ATM - Advent of the Automated

With ADS-B, a cooperative surveillance and management technique, pilots and controllers will have similar radar-like displays containing highly accurate traffic data relayed via satellite displays that update in real time

Air Traffic Management (ATM) is heading towards its most profound transformation since the introduction of radar surveillance over half a century ago. A few years hence an airliner getting airborne anywhere in the US will be able to fly a straight line track from origin to destination, rather than the extended airway-based routeing it follows today. Throughout the journey, pilots will be fully aware of all aircraft operating in their vicinity and cross them without fear of collision. Unlike today’s detailed and repetitive voice-based control system, the entire system will be automatic, with little or no ground intervention.

Is this the stuff dreams are made of? Welcome to the world of Automatic Dependent Surveillance-Broadcast (ADS-B). With ADS-B, a cooperative surveillance and management technique, pilots and controllers will have similar radar-like displays containing highly accurate traffic data relayed via satellite displays that update in real time. The system will also provide pilots with ready access to weather services, terrain maps and flight information services. The resultant improved situational awareness will enable pilots to fly considerably closer to other aircraft, with vastly enhanced safety. And Air Traffic Controllers—some of the most highly-stressed professionals in the world—can heave a sigh of relief.

Powered By GPS

Airliners are generally required to follow circuitous flight paths so as to maintain safe and orderly traffic patterns. While interminably awaiting requisite clearances, they waste much time and fuel as they fly holding patterns before landing and burn excess fuel on the ground. Such delays and inefficiencies are often due to outdated traffic management models that still rely on slow, ground-based radar stations and repetitive voice communication which the US’ ambitious Next Generation Air Transportation System (NextGen), is designed to transform. Instead of radar, NextGen, an umbrella term for the comprehensive overhaul of the US air transportation system, will squarely rely on ADS-B.

ADS-B is an acronym for Automatic (it is fully functional for 365 days of the year); Dependent (dependent on accurate Global Navigation Satellite System [GNSS] signals for position data); Surveillance (it provides surveillance information, akin to radar); Broadcast (continuous broadcasts of aircraft position and relevant data to other aircraft and ground stations). Unlike the accuracy of radar, ADS-B accuracy does not seriously degrade with range, atmospheric conditions, or altitude. ADS-B provides constant surveillance even in remote and inhospitable areas that lack radar cover. And information update intervals do not depend on the rotational speed or reliability of mechanical antennae.

In a typical application, an ADS-B enabled aircraft utilises an ordinary GNSS receiver to derive its precise 3-D position from the GNSS constellation (GPS and Galileo) and then combines that position with a number of aircraft parameters, such as speed, heading, altitude and tail number. The combined data are then broadcast automatically and relayed via satellite to all suitably-equipped ground stations and other aircraft within a radius of 240 km. This provides each aircraft 4-D awareness of all others (the fourth dimension being time). Since ADS-B position reports are updated every second (compared with once every 12 seconds or more for surveillance radars and once every four seconds for terminal radars) the technology will also be the basis for decreasing aircraft separation. As both pilots and controllers would have a constant view of the adjacent airspace, the safe distance between planes may be decreased with ease, both in transit and during approach to land. With this system in place, a single runway may be able to handle an aircraft every 45 seconds, thus increasing capacity by about 25 per cent over current maximum values.

Two degrees of capability are envisaged—Out and In. ADS-B Out is the ability of the aircraft to transmit information to ground stations and to other aircraft. ADS-B In is the ability of the aircraft to receive information from other transmitting aircraft or ground stations. It is currently planned to make ADS-B Out mandatory only in specifically defined airspace, while ADS-B In, which adds greater functionality to the host aircraft, would be purely optional. Three types of airborne equipment are proposed as the physical means of relaying ADS-B position reports:

• 1090 MHz Mode S Extended Squitter,
• Universal Access Transceiver, and
• VHF Data Link Mode 4.