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This FAA release, obtained through The Black Vault, collects material on the radar data from Japan Air Lines Flight 1628 over Alaska on November 17, 1986. It includes a March 5, 1987 explanation by FAA public affairs officer Paul Steucke, a February 1987 Airway Facilities memo, and Dennis Simantel's analysis attributing the returns to uncorrelated primary and beacon targets, considered normal. It also contains regenerated radar image photos and a Philadelphia Inquirer magazine article on the sighting and the FAA's inconclusive review.
ANALYSIS OF UNCORRELATED PRIMARY AND BEACON TARGETS (JAL-1628, 11/17/86 AKST) Approximately 61 minutes of data was extracted from the EARTS CDR printouts relating to the November 18 incident involving JAL-1628 and the alleged UFO sighting. Review of the data involving this incident did not show any abnormalities that could be associated with any type of target as indicated by the pilot - of JAL-1628. Radar returns from the aircraft and surrounding terrain vary with the different segments of the flight, but are considered normal for the area. Returns relating to the incident can be categorized as three types: primary radar reinforced by a beacon reply (primary radar returns and beacon returns are both evident in the same 1/4 mile range cell), beacon only reply and beacon with an associated radar reply. Seventy-two percent of the replies were radar with beacon reinforcement (same range cell) which is normal for the Murphy dome radar system. Approximately 25 percent were beacon only and of those that registered as beacon only, 90 percent of those had a primary only reply within 1/8 of a mile, either ahead or behind the beacon target (.-8" behind, .l-2"' ahead) . ~ ~/3/ 137 ~ 13 These uncorrelated primary returns are not uncommon, due to the critical timing associated with the delay adjustments in the aircraft transponder for beacon systems and the target correlation circuitry within the radar equipment. When an aircraft is being interrogated as it passes through the beginning of adjacent range cells the intricate timing between the two systems very often is off just enough to declare both a beacon and a radar target in different range cells, resulting in uncorrelated radar replies. The data derived from the JAL-1628 flight is representative of the data from another aircraft in the same general area and is considered normal. February 25, 1987 -us.""Dennis R. Simantel ZAN-AAL-ARTCC /
Document, cited by the archive. The PDF is mirrored here; the original link is above. 19 pages are in the text index: search them above, or from the library's search.