The official investigation was carried out by the
Civil Aeronautics Board (CAB, precursor to the
NTSB). It emerged that Peterson had over four years of flying experience, of which one was with Dwyer Flying Service, and had accumulated 711 flying hours, of which 128 were on Bonanzas. He had also logged 52 hours of
instrument flight training, although he had passed only his written examination, and was not yet qualified to operate in weather that required flying solely by reference to instruments. He and Dwyer Flying Service itself were certified to operate only under
visual flight rules, which essentially require that the pilot must be able to see where he is going. However, on the night of the accident, visual flight would have been virtually impossible due to the low clouds, the lack of a visible horizon, and the absence of ground lights over the sparsely populated area.
[7] Furthermore, Peterson, who had failed an instrument
checkride nine months before the accident, had received his instrument training on airplanes equipped with a conventional
artificial horizon as a source of aircraft attitude information, while N3794N was equipped with an older-type Sperry F3 attitude
gyroscope. Crucially, the two types of instruments display the same
aircraft pitch attitudeinformation in graphically opposite ways.[[url=https://en.m.wikipedia.org/wiki/Wikipedia:Citation_needed]citation needed]
The CAB concluded that the accident was due to "the pilot's unwise decision" to embark on a flight that required instrument flying skills he had not proved to have. A contributing factor was Peterson's unfamiliarity with the old-style attitude gyroscope fitted on board the aircraft, which may have caused him to believe that he was climbing when he was in fact descending (an example of
spatial disorientation). Another contributing factor was the "seriously inadequate" weather briefing provided to Peterson, which "failed to even mention adverse flying condition which should have been highlighted".
[7]
[25]