Separation Anxiety: Will Free Flight Fly?


Pilots in Cockpit At first, the idea of letting airliners fly anywhere they want sounds a little suspicious.

If planes don't fly fixed routes, what's to keep them from crashing into each other? Isn't that what air traffic controllers do? What's wrong with leaving things as they are?

Plenty. A chorus of aviation experts is warning that the present system is only a few years away from gridlock, as a growing number of planes vie for a fixed number of lanes in the sky. In 1994, the Federal Aviation Administration predicted domestic air traffic would increase nearly 70 percent by the end of the century and carry 800 million passengers. The airlines are complaining that the system is bad for business and passengers.

Concern is so great that none other than the FAA, the agency responsible for keeping the skies safe, has agreed to try free flight, a new concept being developed by the aviation industry, including researchers at Embry-Riddle Aeronautical University.

Why free flight?

ATC Lab Free flight was first proposed about 15 years ago as a replacement for the FAA-imposed route structure that dates to aviation's early days, when night mail pilots were guided en route by bonfires burning below. If a lake lay between you and your destination, you followed the fires around the lake's edge, instead of flying in a straight line across it.

Bonfires have been replaced by radar and radios, but routes are still arranged along a maze of waypoints, like a connect-the-dots puzzle. Only now, pilots are handed down the chain by air traffic controllers along the way.

Airline traffic is restricted to single-lane skyways, no passing allowed. A lot of sky remains empty, unused. "On a cross-country flight, it's not unusual to fly hundreds of miles out of the way," says Don Tilden, a senior research associate in Embry-Riddle's human factors and systems department.

That translates into lost time and money. For example, the "J" shaped ATC-preferred route between Nashville and Boston adds 172 miles, and costs American Airlines $900,000 extra a year.

Starting in the 1980s, advanced aircraft came equipped with computers that let pilots punch in waypoints, and enabled the plane to fly itself. But the air traffic control system didn't allow for pilots to use these new tools, and free flight was quietly put aside.

Then in 1994, an independent economic analysis claimed the airline industry could save $3-5 billion a year if the system were replaced by free flight. It said planes using existing technology could take off and land without ATC guidance, fly in any direction, and be kept apart by on-board systems monitoring a "bubble" of space around each plane. The document sparked interest in Congress and led to the creation of an FAA advisory committee on free flight.

Down to earth

In its first report the committee took a giant leap forward by calling any activity to remove restrictions in the system a move toward free flight. The FAA responded by ordering ATC centers to cut out all "low-hanging fruit" -- easily removed, unneeded rules that often differ from region to region.

By the time the task force reported on implementing free flight, the concept had come out of the clouds and down to earth. "It was clear that switching the ATC system to free flight overnight would be like changing a piston in a car without shutting off the engine," says Tilden, who served on the task force.

In the simplest form of free flight, operators would select their own path and speed. Pilots would pick up the location of other planes within a 100-mile radius and take appropriate action, if any. On the ground, controllers would monitor air traffic, using data received from aircraft.

The three basics needed for free flight are a navigation aid, such as the satellite-transmitted global positioning system (GPS), an on-board flight management system that receives GPS data, and a system that automatically relays reports on position, speed, intent, and other data between the ground and other aircraft in the vicinity.

"These tools already exist," says Ken Fleming, director of traffic management research at Embry-Riddle. "How we're going to use and integrate them is what the discussion is all about."

Embry-Riddle research

ResearchersA team led by Fleming is using sophisticated software to simulate more than 36,000 recorded flights per day across the U.S. and explore how air traffic would function in a free flight system. The Total Airspace and Airport Modeller (TAAM) program lets researchers Scott Bertin, Gary Fairman, and John Lane display and test real-life scenarios such as overcrowding and rerouting.

In simulations for NASA and Lockheed-Martin they've shown there would be fewer en route violations of separation standards in a free flight environment, because airplanes are allowed to spread out more. "The problems occur when everyone wants to land at an airport at the same time," Fleming says. "Then it's up to the air traffic controllers to schedule landings. You can land planes every 45 seconds. It's doable -- the military does it every day -- but people can't wrap their minds around it yet."

Exclusively licensed by the software's creator, The Preston Group, to use it for research and teaching, Embry-Riddle has conducted most of the TAAM airspace modeling training in the nation since 1994. Clients have included the FAA, NASA, Federal Express, Continental Airlines, and Lockheed Martin.

