Air Traffic Control Systems: Technology, Safety & Reform

Overview of the U.S. Air Traffic Control System

According to Craig Freudenrich (2009), the task of air traffic controllers is to ensure safety for commercial and private aircraft. They accomplish this by coordinating takeoff and landing aircraft at airports while also maintaining safety during bad weather. An air traffic controller is therefore required to ensure the smooth flow of traffic so that minimal delays occur.

In order to make this demanding task manageable, airspace within the United States is divided into 21 zones or centers, each of which is further divided into sectors. Each zone contains portions of airspace called TRACON airspaces, or Terminal Radar Approach Control airspaces. These are approximately 50 miles in diameter and contain a number of airports. Each airport has airspace with a five-mile radius.

The air traffic control system is run by the FAA (Federal Aviation Administration), which uses these airspace divisions to guide the overall system. The ATCSCC (Air Traffic Control System Command Center) is at the head of all traffic control management. Problems such as bad weather, traffic overloads, and faulty runways also fall under the jurisdiction of the ATCSCC. There is one Air Route Traffic Control Center (ARTCC) for each center, whose function is to handle air traffic within each sector except for TRACON and local airspace. Each airport also has an Air Traffic Control Tower (ATCT), which handles takeoff, landing, and ground traffic. The Flight Service Station (FSS) focuses its services and information on small airports and rural areas, where private pilots need information such as weather conditions, routes, terrain, and flight plans. The FSS also handles emergencies and search-and-rescue missions for aircraft that are missing or overdue.

All these air traffic control divisions work in coordination to ensure the safety of aircraft sharing American airspace. Each entity manages the aircraft moving through its designated airspace at any given time.

The FAA's Air Traffic Staffing Plan (Blakey, 2004) appears to be sound in terms of both cost efficiency and employee benefits. There are, however, two elements that raise concern: the reduction of sick leave and the reduction of training time for Terminal and En Route personnel.

FAA Air Traffic Staffing Plan: Key Concerns

It is understood that personnel have shown a tendency to abuse their sick leave allowance, and that there is a need to address these abuses in a targeted and efficient manner. However, an 8% reduction in sick leave does not appear to be an effective deterrent to abuse. The issue of abuse should instead be addressed through measures such as investigation and the requirement of medical certificates or other documentation of illness.

Management should also keep in mind that ATC personnel are subject to very high levels of stress. This will inevitably result in occasional illness. Reducing sick leave by as much as 8% is likely to have a detrimental effect on how personnel experience their work, contributing to both stress and stress-related illness. This does not appear to be the optimal way to handle the problem of sick leave abuse.

The reduction of training times is equally concerning. Training for Terminal personnel is reduced from 2–3 years to a maximum of 2 years, while En Route personnel receive training for a maximum of 3 years, reduced from the previous 3–5 years. Air traffic control is a highly complex and technical profession. Training is one area in which cost reductions are not advisable. Trainees require as much preparation as possible to succeed in the profession. If training times are to be altered at all, they should be increased rather than reduced. Training is a vital part of air traffic control and should not be shortened for any reason.

Aircraft separation criteria are extremely important for maintaining the safety of aircraft and passengers. The current vertical separation minimum is 1,000 feet, dependent upon some form of horizontal separation. At altitudes above 29,000 feet, aircraft should be no closer than 2,000 feet apart. Horizontal separation criteria apply when any two aircraft are horizontally closer to each other than the vertical separation minimum allows. In anticipation of increasing aircraft traffic in American airspace, it may become necessary to revise both vertical and horizontal separation requirements.

Aircraft Separation Criteria

To accomplish this, procedural, lateral, and longitudinal separation procedures may be considered. Procedural separation is based on the reported position of aircraft as communicated by pilots over the radio. When two aircraft are not vertically separated, procedural separation minima are provided by the air traffic controller, generally with radar assistance.

Lateral separation is generally derived from the position of an aircraft as determined visually, from dead reckoning, inertial navigation sources, or radio navigation aids. When beacons are used, aircraft are required to maintain a certain distance from the beacon, as measured by time or DME, and the track to or from the beacon is subject to a minimum angle requirement. Lateral separation can also be determined by the geography of routes.

Longitudinal separation applies when aircraft are not laterally separated and are following the same route. It is based on time or distance and measured by DME. Generally, this is subject to the 15-minute rule, which specifies that no two aircraft on the same route should be within 15 minutes of each other.

Minimum separation criteria can therefore be determined in various ways, some of which are flexible depending on the method used. To accommodate an increase in aircraft traffic, these different methods can be combined while still maintaining safe separation distances.