Carpool lanes for airplanes?; Aviation experts say a $40-billion GPS system is needed to handle the huge volume of traffic expected by 2025.

UPS tests system at Louisville

A midair collision between two airliners over the Grand Canyon in 1956, in which 128 people perished, convinced Congress it must fund an air traffic system that would allow more precise tracking of aircraft by radar. Until the accident, pilots and controllers relied on rudimentary radio communications and a "see and be seen" philosophy to guide aircraft through most of the nation's air space.

The FAA says the proposal for the nation's "next generation air transportation system" will transform air travel, as the "Internet changed computing," in part by replacing antiquated ground-based radar systems with more accurate and reliable satellite technology. The agency hopes Congress will make a funding decision this fall.

The existing system requires pilots to fly a network of rigid routes, often not the most direct paths, over navigational aids on the ground. The system relies on radar, which uses radio beams to scan the sky for objects to determine an aircraft's location.

Because it takes as long as 12 seconds to update information on radar scopes, air traffic controllers must separate aircraft by several miles to make up for the imprecision. The system also doesn't allow pilots to see the location of other planes. Nor does it cover oceans or high mountain ranges.

Global positioning satellite technology, however, updates information to controllers every second, allowing pilots to fly more direct routes. Known as automatic dependent surveillance-broadcast, or ADS-B, the technology also would allow pilots to see what planes are around them, how fast they are flying, their flight numbers and their headings. Officials say the ground infrastructure required to operate the technology would be cheaper than radar to install and maintain.

Pilots say ADS-B also would include airfield maps, allowing them to see aircraft, as well as vehicles, operating around them on the ground, helping to reduce near misses. Pilots now must rely on controllers to warn them when other planes are approaching them on the ground.

"You can have a brand new Boeing 777 and yet still have to rely on a piece of paper and a compass" to find your way around on the airfield, said UPS' Haney. "This system is going to save lives. There's very little question right now that the most dangerous place to be in an airplane with the motor on is on the ground."

Among the challenges in replacing radar with ADS-B is how to equip aircraft with technology that can receive signals from global positioning satellites. Airlines say they are reluctant to pay millions to retrofit planes.

"What we see is a cost on the airlines' side and most benefits on the FAA side," said Basil Barimo, vice president of operations and safety at the Air Transport Assn. of America, a national airlines trade group.

"If the FAA came out today and put a mandate forward and said, ' You have to go equip your fleet, ' ... the airlines would push back," he said.

The FAA this fall will propose requiring carriers to install ADS-B in their fleets by 2020 if they want to access what the agency calls high-occupancy vehicle lanes -- or more direct routes -- in the sky. It will make a final decision by 2010. The agency also plans to award a contract in August to install ground stations that will hand off signals from satellites to aircraft.

Carriers and the FAA agree that the full benefits of the system will not be realized unless most aircraft are equipped with it.

"In order for it to work really well, we need to have everybody, or almost everybody, equipped," said MIT's Hansman. "If half the people do and half the people don't, it becomes very hard to increase the performance of the system."

Some aviation industry experts question whether the agency has done sufficient planning to ensure the satellite system and other technologies proposed by the FAA will succeed. The agency has tried unsuccessfully in the past to overhaul the complex air traffic control network.

"It's like a play that's come back to town," said Ken Mead, a lawyer in Washington, D.C., and former inspector general of the Department of Transportation. "I'm anxious to see the efficiency case for ADS-B. I don't think the case has been made that it really will speed up air traffic control."

The FAA also must rewrite procedures controllers use to guide aircraft and redesign the airspace to establish the high-occupancy lanes. Experts also worry what would happen if a sunspot or other anomaly took down the satellite network. The FAA says it will keep some radar systems in place as a backup.

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