LAX97FA334 · Navion G

The non-instrument rated pilot departed California on a business flight to a South Dakota destination. No flight plan was filed. Radar flight following service was terminated as the pilot approached the western slopes of the Sierra Nevada Mountains, and there were no further radar contacts or voice communications with the pilot. The pilot did not request any en route weather briefings from FAA flight service stations, and his route of flight over the mountains to the accident site was not determined. Instrument meteorological conditions including multiple cloud layers and rain showers existed in the vicinity of the accident site. Additionally, between 0830 and 0900, National Climatic Data Center visible and infrared spectrum satellite imagery revealed an area of rapidly developing cumulonimbus clouds at the site. On May 18, 1998, the wreckage was located scattered over a distance of 0.64 miles, about 26 miles south of the pilot's intended direct route of flight. The engine, wings, flaps, ailerons, elevators and empennage were found separated from the fuselage, along with a handheld GPS receiver. Acquaintances of the pilot reported he kept accurate flight records. The pilot's logbook contained several 'pilot-in-command' entries indicating that cross-country business flights had been performed in actual instrument weather conditions while navigating using a GPS receiver. No safety pilot or CFI was listed as accompanying the pilot during these flights. About 1.5 days prior to the accident the pilot was treated for a periodontal infection. An antibiotic and narcotic pain reliever was prescribed, and partially empty containers of these drugs were found in the wreckage. Insufficient specimens remained to perform an autopsy or toxicological tests.

Verbatim NTSB analysis and probable cause from the NTSB dataset