Radar flaw called simple

Computer problem at BWI caused backups to fail

System safe, FAA says

Delay in responding to controller concerns is not explained

November 21, 2001|By Marcia Myers | Marcia Myers,SUN STAFF

A "simple, simple" computer problem was behind recent failures in the backup radar systems at Baltimore-Washington International Airport, which left air-traffic controllers blind to hundreds of planes they were trying to guide, federal aviation officials said yesterday.

In their first explanation for radar outages that began in August, officials with the Federal Aviation Administration told state legislators in Annapolis that the problems stemmed from a programming error. The flaw caused interruptions in the flow of data to controllers on the positions of jetliners flying through the Baltimore area.

Although the problem at BWI is corrected, FAA officials said at a joint legislative hearing, they have alerted hundreds of airports nationwide that rely on the same computer systems to prevent similar radar breakdowns.

Frank Hatfield, head of FAA's eastern region air traffic division, assured lawmakers and the public that it is safe to fly into and out of BWI. "This system is safe -- I'd tell anybody, it's safe to fly to see Grandma for Thanksgiving," said Hatfield.

But Hatfield could not explain why the concerns of air traffic controllers -- who repeatedly complained that the backup system was unsafe -- were ignored by higher-ups for weeks.

Only after Nov. 4, when the backup systems failed for a second time in a little more than two months, did the FAA begin to acknowledge there might be a problem.

"Why did it take the FAA several months to figure out what was going on?" asked Del. Peter Franchot, a Montgomery County Democrat who chaired the hearing.

"I don't know, I don't know," replied Hatfield. "I certainly share the concerns of the controllers. The flying public of Baltimore and Maryland deserve better than that."

While Hatfield maintained the skies were safe even during the radar outages, Franchot said yesterday he intends to ask Maryland's congressional delegation to request a federal study to determine whether any planes came closer than legally allowed.

The troubles began at 6:34 p.m. Aug. 30, when lightning knocked out the airport's primary radar and its backup system, CENRAP-Plus. For the next 27 hours, air traffic controllers were forced to rely on a secondary backup, called CENRAP. During that time, controllers said, planes repeatedly disappeared from their screens. Some traveled as much as 20 miles before being picked up again.

Controllers were so concerned about the possibility of planes colliding that they asked their bosses to either shut down the airspace temporarily or reroute traffic and hand off some of it to other towers. Those requests were denied.

Tower manager Don Simons later approved bonuses for some controllers, noting their "remarkable" performance in dealing with radar coverage described as "poor to nonexistent." But in other reports, he maintained there was nothing wrong with the system.

Then on Nov. 4, the main radar was shut down for routine maintenance, and both backup systems failed. At that point, the concerns of controllers reached Franchot and other state legislators, as well as Sens. Paul S. Sarbanes and Barbara A. Mikulski.

The concerns also reached Hatfield, whose office is in New York. He set about to find out why backup radar data sent from the Washington Air Route Traffic Control Center in Leesburg, Va., apparently wasn't received in Baltimore.

After two weeks of investigation and testing described as "exhaustive," Hatfield reported yesterday that a problem had been discovered in what he described as an electronic "bucket" in the computers at Leesburg. The system is designed to hold information about plane positions before sending the data to Baltimore. But Hatfield said the holding area had become too small for the amount of data being sent, and what didn't fit was lost.

To fix the problem, a programmer simply doubled the size of the computer's data holding space.

After that change, the backup systems at BWI were tested twice during the morning of Nov. 14: One test lasted 15 minutes, the other 45 minutes. Both were very successful, Hatfield said.

The FAA officials said that the only other airport the agency knows to have experienced similar problems is Washington Dulles International Airport. Controllers there reported a smaller outage about a year ago. The backup system there, as well as at Reagan National Airport and Andrews Air Force Base will be upgraded if necessary, he said.

Rockton Thurman, president of the National Air Traffic Controllers Association local in Baltimore, said that he was reassured by the FAA's recent attention to the problem. But, he said, "Until further testing, we'll continue to have questions about this system."

Hatfield said he expects weekly tests of the BWI systems, but he couldn't promise both backup systems would receive such regular testing.

Thurman said that if there is another radar failure, he is certain tower managers will respond with appropriate safeguards. "We don't think we'll be challenged," he said.

Hatfield tried to reinforce that message yesterday to legislators.

"If we've learned nothing else, it's when a controller tells us there's a problem, there's a problem, and let's fix it," he said.

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