LAX98FA306 · Beech 95-B55

The pilot called the flight service station and obtained a weather briefing prior to the flight. He was told several times that VFR flight was not recommended due in part to IFR conditions along a portion of his route, mountain obscurment along the entire route, and moderate rime and mixed icing along the route between 8,000 and 18,000 feet. Additionally, he was told there were thunderstorms over the Sierra Nevada Mountains, Southern California, and throughout Utah and Nevada. The pilot picked up an IFR clearance moments before he told controllers that he had a "system's failure." The controller asked him what type of system's problem he had and he told the controller that he had lost control of the aircraft and was descending at 2,000 feet per minute. Ground units that were launched to locate the missing aircraft were hampered by inclimate weather, and an H-60 military helicopter that was conducting an airborne search entered clouds and crashed not far from the site of the downed aircraft. Teardown reports on both engines concluded that there were no mechanical malfunctions noted that would have caused an operational problem. The left propeller was found feathered prior to impact, with no preimpact discrepancies noted on either propeller that would have precluded normal operation. The right propeller had indications of rotation and power development on impact. The airplane was not equipped for flight into icing conditions and did not have any propeller or wing deicing boots. Analysis of meteorological data showed that the aircraft entered the clouds where significant light to moderate clear/mixed airframe icing was present, and, encountered a convective cell in the minutes prior to the accident.

Verbatim NTSB analysis and probable cause from the NTSB dataset