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

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

virtue of representing a summary account prepared while all of the details were fresh in the minds of the doctors.

there describing the first ECM connect. It is necessary to explain initially the nature of the ECM gear involved in this case. (Details are no longer available, although all of the basic case-file documents were initially SFCREET) This 1947 find three passive direction-finding (DF) radar monitors for use in securing coordinate information and pulse characteristics on enemy ground-based radar. The 2 monitor, manned by McClure, was an ALA-6 DF-receiver with back-to-back antennas in a housing on the belly of the RB-47 near the tail spun at 150 or 300 rpm as it scanned an azimuth. (Note that this implies ability to scan at 10/sec past a fixed ground radar in the distance.) It's frequency range was 1000-7500 MHz. Inside the aircraft, the signals from the ALA-6 were processed in an APR-9 radar receiver and an ALA-5 pulse analyzer. All subsequent references to the 2 monitor imply that system.

## Number : Monitor

The =1 monitor, manned by Provenzano, was an APD-4 DP system, with a pair of antennas permanently mounted on either wing tip. It was working at a higher frequency. The =5 monitor, with a frequency range from 30-1000 MHz, was manned by Tuchscherer. It was not affected and will not be described here. VHF communications were likewise not affected.

For emphasis, it needs to be stressed that the DP receivers are not radars and do not emit a signal for reflection off a distant target. They only listen passively to incoming radar signals and analyze signatures and other characteristics. When receiving a distant radar set's signal, the scope displays a pip or strobe at an azimuthal position corresponding to the relative bearing in the aircraft coordinate system. For the case of a fixed ground radar, approached from on, the strobe is initially seen in the upper part of the scope and moves down-scope, a point to be carefully noted in interpreting the shading discussion. During compaction the navigational records over the Gulf, Cituse headed across the Mississippi coastline. Flying at an altitude of 34,500 ft. at about Mach 0.75 (258 kt IAS=500 mph TAS). The weather was perfect and practically cloudless under

the influence of a large high-pressure area extending throughout the troposphere. There were no showers or thunderstorms anywhere along the flight route. Shortly after the coast near Gulfport was crossed at a point marked A on the map in page 00. McClure detected on the #2 monitor a signal painting at their 5 o'clock position (aft of the starboard beam). It looked to him as if he were receiving a legitimate ground-radar signal. Upon noting that the strobe was moving up-scope, McClure tentatively decided that it must be a ground radar off to their northwest painting with 180 deg ambiguity for some electronic reason. But when the strobe, after sweeping up-scope on the starboard side, crossed the flight path of the RB-47 and proceeded to move down-scope on the port side McClure said he gave up the hypothesis of 180 deg ambiguity as incapable of explaining such behavior.

Fortunately, he had examined the signal characteristics on his ALA-5 pulse-analyzer, before the signal left his scope on the port side aft. In discussing it with me, his recollection was that the frequency was near 2800 mcS, and he recalled that what was particularly odd was that it had a pulse-width and pulse repetition frequency (PRF) much like that of a typical S-band, ground-based, search radar. He even recalled that there was a simulated scan rate that was normal. Perhaps because of the strong similarities to grour.d-based sets such as the CPS-6B, widely used at that time, McClure did not, at that juncture, call this signal to the attention of anyone else in the aircraft. The #1 monitor was not working the frequency in question, it later developed. The #3 monitor was incapable of working the frequency in question, McClure and the others indicated to me.

I next quote information transcribed from the summary report prepared by the Wing Intelligence Officer. COMSTRATRECONWG 55. Forbes Air Force Base concerning this part of the incident that involved this aircraft (call sign "Lacy 17"):

ECM reconnaissance operator #2 of Lacy 17, RB-47M aircraft, intercepted at approximately Meridian, Mississippi, a signal with the following characteristics: frequency 2995 mc to 3000 mc; pulse width of 2.0 microseconds; pulse repetition frequency of 600 cps; sweep rate of 4 rpm; vertical polarity. Signal moved rapidly up the D/F scopes "cating

a rapidly moving source; i.e., an airborne source. Signal was abandoned after observation . . .

## Initial Visual Contact

If nothing further had occurred on that flight to suggest that some unusual object was in the vicinity of the RB-47. McClure's observations undoubtedly would have gone unmentioned and would have been quickly forgotten even by him. He was puzzled, but at that point still inclined to think that it was some electronic difficulty.

The flight plan called for a turn to the west in the vicinity of Meridian and Jackson, Mississippi (Point B), with subsequent planned exercises wherein the EWOs did simulated ECM runs against known ground radar units. The contemporary records confirm what Chase and McCoid described to me far more vividly and in more detail concerning the unusual events that soon ensued.

They turned into a true heading of 265 deg. still at Mach 0.75 at 34,500 ft. At 1010Z (0410 CST). Major Chase, in the forward seat, spotted what he first thought were the landing lights of another jet coming in fast from near his 11 o'clock position at, or perhaps a bit above, the RB-47's altitude. He called McCoid's attention to it, noted absence of any navigational lights, and as the single intense bluish-white light continued to close rapidly, he used the intercom to alert the rest of the crew to be ready for sudden evasive maneuvers.

But before he could attempt evasion, he and McCold saw the brilliant light almost instantaneously change direction and flash across their flight path from port to starboard at an angular velocity that Chase told me he had never seen matched in all of his 20 years of flying, before or after that incident. The luminous source had moved with great rapidity from the o'clock to about their 2 o'clock station and then blinked out.

The Airborne Observer's Data Sheet filled out by Chase as part of the post-interrogation gives the RB- 47 position at the time of that 1010Z first visual contact as 32-00N. 91- 28W, which puts it near Winnsboro in en-central Louisiana (Point ). The description obtained in the 1969 interviews with these officers are closely supported by the original intelligence