Analysis of Uncorrelated Primary and Beacon Targets (JAL-1628, 11/17/86 AKST)

This document contains a technical analysis of radar data associated with the Japan Airlines (JAL) flight 1628 incident on November 17, 1986. The report, authored by Dennis R. Simantel of ZAN-AAL-ARTCC, examines approximately 61 minutes of data extracted from EARTS CDR printouts. The primary objective of the analysis was to investigate the radar returns that occurred during the flight, which the pilot had associated with an alleged UFO sighting. The FAA's review, conducted using identical equipment at the FAA's research technical center in Atlantic City, New Jersey, concluded that the radar system was receiving what is termed an 'uncorrelated primary and beacon target.' The report explains that this phenomenon occurs when the primary radar energy reflected off the aircraft's surface and the secondary beacon transponder signal do not match up at the exact same location or computer radar cell. The analysis notes that 72 percent of the replies were radar with beacon reinforcement, which is considered normal for the Murphy dome radar system. Approximately 25 percent were beacon-only replies, with 90 percent of those having a primary-only reply within 1/8 of a mile. The document includes several regenerated radar images and charts illustrating the flight path of JAL 1628 and the nature of these radar returns. The FAA concludes that the data does not show any abnormalities associated with the pilot's report and that the observed radar behavior is representative of normal operations for aircraft in that area. The document also includes a memorandum from David F. Morse, Manager of the Airway Facilities Division, concurring with the interpretation provided by the Alaskan Region Air Traffic Division.