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File / rb47-1957

Evidential core

RB-47H over the Gulf of Mexico

More than 700 miles of signal tracking by an electronic reconnaissance aircraft

UnresolvedMilitaryELINTVisualRadarMultiple witnesses
Date17 July 1957
LocationMississippi, Louisiana, Texas, Oklahoma — a transit across the Gulf and the southern US
CountryUnited States
WitnessesSix-man RB-47H crew including three ELINT operators; ground radar stations
Durationabout 1.5 hours
Coordinates32.30° N · 95.30° W

The crew of an RB-47H electronic reconnaissance aircraft reported a simultaneous correlation: a signal on the passive ELINT receivers, a visual sighting of a bright light, and a reported ground radar track — sustained across much of a long transit.

Official position

Blue Book classified the case as unidentified; later analyses suggested part of the data may have been confused with an airliner.

Alternative hypotheses

  • A ground-based S-band radar received by the ELINT suite under anomalous propagation — the strongest sceptical hypothesis.
  • An airliner in the area — part of the data was identified as a possible scheduled flight.
  • A genuine unknown object emitting near 2.8 GHz.

RB-47 is presented in the literature as a case of “three independent radars”. That is untrue, and it matters.

The RB-47H’s onboard equipment was an ELINT / direction-finding suite — a passive receiver of other emitters, not a radar detecting reflections from objects. That means:

  • the system gave bearing and signal characteristics,
  • the system did not measure range,
  • and therefore the onboard data cannot reconstruct a trajectory or a speed.

Without range there is no speed. That sentence is the spine of this database, and nowhere is it sharper than here.

What remains strong

Despite the correction, the case stays in the first class, because we have three different kinds of channel: a passive electromagnetic signal, a visual sighting, and ground reports. Operator Frank McClure described a signal near 2.8 GHz whose bearing shifted relative to the aircraft in a way that did not fit a fixed ground emitter. Pilot Lewis Chase independently described an intense blue-white light.

That is exactly the kind of correlation a single mistake does not readily generate.

What was missing, and will stay missing

No complete, time-synchronised set exists: ELINT tapes plus ground station logs plus aircraft position minute by minute. The reconstructed chronology rests heavily on interviews conducted a decade after the event. That sharply limits what can be claimed today.

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