What is ATC system?
Engr Sabir Hussain
In 1956, a fatal accident of airplanes occurred in the skies known as Grand Canyon which compelled the authorities to regulate and design a monitoring system for aircrafts that was becoming quite congested. Although, Rudimentary air traffic control (ATC) existed well before this grand disaster. In 1920, the earlier air traffic control system was used to guide the aircrafts manually at the vicinity of airports and along the cross-country routes. Lights, flags, beacons, and flashing lights were used to guide the aircrafts but this visual system was useless in bad weather. Moreover, in 1930, for the first-time radio communication system was introduced for ATC which is still base of the current modern ATC system and New York city was the pioneer in adopting it.
With the passage of time, the number of different kinds of planes increased, flying for many different purposes, in a variety of weather condition needed the same kind of system to accommodate all of them. Similarly, with the advent of jet engines resulted a sudden boost in very fast planes and to reduce pilots’ error a practically demanding some set of rules was crucial to establish for keeping everyone well separated and operate them safely in the air.
In 1940, radar and improved radio communication brought by the World War II, improved the ATC centers. Controlled airspaces, which are the areas which lie under the concerned aviation authority divided the air vicinity in three regions. In general, from 365m above the airspace lies under the authority all over the country, but certain areas, mainly near airports it extends down to 215m, above the ground while the main airports airspaces are completely under the concerned authority.
In controlled airspaces the pilots are completely bound by the rules of regulating authority while in uncontrolled airspaces they are bound by fewer regulations. For instance, a recreational pilot who simply wishes to go for flying for a while without all restrictions imposed by the authority has to stay in uncontrolled airspaces, however, to avail all the safety protection offered by the authority can easily enter into controlled airspace.
The operational environment is divided into two types. The first one is Visual Flight Rules (VFR) which completely relies on visual cues to maintain an acceptable level of safety while the other is called Instrumental Flight Rules (IFR) for poor visibility under which the pilot relies on altitude and navigational information provided by the plane’s instrument panel to fly safely. In a good meteorological condition, a pilot in a controlled airspace has the choice to choose either VFR or IFR flight plan, however, holding the required license for the IFR is mandatory which is above than the basic pilot’s license.
Controlled airspace is divided into several types represented by letters of alphabets. Uncontrolled airspace is designated class F while controlled airspace below 5,495m above the sea level and not in airport vicinity is class E, where generally one finds general aviation aircrafts and commercial turboprop aircrafts. Similarly, all airspace above 5,495m is class A and dedicated for heavy jets as jet engines operate more efficiently at high altitude. The major difference between class A and E airspace is that in class A all operations are IFR and the pilot must be skilled and licensed in aircraft instrumentation.
Furthermore, the other three types are B, C and D, govern the vicinity of airports. These classes have their own set of rules for aircrafts. For example, all VFR pilots must establish two-way radio contact with ATC before entering class C airspace, however, no permission is mandatory but following ATC regulations governing VFR flight is must. Similarly, to enter class B airspace such as an airport, an explicit ATC permission is needed on approach. Therefore, any private pilot who enters in this vicinity without permission risks losing license.
The writer is a satellite engineer by profession. He did B.Sc Electrical Engineering (Telecom) from the COMSATS University, Lahore Campus and M.Phil in Space Science from the University of Panjab, Lahore. He can be contacted at: firstname.lastname@example.org.