HEATHROW CONTROL TOWER

The control tower at Heathrow contains the visual control room - the glazed room at the top of the tower. The VCR team consists of the Ground Movement Planner, the Ground Movement Controller, and their Assistants. On a raised area in the centre of the room sit the Air Arrivals Controller (AAC) and the Air Departures Controller (ADC). These two Controllers sit alongside each other facing the runways in use - the holding point of the departure runway and the touchdown point of the arrival runway. If the runways in use are reversed, the AAC and the ADC turn to face the opposite direction, facing again the appropriate runways. The Approach Controllers are located at West Drayton in a new operations room together with colleagues from Gatwick Airport.

In practice, the use of an airband radio at a busy airport like Heathrow, where there are many radio frequencies in use, can be disappointing if the set does not have the ability to pinpoint each frequency. The effect, with a poor quality radio receiver, is that adjacent frequencies will swamp each other. A more sophisticated set can, of course be turned in very accurately to the precise frequency and the ‘overlapping’ effect is thereby eliminated.

The various ATC operations are subdivided among the control staff because of the volume of traffic.

The first frequency is 121.97 for start-up clearance. Then the radio frequency is changed to 121.9 to monitor messages giving clearance to pushback and taxi. Arriving aircraft are also transferred to this frequency on vacating the runway. A further change of frequency to 118.5 is for departure clearances.

After departure, the aircraft will be banded on to the London Area Terminal Control Centre at West Drayton for onward clearance through the London FIR airways system. Note that the words ‘take off’ are used exclusively as a part of the clearance to actually leave the ground at all other times the word ‘departure’ is used.

Arriving flights are monitored on the Distance From Touchdown Indicator (DFTI), a small radar screen, so that aircraft arrive in a safe and orderly stream. Pilots call ‘established’ when the aircraft is locked on to the Instrument Landing System, and also when the aircraft passes over the ‘outer marker’, approximately four miles from touchdown, and the middle marker, approximately one mile from touchdown.

The ILS consists of two radio transmissions: the ‘localizer’ which indicates the centreline of the runway, and the ‘glidepath’, a horizontal beam angled upwards at three degrees to provide the correct angle of approach.