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Whether the technology can make similar inroads elsewhere is less clear. One concern has been whether GPS satellite signals are robust and reliable enough to serve as a foundation for air traffic control. But a 1999 report by the Johns Hopkins Applied Physics Laboratory helped allay fears that satellite signals-weak compared to ground-based radar-are at risk of disruptions from solar radiation, atmospheric disturbances or terrorist hackers. “Technologies are emerging that can greatly reduce vulnerability to GPS signal jamming,” according to the study. And to the extent that satellite signals are warped by the atmosphere or other interference, they can be verified and tweaked for extra accuracy with ground-based augmentation systems like those being installed by Raytheon.

Another fundamental question is whether new displays in the cockpit might distract pilots, and whether new navigation responsibilities will overload them. “Human error is involved in at least 80 percent of all accidents and incidents in aviation,” says Kim Cardosi, manager of “human factors” programs at the U.S. Department of Transportation’s Volpe Center in Cambridge, MA. “The work environment is so complex, it can set them up to make mistakes, and that’s what we have to guard against in these systems and displays. We have to make sure [pilots] aren’t overwhelmed by information, and that when they do make a mistake it can be corrected before it has serious consequences.”

The infusion of data and displays brings with it new sources of confusion. Kuchar cites “a number of accidents in which there has been a mismatch between what the computer was thinking and what the human was thinking,” such as the 1995 crash of an American Airlines Boeing 757 on approach to Cali, Colombia. The airplane slammed into a mountain, killing 160 people, when the autopilot was instructed to fly toward a radar beacon the pilot thought was near Cali, but which was actually near Bogot. In this case, radar beacon technology and the autopilot system helped lead passengers to their deaths after a seemingly trivial pilot error. “If the United States switches to widespread use of [satellite-based technology], there will be other areas in the world that haven’t, requiring pilots to use different procedures in different places. This can lead to additional errors and problems,” Kuchar warns.

Despite these questions, prototypes are advancing. A key day for UPS’s effort came last October, when FAA administrator Jane Garvey flew into Louisville for a joint FAA/UPS evaluation of the technology. Garvey stepped inside a UPS Boeing 727 whose fuselage had none of the usual furnishings-just several pods of computer equipment in the front, and 16 leather-upholstered first-class seats bolted to the floor in the rear. Taking a seat in the front row, she glanced at a computer monitor displaying a graphical depiction of the Louisville airport. The runways were dotted with slow-moving brown triangles. These represented airplanes equipped with the datalink system, exchanging position data with each other. “This is cool,” Garvey said.

“Wait until you see the in-flight movie,” quipped George Cooley, an engineer at UPS Aviation Technologies. The “movie” began as the 727 rolled slowly along the airport’s taxiways. Other taxiing airplanes were plainly visible on the screen. Suddenly, a blue triangle appeared on the screen, its tip elongated with a needle-nose indicating high speed. A moment later, the blue blip turned brown. Jim McDaniel, head of the FAA’s technology assessment programs, announced that an airplane had just taken off. But in fact, blue denoted an airborne airplane, brown an airplane on the tarmac. A moment later, he corrected himself. “I thought it was taking off at that moment, but it was landing,” he said.

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