Accident Synopsis
The aircraft crashed on the side of a mountain during visual meteorological conditions. The pilot had been in voice and radar contact with air traffic control until the aircraft disappeared from radar. A sigmet had been issued for the region, and severe turbulence was confirmed by another pilot.
Sequence of Events
The pilot reported severe turbulence and a rough running engine to ATC as he was nearing a mountain pass. He stated that he thought the rough running engine was due to fuel contamination. A witness reported that the pilot had said the fuel had contained a lot of water. The pilot then reported to ATC that he had just lost the engine and was attempting to make it through a saddle. The aircraft subsequently collided with terrain.
Investigation Findings
Engine teardown revealed no evidence of preimpact mechanical failure or malfunction. The official probable cause analysis identified three occurrences: an in-flight encounter with weather (turbulence, clear air), flight into known adverse weather attempted by the pilot, fuel contamination, and inadequate preflight planning leading to partial powerplant failure; followed by loss of control in flight due to turbulence and inadequate preflight planning, and total powerplant failure; culminating in an uncontrolled descent and collision with terrain.