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This Project Blue Book file, released through The Black Vault, covers the RB-47 encounter of 17 July 1957 over Mississippi, Louisiana, Texas and Oklahoma. It includes the record card, which lists the sighting as identified as American Airlines flight 655, and Air Defense Command correspondence that carried the sighting as unknown. There is also Major Lewis D. Chase's observer data sheet and an electronic analysis finding it difficult to conclude nothing was present. James McDonald's reconstructed account is included, along with a CAA letter about airliner incidents.
Read from the scan by GLM-OCR; expect the odd misread word.
The same toggle switch that applies, or removes, the +28 volts from relay K-701 also does the same for relay K-301, whose function is to apply the correct polarity excitation to the synchro-resolver rotor. IF RELAY K-301 SHOULD FAIL TO ACTUATE WHEN THE TOGGLE SWITCH IS THROWN TO THE "VERTICAL" POSITION, THEN THE BEARING-TO-THE-RADAR DISPLAYED BY THE ALA-6 WILL BE 180° IN ERROR. AS THE AIRCRAFT FLIES PAST THE RADAR, THE INDICATED BEARING THEN WILL MOVE UP-SCOPE INSTEAD OF DOWN-SCOPE.
Thus, if K-301 failed to actuate when McClure positioned the toggle switch to the "Vertical" position (to coincide with the known vertical polarization of the CPS-6B radar at Biloxi), the bearing displayed on the ALA-6 not only would be $ 1 8 0^{\circ} $ in error (pointing out toward the Gulf, as reported), but the bearing would move up-scope as the RB-47 proceeded toward Meridian, also as reported. [This is shown in Fig. 4 in a not-to-scale representation.]
According to McClure's recent recollection, the displayed bearing moved from approximately 5 o'clock to roughly 1 o'clock during the approximately 5 minutes which he "worked" the signal. This would be the angular movement expected if the RB-47 was within approximately 20 miles of the Biloxi radar.
In the mid-1950s, at the time the ALA-6 was built, the two principal sources of equipment malfunctions were vacuum tubes and relays. Analysis of subsequent events in the RB-47 mission, to be discussed shortly, suggests that the malfunction of K-301 was an intermittent or temporary one and that it later resumed normal operation.
This could have resulted from an imperfect, cold-soldered, connection to relay K-301 terminals, or within its solenoid coil. Another possibility is that moisture accumulated in the relay during a humid July day may have frozen as the RB-47 climbed to altitude, preventing the K-301 armature from operating when McClure first applied power to the ALA-6 as he neared Biloxi. However, after a few minutes of operation, the heat from the relay solenoid and other electrical devices on the antenna could have melted the ice, allowing the relay armature to operate normally, thereby curing the $ 1 8 0^{\circ} $ ambiguity.
ANOMALOUS BEARING Caused by malfunction of K-301 or K-701.
The same sort of $ 1 8 0^{\circ} $ ambiguity could also result if relay K-301 functioned properly but antenna-dish switching relay K-701 failed to actuate. Under this condition, the ALA-6 would be operating from an antenna dish of the opposite polarity to that selected by the operator. Normally this improper polarization discrepancy should be readily apparent to the ALA-6 operator as his flipped his toggle switch seeking the optimum signal. However, because the RB-47 was so close to the powerful CPS-6B at Biloxi, the difference in signal strength might not be detectable.
Beyond the possibility of an $ 1 8 0^{\circ} $ ambiguity caused by a malfunction of relay K-301 or K-701, there are other sources, such as an intermittent malfunction in the deflection amplifiers or in the synchro-resolver.
McClure says that he abandoned the anomalous S-band signal after about 5 minutes, without notifying the aircraft commander or the other two Elint (ECM) operators. Some Document, cited by the archive. The PDF is mirrored here; the original link is above. The text was read from the page images by GLM-OCR; expect the odd misread word. 57 pages are in the text index: search them above, or from the library's search.