July 28-29, 1952; 20 miles W. of Port Huron, Mich. (BBU) [CCL Item #17)

9:40-10 p.m. (EST). One of 3 USAF F-94B's on an ECM exercise at 9,000-9,500 ft from 61st FIS at Selfridge AFB climbed to 20,000 ft on a 270° heading when it was vectored to a UFO headed S [or SE?] at 625 mph from Saginaw Bay by a GCI air defense radar (callsign Avenger) [tracked for about 7 mins evidently]. Ground radar told pilot Capt. Edward J. Slowinski (Sloan) to look at his 3 oclock low position for a target (to the N), but nothing was found, then told to look at 3 oclock high (radar man remembered being told low then high, pilot said he was told high then low). F­94 turned right to pursue. Object suddenly reversed course with a tight 180° turn back N on ground radar scope [evidently at 300 mph to match F-94s speed, in a visible loop on the radar scope on a right turn paralleling the F-94s right turn but tighter]. As the F-94 continued right turn, radar observer Lt. Victor Helfenbein picked up target at 4 miles range on APG­33 airborne radar, level with jet altitude, at 60° relative or 2 oclock (about 330° to 360° azimuth depending on how far into the turn) (pilot said Helfenbein reported 2:30 oclock). Airborne radar contact made [for possibly 20 secs during the turn] then at dead ahead 12 o'clock position radar got lockon for 30 secs until target jumped lock when it apparently almost doubled its 4-mile [or 4-5 mi] distance in one sweep of the ground radar accelerating to 1,400 mph average speed [4-mile jump in 10-sec sweep of radar, thus reaching peak 2,600 mph at about 20 gs]. Jet briefly put on afterburner to try to close distance with object on 360° heading at 21,000 ft increasing speed with afterburner to about 350 knots IAS (about 490 knots TAS or 560 mph) [for about 5 mins?], but object would put on a burst of speed and pull away from the jet. F-94 pilot first saw multiple lights ahead as if from a jet aircraft, but no exhaust or trail, and followed the GCI vectoring to target ahead between 12 oclock and 1 oclock positions. Object appeared many times larger than a star then took on a reddish tinge, and slowly began to get smaller, as if reddish then bluish-green then white then red again in sequence (both crewmembers in agreement) low on the horizon to the N (possibly the star Capella and unrelated to radar target, though Helfenbein was an expert celestial navigator since 1943 with 1,400 flying hours and had never seen anything like this before). F-94 continued N heading [for about 5 mins] at about 300 mph as object maintained lead at 6-10 miles range, with GCI telling F-94 crew they were not gaining on the target on scope. Chase ended with F-94 about 5 miles N of peninsula at Burnt Cabin Point (at 44°10N, 82°45W) having to return because of low fuel, object then slowed to 200-300 mph before disappearing after another 1-2 mins. 20-mins. (McDonald 1968; McDonald papers; Mary Castner/CUFOS; Loren Gross July 21-31, 1952 SUPP pp. 71-77; Ruppelt pp. 171-172, 190; BB Status Rpt 8; Todd Lemire)