Event Sequence
While en route to his destination, the private pilot began experiencing a rough-running engine that soon led to a total loss of power. Unable to divert to the nearest airport, the pilot elected to execute a landing in a farm field. During the landing roll, the nosewheel contacted a burrow, resulting in the separation of the nosewheel assembly and subsequent loss of control. The aircraft came to rest upright, and the pilot exited the cockpit without needing assistance.
Engine Examination
Post-accident examination of the engine identified a sub-surface fatigue fracture on the number 5 crankshaft cheek. This fracture caused the crankshaft to fail, leading to the complete loss of engine power.
Maintenance History
The engine had last been overhauled approximately 17 years prior to the accident, while the engine manufacturer specifies an overhaul interval of 12 years. On January 23, 1998, the Federal Aviation Administration released a guidance document recommending replacement of the crankshaft at the next overhaul or the next time the crankshaft was removed. At the time of the accident, compliance with this guidance was not required and had not been accomplished.