Accident Overview
On July 23, 2022, at approximately 1400 eastern daylight time, a Stinson 108-3, registered as N6020M, sustained substantial damage during an accident near Batesburg, South Carolina. The private pilot and a passenger were not injured. The flight was operating under Title 14 Code of Federal Regulations Part 91 as a personal flight.
The pilot reported that during cruise flight at about 2,300 feet above mean sea level, the engine suddenly stopped producing power. He executed a forced landing to a field, but after touchdown, the airplane collided with trees bordering the field.
Engine Examination
Following recovery, a postaccident examination of the engine revealed no valvetrain continuity when the crankshaft was rotated. Partial disassembly showed that the crankshaft gear was fractured. The National Transportation Safety Board Materials Laboratory examined the gear and determined that the failure was due to fatigue originating from multiple initiation sites at a corner of a keyway cut in the gear. No plating was present at the fatigue initiation site.
Maintenance History
A review of maintenance records disclosed a gap of nearly 15 years in entries. Subsequently, the engine was overhauled by an airframe and powerplant mechanic on June 18, 2014, and installed on the airframe on June 1, 2016. Records associated with the engine overhaul indicated that the crankshaft gear had been magnafluxed and approved for return to service on April 25, 2012. After installation, the engine remained in the airframe and underwent routine inspections and maintenance, accruing about 247 hours since major overhaul at the time of the accident.