The work of controllers in a key air traffic center in Aurora is deemed so important that the sprawling complex is constructed to survive a nuclear attack.
To ensure that the Chicago Air Route Traffic Control Center can safely track hundreds of planes in the air at any given time in five states, backup systems stand at the ready for computers, communications and electrical power.
But all it took was one electrician making one bad connection to plunge controllers’ radar screens into darkness Wednesday morning.
The resulting computer failure caused flight delays nationwide, including scores at O’Hare International and Midway Airports. But more important, it raised concerns about safety and questions of the adequacy of air traffic control hardware and its fail-safe systems.
After the primary computer system went down at the building at 619 Indian Trail Rd., controllers said they were reduced to using strips of paper and radio conversations with pilots to plot the paths of an estimated 400 planes in the air over five Midwestern states.
“It was 1930s air traffic controlling,” said veteran controller Pat Peace. “That’s what it was.”
Despite Wednesday’s problems, no close calls were reported.
How long the system was out of commission was a matter of debate.
Federal Aviation Administration officials put the loss of coverage at two minutes for most airspace segments in the 120,000 square-mile area, and seven minutes in others.
But officials of the National Air Traffic Control Association, the controllers union, said screens were dark for seven minutes for most segments of the airspace they cover until the system resumed operating. They said coverage was out in six areas, including over Joliet, Gary, Grand Rapids, Mich., and western Illinois, for 45 minutes.
And, according to the union, one section of airspace over central Illinois not only lost radar, but lost radio communications as well. No airliners were in the area, but private planes were, they said. The FAA denied any loss of radio communications.
But even with a two-minute gap, jets traveling several hundred miles an hour can cover sizable distances.
Controllers are trained to guide airplanes without radar, and commercial jets have collision-avoidance systems that warn of nearby planes, said Cathy Asselborn, quality assurance specialist with the FAA.
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“There was danger, but it was minimal danger, mostly because of the training our people receive and the procedures we have,” she said.
But Mark Scholl, president of the local branch of the controllers union, characterized the breakdown as more serious.
“It was your worst nightmare as an air traffic controller,” he said. “These guys did a great job to keep a disaster from happening.”
Controllers have a long-standing disagreement with the FAA over the quality of the equipment at the Aurora center.
The problem hit at 8:45 a.m. when an electrician testing the electrical system in the control facility touched a nut with a needle-like probe and accidentally also hit the metal cabinet that encases the component, the FAA reported.
The contact produced a spark, and a millisecond-long interruption in electrical power, said Don Yardley, the agency’s environmental supervisor at Aurora. That knocked out the primary computer system, and a backup system began providing radar images two minutes later, officials said.
“It was human error,” Yardley said. “The system performed exactly as it was supposed to. But you can never rule out human error as you can see with the space program or anywhere else.”
Controller Peace said he was handling about six passenger jets in the Milwaukee area when he heard a startling noise and his screen went blank.
“I heard a very loud clicking and the radar went out,” he said. “For about 10 or 15 seconds, we lost our radio frequencies too. I yelled at a supervisor, `The radar is gone,’ and he said it was the same everywhere.”
Peace said he called pilots in his sector and asked them their positions and altitudes. Then, in his head, he figured whether any of them would collide.
Peace said he told pilots to descend so they could be picked up by functioning radar that operates at lower altitudes at local airports.
The Aurora center has had problems before. On Aug. 1, 1985, a construction crew accidentally cut through an electrical conduit, knocking out the facility’s main computer and preventing a backup from taking over immediately.
Controllers were without radar for a full 12 minutes.
Then-U.S. Rep. Guy Molinari (R-N.Y.), a member of the House Public Works and Transportation Committee, had a pointed response to FAA claims that the agency could not have anticipated what happened.
“I say, hogwash,” he said. “That is something they must anticipate. They are too many lives depending on it.”
Weather in the Chicago area was sunny and clear Wednesday, making it easier for pilots to spot other planes.
The Aurora center covers airspace mostly at high altitude in parts of Illinois, Indiana, Michigan, Ohio and Iowa. Generally, the service area extends from Green Bay to Springfield, from Ft. Wayne, Ind., to Des Moines.
The center directs aircraft through the region until handing them off to other controllers, who handle airport landings.
“At one point, we had 100 (departing) flights on the ground” at O’Hare, said Lisa Howard, spokeswoman for the city’s Department of Aviation.
O’Hare’s biggest operators, United and American Airlines, between them had about 170 flights at one time after the outage that were held up either leaving or coming to the airport, officials said.
The morning delays had a ripple effect through the afternoon.
“You just can’t `go’ and everybody takes off,” said Mary Frances Fagan, a spokeswoman for American. “It’s not like a flock of seagulls at North Avenue Beach. Planes have to go up in an orderly, timed fashion. The air traffic controllers dictate when those planes take off.”
United on Wednesday afternoon was reporting arrival delays of up to one hour and 26 minutes and departure delays of up to two hours.
By 4 p.m., however, “flight schedules were back on track, back to normal, with only a few exceptions,” Howard said. “Tomorrow, all will be well in the kingdom again.”
The Aurora control facility, which opened in 1962, was part of a national building design program to help vital government buildings survive nuclear attack. The control room, where the radar screens are located, has walls made of 16 inches of reinforced concrete and was designed to reduce radiation to an acceptable level.
Air intakes are shuttered with steel to provide protection from a bomb blast.
The control center has two IBM 3083 computers. The first forwards to controllers flight and radar data, while the second acts as a backup. In addition, there is another backup, called the Direct Access Radar Channel system. It bypasses the computers and provides data directly to the controller’s screen.
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If the primary radio system fails, the center switches to a backup that uses a different route of transmission.
If the main electrical supply is cut, backup systems use battery power and power produced by on-site generators.
But there apparently is no backup to guard against an electrician who makes a bad connection.