THE CONTROL TOWER (Part 2)

The control of air traffic on, or in the vicinity of an aerodrome, is provided by the control tower. In most cases the tower is located on top of the terminal building and, is restricted to authorized personnel only. The aerodrome controller, who is located in the "tower cab", provides separation between aircraft arriving and departing, and also controls aircraft and vehicles manoeuvring on the manoeuvring area.

Approaching aircraft, particularly those operating under VFR, generally contact the aerodrome controller while still several miles away. The aerodrome controller informs the pilot of the runway in use, the wind direction and speed, the altimeter setting, as well as information on other traffic in the area.

Approaching the aerodrome, the pilot joins the traffic circuit on the downwind leg. The aerodrome controller then advises the pilot of his landing sequence giving such instructions as, "You are number two to land following the Cessna on final approach", or, "You are number three following the 707 on base leg".

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AERONAUTICAL INFORMATION SERVICE (Part 1)

Each country provides aeronautical information concerning its own territory. This is published in the Aeronautical Information Publication (AIP) and in Notices to Airmen (NOTAM).

A pilot planning a flight will prepare his Flight Plan from the information in these publications.

What sort of information does a pilot need to know when flying to another country or another aerodrome? For instance, he will want to know which airway to follow.

Further information the pilot needs is, what sort of facilities are available en route and at the aerodrome of his destination. Whether the aerodrome has suitable fuel available; paved runways; the length of these runways; the elevation of the aerodrome; what hangar space is available; the communication frequencies, and what meteorological information is available. This is some of the useful information that is in the AIP and NOTAM.

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VISUAL AIDS FOR NAVIGATION

MARKING AND LIGHTS

Additional visual aids to navigation consist of markings on the aerodromes. These markings comprise single lines or rows of lines which, for the pilot, are very important for holding positions, runway thresholds, the runway centre lines, the sides of the runways, etc.

However, at night or during poor visibility by day, lights are required. For lights to be effective they must be of adequate intensity. At certain aerodromes the controller can vary the intensity of some of the lights so that they can be reduced to avoid momentarily blinding the pilot and strong enough so that he can see them in the weather.

The first light a pilot sees on approach is generally the aerodrome beacon. It may rotate and can be seen at a great distance distinguishable by its coloured flashes alternating with white, or white only. There might be an identification beam which shows green flashes of light which identify the aerodrome in Morse code. Red lights, the usual danger signal, warn pilots of the obstacles such as hangers and other high buildings, telephone poles, etc. Runway edge lights identify the runway and approach lights assist the pilot to align himself with the runway.

Lights may also be used to provide a glide path similar to what an ILS provides electronically. The Visual Approach Slope Indicator System, better known as VASIS, is a beam of light having a white colour in its upper part and a red colour in its lower part. A pilot of an aeroplane during an approach will:

a) when above the approach slope, see the lights to be white in colour;

b) when on the approach slope, see the lights to be pink in colour; and

c) when below the approach slope, see the lights to be red in colour.

By reference to VASIS, combined with ILS, the pilot can bring an aircraft down safely almost to touchdown by day or night.

After landing, he follows the blue taxi lights along the taxiway to the apron, and the service areas.

At the service area a marshaller with illuminated wands directs the aircraft with signals to its proper position for unloading and, finally, signals pilot to cut his engines.

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APPROACH CONTROL

Approach control can be situated at the aerodrome or at some other site. Normally, if there are two aerodromes in the 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 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 VHF range with some in the UHF.

Aircraft operate under two different types of rules: IFR and VFR. If Visual Meteorological Conditions prevail, flight under

Visual Flight Rules (VFR) is permissible. In Instrument Meteorological Conditions, Instrument Flight Rules (IFR) are applied.

When airports are very busy the approach controller may have 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 expected approach time. Because of their high fuel consumption at low levels, jet aircraft and, particularly supersonic aircraft, prefer Co remain at higher altitudes before starting their descent.

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Date: 2015-12-11; view: 846