Waiting in the Wings: Technology to Fight Gridlock in the Skies

It is so congested at US airports these days that planes coming from the West Coast to New York often start lining up around Chicago.

That may sound like a vaudeville line, but unfortunately it is a fact. And the situation is only going to get worse: While more than 650 million commercial passengers flew in the United States last year, that number is expected to grow to 1 billion by 2015, the Federal Aviation Administration says.

With gridlock only a breath away, a handful of technologies have emerged those proponents say will increase the capacity of strained airports and reduce delays at squeeze points in the air traffic control system. Right now, air traffic controllers locate planes with radar and guide them by voice communication — safely but relatively slowly — to increase the space between planes or hold them back at the first sign of a problem.

While the computer support available to controllers is limited now, satellite, computer and communications technologies may lend a hand in the future. New software may help adjust traffic as planes approach the airport and calculate flight trajectories to give more warning of possible problems. One of the most powerful systems, based on Global Positioning System technology, may one day supplement or even replace radar.

“Possibly you can get more aircraft through the pipeline," said Richard Lay, a programme manager at the Federal Aviation Administration who is evaluating the GPS-based technology. “When the whole system goes to pot because of one little choke point, this technology is designed to keep planes going at a certain speed and not have tie-ups.”

The technology Mr. Lay is evaluating tells pilots in their cockpits the exact position, speed and altitude of nearby aircraft, information that can now be picked up only by the controllers in their control centres and airport towers.

Larry Speelman, director of business development at UPS Aviation Technologies, a subsidiary of United Parcel Service of America Inc. that manufactures the technology, said that with global positioning technology, each airplane would broadcast its position to other planes. "Instead of radar having to paint all the airplanes to get their location,” he said , “each aircraft will have a lighted sign saying, ’Here’s where I am, and here's where I am going.’ ”

The system, called ADS-B, for Automatic Dependent Surveillance-Broadcast, works this way: Pilots know their own positions from their GPS receivers, which use precise timing signals emitted by a network of satellites. The planes can broadcast that information from cockpit to cockpit, letting nearby aircraft know exactly where they are, and they can send the information to ground systems. ADS-B can be more accurate than radar. It updates itself every second, while radar information is relayed only after a complete sweep or two of the area surveyed, which often takes as long as six seconds. And unlike radar, it works at low altitudes and can be used to track lanes on runways. It also would be a simple matter to equip fuel trucks and other vehicles that operate on runways and taxiways with a GPS receiver and a low-power transmitter to broadcast the data. Controllers would then be able to monitor all the traffic on the ground, even when visibility is poor.

Another innovation being tested by the Federal Aviation Administration is software that predicts where planes will be in 10 or 20 minutes, something that turns out to be very hard to estimate.

“It's surprisingly difficult to predict when, for instance, a cross-country flight will actually show up,” said R. John Hansman, a professor in the department of aeronautics and astronautics at the Massachusetts Institute of Technology and director of the international centre for air transportation there. "If you look at the times for a year of flights from Los Angeles to New York, there’s 20 to 30 minutes' variability, depending on, say, how strong the tailwind is."

The new software, known as conflict probe technology, predicts the aircraft’s trajectory, allowing time for controllers to make necessary changes and avoid backups.

Digitized communication between pilots and ground controllers is also expected to speed the flow of traffic Right now, such communication is almost entirely by voice; with digital communication, text and graphics will be sent straight to the cockpit. “Graphical information to the cockpit is important," Mr. Hansman said. “Presently you can get better weather information in your hotel room by turning on the cable TV than you can in the cockpit"

Another tool is being developed by the National Aeronautics and Space Administration under the direction of Heinz Erzberger, a senior scientist at the agency's Ames Research Center in California. Mr. Erzberger is the chief designer of an air traffic controller system called CTAS.

The software has a traffic management system, “software that helps controllers push the right amount of traffic through the system — neither more nor less,” Mr. Erzberger said, “as well as final-approach spacing software that helps controllers order the flow of traffic so aircraft get to the correct runway in the best order.”

A CTAS prototype is at work at Dallas-Fort Worth International Airport. Contractors are adapting the technology to other airports although Mr. Erzberger said the process could take another three to four years.