Incident Overview
The pilot of a single-engine airplane reported a partial loss of engine power shortly after departing from a rural village. While climbing through approximately 600 feet above ground level, the pilot heard a loud 'clunk-clunk' sound and felt an engine vibration. In response, the pilot reduced power and turned downwind to return to the same runway for landing.
Sequence of Events
During the turn from base to final approach, the engine continued to lose power. The pilot was unable to maintain sufficient altitude to reach the runway and executed a forced landing in deep snow. The airplane came to rest safely in the snow-covered terrain.
Postaccident Examination
A postaccident inspection of the engine disclosed a fractured connecting rod bolt. The bolt was sent to the NTSB materials laboratory for metallurgical examination, which revealed that the failure was due to fatigue.
Engine Maintenance History
The engine had been rebuilt approximately 1,642 service hours prior to the accident. The engine manufacturer recommends an overhaul at 2,000 service hours.