Accident Overview
During cruise flight at an altitude of 7,500 feet, the pilot heard five loud bangs, after which the engine seized. The pilot attempted an emergency landing in a farm field. During the landing, the aircraft collided with rough terrain and a fence.
Maintenance History
Examination of the maintenance records revealed that the engine had been in service for approximately 35 years. It had been majored twice during a total operating time of 2,000 hours. The most recent major overhaul had occurred 13 years and 344 hours prior to the accident.
Engine Examination
An internal examination of the engine disclosed that the crankshaft had failed in fatigue at the number two main journal. A detailed metallurgical examination further revealed that the number one bearing insert had been mispositioned during assembly of the crankcase. This mispositioning caused a localized oil flow restriction to the main bearings, leading to an eventual fatigue failure of the crankshaft.