Air Traffic Control | The Canadian Encyclopedia


Air Traffic Control

Air Traffic Control (ATC) is the service provided to pilots to assist them in operating their aircraft in a safe, orderly and efficient manner.

Air Traffic Control

Air Traffic Control (ATC) is the service provided to pilots to assist them in operating their aircraft in a safe, orderly and efficient manner. In Canada the air traffic controllers of the Air Traffic Services Branch, Transport Canada, are responsible for providing vertical and horizontal separation (known as a "block of protected airspace") between each aircraft being flown in controlled airspace using Instrument Flight Rules (IFR). Canadian airspace extends from the Canada-US border to the North Pole and from the Pacific Ocean to halfway across the North Atlantic.

Most flying in Canada is done under what is called Visual Flight Rules (VFR), in which the pilot navigates the aircraft by visual reference to the ground and is responsible for seeing and avoiding other aircraft. Only near busy airports which have a control tower will the pilot's VFR flight come under the direction or guidance of Air Traffic Control. The other type of flight operations are conducted under IFR, in which the pilot uses navigational aids, either ground- based or on board the aircraft, to fly from one location to another. All scheduled airlines operate IFR and thus it is the type of flight most people experience as passengers. Under IFR and in controlled airspace, Air Traffic Control is responsible for separating flights and providing them with a moving block of protected airspace to prevent collision.

In VFR conditions the pilots can, to a very large extent, separate themselves from other aircraft, including those operating IFR. The IFR flight may be operated regardless of weather conditions such as clouds that do not permit the pilots to see and avoid other aircraft; responsibility for these flights is shifted to the air traffic controllers.

There are several closely interrelated air traffic controller positions, probably the best known of which are the control tower operators. Two types of functions are performed from the control tower. The ground controller issues radio instructions to all aircraft and service vehicles moving on or near the runways and the airport controller monitors (visually or on radar) all aircraft landing, taking off or flying within the airport control zone. When aircraft get too close to each other, the airport controller gives one or both planes a new course or altitude to avoid a "confliction."

Using radar and providing control by radio as required, the terminal controller guides and directs all IFR aircraft operating within 65 km of major airports. Near the airport but outside the control zone the terminal controller may also provide radar services and flight advisories to VFR aircraft.

The area controller guides aircraft that are flying "on instruments" along the airways which link most airports across the country or lead to tracks taking the aircraft to international destinations. This controller also co-ordinates with towers, terminals, other centres and flight service stations as necessary.

Finally, the oceanic controller monitors aircraft flying through Canadian airspace over the North Atlantic. Most of these flights are controlled by the Gander Oceanic Area Control Centre. The pilots issue position reports which allow the oceanic controller to estimate the actual time that each aircraft is expected to cross each 10 meridians of longitude. In this way, ATC safely "shepherds" the flight to its destination.

In addition to these various types of air traffic controllers the pilot is also aided by flight service specialists who provide a wide range of services mostly at airports with a low density of traffic. These include airport and vehicle advisories, flight information, alerting and emergency services, and preflight briefings.

After a pilot files an IFR flight plan, the flight comes under ATC supervision. The flight plan consists of the "airways" that are to be used, the highways in the skies formed by radio navigational aids located on the ground. It also includes the cruising altitude, the estimated time en route and other information such as aircraft type and speed. After checking the flight plan for accuracy the details are entered into the ATC system. The pilot then boards the aircraft and establishes radio contact with the ground controller to receive taxi instructions: which taxiways should be used to safely enter the runway, the exact time and current altimeter setting plus the present wind direction and speed, and an Air Traffic Control clearance. ATC clearance authorizes the pilot to fly, under specified conditions, from one airport to another.

Control of the aircraft then passes to the airport controller who, when it is safe, clears the aircraft onto the runway and for the takeoff, fitting the flight into the sequence of arriving and departing aircraft at the airport. At most major airports, before takeoff, the controller instructs the pilot to make a Standard Instrument Departure, which takes the flight to a predetermined heading and altitude before moving to the enroute airways.

The terminal controller then follows the flight's progress on radar until the limit of his or her responsibility is reached (about 65 km from the terminal), after which an area or enroute controller has charge of the flight until it crosses into the adjoining area. The aircraft continues to be "handed off" from area controller to area controller until it reaches the vicinity of its destination and the process is reversed.

Throughout the whole process, from filing the flight plan to landing at the final destination, Air Traffic Control monitors the aircraft's progress and directs the pilots as necessary, and provides current weather, the status of navigational aids or other information important for flight safety. All this makes the controller's job one of extreme responsibility. In Canada there are 61 control towers handling in peak months over 500 000 landings and takeoffs. Vancouver International Airport and Toronto-Lester B. Pearson International Airport are the busiest in the country, with peak days exceeding 1000 operations. In addition to the control towers there are 7 Area Control Centres (ACC), 8 stand-alone Terminal Control Units (TCU) and over 100 Flight Service Stations.

The basic training for air traffic controllers is provided in a residential college environment at the Transport Canada Training Institute (TCTI) in Cornwall, Ontario. To qualify, applicants must be at least 18 years old and have successfully completed secondary school. Excellent diction and hearing are required in addition to passing a rigid medical exam. In the Québec region knowledge of both official languages is essential while in the rest of Canada English is essential. The overall training program offered in English and bilingual formats normally takes one to two years depending on the assigned control specialty. The formal training covers both radar and procedural control functions including the control of aircraft flying under VFR and IFR. Through classroom instruction and practical exercises using various simulators, the curriculum includes regulations, aircraft operating characteristics, navigation, radio communications and weather.