Engine Failure Leads to Ditching in Reservoir During Return from Spraying (N731BG)

What happened

The incident occurred while the aircraft was returning from an agricultural spraying operation. The engine began running roughly, and within seconds, it lost all power. The pilot attempted to restart the engine but was unsuccessful. Consequently, the pilot executed a forced landing by ditching the aircraft in a nearby reservoir.

The investigation

A detailed examination of the engine was conducted following the recovery of the aircraft. An engine teardown revealed that the crankshaft had failed due to subsurface fatigue located through the number four crankcheek.

Findings

The mechanical failure of the crankshaft was the primary factor in the loss of power. The pilot's decision to ditch in the reservoir was a direct result of the inability to restart the engine or maintain flight.