WASHINGTON - The Federal Aviation Administration said yesterday that it will adopt a radically different concept of air-traffic control in which pilots would pick their routes, altitudes and speeds, and air-traffic controllers intervene only if flight plans conflict.
Proponents argue that this concept, called free flight, would save time for passengers and money for airlines by easing delays.
Over the next 10 years it would gradually replace the 35-year-old "positive control" system in which a controller at a radar screen orders every change a pilot makes.
Under positive control, planes do not fly from one airport directly to another; they fly from one checkpoint in the sky to the next.
As a result they end up flying extra miles in long lines and bunching up at checkpoints, producing delays.
New technology to allow free flight is needed to enable the nation's air-traffic system to handle the 40 percent increase in flights expected in the next 20 years, said the agency's administrator, David Hinson.
Mr. Hinson was backed up by representatives of the pilots, the air-traffic controllers and the airlines.
"We will not be able to maintain our premier status in the world unless we take action now to provide improvements on our airspace," said Robert Baker, executive vice president of American Airlines.
Mr. Baker said that this year there would be 63.2 million landings and takeoffs and that by 2007 the number would reach 74.5 million.
Shaving a few miles and a few minutes off each flight would add up to a major improvement for both airlines and passengers, he said.
A NASA study cited yesterday by the aviation agency found that letting planes pick their own routes instead of following the airways laid out by the radio beacon routes would have saved $1.28 billion last year for the airlines.
But most of the cost of delays is in lost time to passengers, which is difficult to quantify.
Michael Baiada, an aviation consultant who advocates free flight, estimated last year that airline productivity, as measured by how long it takes to move planes from one point to another, had dropped 8 percent in 15 years.
The aviation agency often finds it difficult to change its systems without the agreement of the many factions interested in airspace: airlines, cargo haulers, the Air Force, private plane owners, business jet operators, unions for pilots and air-traffic controllers, and even the airport authorities.
For the moment, all these groups support free flight.
The aviation agency said the new system would begin operating gradually in the coming years as more planes navigate by using the Global Positioning System, a network of satellites launched by the Pentagon, rather than the system of radio beacons now in use.
The satellites allow anyone with specialized electronic receivers to pinpoint his position in three dimensions to within a few meters.
Planes would radio their positions back to the ground, either directly or through communications satellites, and FAA computers would then track them as blips on screens, rather than using radar, which is less accurate.
Near airports, planes must now be separated by 1,000 feet in altitude and three miles horizontally; under free flight, they could fly much closer together, FAA officials said, because their positions would be known with much more precision.
Under the free-flight concept, planes could reduce flight-path conflicts between them, according to Lane Speck, director of air-traffic program integration for the FAA.
"If you spread the traffic out, what you do is you spread out the conflicts," he said.
Under the concept as laid out yesterday, a computer would assign each plane a "protected zone," an area shaped like a hockey puck that was not to overlap with another under any circumstances, and a larger "alert zone."
When two alert zones overlapped, a computer would tell a human controller and offer advice on what should be done.
The size of the alert zone would depend on the planes' speeds and other factors.
All of this will require a new generation of computers and software.
Acquiring them has always been a problem for the agency.
Even with no unexpected glitches, phasing in free flight will take years, officials said, and they do not know precisely what the final system will look like.
While the FAA did not formally commit itself to widespread use of free flight until yesterday, some aspects are already in use.
For example, since 1992 some aircraft flying at high altitudes on routes of more than 300 nautical miles have been allowed to pick their own routes, and this has saved airlines millions of dollars in fuel and crew pay, officials say.
In addition, last year the FAA began using related technologies over the Pacific Ocean, where there is no radar.
Pub Date: 3/16/96