What happened
While flying at 3,000 feet approximately 3 miles east of the shoreline, the pilot experienced a short tremor in the left engine followed by a complete loss of power. The pilot declared an emergency with air traffic control and attempted to return to the departure airport. While attempting to secure the left engine, the pilot observed that the propeller failed to feather, resulting in a rapid descent. The pilot subsequently maneuvered the aircraft and ditched in a lake.
The investigation
Post-accident examination of the left engine revealed that the main oil screen contained metal flakes and fragments. The oil scavenge pump was seized due to internal metal deposits. Investigators found catastrophic damage to the accessories drive gears, the oil transfer tube, and the protection covers in the front accessory area. Visual inspections of the crankshaft and bearings showed damage to the front journal and front crankpin, with sections of the bearings missing. Additionally, the master rod bearing had suffered a catastrophic failure, and several cylinder skirts exhibited impact marks from piston rods.
An examination of the propeller assembly revealed metal contamination throughout the system, specifically noting that the governor screen gasket was clogged. Regarding maintenance history, the engine (serial number 34592) had been removed for high oil consumption and later reinstalled after being taken out of preservation. The mechanic performing the preservation did not confirm completing all required tasks specified in the manual, such as thrust bearing, cylinder, and propeller shaft treatments. Furthermore, there was no documentation regarding the condition of the dehydrator plugs or whether the oil system had been flushed of contamination from a previous metal-producing engine prior to installation.
An FAA review of the cargo manifest revealed discrepancies in weight. The manifest found at the accident scene listed 267 pieces of cargo weighing 10,837 lbs, while a sealed cargo manifest package listed the same 267 pieces at 14,182 lbs. This exceeded the aircraft's maximum payload capacity of 13,586 lbs.