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NASA Project Seeks to Save Air Travelers 700,000 Hours

System to predict wing turbulence may cut delays

Who couldn't use more time?

NASA is spending $12 million to save air travelers 700,000 hours in the next decade by landing planes a little closer together.

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One way to do that is to better understand a phenomenon called wake vortex - the turbulence that spirals off aircraft wings, forcing air-traffic controllers to space out landings.

Decreasing the spacings may save only half a minute or so between individual flights, but the long-range benefits of the wake-vortex project are sweeping.

At 10 major airports researchers studied in a computer model, the time savings over 10 years would not only save passengers hassle, but also save air carriers hundreds of millions of dollars in fuel costs and other expenses as planes spend less time in holding patterns.

The program is still in its early stages, but one of the biggest defenders of airline safety has already given its seal of approval. "The capacity and safety sides of things are all in one," says Michael Lewis, director of NASA's aviation-safety program. "The only way to get increased capacity is if it can be done safely."

NASA's Aircraft Vortex Spacing System, which is being run out of the Langley Research Center in Hampton, Va., is one of three programs aimed at helping the industry increase airport capacity by as much as 15 percent. Preliminary tests were held at the Dallas-Ft. Worth airport in October, and all three programs are scheduled to end by 2000.

The system is expected to improve airport capacity primarily during poor visibility, when pilots rely on their instruments instead of their eyes - conditions that NASA researchers conservatively estimate exist about 12 percent of the time.

When pilots must rely on their instruments to land, the Federal Aviation Administration requires that inbound planes be spaced 2.5 to 6 nautical miles apart. These distances could be cut if the project can more accurately predict how long it takes wake vortices to dissipate.

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Typically, the bigger the plane, the stronger the vortices it leaves in its wake. Smaller planes following too closely behind a larger plane can lose control if they encounter a strong wake vortex. But vortices can also be unruly as wind conditions change.

"I can show you pictures that have these things all over the sky," says Brad Perry, a NASA project manager.

While wake vortices are blown out of the flight path quickly if there is a crosswind, they can hang in the air for minutes during calm weather.

Through their research, the NASA scientists hope to develop a system that will be able to predict what happens to wake vortices in various conditions, so air-traffic controllers can line up planes earlier.

"Once a plane is aligned with the runway, it is too late to adjust," says Dave Hinton, the NASA aerospace technologist heading up the program. "Controllers are controlling the airspace 25 to 50 miles out, and they coordinate with controllers who direct multistate air traffic. Our system will be able to make wake predictions for [15- to 60-minute] periods, based on weather."

According to a 1994 National Transportation Safety Board report, at least 51 incidents in the US between 1983 and 1993 were the result of "probable encounters with wake vortices." In those incidents, 27 people were killed and eight were seriously injured.

And although NASA's primary concern is capacity, officials say their research may improve wake-vortex safety through the system's ability to predict turbulence problems before they happen. Indeed, one possible spinoff of the research could be airborne-detection systems that would allow pilots to see wake turbulence in their flight paths.

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