe (TCC): See Can multiple airfields be in the same airspace?
What is the difference between TRACON, En Route and Tower?
Taking the US ATC system only into account for this discussion.
1/ Airport operations are controlled by controllers in the tower. They need a view on the runways and other location of the airport. Radar is only used for tracking aircraft on the ground (ground radar). Takeoff and landing clearances are delivered after visual check of the runway status.
O’Hare International Airport air traffic control tower (source)
From Nasa's page:
Control towers were established to provide for a safe, orderly, and expeditious flow of air traffic at an airport and in its vicinity. There are four major controller classifications at control towers:
- Flight Data Controller
- Clearance Delivery Controller
- Ground Controller
- Local Controller.
Inside an air traffic control tower (source)
2/ Enroute traffic is controlled by Air Route Traffic Control Center (ARTCC)
Typical sector radar team (source)
From Nasa's page:
ARTCCs, usually referred to as "Centers," are established primarily to provide Air Traffic Service to aircraft operating on IFR flight plans within the controlled airspace, and principally during the en route phase of flight.
There are 21 Air Route Traffic Control Centers (ARTCC) in the United States.
US ARTCC boundaries (source)
Any aircraft operating under Instrument Flight Rules (IFR) within the confines of an ARTCC's airspace is controlled by air traffic controllers at the Center. This includes all sorts of different types of aircraft: privately owned single engine aircraft, commuter airlines, military jets and commercial airlines.
ARTCC manages flights between TRACON airspaces, while they are cruising at high altitude.
(You can listen to ARTCC traffic at LiveATC.net)
First off, there needs to be a distinction between the IFR facility and the Tower. Control towers in the US control runways and surface movement areas, they do not "control" airspace. They do sequence aircraft in the local traffic area but that is a topic for another discussion. TRACONS/RAPCONS are IFR facilities and can issue IFR routes/clearances in the air.
TRACONS typically control airspace around busy airports from the ground up to 15,000ft and about 30 miles around including all airports therein. ARTCC's (Centers or Area control Facilities) cover EVERYTHING else. They provide IFR service from the surface up to the top of controlled airspace in the vast majority of the continental US. There are plenty of smallish airports (especially out west) that have towers without an overlying TRACON. In those areas, the ARTCC is the next layer providing arrival/departure separation, sometimes without radar.
I've been a Professional Airway System Specialist for 29 years. Some of the information in the above article is either misleading or downright incorrect.
Air Traffic Control Towers large enough to require a nearby or co-located TRACON include Digital BRITE Radar displays overhead in the towers.
In my day they were fed by Automated Radar IIA and IIIA systems that were in turn fed by short range (60 mile radars).
Today the Standard Terminal Automation Replacement System (STARS) has replaced the ARTS systems but STARS Automated Radar is still either microwaved to the larger towers or sent via advanced telecommunications.
That information IS NOT used for ground separation it is used by tower controllers to control traffic IN THE AIR that they cannot see which is the majority of the traffic that they control.