Introduction
An airline transport pilot was repositioning an airplane to an airport near the owner's summer home. The aircraft was not equipped or maintained for instrument flight conditions.
Flight Details
The day before the accident, the pilot diverted due to weather. On the accident day, the pilot departed for the destination but returned shortly after because of weather. After waiting for conditions to improve, the pilot departed again that afternoon and refueled at an intermediate airport before continuing toward the destination. The route followed a highway that traversed a mountain pass.
Witness Observations
A witness located along the highway reported seeing the airplane traveling northbound toward the mountain pass below an overcast cloud layer. The witness stated that the mountain pass was obscured and that a thunderstorm was developing to the west and moving east toward the pass. A second witness near the accident site observed the airplane descending vertically from the base of the clouds while spinning in a level attitude and impacting the ground. The second witness noted that it was snowing and visibility was about one-quarter mile at the time of the accident.
Examination
The airplane impacted terrain in a level attitude and was consumed by a postcrash fire. Examination of the flight controls, airframe, and engine revealed no mechanical malfunctions or anomalies that would have precluded normal operation.
Probable Cause
It is likely that the pilot experienced spatial disorientation and a subsequent loss of aircraft control upon encountering instrument meteorological conditions. The airplane exceeded its critical angle of attack and entered a flat spin at low altitude, resulting in an uncontrolled descent and impact with terrain.