Project Blue Book file, RB-47, July 17, 1957

Read from the scan by GLM-OCR; expect the odd misread word.

would be approximately 20 $ ^{\circ} $ . Chase accelerated the RB-47 as the "object pulled ahead" [Piwetz account] in an effort to close on it. [Chase's original Airborne Observer's report says the RB-47 accelerated to Mach 0.83, but his more recent recollection is that he was near maximum speed, or at roughly Mach 0.87.]

At 10:42.52, the ALA-6 once again showed TWO S-band signals, with bearings of $ 4 0^{\circ} $ and $ 7 0^{\circ} $ . If the RB-47 had by this time completed its turn onto the new $ 3 2 0^{\circ} $ heading, the bearing to Duncanville would have been roughly $ 1 5^{\circ} $ , but the bearing would be larger if the turn was still in process. So far as the Piwetz report shows, and Chase's current recollection, there was only a single visual target.

At 10:44Z, the ALA-6 once again showed only a single S-band signal, with a bearing of $ 5 0^{\circ} $ . The estimated bearing to Duncanville, assuming the aircraft was not maneuvering, should have been roughly $ 1 0^{\circ} $ .

At 10:48Z, the Duncanville station asked the RB-47 to turn on its radar transponder to Mode III "for positive identification, then requested (crew to advise) position of object." [This seems curious because the air defense radar personnel should have been able to identify the RB-47 some minutes earlier when assistance was first requested, considering the typically light traffic in the pre-dawn hours. The radar had height-finder beams so it should have been quite easy for experienced operators to identify the RB-47 from the pilot's estimated position and reported altitude.]

When the RB-47 crew "reported position of object as 10 nautical miles northwest of Ft. Worth, Texas" [Piwetz account.], the radar station "immediately confirmed presence of object on their scopes." [Again, it seems curious that an air defense radar station had overlooked an unidentified craft until the RB-47 called attention to it. This almost suggests an inexperienced or inattentive radar station crew.]

At "approximately 10:50Z object appeared (to flight crew) to stop and aircraft overshot. Utah (radar) reported they lost object from scopes at this time, and EC4 #2 (McClure) also lost signal." If the ALA-6 signal was coming from the Duncanville radar, it would logically disappear from McClure's scope at about this time because the RB-47 was now so close that it no longer would be illuminated by the Vertical- Center beam to which the ALA-6 and APR-9 were tuned (2,995-3,000 mc.) A possible explanation for why the Duncanville radar lost its unidentified target and the RB-47 crew lost its visual target will be discussed shortly.

The RB-47 commander, thinking he had overshot the UFO, began a turn to the left shortly after passing between Dallas and Ft. Worth. At roughly the same time (which estimate to be 10:51Z), "ECM #2 picked up signal at $ 1 6 0 ^{\circ} $ relative bearing." Reference to Fig. 6 shows that by this time the RB-47 would now be far enough away from the Duncanville radar so that it would again be illuminated by the Vertical-Center beam. And the bearing to the radar would be roughly $ 1 6 0 ^{\circ} $ , as McClure observed. [For coverage of Vertical-Center beam at RB-47 flight altitude, see Appendix B.]

At the same time, "Utah (radar) regained scope contact and aircraft commander regained visual contact." This is believed to be an error in the Piwetz account, according to extended correspondence with pilot Chase, who is certain that the new visual contact did not occur until several minutes later. IF there was visual contact at this time, the "object" could NOT POSSIBLY BE THE ONE GENERATING THE S-BANU SIGNAL ASTERN OF THE RB-47 (160 $ ^{\circ} $ ) BECAUSE THE FLIGHT CREW COULD NOT LOOK IN THIS DIRECTION AT AN OBJECT BELOW RB-47 FLIGHT ALTITUDE. IF the Utah radar operators advised of the position of their new unidentified radar target, this is not indicated in the Piwetz account.