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Subject:   RADCAT No. 1.
Date:       October 15, 1948   TIME: 2305 local   CLASS: R/V   air radar/air visual                     
Location: Kyushu, Japan
Sources:  Hynek 1978, 135; McDonald 1968 (House Symp.), 69; Ruppelt, 65

RADAR DURATION: 10 minutes overall

(6 separate episodes)
EVALUATIONS: Blue Book - unknown
Martin Shough:
PRECIS: At 2305 a 2-seat F-61 Black Widow night-fighter was flying off the NW coast of Kyushu, 50 miles at 330 degrees from Fukuoka, when the radar operator picked up a target, range 5 miles at 12 o'clock & slightly below the aircraft (a/c). The a/c speed was between 200 & 220 mph; that of the target was 200 mph, range slowly closing. The aircrew thought they had a friendly fighter. Then the target showed a "slight" change in azimuth and "rapid" closure, appearing at the same time to dive below the a/c. The pilot attempted to follow in a 3500 fpm dive at 300 mph, but air intercept (AI) radar did not immediately reacquire the target. Shortly the radar operator called a second contact, but the target outdistanced the a/c with "a burst of speed dead ahead". On a third intercept the pilot called a visual at 60 degrees to port; the object was visible in clear silhouette against moonlit cloud and the radar acquired a target crossing ahead of the a/c from 45 degrees to port, range 3000' at -5 degrees elevation. The pilot turned to starboard to head off the object, but the radar target put on a "burst of speed" and was lost at 9-10 miles (maximum radar range was 10 miles). At this time the pilot decided that the object he had seen was unfamiliar and queried his ground control station, who reported that there were no known aircraft in the area. The fourth intercept again began with a pilot visual, the object passing above and from the rear. AI radar again picked up the target slightly above at 12 o'clock, range 5 miles, but again it was lost off the set at 10 miles. The fifth and sixth intercepts were similar: The target was picked up at > 9 miles range at 200 mph, the a/c closing with a speed advantage of 20 mph to a range of 12,000', at which point the target pulled ahead to the maximum radar range of 10 miles in about 15-20 seconds.

Visuals: an "excellent silhouette" against a reflective moonlit undercast on the 3rd intercept, and a "fleeting" glimpse of the object passing from above and behind on the 4th intercept. The object appeared as a stubby cigar with a tapering, squared-off tail-end, a little like a "rifle bullet" the approximate size of an a/c fuselage; it had a dull or dark finish, with no visible features or control surfaces. There were no other a/c in the area, and there was no ground radar contact with the object. Target altitudes were between 5-6000'.

NOTES:  The fact that no ground radar contact was reported is difficult to interpret; according to the intelligence report the F-61 was detected by ground radar during the incident, but only intermittently. According to McDonald, "The report indicates that this may have been due to 'ground clutter'." However the area of the incident is 50 miles out in the Korea Strait between the Tsu Islands and the west coast of Japan. A more likely reason for intermittent painting of the F-61 is that it was flying at or below 6000' at range 50 miles, a line-of sight elevation on the order of 1 degree and thus close to the likely radar horizon. This might well make the a/c a marginal target whose detectability was critically dependent on aspect. The visual description of the "UFO" - a smoothly moulded appearance without visible canopy, wings, power section or tail assembly - is consistent with a target of very much smaller radar cross-section than the F-61 at any aspect, making it a very much more marginal target even than the "intermittently" detected F-61.

Of six separate AI contacts two were visually corroborated, one by an "excellent silhouette" which resembled no known controlled aeroform of 1948 and is difficult to equate with birds, clouds, windblown debris or balloons. Perhaps the most plausible explanation is that the pilot saw the shadow of his own a/c on the moonlit undercast. The second "fleeting" glimpse might be dismissed. Nevertheless on each occasion the AI contacts corroborated the visual observations in a natural way, picking up the target as the object would have moved into the forward scanning coverage of the radar - first time moving into the pattern at 45 degrees to port, range 3000' following a visual at 60 degrees; second time being picked up slightly above and at 12 o'clock, range 26,000', moving ahead of the a/c after a visual of the object passing above and from behind. Both acquisitions are consistent with the typical elevation-scan limits of this type of AI radar. The speeds and relative movements of the 6 targets on different headings and at different elevations are individually difficult to interpret in terms of anomalous propagation of ground returns, and collectively impossible to interpret in terms of the same set of AP conditions. At the same time the behavior of the targets exhibits a rational consistency which, supported by two corroborative visual observations, is strongly suggestive of a real radar reflective target.

On the 5th & 6th intercepts, the target accelerated away from the F-61 at a minimum relative speed of about 1400 mph, which, added to the aircraft speed, yields a true airspeed of well over 1600 mph. Clearly the target could not have been another aircraft. Yet the intelligence report notes that "the object seemed cognisant of the whereabouts of the F-61 at all times" as though it carried "radar warning equipment" and concludes that the airmen were "of excellent character and intelligence".  Both men felt strongly that the object was a controlled vehicle: "In my opinion," offered the radar operator, "we were shown a new type aircraft by some agency unknown to us." The first jets, the Gloster Meteor and the Messerschmidt 262, entered service in 1944, but the first flight to exceed Mach 1 was not achieved until 1947 by the experimental Bell X-1 rocket aircraft, and even if some historically unrecorded prototype development of the X-1 had achieved Mach 2 combined with combat-agility within 12 months one would hardly expect it to be idling around over the Sea of Japan.

In summary the 6 radar and 2 concurrent visual contacts are not easily interpreted in terms of known propagation anomalies or other natural phenomena, and there is a convincing impression of intelligent evasive flying by a vehicle with a performance greatly in excess of known aircraft capability in 1948.

STATUS: unknown