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History of Air Traffic Control



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The History of Air Traffic Control

When the Wright Brothers took off in 1903, theirs’ was the only plane in the sky. Today there are over 87000 flights in the air every day guided by Certified Professional Air Traffic Controllers in Towers, Approach Controls and Enroute Centers. Their mission is for the safe and efficient movement of aircraft through the National Airspace System.

In the early days of aviation there wasn’t much need to keep airplanes from hitting each other, the main concern was how to get from point A to point B. In the 1910’s, Aircraft flew relatively close to the ground and navigated by sight from one landmark to another.

As the planes became a bit more sophisticated in the 1920‘s, postal route planes flew across the nation using bonfires as navigational aids, creating the nation‘s first airways. The late 20’s saw the nation’s first air traffic controllers waving flags to instruct pilots when to land and take off. The Air Commerce Act of 1926 was the first legislation concerning Air Traffic rules.

The 1930’s saw the advent of both thousand of rotating light beacons and radio to guide aircraft. More aircraft were getting equipped with radios and the first radio equipped air traffic control tower was established and began operations at the Cleveland airport. By 1935 there were about 20 ATC towers across the country. In the 30's and 40's ATC relied on radios, telephones and aircraft positions over fixes and estimates to the next fix to establish where the Aircraft were and where they were going. The controllers used a large board with magnetic ... or flight progress strips. During world war 2 the British developed Radar which would change air traffic control forever. One of the first uses was when the British used Radar to see the German planes coming and get their planes up to meet them and win the battle of ....

The 50's saw increasing need for radar across the united states. The mid air collision over the Grand canyon between a TWA Super Constellation and a United Airlines DC-7 in 1956 proved to be the catalyst to modernizing the air traffic control system. The Air traffic controllers were using equipment used 20 years earlier. This would become a common theme in ATC technology. In 1958 a United Airlines flight and a military jet collided near Las Vegas killing 49. The increasing number of near misses created a public outcry. After congressional hearings the Federal aviation Act of 1958 was passed. The act dissolved the CAA and created the FAA. The FAA then had total control of American Airspace. In the late 50’s, Radars were widely deployed to assist controllers with aircraft still flying along fixed air corridors. Controllers used the radars along with paper information termed “shrimp boats “that the controllers moved along the horizontal scope following the plane.

Aircraft became equipped with radar beacons called transponders in the 1960’s. This allowed the plane to send a signal to the Radar and the radar could differentiate between different aircraft, allowing the controllers to see which plane was which on their scopes.

The 1970's heralded the use of DARC (Direct Access Radar Channel) which was the first step to the continuing computerization of ATC centers. DARC allowed controllers to see on their scope a data block with the plane's call sign and altitude, eliminating the need for shrimp boats. Radar sights were continuing to be placed and most of the united states was covered by radar. This combined with Flight Progress Strips allowed the controllers an enhanced ability to see traffic and work more airplanes in the increasingly complex environment.

Air Traffic Controllers made the news in 1981 by going on strike for stressful working conditions and demanding higher pay. After several warnings, President Ronald Reagan fired the striking controllers. This caused a lot of delays and overworked controllers, but also opened the door to the hiring of new controllers. The equipment continued to see growth as the DARC system was replaced by a computer system called HOST, which stored all of an aircraft's flight plan information displayable. The 1980's saw high growth in air traffic and an evolving computer system. The controllers' scopes remained basically the same technology as the 1950's.


The 1990's brought tremendous change to the airline industry. Computers were becoming commonplace in cockpits and navigation no longer required the ground based aids. Air Traffic Controllers received their first upgraded scope called DSR or Display System Replacement. The displays had numerous new features and integrated the older mainframe Host system and individual computers to each position similar to today’s PC.


A huge step was taken in 1999 when Reduced Vertical Separation first came into being. This allowed center controllers to have aircraft above 29000 feet to be only 1000 foot different in altitude. Previously, those aircraft had to have a separation of 2000 feet, effectively doubling the amount of aircraft that could occupy the same pace.

The 2000's brought another major equipment change to center controllers with URET (User Request Evaluation Tool) This computerized Flight progress strips and also allowed conflicts to be seen well in advance of them occurring and before the planes showed up on a controllers scope.

Currently, there is a nationwide effort to replace the host computer system with a system called ERAM. When complete this system will allow center controllers more automation between centers and other enhanced computer functions. Salt Lake City Center is the recipient of the first ERAM system and is currently in the testing and debugging mode.

The National Airspace system has come a long way since waving flags at aircraft. Virtually all of the planes today are tracked on radar and most pilots are speaking with an air traffic controller. It may be possible in the future where even talking on the radio becomes a back up with the advent of data link. The controller would type an instruction to an aircraft and either the pilot or the plane responds to the instruction through data link.




Sources: http://www.usatoday.com/travel/flights/2008-10-10-atc-history_htm, http://en.wikipedia.org/wiki/Air_traffic_control

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