Approach control

Approach control can be situated at the aerodrome or at some other site. Normally, if there are two aerodromes in a vicinity, there will be one approach control unit to cover them both. Generally speaking, the approach controller's main task is to provide separation to departing and arriving aircraft operating under instrument flight rules. The approach controller generally takes over the control of an arriving aircraft from the airways controller and eventually hands over that aircraft to the control tower. For departing aircraft the procedure is reversed. A considerable degree of (1) co-ordination is therefore required between the various units in air traffic services.

The approach control unit has radio equipment similar to that in the control tower. This enables the controller to communicate with aircraft on several different radio frequencies. Most of the frequencies are in the (2) VHF range with some in the (3) UHF.

Aircraft operate under two different types of rules: IFR and VFR. If (4) Visual Meteorological Conditions prevail, flight under Visual Flight Rules (VFR) Co­ordination between unit in ATS is permissible. In (5) Instrument Meteorological Conditions. Instrument Flight Rules (IFR) apply.

When airports are very busy the approach controller may have (6) to stack the aircraft at different levels so that each may descend in turn towards the airport. In such cases the approach controller usually gives aircraft their (7) expected approach time. Because of their high fuel consumption at low levels, jet aircraft and, particularly (8) supersonic aircraft, prefer to remain at higher altitudes before starting their descent.