Incident Details
A pilot of a single-engine amphibious float-equipped airplane reported that the propeller RPM began to fluctuate during cruise flight. When she attempted to adjust the RPM, the engine emitted a clunking sound twice and subsequently lost all power.
Pilot Account
The pilot executed a forced landing on a grassy field. She stated that the main float wheels touched down and dug into the soft ground. Following the touchdown of the nosewheels, the airplane nosed over onto its back.
Examination Findings
Post-accident examination of the engine revealed that it had previously been installed on another aircraft before being placed on the accident airplane. The crankshaft had completely failed at the forward radius of the number 3 main bearing journal. Additionally, the number 3 main bearing had shifted forward. The engine had accumulated 1,056 hours since its factory remanufacturing.
Relevant Handbook Guidance
The airplane's pilot operating handbook includes a directive that landings on land without engine power should be made with the landing gear up on soft or rough ground, and with the landing gear down on firm or smooth ground.