New England air traffic control systems crash

A bad data interface may have frozen the IBM Corp. mainframe the Federal Aviation
Administration uses for air traffic control, causing radar screens to go blank at New
England airports for more than 37 minutes on Aug. 19, FAA officials said.

The systems failure kept airplanes grounded as air traffic controllers passed
handwritten notes to each other to keep track of aircraft already in flight.

A technical group from FAA’s William J. Hughes Technical Center in Atlantic City,
N.J., is studying whether the breakdown occurred when systems in the Bradley International
Airport Control Tower in Windsor Locks, Conn., tried to send data to the IBM 3090 Host at
the Boston Air Traffic Control Center in Nashua, N.H., an FAA official said.

“We don’t know why it happened,” the FAA official said.

The interface problem is likely the leading cause, a National Air Traffic Controllers
Association official familiar with the failure said.

“We heard there was a problem with software. We also heard there was flight data
information that was sent from Bradley that the Host interpreted as erroneous,” said
Mike Blake, regional vice president of NATCA’s New England Region and a controller at
the center. “We heard it got to the point where it kept sending erroneous
information, and the computer shut down.”

Controllers use the Host in tandem with the Computer Display Channel displays, which
provides aircraft identification, altitude, beacon code and other information concerning
aircraft, Blake said. The CDC displays went black when the Host locked up, he said.

The computer failure occurred at 7:51 p.m.. The Host failure occurred as 75 controllers
were directing 340 aircraft, FAA spokesman Jim Peters said.

As soon as the screens went black, the center switched to the Direct Access Radar
Channel, the backup system that processes display information, Peters said.

The transition takes several seconds, Peters said. Radar target information is updated
every 10 seconds at remote radar sites across FAA’s New England region, so navigation
data wasn’t lost and safety was not compromised, Peters said.

FAA rebooted the IBM mainframe and returned to normal service at 8:28 p.m. Air traffic
was reinstated at 8:38 p.m., Peters said.

DARC also experienced glitches when it was turned on, Blake said. “Information was
coming up on DARC saying that it was not certified. We did not know if the information was
reliable,” he said.

Maintenance had been scheduled for DARC eight minutes after the lockup occurred, which
may have explained why the “not certified” errors came up, Blake said. If DARC
maintenance had occurred before the failure, controllers would have been without a backup
system, he said.

“This is one of several hundreds hits the computer has taken recently,” Blake
said. “I attribute these outages to the age and use of the equipment. The computers
use 1960s technology, which shelf-life expired in 1988.”

A similar computer lockup occurred in mid-June but was shorter than the Aug. 19
incident, Blake said.

The CDC displays’ reliability was 98.71 percent between June 1997 and June 1998,
Peters said. FAA officials will begin replacing the aging CDC with the Display System
Replacement this month, Peters said.

The new system will replace 20- to 30-year-old displays, controller workstations,
network infrastructure and associated software used in the control of aircraft before
landing and after takeoff, Peters said.

It will receive aircraft track information and other data from the Host and the
Enhanced Direct Access Radar Channel, he said. 

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