Incident Overview
During a short cross-country flight, the engine quit. The pilot was unable to restart the engine. During the subsequent forced landing on a road, the aircraft collided with a tree and then a guardrail.
Engine Examination Findings
Examination of the engine revealed that the crankshaft gear, which drives two crankshaft idler gears that in turn drive each magneto drive gear, failed to do so when the bolt securing it to the crankshaft backed out approximately three turns. This condition was due to a foreign object located under the gear for an undetermined time. The loose bolt resulted in the torque from the crankshaft being transmitted to the crankshaft alignment dowel, which is a non-load carrying member. The alignment dowel failed due to fatigue, resulting in the total loss of engine power. The foreign object was reportedly not located.
Maintenance History
Review of the engine logbooks revealed that the engine was overhauled 1,574 hours earlier.