Incident Overview
A scenic tour flight experienced a loss of engine power in flight. The pilot switched fuel tanks to the fullest tank, and power was momentarily regained. However, the engine subsequently stopped, and the propeller did not windmill. The pilot executed an off-airport landing in rugged mountainous terrain.
Damage and Injuries
The aircraft was destroyed. All three occupants sustained serious injuries.
Engine Examination
Disassembly of the engine revealed that the crankshaft had fractured. Examination of the fracture showed subsurface metal fatigue.
Probable Cause
The official finding stated the probable cause was the in-flight failure of the airplane's powerplant as a result of metal fatigue, which allowed the crankshaft to fracture. Contributing to the accident was the mountainous terrain of the Grand Canyon, which did not allow a suitable forced landing area.