London Terminal Control Centre

The London Terminal Control Centre (LTCC) was an air traffic control centre based in West Drayton, in the London Borough of Hillingdon, England, approximately 2.5 miles (4.0 km) north of London Heathrow airport. Operated by National Air Traffic Services (NATS) it provided air traffic control services to aircraft arriving and departing from six London airports, one Royal Air Force station, plus en-route services to other aircraft that entered its airspace. Internally within NATS it is usually known by the initials TC. The civilian part of the West Drayton site closed in November 2007, when its functions moved to Swanwick, Hampshire. 'TC' and 'AC' (London Area Control Centre) remain separate organisations but now share the same site.

Unlike New York TRACON, LTCC uses Class A airspace. Therefore, VFR operation is prohibited.

History

The centre was opened as RAF West Drayton, a military air traffic control facility, located roughly midway between the then London airport (now London Heathrow) and RAF Northolt. The civilian control function present at this centre in 1971 became the London Air Traffic Control Center (LATCC), operating alongside the RAF. In the early 1990s the 'Central Control Facility' (CCF) was formed within the centre to provide terminal control services to aircraft arriving at and departing from the main London airports, subsuming the existing terminal sectors in preparation for the arrival of the London area airport approach units. For this, the CCF Display and Information System (CDIS) was developed.

In 1992 the Heathrow and Gatwick approach control units moved to West Drayton to share facilities with the CCF. The CCF and the two approach control units were moved into the new Terminal Control room in 1995, and thus became a separate entity to Area Control. To reflect the fact that there were now two civil control rooms (Area and Terminal) the centre was renamed the London Area and Terminal Control Centre, whilst retaining the same LATCC abbreviation.

RAF West Drayton formally closed in the 1990s, though military personnel remained on site until 2008.

In 1995 Stansted approach control, soon after to be renamed Essex Radar, moved to West Drayton to take their place in the TCR. In 2002 Luton approach control also moved in. In the same year, the Area Control function moved from West Drayton to the new London Area Control Centre (LACC) in Swanwick, Hampshire. The West Drayton facility was renamed the London Terminal Control Centre (LTCC - though still pronounced "latsea") at this time. In 2004, Thames Radar (London City and Biggin Hill radar approach control) moved in from its former home at Heathrow Tower.

Civilian operations at the centre ceased in November 2007, after Terminal Control moved to Swanwick to be reunited with Area Control. Military operations moved to a new control room also at Swanwick in January 2008.

One of the last PDP11 based air traffic control systems from LATCC is now on display at The National Museum of Computing.

TC today at the NATS Swanwick, Hampshire facility

Terminal or TMA sectors

TC-based controllers provide air traffic services within the London Terminal Control Area (TMA). This airspace is split into two groups or banks, TC North and TC South, which not only relates to the position of the airspace sector relative to London Heathrow, but also the direction in the Terminal Control Room in which that sector's controllers face when at their radar consoles. TC North is further split into North East (3 sectors) and North West (2 sectors). TC South is further split into South East (3 sectors) and South West (3 sectors). All sectors have the RT callsign "London Control".

At its busiest, each sector will have a radar controller. Also, when it's very busy, each one of the four sectors will be bandboxed for departures and arrivals. This means one sector has two controllers. However, when it is quieter sectors are also "bandboxed" with one controller operating multiple sectors, until at night there may only be one controller operating the whole bank. Each bank will also have up to two further supernumerary controllers acting as co-ordinators (to liaise with other sectors and other units, and generally assist the radar controllers), and up to two assistants to prepare flight progress strips, operate computer systems and assist with flight data duties.

Aircraft departing Heathrow, Gatwick, Luton and Stansted mostly depart on a free-flow principle: the radar controllers do not release each individual flight for departure, they just receive a pre-note via a computer system that the flight is pending. This cuts down on inter-unit co-ordination and allows the tower controller at the airport to decide the most efficient departure order. In many cases the aircraft's Standard Instrument Departure (SID) routing does not conflict with the approach sequence of aircraft arriving at the airport, so the airport's approach control does not need to handle the aircraft and it is transferred straight to the TMA controller on departure. The TMA controllers then climb the departures through the arrivals to the airports that they are also working.

Arrivals to the London airports are handed over from LACC at Swanwick or the TC en-route sectors, usually following Standard Terminal Arrival Routes (STAR) and are descended against the departing traffic, and sorted out into different levels, then routed to various holds, where they will hold until the approach control units are ready to position them into an approach sequence to land.

Approach sectors

The Approach Control units for the five major London airports are also controlled from TC, plus the radar approach services for Biggin Hill. Each approach unit has more than one sector. The majority of the work for the approach units is controlling the sequence of aircraft making an approach at an airport from the holds until established on final approach about 4 miles away from the airport. The approach units also handle some aircraft departing from the airport, when that aircraft's departure conflicts with the approach sequence.

Slightly unusual to the approach sectors at TC is that some of them can be staffed by two controllers at a time, making transmissions on the same frequency.

LTCC Approach Sectors
Unit	Sector	RT Callsign	Role
Heathrow	Intermediate Director North	Heathrow Director	Initial approach sequencing from the north for Heathrow and RAF Northolt
	Intermediate Director South	Heathrow Director	Initial approach sequencing from the south for Heathrow and RAF Northolt, some departures
	Final Director	Heathrow Director	Final approach sequencing
Gatwick	Intermediate Director	Gatwick Director	Initial approach sequencing
Gatwick	Final Director	Gatwick Director	Final approach sequencing, some departures
Stansted	Intermediate Director	Essex Radar	Initial approach sequencing for Stansted and Luton
Stansted	Final Director	Stansted Director	Final approach sequencing, some departures
Luton	Intermediate Director	Luton Radar	Initial approach sequencing, some departures
Luton	Final Director	Luton Director	Final approach sequencing
Thames	Intermediate Director	Thames Director	Initial approach sequencing for London City and Biggin Hill, and Southend departures
	Final Director	Thames Director	Final approach sequencing for London City and Biggin Hill
	Special VFR	Heathrow Radar	Low-level and Special Visual Flight Rules traffic around London Heathrow

En-route sectors

TC is slightly unusual for a Terminal Control Centre in that it also has a number of en-route sectors responsible for lower levels of airspace immediately outside and on top of the TMA. These are controlled from TC because they mainly feed traffic into and out of the main London airports. They are grouped as TC East (4 sectors), TC Midlands (4 sectors) and TC Capital (2 sectors). TC Midlands is somewhat of a hybrid since it also interacts directly with airports and the aircraft departing from them in the same way as the TMA sectors.

All sectors have the RT callsign "London Control". TC East's airspace adjoins the international boundary with Amsterdam and Brussels airspace.

External links

Our control centres, NATS
"NATS - A Case Study (presentation)" (PDF). British Computer Society. 11 January 2005. Retrieved 14 December 2014.

Coordinates: 51°30′19″N 0°27′36″W / 51.5053°N 0.4600°W / 51.5053; -0.4600

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