Accident Summary
The pilot-owner decided to overfly a glacier located in the Sierra Nevada Mountains, near the 12,000-foot msl base of a 14,000-foot msl mountain at the head of a box canyon. Witnesses reported observing the aircraft enter the canyon area. When the aircraft was nearly over the glacier, it commenced a course reversal. During the turn, the aircraft stalled, descended rapidly, and crashed into rocky terrain with a 40° upslope. The aircraft burned. The pilot, sole on board, was killed.
Probable Cause and Findings
The official probable cause was that the pilot intentionally flew over an area of high terrain in which he failed to maintain the proper altitude and delayed his decision to reverse course. A contributing factor was the pilot's improper inflight decision. Findings included: Occurrence #1 (loss of control in flight during maneuvering turn to reverse direction) – terrain condition: blind/box canyon and high terrain; remedial action delayed by pilot; in-flight planning/decision improper. Occurrence #2 (in-flight collision with terrain/water during uncontrolled descent) – proper altitude not maintained by pilot; inadvertent stall by pilot.