Accident Summary
A commercial aircraft operating under Part 135 as an on-demand lodge/hunting guide flight was observed entering a valley flanked by mountains on both sides. The pilot initiated a left turn to reverse course, during which the airplane collided with terrain. Witnesses reported that the engine sounded normal prior to impact. Weather conditions were described as good, with clear skies, unlimited visibility, and light wind. A pilot who flew over the accident site minutes afterward reported the absence of turbulence.
Occupants and Damage
The aircraft carried three occupants, all of whom were killed in the accident. The aircraft sustained substantial damage upon impact with the mountainous terrain.
Investigation and Findings
Investigators determined that the flight was conducted under visual flight rules. The box canyon environment, characterized by rising terrain on both sides, provided limited maneuvering space. The pilot's decision to enter the valley and subsequent left turn led directly to the collision.
Probable Cause
The official probable cause of the accident was improper in-flight planning/decision by the pilot, and his failure to remain clear of mountainous terrain. Contributing factors included the box/blind canyon and the proximity of mountainous terrain.