The human factor

Economic BenefitsBut technology alone won't make free flight fly. A major unresolved issue is the interaction between pilots, responsible for their aircraft, and air traffic controllers, responsible for keeping planes separated. "Traffic displays in the cockpit raise questions," says David Hopkin, a world-renowned British authority on human factors of air traffic control and a visiting distinguished professor at Embry Riddle. "Who's responsible if a pilot, acting on information from the cockpit, diverts the aircraft from its planned position and throws everybody else off? Will the ATC have authority to order the pilot to divert from a planned route?"

Another question is what, if anything, would be gained from free flight in congested areas such as the East Coast and Western Europe. "In the Washington-to-Boston corridor, free flight might be a problem because much of the traffic is in climb and descent," Hopkin says. "Plus, the farther away you are, say Orlando, the earlier you'd ask for a descent time, and thus be favored for landing over flights coming in from New York. You'd need a system that doesn't discriminate."

Hopkin says now is the time to scout for the possible pitfalls of free flight, which is certain to introduce new forms of human error. "For example, it would be easy to reach a point where the pilot and ATC are only to monitor what's going on, not touch it," he says. "But that's impossible. People must be given things to do to interact with information. You can't intervene in a situation you haven't been involved with. 'Use it or lose it' applies here."

A new tool: collaboration

From the start, airlines saw little benefit in gaining more freedom in the air if the government still controlled scheduling, departures, and arrivals, says Margaret Jenny, who heads business and operations analysis at US Airways and co-chairs a select committee that advises the FAA on free flight.

Fight2000 That realization paved the way for the most potent tool to come out of the free flight debate so far: cooperation.

"The initial steps toward free flight will be largely a function of improved strategic air traffic management planning," declares James Wetherly, who manages the FAA's Collaborative Decision Making Program between his agency and the airlines. One of the program's first fruits was AOC Net, a network of 10 major airlines' operations centers that share sensitive, proprietary FAA airline data in order to do better strategic planning. The network has shifted more economic control to the airlines, says Wetherly.

Another important spin-off was Flight Schedule Monitor, software used by the FAA command center and airlines' operations centers to display real-time schedule information and help airlines better manage imbalances in airport capacity and demand.

United Air Lines saved at least $1.5 million using the tool during a three-week period in January and February at O'Hare and San Francisco airports. "The savings came from not canceling flights due to bad weather," says Chris Pear, manager of the carrier's flight dispatch operations.

A 180-degree turn

Pear says the airlines' relationship with the aviation agency has taken a 180-degree turn. "It used to be the airlines against the FAA," he says. "Now it's the airlines and the FAA against the weather."

It's paying off, too. When a snowstorm started moving into St. Louis last Christmas Eve, the FAA prepared to ground and cancel flights there. But the airlines, backed by software that showed the problem would improve in an hour, persuaded the agency to hold off. Aircraft did more airborne holding than usual, but all planes got to where they were going that night and the carriers didn't have to put passengers in hotels, pay overtime to crews, and burn extra fuel. An estimated $1 million was saved.

But, as they say in the industry, "airlines fly schedules, not airplanes." Free flight's real payoff will be measured in months and years, not a single holiday weekend. Shaving minutes from each flight by flying more direct routes saves labor, fuel, and cargo costs and, eventually, an extra engine overhaul.

"The bulk of free flight will be done before the flight ever takes off," Tilden says, "because you'll want to file the best possible flight plan."

Free flight's future

Will free flight ever become a reality? It depends on whom you ask.

Fleming is concerned the concept will be studied to death. "If there had been an elevator control organization in the 1930s, we'd never have had automated elevators," he quips.

Hopkin is more optimistic, but says most air traffic controllers he knows are cautious. "Their job is safety," he says. "They need to be convinced."

Tilden sees free flight evolving slowly. "It's a road map for the future that changes every year," he says. "Maybe our original concept wasn't what free flight is, after all." For example, he says, removing ground delays that can put an entire fleet behind schedule may turn out to be just as important as freeing up routes in the air.

Whatever free flight becomes, airlines are gaining already from the changes leading up to it. "Users now are being given the flexibility to make economic decisions, while the FAA makes safety decisions," Jenny says. "Free flight has become the term for a future air traffic control system that's safer, more efficient, and more collaborative," she says. "It's now seen as a continuum from scheduling to gate-to-gate operation."

It looks like free flight is taking off.

By Robert Ross