Telephone glitch lets planes get too close

By Rogers Worthington Tribune staff reporter July 10, 2001 A problem with telephone lines led to a communications breakdown Monday at the air traffic control facility in Aurora, playing a key role in the failure of two planes to maintain safe distances between them, federal officials said.

Air traffic controllers lost contact with four remote radio transmitters and could not communicate with a TWA MD-80 bound from O'Hare International Airport to St. Louis, and a Beechcraft Super King Air 200 traveling from St. Louis to Minneapolis-St. Paul as the planes approached Burlington, Iowa.

"At the time it was a pretty critical situation. We had two aircraft on a converging course and no way to talk to them," said Bryan Zilonis, the representative for the National Air Traffic Controllers Association at the FAA's Chicago Air Route Traffic Control Center in Aurora.

"The pilot [of the TWA MD-80] would go to a different frequency, but there was no answer," said Julia Bishop Cross, a spokeswoman for TWA in St. Louis.

Instead of the required lateral and vertical separation distances of 5 miles and 1,000 feet, the two planes were about 4 miles apart laterally and 500 feet vertically, according to the FAA. The incident occurred about 10:45 a.m. The loss of separation was not great enough to be classified as a near collision or to activate onboard collision-avoidance alarms, officials said.

The communication problem, which lasted at least two hours, was caused by an unexplained disruption of the telephone land lines that relay instructions from air traffic controllers at the Aurora facility to radio transmitters in four sectors of eastern Iowa. The disruption was likely to have occurred near the Aurora center because the lines separate as they proceed toward transmitters in different sectors.

The MD-80 was carrying 140 passengers. The King Air, owned by Thunder Aviation Acquisitions of Dover, Del., can carry eight passengers, but it was not known how many were on Monday's flight.

FAA spokesman Tony Molinaro said MCI handles the telephone lines that carry radio traffic from the Aurora facility.

What was especially unusual about the situation Monday, said air traffic controllers, was that there were no backup telephone lines available.

"If there were backup lines, they didn't work," said Bill Cound, air traffic manager at Aurora. "I can't recall the last time we had that kind of outage. We lose a radio site from time to time ... but we have at least two levels of backup [telephone lines] for every frequency. So it is a fairly rare occurrence," he said.

Communications have been restored, but the source of the problem was still being investigated late Monday, Cound said.

The breakdown did not cause delays at O'Hare, but westbound traffic was rerouted to avoid the sectors in Iowa where communications were out, said Monique Bond, the airport's spokeswoman.

http://www.chicagotribune.com/news/metro/lake/article/0,2669,SAV-0107100321,FF.html

-- Martin Thompson (mthom1927@aol.com), July 10, 2001