Air Traffic Control​—How Does It Keep You Safe?

BY AWAKE! WRITER IN THE PHILIPPINES

WHILE flying, have you ever wondered how the pilot knows where he is going? Perhaps you felt uneasy as you thought of the dozens or even hundreds of airplanes crisscrossing the skies at the same time. How do they keep from colliding?

Such questions are natural concerns for travelers. However, statistics show that travel by commercial airliner is quite safe, * in fact safer than traveling by motorcycle or car. A key factor contributing to its safety is the air traffic control system.

Guiding Your Flight Safely

The captain, or pilot in command, is the one primarily responsible for the safe operation of an aircraft. However, there are many occasions when he cannot see other airplanes flying around him and he is unaware of their presence. For this reason, most nations have an air traffic control system. Ground-based workers keep track of every phase of flights that operate under instrument flight rules.

Samuel, an air traffic controller in California for 13 years, says: “Air traffic control specialists play a vital role in the safety of air traffic. The first priority is to provide separation between aircraft.” Melba, an air traffic supervisor, gives a further explanation, “First and foremost is safety, but aside from safety, we also provide for the expeditious and orderly flow of traffic.” Thus, in addition to helping avoid collisions, air traffic controllers assist in keeping planes moving.

What all of this means is that while the pilot is tending to his cockpit duties, there are many ground-based eyes and ears following the flight. The pilot regularly talks by radio not only to controllers at the departure and destination airports but also to those at several points in between.

Monitoring what the pilot cannot yet see is very important in this age of high-speed aircraft. Imagine that two commercial jets are on a head-on course. By the time the pilots spot each other with the naked eye, they may have only seconds to avoid impact! It is air traffic control’s responsibility to prevent that situation from occurring. Long before the  pilots see each other, they will have been given instructions to keep them a safe distance apart.

Tracking Your Flight

Ground-based directional radio transmitters provide signals to guide aircraft. The pilot has instruments that pick up the signals from these transmitters and tell him exactly where he is. Since the transmitters are located at specific points, airplanes fly from point to point until they reach their destination. In effect, these navigational aids have created specific airways.

Air traffic controllers track planes along the airways. Before departure, pilots are required to file a flight plan that shows their intended route of flight. The controller has a copy of what is called a flight progress strip. Salvador Rafael, an air traffic control chief, explains how this is useful: “There are intersection points on the airways. When a pilot comes over those, he has to report that information to the controller. Then the controller will mark that on his flight strip.” The controller now has a mental picture of the path of that aircraft.

To get those reports, the controller has another tool​—the radio. He knows where the plane is, and the pilot receives instructions to help him keep a safe distance from other aircraft. Controllers and pilots usually have a selection of radios and frequencies. Should one fail, they can use another.

What about international flights where different languages are encountered? To avoid dangers that could result from miscommunication, the International Civil Aviation Organization selected English as the common language in aviation. Also, since certain words, letters, and numbers sound similar when spoken over the radio, air traffic controllers are taught to use standard phrases and pronunciation when giving instructions to pilots. To take the level of safety one step further, pilots are asked to “read back,” or repeat, certain instructions given by controllers.

Radar is another tool that air traffic controllers use. Radio waves that bounce off airplanes are picked up by a radar antenna. The planes then show up as objects, or targets, on the controller’s radar screen. Many airplanes are equipped with a transponder, which returns an identification signal to the radar. When this signal is combined with computer input, the aircraft show up on a radar screen, complete with flight number, speed, altitude, and aircraft type.

If the controller sees a need to maneuver aircraft to prevent a collision, he has several options. He may instruct a pilot to change (1) heading, or direction. This is called vectoring. Or he may direct a change in (2) speed if, for example, one airplane is overtaking another. A very common way he may separate aircraft is by directing a change in (3) altitude.

As a safety enhancement, many radar systems can alert the controller when dangerous situations exist. For example, visual and audible alarms go off if the system anticipates that two aircraft will get too close to each other. Another alarm goes off if an airliner appears to be getting too close to the ground.

The Goal​—Your Safety

Plans are already being implemented to enhance the air traffic control  system. Earth-based navigation systems often require restricting aircraft to specific routes and altitudes. This results in wasted airspace and longer flight routes. Future flights will rely even more on satellite-based systems, such as the Global Positioning System, which will allow for much more flexibility in routing airplanes and will result in easier control of transoceanic flights.

As our brief coverage of air traffic control has shown, your pilot is not the only one who knows where your airplane is at any given moment. In fact, several others on the ground are monitoring the progress of your flight. The system has been designed to minimize dangers and maximize safety. No wonder accident rates for commercial aircraft are very low!

So if you are a passenger, there is little reason for apprehension. The next time you take a long-distance flight, remember that the eyes and ears of air traffic control are attentive to your safety. Sit back, relax, and enjoy a comfortable flight!

[Footnote]

[Diagram on page 14, 15]

(For fully formatted text, see publication)

TRACKING YOUR FLIGHT

Global Positioning System

Air traffic control system

Ground-based directional radio transmitters

Radio

Radar antenna

[Picture on page 15]

Air traffic control tower

[Picture on page 15]

Air traffic controllers

[Picture on page 15]

Air traffic control center

[Picture Credit Lines on page 15]

Tower and controllers: NASA Ames Research Center; control center: U. S. Federal Aviation Administration