Air to Ground
The History of Air Traffic Control Part 2 – Air Route Traffic Control Centers
In each of 22 buildings across the U.S., in rooms as big as a football field, as many as 100 air traffic controllers are actively watching the skies over their assigned territories at any given time of day or night. Unlike the towers and approach controls, the Air Route Traffic Control Centers (ARTCCs or “Centers”) are not associated with any specific airport. They were designed from the very beginning to regulate air traffic over large areas from just above the surface to as high as their equipment can function.
It began back in the 1930’s. The steel magnates and auto industry had begun using air travel heavily from Chicago to the east coast. Construction of airports with good runways and services also encouraged the development of airline travel. Though aviation was only a couple decades old, the skies were already becoming crowded. Radio communications had been set up with the Airway Radio Stations (ARS)-the precursor of today’s Flight Service, and the airlines had set up other radio transmitters/receivers from the Great Lakes to Newark and Washington D.C.
Although the government was aware that something needed to be done, they did not have the money or congressional approval to do anything – so the airlines created a method to track their aircraft, built a central communications structure, and hired people to run it. In 1935 the first Airway Traffic Control Center opened in Newark, New Jersey. Within six months there were ATCC’s open in Chicago and Cleveland.
The Air Commerce act of 1936 gave the government the powers to take over the administration of all three Centers, and to construct new ones as needed. If you look at a map of the Centers, the first thing you notice is their odd shapes – they definitely do NOT conform to state boundaries. The airspace was defined according to the areas most used by pilots at the time. Future facilities were defined the same way, so that the Center maps look like a big patchwork quilt.
There was no RADAR when this all began. In the Centers, geographical maps with the locations of navigational aids and airports (what we call Sectionals today) were laid on top of a large table, and overlaid with glass. Small markers called “shrimpboats” representing aircraft were pushed along the routes of flight which they had filed prior to flight. As aircraft passed over various checkpoints they called the Centers, or the ARS, or whatever Air Traffic Facility had receivers in the area and gave their positions. If the ARS or Airport towers took the position they would transmit the data back to the Centers via telegraph or telephone. The Center controllers would move the markers based on the filed route and airspeeds.
How can you actually control aircraft if you can’t see them? What made it more challenging was that not all aircraft flying were participating – only the airlines. General Aviation was so prevalent it wasn’t even a category at that time. Nonetheless, the controllers of the day developed methods to keep track of the aircraft and would relay instructions to keep them separated based on altitudes and speed/time/distance calculations. These non-radar techniques were still be taught as the first phase of air traffic control instruction when I went through the academy in 1983.
A big shakeup in governing aviation came under the Roosevelt administration. In 1938 the Civil Aeronautics Act created an agency independent of the Commerce Bureau – the Civil Aeronautics Authority. FDR also split the CAA into two agencies – one oversaw the actual control of air traffic, airports, aircraft cerficiation and airway development, the other was entrusted with accident investigation, safety and the economic regulation of the airlines.
1941 saw the advent of a new method of air navigation, Very High Frequency omnidirectional radio range (VOR), at its experimental station in Indianapolis. Using the new system, a pilot could remain on course by watching a dial on his instrument panel, and he could give the ATCC controllers valuable information – the exact radial he was reading on the VOR.
RADAR!!! In 1952 Radio Detection and Ranging (RADAR) dramatically improved the ability of the controllers to determine aircraft position. Early radar saw aircraft, but it also saw rain, making it difficult during storms to see aircraft…but it was a start.
By 1965, 42 million people, or 38% of the adult population of the U.S. had flown in a commercial aircraft. It was not until 1967 that technology advanced to the point where early computers were married to RADAR to electronically tag the aircraft with it’s ID, altitude and airspeed. The IBM 9020 computer took up a large room, and was still in operation through the 1980’s. In addition to the radar display, the computer took over the task of mathematically determining how long it would take an aircraft to transit its route, and would print out strips for the controllers with those calculations.
1976 saw the implementation of the Conflict Alert System into the ATC computers. Known to controllers as the “snitch patch”, this program provided a visual and audio alert when it sensed the potential for aircraft flight paths to intersect resulting in a loss of separation.
The aftermath of the union strike in 1983 meant a nationwide slowdown in aviation as the government dealt with the problem of how to handle aircraft with one third its original staff. It also defined a need for better methods of achieving an efficient flow into the major airports – especially those that served as hubs for airlines. In 1985 the FAA published rules for Flow Control wherein aircraft were issued takeoff and landing reservation times at high traffic density airports. Center controllers were required to set aircraft up five miles in trail along specified pathways into high traffic airports beginning hundreds of miles away from the destination.
The next level of technology to dramatically affect aviation was the Global Positioning Satellite (GPS) method of determining position. Up to this time IFR aircraft were routed along pre-determined airways. GPS allowed pilots to fly direct from beginning to end – which they loved, but controllers did not. Imagine all cars on the road, taking each turn in a calculated manner, but now one jumps the curb and drives across a field then wants to jump back onto the road between two Mac trucks! Aircraft can’t just stop and wait for the trucks to pass…
So what’s next? ERAM technology, being installed at the Centers now, is the heart of the Next Generation Air Transportation System (NextGen) helping to advance our transition from a ground-based system of air traffic control to a satellite-based system of air traffic management. The FAA is studying the feasibility of having GPS based computers on the ground giving direct control instructions to the computers in the aircraft. This would allow tighter spacing and greater efficiency of air traffic – and reduce the need for human intervention.
It’s only been a hundred years since the sound of an aircraft engine added a new note to the symphony of the sky. Step by step we’ve created the most advanced aviation system in the world. I wonder what the next decade will see.
Rose Marie Kern has worked in ATC since 1983. For more ATC information contact her at author@rosemariekern.com.