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This combined Project Sign file, drawn from USAF records, documents the 1 October 1948 encounter over Fargo, North Dakota, in which Air National Guard pilot 2nd Lt. George F. Gorman chased a small round white light in his F-51 for 27 minutes. The file holds checklists, interrogation reports by Major Paul Kubala of the ATI Field Office at Wright-Patterson, tower witness statements, Geiger readings on the aircraft and press clippings. It concludes that Gorman's statements should be accepted as truth until proven wrong.
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# CONFIDENTIAL Field Investigation Report Subject: "Geiger Radiosactivity Check of F-51 #511435 Air National Guard,argo, North Dakota" 4. The actual tests were performed in a hangar containing other aircraft and motorized equipment since the Geiger instrument required the use of an electric cable and outlet. 5. For practical purposes, the "click" method (using earphones) was selected since this method proves more accurate in detecting minimum radio- activity. It shows any activity above .001 "r" units. (The standard of eight clicks per minute for normal ionization of the atmosphere due to cosmic ray activity and natural radioactivity is present everywhere.) NOTE: The standard of measurement utilized by the counter is calibrated in "r" units (Hoentgen units) per day and is calibrated from individual measurement with known gamma radiation intensities obtained from a standard radium source. This unit of measurement is applicable only in checking safe radiation conditions. (One "r" per day equals 130 millicurie meters for radium gamma radiation.) The actual number of rays passing through the Geiger Kueller counter tube gives a meter reading indicating the average instantaneous number of detected rays and causes the needle to fluctuate around a mean value. Since the given calibration is strictly correct only in the vicinity of radium-gamma type emissions, other radiation (very hard) would have to be multiplied by a "k" factor to give a correct reading. ## FACTUAL DATA 1. Pointing the Geiger tube at a tractor resulted in a zero indication at 10 seconds. Directing the counter in the general vicinity of the test planes at a distance of 10 to 12 feet, gave a reading of about 16 clicks per minute (an average normal for recently flown aircraft). 2. Readings taken on the subject aircraft and the five other F-51's are appended hereto as Exhibit "A". CONTENTS: 1. More positive readings were found to be concentrated in those portions of the aircraft where luminous-dialed instruments or other sources of radiation were located. All aircraft gave similar readings, for the most part, at these points. Readings obtained from the wings, empennage and tail were of very low intensity tending to show that radioactive instruments in the aircraft accounted for the higher readings. 2. Explanation of the varied readings can be accounted for to some extent by the fact that ultra-violet radiations (to which the counter responds) are absorbed from the sun by the aircraft to a greater or lesser degree as the altitude is increased or decreased. CONFIDENTIAL page 2 of 4 page
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