Birds swamp airport radar in Midwest


WASHINGTON -- Great flocks of migratory birds overwhelmed the radar systems at three Midwestern airports Thursday night, forcing them to shut down. Experts at the Federal Aviation Administration said that they could not recall a similar failure.

There were no accidents, but some flights were delayed.

The computerized radar systems at Des Moines, Iowa; Omaha, Neb., and Kansas City, Mo., were knocked out for hours after they tried to process information on hundreds of birds. A computer is supposed to filter out the radar echoes that come from birds by tracking their speed, but the filtering system failed.

"It caused our primary system to overload," said Donna Genest, the air-traffic manager at Des Moines. The radar system there can process "700 bona fide aircraft returns and 300 nonaircraft returns," she said, referring to the electronic echoes that come back to the radar dish.

If controllers know that a big flock of birds is on the way, they can turn off the primary radar system, the one that reads echoes back from objects in the sky, and rely on secondary radar, or the messages sent by the transponders. But Thursday night the system failed so fast that the controllers lost primary and secondary radar.

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