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THE CONTROL TOWER (Part 1)

The tower's ‘tools’ include a number of radio transmitters and receivers used to communicate with pilots, and a signalling lamp to send control signals to any aircraft not radio equipped or with a radio that is not properly working. The tower's radio equipment may be used with microphone and loudspeakers or with a headset. There is a wind speed indicator and a wind direction indicator at each controller console. A further instrument is the altimeter setting indicator. It is from this instrument that the controller advises the pilot of the current altimeter setting which the pilot sets on his aircraft altimeter.

At some busy airports an Automatic Terminal Information Service (ATIS) is available to pilots of departing and arriving aircraft. This service consists of a continuous radio broadcast on a special frequency of recorded and periodically updated noncontrol information. Included is information regarding ceiling, visibility, wind direction and speed, altimeter settings, and runway in use. Where ATIS is not available, the tower provides this information.

A controller has to decide which separation standard he will apply to aircraft in flight. If he applies lateral separation he must maintain aircraft on different routes or in different geographical areas-

In applying longitudinal separation the controller maintains an interval between aircraft. Longitudinal separation is established by requiring aircraft to depart at a specified time; to arrive over a reporting point at a specified time; or • hold over a reporting point until a specified time. A 15-minute, time-spacing interval. between two 600 mph jet aircraft means that they are separated longitudinally by 150 miles.

Vertical separation is obtained by assigning different flight levels to aircraft, in other words, they are separated by a specified vertical distance.

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Area control service

The function of area control is to provide air traffic control service for controlled flights except for those parts of flight where the ATC service is provided by approach control or by aerodrome control. Its area of control usually includes many thousands of square miles of airspace. With radar, controllers can position aircraft and achieve the desired safe and expeditious flow of traffic. (However, area control can be provided without radar). Some centres have computers which automate many of the routine functions of the controller.

In order to maintain a controller's workload at a level within his capability the centre's airspace is divided into sectors.

It is essential that the controller know the position and future plan of ever; aircraft within his sector. To accomplish this, flight progress boards are used on which are placed flight progress strips which contain all the pertinent current flight data such as the following:

Aircraft identification

Type of aircraft

Point of departure

Destination

Flight planned route

Filed true airspeed

The controller's and pilot's estimated time over the current reporting point

Actual time over reporting point or fix Flight level in hundreds of feet

Clearance information

Where a centre docs not have the requisite computer, flight progress strips are manually prepared and handled.

Approach control facilities use radar and flight progress strips in the same manner as area control centres.