ATM Modernization, Business & GA, Commercial, Military

Safety in Avionics: The Fallacies of Free Flight

By David Evans | May 1, 2000

More, not less, top-down control of the national airspace system (NAS) is seen as the solution to the rising tide of flight delays. What does that say about the concept of Free Flight? After all, proponents have bruited Free Flight as a solution to delays. Free Flight has come to mean "freedom to fly" with less centralized control of flight times and routes. The concept has been shaping avionics investments for the future.

At a March 10 press conference, a brace of industry officials announced their plan to ease congestion and delays through better synchronization at the strategic level. Jack Kies of the U.S. Federal Aviation Administration (FAA) explained that in the past–such as during last summer’s unprecedented season of discontent from weather-related delays–the airlines each diverted their planes around convective weather systems. One airline’s planes might go north, another south, and ultimately all these individual carrier decisions "may conflict," Kies explained.

Effective April 1, the industry will start each day with a conference call between the FAA’s national operations center in Herndon, Va., to meteorologists at the National Weather Service, and with airline representatives patched in from their operations centers nationwide. They will agree on a common weather forecast, using it to generate a strategic plan for the day’s flight activities. As the FAA’s Monte Belger declared, "Everybody was at the table except Mother Nature" concocting this plan.

These early morning coordinating meetings will be repeated every two hours until 10 p.m. at night, sort of a rolling planning process. The idea, said Kies, is to avoid getting stuck later in the day with a plan developed early in the morning that has been overtaken by events.

New departure spacing software and a new flight scheduling monitoring system at the command center ("Nothing like it in the world!" Belger exclaimed.) will facilitate the forecasted efficiencies. Robert Frenzel, senior vice president of operations for the Air Transport Association (ATA), representing the airlines, added that a "playbook" with scripted alternate routes would be used for "quicker modification" of the day’s plan.

These changes all suggest more, not less, in the way of centralized air traffic control (ATC). Free Flight had always suggested less, not more, centralized control as the path to more efficient use of the NAS. Free Flight was seen as roughly akin to everybody driving a sports utility vehicle, getting off the congested highways to go cross-country if need be. The analogy was applied to the increasingly congested "highways in the sky."

There is always a danger to over-promising. "Great advances are not produced by systems designed to produce great advances," declared author John Gall in his seminal and witty 1975 book, Systemantics: How Systems Work and Especially How They Fail. Gall cautioned, "New systems generate new problems."

So it is, it seems, with Free Flight. At the 1996 annual meeting of the Human Factors and Ergonomics Society, an important paper was presented, entitled "Initial Experiences With the Expanded National Route Program" (NRP). The paper, presented by Phillip Smith from Ohio State University and a half-dozen colleagues, contained several observations about the first experience allowing greater flexibility in preflight planning, an important step in the heavenly path to Free Flight.

Observation: The increase in direct routes and the decrease in preferential routes meant that flights "are now going direct through sectors where they previously were not direct." Impact: "Some aircraft had to be held at the Chicago Center, Cleveland Center, and Indianapolis Center boundaries because sequencing multiple flows became nearly impossible."

Observation: The best routes in terms of fuel consumption, time, sequencing, etc., may not be the direct routes. For example, a direct route won’t necessarily capitalize on a favorable jetstream. When everybody’s got the same preference, some form of overall control has to be exercised. One controller commented thusly: "...(I)f we get a jetstream right out of the southwest part of the country, everyone rides it (into O’Hare). Seventy-five percent of these airplanes are all coming in at the southwest cornerpost, creating a major volume saturation point. The old solution was to create a delay program to avoid launching too many flights into traffic...and to (increase capacity by moving) half a dozen flights to the northwest cornerpost...we’re not allowed to do this under Free Flight. If they (the airlines) create a bottleneck, then they have to live with it."

Observation: The air traffic controller’s situational awareness could suffer under Free Flight. "When we went to Free Flight...we cut off the feedback loop for those flights filed under the NRP.... How do we all get the same picture?" wondered one ATC coordinator.

Observation: A lack of information could lead to inefficiencies. "A global perspective is important in revising a flight plan," declared one ATC coordinator. "There may be a perception that a restriction is unnecessary while a plane is early in the flight, but you then hit a wall at a later point."

Observation: Some airlines sought to route their high altitude flights over arrival and departure routes. These flights, criss-crossing departure lanes, created a "very tricky, complex operation" for ATC. The scenario raised a difficult tradeoff. Should three or four planes be allowed to cross at the cost of slowing departures 20%?

More recently, Christopher Wickens, head of the Aviation Research Laboratory at the University of Illinois, led a 1998 study for the National Academy of Sciences on the human-factors implications of Free Flight. Wickens and colleagues were concerned about the shift in strategic control from the ground to the cockpit, where the workload involved in flight systems management and tactical separation already is an issue. Does Free Flight make strategic control a non-entity? Not at all. According to Wickens, "Without strategic control you will have problems."

One is reminded of a perceptive comment by the late CBS news commentator Eric Sevareid. In one of his television homilies, Sevareid said, "People, if given the choice between anarchy and dictatorship, will always choose dictatorship because anarchy is the worse dictatorship of all."

This is not to suggest that Free Flight portends anarchy in the skies, but the recently increased focus on a synchronized plan suggests that the set of all individual free flights could be an infeasible problem.

David Evans is editor of the award-winning newsletter Air Safety Week.

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