Pilot Report
The pilot was conducting a visual flight rules (VFR) flight transporting mail to a remote village. Approximately 15 minutes from the destination, he checked the Automated Weather Observing System (AWOS) for updated weather and recalled the visibility as 7 miles. However, this recollection was inconsistent with the actual AWOS report: 18 minutes before the accident, the AWOS indicated visibility of no more than 1 3/4 miles. As the pilot descended the airplane from 2,500 ft to 1,500 ft in the terminal area, he observed reduced visibility conditions that would necessitate an instrument approach procedure.
Autopilot Disconnect
According to the pilot, while maneuvering toward the initial approach fix, he heard the autopilot disconnect and the airplane began an uncommanded descent. He stated that he remembered pulling on the control wheel and thought he had leveled off, but the airplane subsequently impacted terrain, resulting in substantial damage to the fuselage, vertical stabilizer, and rudder. The pilot could not recall whether he heard terrain warnings or alerts before impact.
Performance Analysis
An airplane performance study revealed that the airplane was in a continuous descent from 2,500 ft until the final data point about 12 ft above the surface; the airplane did not level off at any time during the descent. In the final 15 seconds of recorded data, the rate of descent increased from about 500 fpm to about 2,300 fpm before decreasing to 1,460 fpm at the last recorded data point.
Postaccident Examination
Postaccident examinations of the airframe, engine, flight control, and autopilot components found no mechanical malfunctions or failures that would have precluded normal operation or affected flight controllability.
Probable Cause
The probable cause of the accident, as determined by investigators, was the pilot's decision to continue a visual flight rules flight into an area of instrument meteorological conditions and his subsequent failure to level the airplane after the autopilot disconnected, which resulted in a collision with terrain.