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

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

From 11:20Z (or 11:02Z) until 11:40Z, the ALA-6 was again showing an S-band signal with a measured bearing of "between 180 $ ^{\circ} $ and 190 $ ^{\circ} $ . " The signal "faded rather abruptly" as the RB-47 neared Oklahoma City, according to the Piwetz account.

This is precisely what would be expected if the S-band signal were coming from the Vertical-Center beam of the Duncanville radar, which would be at a bearing of roughly $ 1 8 0^{\circ} $ as the RB-47 headed north. (See Fig. 6.) Furthermore, the signal should disappear as the RB-47 neared Oklahoma City, for this would be the outer limit of coverage of the beam at the airplane's flight altitude.

On Sept. 5, 1971, I first wrote to ALA-6 operator McClure, seeking clarification of some aspects of this case. In his reply, dated Sept. 10, McClure volunteered the following view:

"I personally think that there was no airborne signal of this nature, so I can only say that it [i.e. the anomalous signal near Biloxi] must have been caused by some other reason, unknown to us. I also think later we became mixed up with signals from Houston, Dallas or Oklahoma City, all of which had operational CPS-6B radars." [Actually, these were FPS-10 radars with signal characteristics identical to the CPS-6B.]

In a subsequent telephone conversation and later correspondence, McClure re-stated his opinion even more emphatically.

If the CPS-6B type signal had indeed come from an airborne vehicle, the signal would have been within receiving range of the air defense radars at Houston, Dallas and Oklahoma City at various times between 10:40Z and 11:40Z. Such a signal could be expected to cause severe interference with one or more of these ground radars, if it came from an airborne source within receiving range. YET THERE WAS NO REPORT OF ANY SUCH INTERFERENCE FROM ANY OF THESE RADARS, SO FAR AS IS KNOWN.

Furthermore, if there had been an unknown craft flying in the vicinity of the RB-47 from the time it neared the coast until roughly two hours later when it neared Oklahoma City, it is strange that the unknown craft was not spotted by any of the many air defense radar stations in Mississippi, Arkansas, Louisiana, Texas or Oklahoma, except for the brief, sporadic report from the Duncanville station.

Curiously, the formal teletype report filed by the Duncanville radar station commander to Air Defense Command Headquarters within four hours of the incident (14:45Z, July 17, 1957) denies that the UFO appeared on the station's scope! The report says: "UTAH (Duncanville radar) HAD NEGATIVE CONTACT WITH OBJECT."

This seems to contradict statements by the RB-47 crew members, yet there is no reason to question the veracity of the latter. The most logical explanation for this apparent discrepancy is that between the time of the incident (roughly 10:50Z) and the time of the report (14:45Z) the unknown target on the Duncanville radar scopes had been identified as an ordinary airplane!

If this were the case, the Duncanville station commander might well have been too embarassed to admit the temporary "goof" of possibly inexperienced operators and would logically try to minimize the whole incident with the cryptic report: "NEGA- TIVE CONTACT WITH OBJECT." By the time the unknown was identified, the RB-47 could have been well beyond direct radio communications range of Duncanville.