Accident Narrative
The aircraft was in cruise flight at 3,000 feet MSL over remote terrain when the engine abruptly stopped producing power. The pilot identified a flat area suitable for an emergency landing and maneuvered the airplane toward it. Upon touchdown, the float assemblies were torn from the fuselage, and the airplane nosed over, coming to rest inverted.
Postaccident Examination
Following the accident, a thorough examination of the engine was conducted. Inspectors found that one cylinder bolt was loose, and the engine case showed evidence of fretting wear. The crankshaft was broken, which prompted a detailed metallurgical analysis.
Metallurgical Findings
The metallurgical examination of the broken crankshaft determined that the fracture surface displayed a pattern characteristic of fatigue cracking. This indicates that the crankshaft had been progressively weakening due to repeated stress cycles before the final failure.
Additional Details
The number one engine cylinder had been replaced approximately 585 service hours prior to the accident. No other anomalies were reported in the engine examination report.