he US aviation regulator has selected ITT Corp to provide a new generation of GPS satnav-based air traffic control equipment, awarding a $207m, three-year initial contract.
Current air traffic control systems worldwide use radar to detect and track aircraft: either "primary," in which radio pulses from the radar reflect back from the plane's skin, or "secondary," where a transponder emits a code or "squawk" in response to the radar transmission.
In either case, the controller's picture updates only as fast as the radar antenna can spin round, which typically means every six seconds or so. During that time a jet can travel a mile, and usually the radar location info isn't very precise either, which means that, in congested airspace, a substantial margin of error must be maintained. This in turn means fewer planes can move through a given amount of airspace, leading to delays.
Now, however, the Federal Aviation Administration (FAA) intends to move to a system called Automatic Dependent Surveillance-Broadcast (ADS-B), which will lay the groundwork for the Next Generation Air Transportation System, or NextGen.
Under ADS-B, each plane is fitted with GPS satellite navigation, and thus knows its own location precisely. This information will then be broadcast in real time to a ground network, updating every second. Controllers will have a much more accurate idea where all the aircraft are, which could potentially allow them to move planes through bottlenecks more quickly.
“This signals a new era of air traffic control,” according to FAA number-two, Bobby Sturgell. “ADS-B - and, in turn, NextGen - will attack the delay problem head on by dramatically increasing air traffic efficiency.”
ADS-B will also be a two-way street, allowing pilots to see full information on all the planes in the sky around them, just as controllers do. At the moment, most aircraft don't have a proper radar of their own, though they may have proximity warning systems or weather radars. For monitoring other planes, today's pilots are mostly dependent on ground controllers - or the limited capabilities of the naked eye.
