What happened
During the initial climb, approximately 1,500 feet above ground level, the engine failed as the pilot performed the first power reduction. The pilot reported that the engine failure occurred so rapidly that the problem was immediately apparent.
After clearing nearby trees, the pilot extended the landing gear and executed a landing on a road. During the landing, the landing gear failed to lock into the down position and subsequently collapsed. Additionally, the right wing of the aircraft struck a snow berm during the sequence.
The investigation
Mechanical inspection of the engine revealed that a bolt connecting the number six connecting rod to the crankshaft had separated. The corresponding nut was located in the bottom of the crankcase.
Testing conducted at the NTSB metallurgical laboratory showed no evidence of pre-accident damage to the threads of either the bolt or the nut. Investigators also verified the torque on the remaining 11 connecting rod attachment nuts, which was measured at 480 inch-pounds. The engine had undergone an overhaul 241 hours before the accident.