Air Force Project Blue Book Special Report 14 (Hynek's annotated copy)

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

C.A-52-458

RELEASE: AIL'S THURSDAY, Dec. 11

1952

A report just issued by the Civil Aeronautics Administration on last

summer's wave of "flying saucers" trashes many of the "unidentified targets"

to secondary reflections of the radar beam by atmospheric conditions.

Concerned with the possible detrimental effects on air traffic control, the OIA Technical Development and Evaluation Center made a study concentrating on the scores of such targets sighted by the Washington Air Route Traffic Control Center radar. It also surveyed experience of the CAA tower radars at Atlanta, Boston, Chicago, Cleveland, Minneapolis, and New York.

Correlation of controllers' reports with Weather Bureau records indicated that a temperature inversion almost always existed when such targets appeared on the radar.

Irparently, the study says, reflections were produced by isolated refracting areas which traveled with the wind at or near the temperature inversion levels. Those areas, possibly atmospheric eddies created by the shearing action of dissimilar air strata, were not of sufficient density to produce direct returns, but could bend the radar beam downward to give a ground return.

Horizontal movement of these areas would produce a movement twice as great in the image being received on the radar scope, and in a parallel direction. This ties in with the fact that when the speed of targets on the radar was divided by two, their motions correspond closely to the report of wind directions and velocities at certain altitude levels. In nearly all areas, the temperature inversion levels were at or adjacent to those altitudes.

The fact that the radar targets always moved in one direction eliminated the possibility that they were surface vehicles, the report says, since some vehicles would have been moving in the reverse direction.

To evidence the found of hovering or of sudden increases in speed by any target. The study describes reports of sudden accelerations of targets to supersonic velocities to a controller's transfer of identity from a faded target to another target which was just appearing on a different section of the scope.

CAA-52-/58

Atlanta, Minneapolis, and New York International (Idlewild) reported no unidentified targets. The CAA tower at Boston's Logan Field has noticed them on rare occasions, and the tower at La Guardia had one instance. Chicago Midway and Cleveland Municipal have observed unidentified targets many times, the former particularly when temperature inversions have been in effect.

The report concludes that the presence of such targets has little effect on the control of air traffic, except that they can become a nuisance where helicopter operations are prevalent, since radar returns from small 'copters sometimes present the same characteristics. Where a collision course is involved, the controller gives traffic information, since pilots would rather be warned about a spurious target than not be warned about a legitimate one.

The report recognizes the need for securing additional evidence on the problem, through observations with more versatile equipment.