STINSON 108

Full Narrative

On July 23, 2022, about 1400 eastern daylight time, a Stinson 108-3, N6020M, was substantially damaged when it was involved in an accident near Batesburg, South Carolina. The private pilot and a passenger were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.
The pilot stated that during cruise flight, while flying about 2,300 ft above mean sea level, the engine “went dead.” He made a forced landing to a field, and after touchdown the airplane collided with trees that bordered the field.
Postaccident examination of the engine following recovery of the airplane revealed no valvetrain continuity with rotation of the crankshaft. Partial disassembly of the engine revealed that the crankshaft gear was fractured. Examination of the crankshaft gear by the National Transportation Safety Board Materials Laboratory revealed it failed due to fatigue that initiated from multiple origins at a corner of a keyway cut in the gear. There was no plating at the fatigue initiation site.
A review of the maintenance records revealed a nearly 15-year gap in entries, and then the engine was overhauled by an airframe and powerplant mechanic on June 18, 2014, and installed on the airframe on June 1, 2016. Further review of the maintenance records associated with the engine overhaul revealed the crankshaft gear was magnafluxed and approved for return to service on April 25, 2012. Since installation, the engine remained installed in the airframe and underwent routine inspections and maintenance, accruing about 247 hours since major overhaul at the time of the accident.