What happened
The aircraft was operating in straight and level flight at an altitude of 3,100 feet MSL when the engine began to vibrate significantly. The pilot determined that the vibration was severe enough to potentially cause the engine to separate from the airframe. In response, the pilot selected a nearby field to set up for an emergency approach.
Upon reaching the final approach segment, the pilot assessed the landing site and decided it was unsuitable for a safe touchdown. Power was applied, and the pilot executed a 180-degree turn to identify an alternate landing area. During the maneuver to this second field, the pilot noted that airspeed was too high to stop within the available distance. Consequently, the pilot turned right approximately 45 degrees, aiming for a narrow gap in the tree line.
The aircraft struck and severed three small trees before nosing over and rotating until it came to a complete stop. The aircraft ultimately rested in an upright position.
The investigation
Examination of the aircraft revealed that an engine mount joint was cracked directly within the weld itself. Analysis of the fracture surfaces indicated that the crack had likely existed prior to the accident flight, suggesting pre-existing structural fatigue or defect rather than immediate overload during the event.