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This FAA package, released through The Black Vault, covers regenerated radar data for Japan Airlines flight 1628 over Alaska on November 17, 1986. It contains photographs of the regenerated radar image taken by Paul Steucke on January 7, 1987, and a chart of the flight track. It also includes a March 5, 1987 public affairs release, a February 27, 1987 Airway Facilities memo and Dennis Simantel's analysis. These attribute the radar returns to uncorrelated primary and beacon targets, which they call normal for the area.
UNCORRELATED RADAR SIGNALS An "uncorrelated primary and beacon(secondary) return on a radar screen occurs when the radar energy that is sent up toward the aircraft (primary signal) returns off the surf ace of the aircraft at a slightly different moment than tbe beacon (secondary) transponder signal and the two do not match up as being at the same place or same computer radar cell. ----------11~--------- --RADAR COMPUTER CELL, 1/4 MILE-- --v'- SECONDARY RADAR RETURN (Beacon) (Transponder) 1/ FAA RADAR Drawing by Paul Steucke March 5, 1987 SAME AIRCRAFT PRIHARY RADAR RETURN (Skin- Surf ace) RADAR CELL =PRIMARY RAD~ RETURN =SECONDARY RADAR RETURN =CORRELATED RETURN (Combined Return) =UNCORRELATED RETURN /
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