Radar system failures alarm BWI controllers

Aircraft disappeared in `black hole'

call to stop traffic rejected

`Unreliable' radar, `black holes' alarm controllers at BWI

Scores of flights vanish from screens

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

Baltimore-Washington International Airport's main radar system went down and its two backup radar systems severely malfunctioned during a 27-hour period in late August, repeatedly rendering air traffic controllers blind to hundreds of planes they were trying to guide.

So concerned were BWI controllers about possible aircraft collisions during this time - Aug. 30-31 - that they asked supervisors to temporarily shut down the airspace, a request that veteran controllers describe as unprecedented at BWI and one that airport control tower administrators rejected, controllers said.

Instead, air traffic continued at almost normal levels, and tower managers apparently kept quiet about the problems - not even notifying pilots flying through the airport's airspace who thought the backup radar was working.

About 1,700 planes flew through BWI's airspace during this time, with about 800 of them taking off from or landing at the airport, controllers said.

No collisions or near-collisions resulted. But controllers were reduced to tracking planes and keeping them the required distances apart by, at times, jotting notes on paper and employing guesswork as images disappeared from their radar screens for as much as 20 miles at a time, they said.

"Without wanting to sound alarmist, the potential scenario was the worst-case scenario," said Rockton Thurman, a senior BWI controller, who estimates that more than 1,000 flights during this time disappeared for uncommon lengths of time from controllers' screens.

"All it would have required was an aircraft not checking in when it was supposed to or misreporting an altitude or anybody not following an instruction or a controller making a mistake," he said. "We got lucky."

Mary Schiavo, former inspector general of the U.S. Department of Transportation, said such failures of backup systems are not uncommon. But she added that, in those cases, air traffic managers ordinarily take some of the extra precautions the controllers at BWI were suggesting.

"What's the harm in handing off some of the traffic to another center?" she said. "What's disappointing is that no one took the extra effort to do it. They were just trusting luck."

Federal Aviation Administration and Maryland Aviation Administration officials said last week that they had not been notified of problems with the backup radar. An FAA spokesman said Friday that reports indicate the backup system, known as CENRAP, had worked properly and denied that conditions were unsafe.

FAA spokesman Jim Peters would say only that, eventually, the agency was able to restore BWI's main radar system late the second day.

"That's all we're going to say," he said.

`Safety not compromised'

On Friday, after learning for the first time about the problems of Aug. 30-31, the acting executive director of the Maryland Aviation Administration, Beverley Swaim-Staley, called the FAA.

The federal agency is solely responsible for managing the airspace but notifies state officials of unusual problems. "I've been assured that safety was not compromised during that period," she said.

Radar failure, usually from storms, occurs a couple of times a year at BWI, forcing controllers to depend on backup systems. But the controllers interviewed describe what happened at the end of August as a uniquely dangerous problem that remains unresolved.

The trouble began when lightning knocked out the airport's primary radar, known as ASR-9, and its immediate backup system, called CENRAP-Plus, at 6:34 p.m. Aug. 30.

Departures were halted and arrivals diverted over the next hour. Meanwhile, technicians tapped into CENRAP, a less sophisticated backup system that works off a radar feed from the Washington Air Route Traffic Control Center in Leesburg, Va.

Controllers began receiving new radar images 16 minutes later but said they immediately encountered problems.

In addition to Thurman - head of the local chapter of the air controllers union, the National Air Traffic Controllers Association - three other BWI controllers who were working in the airport's control tower during this period described the problems to The Sun.

They asked that their names not be published for fear of losing their jobs.

Soon after the second backup system kicked in, controllers said, they noticed significant "blind spots." Some aircraft traveled distances as much as 20 miles before being picked up by radar. Other planes that were being tracked suddenly disappeared for the same distances.

"The presentation we were getting was horrendous and very unsafe," said one longtime controller. "You usually get consistent [plane] tracks. It wasn't like that.

"You could be watching eight to 10 airplanes and five or six of them are dropping off. That could go on anywhere from three to four minutes."

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