Air Force One Lost on Radar Again

For the second and then third time in three months, Air Force One disappeared Friday from radar screens while approaching New York’s crowded airspace, bringing into focus an aviation safety problem that air traffic controllers warned is much more widespread than is publicly recognized.

Controllers and the Federal Aviation Administration, often at odds with each other, agreed that President Clinton and others aboard the modified Boeing 747 were not in danger as they flew from Andrews Air Force Base to Massachusetts. Radio contact with the ground was not interrupted, officials said.

But controllers said--and the aviation agency eventually acknowledged--that the problem which caused Clinton’s plane to blink out of sight for perhaps a minute occurs routinely. Controllers said that as many as 50 aircraft are lost each day for up to a minute along one of the nation’s busiest air corridors and no accidents have resulted.

The loss of radar data is but one of a wide range of problems raising questions about the effectiveness of the nation’s burdened air traffic system.

Air traffic controller errors have increased 21% in the last year, with the most troublesome trends involving communication snafus and memory lapses that can compromise air safety, the Washington Post reported Friday.

In airport control towers, where controllers handle numerous complicated aircraft movements, these lapses often involved visual misjudgments, according to internal FAA documents obtained by the newspaper. The documents showed that error rates were the highest in the New York region, with tower operations making 1.69 errors per 100,000 operations at La Guardia Airport and 1.38 errors at John F. Kennedy International Airport. The New York regional control center, which handles flights entering the New York airspace, also had the highest error rate, 1.98, compared with a national average of 0.55, the newspaper said.

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Responding to an incredibly close near-collision in which two passenger jets came within 20 feet of each other over La Guardia on April 3, the FAA said Thursday that it was sending 10,000 of the nation’s 18,000 air traffic controllers to a proficiency retraining program.

On Friday, a problem in computers handling arrivals and departures from New York area airports caused massive delays there.

Controllers said Friday that the problem involving Air Force One was one of equipment failure rather than human error or the intense pressure they experience on the job every day as they direct the nation’s aircraft through 180,000 landings and takeoffs.

“Preliminary information indicates that, for three sweeps of the radar, complete information on Air Force One was not available,” the aviation agency said in a carefully worded statement. Each radar sweep takes about 12 seconds.

“The incident occurred at 8:11 a.m. [EDT] and involved the Gibbsboro, N.J., radar. Safety was not compromised and communications were maintained with the aircraft at all times,” the FAA said.

In a subsequent statement, the agency said that a similar problem occurred six minutes later, when the aircraft had traveled about 42 miles to the northeast.

As described by FAA spokesman Eliot B. Brenner, such problems occur when aircraft, although separated by significant distance in altitude, momentarily fly close enough together to confuse radar-receiving computers. The planes cancel each others’ signals, much as the music broadcast on two nearby radio frequencies are heard as static. Unable to distinguish which plane is which, the radar computer is programmed to momentarily drop both from its screen.

The FAA said that one hour after the second problem with Air Force One, controllers tracking a commercial airliner 15 miles west of JFK observed the same effect coming from a radar station in Pennsylvania.

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On March 10, Air Force One’s radar signal, which tells controllers the plane’s position, its speed and direction, disappeared from air traffic controllers’ screens while the plane was flying at 21,000 feet about 10 miles southeast of JFK. It was traveling from Andrews to Hartford, Conn.

The incidents Friday began at 27,000 feet over Robinsville, N.J., southeast of Trenton, air controllers said. Clinton was flying to Hanscom Field, in Bedford, Mass., at the start of a trip during which he spoke at the Massachusetts Institute of Technology commencement and at Walden Pond outside Boston.

The president’s aircraft is routinely assigned an altitude from which all other aircraft are barred to provide it with a secure corridor and thus decrease the likelihood of a collision.

At the time of the March incident, the FAA said, the disappearance lasted 12 seconds; controllers said it was 24 to 36 seconds.

Joseph S. Fruscella, an air traffic controller and Eastern regional vice president of the National Air Traffic Controllers Assn., attributed that incident to a crack in a radar antenna in the agency’s Gibbsboro center, which went into operation in October and which led controllers to complain to agency officials.

“We told them, ‘Please do not put that radar back in service; it’s not working,’ ” he said.

The FAA’s Brenner acknowledged such a crack was found but said it was repaired.