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| The ADS-B air-traffic-control system will be managed from a state-of-the-art center. |
In the face of mounting public and congressional outcry, the FAA claims it has an answer: a planned overhaul called NextGen. For $15 to $22 billion, it will replace the nation's aging, radar-powered air-traffic-control network with one that relies on GPS and advanced avionics.
A much-needed upgrade, the new system may help defuse growing concerns over air traffic safety. The Associated Press reported this week that a secret NASA study found incidents of near collisions, bird strikes and last minute changes to landing plans occur far more frequently than previously known.
But some argue the planned upgrade ignores the core issues facing air traffic control, or ATC, and a bitter debate is raging over who should pay for the new system.
Getting an aircraft from point A to point B safely is currently no easy task. Air traffic controllers based at a flight's departure airport direct taxi, takeoff and initial climb. Then they hand planes off to one of 21 regional ATC stations scattered across the country, where controllers monitor flights using a patchwork of short- and long-range radar equipment. Flights are passed from station to station until approaching their arrival airport, where another crew of controllers handles descent and landing.
Built on World War II technology, the system is showing its age. Planes move quickly, and radar takes anywhere from three to 12 seconds to accurately read a position. So, the FAA requires separation of at least 1,000 feet vertically between planes, and three to five miles horizontally.
Controllers organize up to 5,000 planes in the sky in any given hour by slotting them into a series of fixed flight paths. But these highways in the sky are susceptible to rush-hour backups, especially at intersections. When a route or hub closes because of weather, delays often reverberate through the rest of the system.
That's where NextGen comes in. The biggest component of the planned system is a satellite-based network known as Automatic Dependent Surveillance-Broadcast. ADS-B uses a GPS signal to determine an aircraft's position in the sky and transmit this information once per second to other aircraft, and to a national network of ground stations that relay it to air traffic control.
ADS-B-enabled planes will be equipped with onboard monitors that allow them to see not only their own precise location, but that of other aircraft. Monitors will also display external data like weather and aeronautical information, a part of the system known as Flight Information Services-Broadcast, or FIS-B. Today, pilots receive weather reports from commercial services or verbal updates from air traffic controllers.
The FAA's Laura Brown says ADS-B will help reduce congestion in several ways.
"Because it will provide such precise information about where planes are located, we think we'll be able to operate them closer to one another in some parts of the air space," she says. "Which means more capacity." Brown adds that the system will allow controllers to handle more aircraft, which means fewer handoffs from controller to controller. "Ultimately, the system is more effective if you are able to limit the amount of communication back and forth."
In late August, the FAA awarded ITT a $207 million initial contract to develop and deploy the ADS-B infrastructure. ITT will build 794 ground stations, each of which are "the size of a dorm-room refrigerator" according to Brown, as well as control and network-operation centers, a telecommunications network and service-delivery points that interface with existing air-traffic-control stations. Many of the ground stations will be housed in existing cell phone towers owned by AT&T.
"The use of commercial towers for deploying government assets is not uncommon," says John Kefaliotis, ITT's director of business development fo FAA & ATC programs, "though it may be a first for the FAA." ITT will own the ADS-B system, and will essentially lease it to the FAA. "It means we're not building a duplicate of a system that already exists," Brown says. "And it allows our vendors to utilize their existing assets."
