-4-
them about one year. He had been flying since October of 1954, and had accumulated 711 flying hours, of which 128 were in Bonanza aircraft. Almost all of the Bonanza time was acquired during charter flights. He had approximately 52 hours of dual instrument training and had passed his instrument written examination. He failed an instrument flight check on March 21, 1958, nine months prior to the accident. His last CAA second-class physical examination was taken March 29, 1958. A hearing deficiency of his right ear was found and because of this he was given a flight test. A waiver noting this hearing deficiency was issued November 29, 1958; According to his associates he was a young married man who built his life around flying. When his instrument training was taken, several aircraft were used and these were all equipped with the conventional type artificial horizon and none with the Sperry Attitude Gyro such as was installed in Bonanza N 3794N. These two instruments differ greatly in their pictorial display.
The conventional artificial horizon provides a direct reading indication of the bank and pitch attitude of the aircraft which is accurately indicated by a miniature aircraft pictorially displayed against a horizon bar and as if observed from the rear. The Sperry F3 gyro also provides a direct reading indication of the bank and pitch attitude of the aircraft, but its pictorial presentation is achieved by using a stabilized sphere whose free-floating movements behind a miniature aircraft presents pitch information with a sensing exactly opposite from that depicted by the conventional artificial horizon.
The Weather
The surface weather chart for 0000 on February 3, 1959, showed a cold front extending from the northwestern corner of Minnesota through central Nebraska with a secondary cold front through North Dakota. Widespread snow shower activity was indicated in advance of these fronts. Temperatures along the airway route from Mason City to Fargo were below freezing at all levels with an inversion between 3,000 and 4,000 feet and abundant moisture present at all levels through 12,000 feet. The temperature and moisture content was such that moderate to heavy icing and precipitation existed in the clouds along the route. Winds aloft along the route at altitudes below 10,000 feet were reported to be 30 to 50 knots from a southwesterly direction, with the strongest winds indicated to be closest to the cold front.
A flash advisory issued by the U. S. Weather Bureau at Minneapolis at 2335 on February 2 contained the following information: "Flash Advisory No. 5. A band of snow about 100 miles wide at 2335 from extreme northwestern Minnesota, northern North Dakota through Bismarck and south-southwestward through Black Hills of South Dakota with visibility generally below 2 miles in snow. This area or band moving southeastward about 25 knots. Cold front at 2335 from vicinity Winnipeg through Minot, Williston, moving southeastward 25 to 30 knots with surface winds following front north northwest 25 gusts 45. Valid until 0335." Another advisory issued by the U. S. Weather Bureau at Kansas City, Missouri, at 0015 on February 3, was: "Flash Advisory No. 1. Over eastern half Kansas ceilings are locally below one thousand feet, visibilities locally 2 miles or less in freezing drizzle, light
