EQUIPMENT AND AVIONICS

By virtue of distance and time savings, minimizing traffic congestion, and increasing airport and airway capacity, the implementation of RNAV routes, direct routing, RSVM, PRM, and other technological innovations would be advantageous for the current NAS. Some key components that are integral to the future development and improvement of the NAS are described below. However, equipment upgrades require capital outlays, which take time to penetrate the existing fleet of aircraft and ATC facilities. In the upcoming years while the equipment upgrade is taking place,ATC will have to continue to accommodate the wide range of avionics used by pilots in the nation’s fleet.

ATC RADAR EQUIPMENT

All ARTCC radars in the conterminous U.S., as well as most airport surveillance radars, have the capability to interrogate Mode C and display altitude information to the controller. However, there are a small number of airport surveillance radars that are still two-dimensional (range and azimuth only); consequently, altitude information must be obtained from the pilot.

At some locations within the ATC environment, secondary only (no primary radar) gap filler radar systems are used to give lower altitude radar coverage between two larger radar systems, each of which provides both primary and secondary radar coverage. In the geographical areas serviced by secondary radar only, aircraft without transponders cannot be provided with radar service. Additionally, transponder- equipped aircraft cannot be provided with radar advisories concerning primary targets and weather.

An integral part of the air traffic control radar beacon system (ATCRBS) ground equipment is the decoder, which enables the controller to assign discrete transponder codes to each aircraft under his/her control. Assignments are made by the ARTCC computer on the basis of the National Beacon Code Allocation Plan (NBCAP). There are 4,096 aircraft transponder codes that can be assigned. An aircraft must be equipped with Civilian Mode A (or Military Mode 3) capabilities to be assigned a transponder code. Another function of the decoder is that it is also designed to receive Mode C altitude information from an aircraft so equipped. This system converts aircraft altitude in 100-foot increments to coded digital information that is transmitted together with Mode C framing pulses to the interrogating ground radar facility. The ident feature of the transponder causes the transponder return to “blossom” for a few seconds on the controller’s radarscope.

An integral part of the air traffic control radar beacon system (ATCRBS) ground equipment is the decoder, which enables the controller to assign discrete transponder codes to each aircraft under his/her control. Assignments are made by the ARTCC computer on the basis of the National Beacon Code Allocation Plan (NBCAP). There are 4,096 aircraft transponder codes that can be assigned. An aircraft must be equipped with Civilian Mode A (or Military Mode 3) capabilities to be assigned a transponder code. Another function of the decoder is that it is also designed to receive Mode C altitude information from an aircraft so equipped. This system converts aircraft altitude in 100-foot increments to coded digital information that is transmitted together with Mode C framing pulses to the interrogating ground radar facility. The ident feature of the transponder causes the transponder return to “blossom” for a few seconds on the controller’s radarscope.

AUTOMATED RADAR TERMINAL SYSTEM

Most medium-to-large radar facilities in the U.S. use some form of automated radar terminal system (ARTS), which is the generic term for the functional capability afforded by several automated systems that differ in functional capabilities and equipment. “ARTS” followed by a suffix Roman numeral denotes a specific system, with a subsequent letter that indicates a major modification to that particular system. In general, the terminal controller depends on ARTS to display aircraft identification, flight plan data, and other information in conjunction with the radar presentation. In addition to enhancing visualization of the air traffic situation, ARTS facilitates intra- and inter-facility transfers and the coordination of flight information. Each ARTS level has the capabilities of communicating with other ARTS types as well as with ARTCCs.

As the primary system used for terminal ATC in the U.S., ARTS had its origin in the mid-1960’s as ARTS I, or Atlanta ARTS and evolved to the ARTS II and ARTS III configurations in the early to mid-1970’s. Later in the decade, the ARTS II and ARTS III configurations were expanded and enhanced and renamed ARTS IIA and ARTS IIIA respectively. The vast majority of the terminal automation sites today remain either IIA or IIIA configurations, except for about nine of the largest IIIA sites, which are ARTS IIIE candidate systems. Selected ARTS IIIA/IIIE and ARTS IIA sites are scheduled to receive commercial off the shelf (COTS) hardware upgrades, which replace portions of the proprietary data processing system with standard off-the-shelf hardware.

STANDARD TERMINAL AUTOMATION REPLACEMENT SYSTEM

The FAA has begun modernizing the computer equipment in the busiest terminal airspace areas. The newer equipment is called STARS, for Standard Terminal Automation Replacement System. The system's improvements will enhance safety while reducing delays by increasing system reliability and lowering lifecycle operating and maintenance costs. STARS also will accommodate the projected growth in air traffic and provide a platform for new functions to support FAA initiatives such as Free Flight. STARS offers many advantages, including an open architecture and expansion capability that allow new software and capacity to be added as needed to stay ahead of the growth in air traffic. Under the first phase of terminal modernization, STARS is being deployed to 47 air traffic control facilities. As of July 2005, 37 FAA and 22 Department of Defense sites were fully operational with STARS. The first phase is expected to be complete in fiscal year 2007. By then, STARS will be operational at 18 of the FAA's 35 most critical, high-volume airports, which together handle approximately 50 percent of air traffic. STARS consists of new digital, color displays and computer software and processors that can track 435 aircraft at one time, integrating six levels of weather information and 16 radar feeds.

For the terminal area and many of the towers, STARS is the key to the future, providing a solid foundation for new capabilities. STARS was designed to provide the software and hardware platform necessary to support future air traffic control enhancements.