What happened
The aircraft sustained substantial damage during a forced landing following an in-flight engine failure. The pilot reported that the engine ceased functioning at an altitude of 3,000 feet mean sea level while the airplane was in cruise flight. Unable to maintain power, the pilot executed a forced landing on a sod field. During the landing roll, the aircraft struck a concrete marker located on the airfield, which caused the airplane to nosed over.
The investigation
A physical inspection of the damaged airplane revealed that the accessory gear drive was fractured into two separate pieces and had become dislodged from the crankshaft. To determine the root cause of the mechanical failure, a metallurgical examination was conducted on the failed component.
Findings
The metallurgical analysis identified a fatigue fracture at the key way of the accessory gear drive as the primary reason for the component's separation. This structural failure led directly to the loss of engine power and the subsequent forced landing.