Radar unit shut down after Air Force One incident
     WASHINGTON - March 12, 1998 12:24 p.m. EST -- A radar unit that
 failed to display complete tracking information about Air Force One
 this week has been taken off line for unrelated repairs.
     The shutdown slowed flights between Boston and Philadelphia,
 which had to be tracked on two backup systems Wednesday. When the
 aircraft descended below 8,000 feet, they were controlled using non-
 radar procedures such as voice commands.
     The long-range radar unit in question, based in Gibbsboro, N.J.,
 was the same one in use last October when a Swissair Boeing 747 was
 forced to make a steep dive over New Jersey after the radar failed
 to spot a single-engine plane 400 feet away from the jumbo jet.
     Officials at the Federal Aviation Administration said that was
 the result of a radar coverage problem that had since been corrected,
 but air traffic controllers said they have been having daily data
 "dropouts" since the unit was put back into service on Feb. 15.
     Randy Schwitz, executive vice president of the National Air
 Traffic Controllers' Association, said the problems have included
 "missing targets, jumping targets and multiple targets."
     The controllers' union joined the FAA in saying that the presi-
 dent was never in danger.
     After a daylong investigation, the FAA said Wednesday it had
 determined that the Gibbsboro ARSR-4 unit displayed incomplete in-
 formation on two of three consecutive sweeps Tuesday, as Air Force
 One flew past New York City en route to Connecticut.
     The incident occurred at 8:34 a.m. as the plane was descending
 from 22,000 feet about 10 miles southeast of Kennedy Airport.
     On the first 12-second sweep, an air traffic controller on Long
 Island saw Air Force One's identification label and airspeed indica-
 tor, but not an altitude indicator or a dash symbol that normally
 represents an airplane, FAA spokesman Eliot Brenner said.
     On the second sweep, all four data elements appeared, but on
 the third sweep, the altitude information again disappeared from
 the controller's screen. The controller never lost radio contact
 with the plane during the 36-second span, and no other aircraft were
 in the area.
     "There was never any kind of safety question about the presi-
 dent's aircraft and there was never any loss of contact with it,"
 Brenner said. He said the problem may have resulted from computer
 confusion as the aircraft traveled between radar boundary areas or
 as its radar signature mirrored that of another plane traveling in
 the same direction.
     The radar was taken out of service Wednesday, but only to repair
 a cracked strut on its antenna support.
     Forty-four of the $8 million digital radar units are in use
 across the country. Brenner said the FAA would consider a unit
 problematic if it did not display data for three consecutive sweeps,
 but it has no report on any such extended blackout.
     The incident off Long Island is the latest in a string involving
 the president's plane, which is always referred to as Air Force One
 whether it's the Boeing 747 in use Tuesday or any number of smaller
 aircraft in the VIP fleet at Andrews Air Force Base.
     On Jan. 28, Air Force One passed a Delta jet outside Washington
 slightly inside the normal three-mile separation buffer. Later that
 same day, as the plane was preparing to leave Champaign, Ill., it
 ran off a narrow taxiway and got mired in mud. A backup aircraft had
 to be used to complete the trip.
     On May 27, air controllers ordered Air Force One to turn and
 gain altitude after it came close to a United Parcel Service plane
 off the coast of Ireland. The two planes were never closer than
 1000 feet in altitude and three miles in distance.
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