Simulated radar data, black-and-white

Paul Steucke
FAA Public Affairs
701 C Str eet, Box 14
Anch. AK 99513 March 5 , 1987
l:JNCORRELATED RADAR SIGNALS
Radar data received by the FAA and used to track Japan Airlines flight 1628
on the night of the November 17, 1986, was retained by FAA. Review of this
r adar data by FAA experts using identical equipment at the FAA's research
technical center in Atlantic City, New Jersey, revealed that the radar system
was receiving what is called an "uncorrelated primary and beacon target".
This electronic phenomena is not unusual according to Steucke who said, "It
is unfortunate that the uncorrelated target phenomena. occurred just when a
pilot was reporting seeing something outside his aircraft.
The controller's statements, released by the FAA, indicate that they thought
t here might be another aircraft or object in the area of the JAL flight.
Steucke said, "The controllers were doing their job right because they have to
work with what is right there in front of them on the screen, especially when
you have a Captain that is reporting "other traffic" in his immediate area.
The radar data they had was one target, moving slowly across the radar screen.
They don't have the benefit of "monday morning quarterbacking" with multiple
r adar images as was the case in regenerating the radar data." Review of the
radar data by FAA experts revealed the "uncorrelated target" phenomena.
FAA electronic technicians explained that an "uncorrelated primary and
beacon target" on the radar screen occurs when the radar energy that is sent up
toward t he aircraft, (primary signal) returns to the radar receiver along with
the aircraft transponder (beacon) signal and the two do not match up as being
at the same exact location.
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