Aircraft Ditching After Left Engine Power Loss (N41626)

Incident Overview and Pilot Actions During the flight, the pilot reported feeling a short tremor in the left engine while the aircraft was 3 miles east of the shoreline at 3,000 feet. This was immediately followed by a loss of power from the left engine. The pilot declared an emergency to air traffic control and elected to return to the departure airport. While attempting to secure the left engine, the pilot observed that the propeller did not feather and the aircraft began descending rapidly. The pilot maneuvered the aircraft and ditched it in a lake. ## Engine Maintenance History On September 26, 2003, engine serial number 34592 was removed from the accident airplane due to high oil consumption after 1,225 hours of time in service. The engine was reportedly preserved and stored at the operator's warehouse. A mechanic stated that he followed the steps in the manual provided by the operator for the preservation process. On October 27, 2004, the left engine, serial number NK510332, which had been producing metal for months, was removed. Engine serial number 34592 was then taken out of preservation and installed in the left position on the accident airplane, along with a new overhauled propeller assembly. On November 6, 2004, the propeller governor for the left engine was replaced because the propeller was slow to respond to power settings. ## Post-Accident Engine and Propeller Examination During the post-accident examination, metal flakes and fragments were found in the engine's main oil screen. The oil scavenge pump would not rotate and had internal deposits of metal fragments. The engine was seized and would not rotate. Catastrophic damage was observed to the accessories drive gears, oil transfer tube, and protection covers in the front accessory area. Visual inspection of the crankshaft and bearings revealed damage to the front journal and front crankpin, with sections of their respective bearings missing. The master rod bearing had incurred a catastrophic failure. Several cylinder skirts showed impact marks from piston rods. Before removing the propeller assembly, the propeller feather system was flushed with fresh oil and pressured with a feathering pump; the propeller blades were observed moving toward the feather position. Examination of the propeller assembly revealed metal contamination throughout the system, and the propeller's governor screen gasket was clogged with metal contamination. ## Maintenance Documentation and Cargo Manifest Review The maintenance manual provided by the operator for engine preservation details several tasks required for proper preservation, including thrust bearing, cylinder, and propeller shaft treatments, which the mechanic did not mention performing. No documentation was available for the inspection and condition status of the dehydrator plugs. Documentation for flushing contamination from the metal-producing engine, serial number NK510332, was not available, and the operator did not know if a process was performed on the left engine's oil tank and its system before the installation of engine serial number 34592. An FAA review of the cargo manifest discovered two different manifest weights. The cargo manifest obtained at the accident scene showed a total of 267 pieces of cargo annotated at a total weight of 10,837 lbs. The sealed cargo manifest package showed a total of 267 pieces of cargo annotated at a total weight of 14,182 lbs. The maximum payload weight for the accident airplane is 13,586 lbs.