What happened
While flying at 3,000 feet approximately 3 miles east of the shoreline, the pilot of the aircraft experienced a brief vibration in the left engine, which was immediately followed by a loss of power. The pilot declared an emergency with air traffic control and attempted to return to the departure airport. During the emergency procedures to secure the engine, the pilot observed that the propeller failed to feather, leading to a rapid descent. The pilot was unable to maintain altitude and ultimately ditched the aircraft in a lake.
Investigation into the engine components revealed that the engine, serial number 3/4592, had been previously removed due to high oil consumption and placed in storage. This engine was later reinstalled in the left position following the removal of a different engine that had been producing metal debris. During the post-accident examination, the engine was found to be seized. Significant internal damage was identified, including metal flakes and fragments within the main oil screen and the oil scavenge pump. The accessories drive gears, oil transfer tube, and various protection covers sustained catastrophic damage. Additionally, the crankshaft and bearings showed severe damage, and the master rod bearing had suffered a catastrophic failure.
Findings
- The propeller assembly contained metal contamination throughout the system, and the governor screen gasket was clogged with metallic debris.
- The mechanic responsible for the engine preservation did not confirm performing all required tasks specified in the maintenance manual, such as treating the thrust bearing, cylinder, and propeller shaft.
- There was no available documentation regarding the inspection or condition of the dehydrator plugs.
- It was unconfirmed whether the oil tank and system of the reinstalled engine had been properly flushed of contamination from the previous engine.
- Discrepancies were found in the cargo manifest weights, with one version listing 10,837 lbs and a sealed version listing 14,182 lbs, the latter of which exceeded the aircraft maximum payload capacity of 13,586 lbs.