Accident Overview
On September 21, 2012, at approximately 1515 central daylight time, a Cessna 150G (registration N8465J) was substantially damaged during a forced landing following a total loss of engine power while in cruise flight near Corinth, Mississippi. The certificated commercial pilot and a passenger received minor injuries. Visual meteorological conditions prevailed, and no flight plan was filed for the personal flight conducted under Title 14 Code of Federal Regulations Part 91.
According to the pilot/owner, the flight originated from Paulding Northwest Atlanta Airport (PUJ) in Georgia with the intention of returning the aircraft to his home in Oregon, having recently purchased it. After receiving two hours of dual instruction in the airplane, the pilot and his wife departed and leveled off at 4,500 feet for cruise. Approximately two hours into the flight, with everything reported as normal, a loud noise emanated from the engine compartment, the cowling shook violently, and the engine experienced a complete loss of power.
During the ensuing descent, the pilot attempted to restart the engine. The propeller continued to windmill, but the engine did not restart. The pilot selected a soybean field for the forced landing. During the landing roll, the landing gear became entangled with the crop, causing the airplane to nose over and come to rest inverted. The pilot and his wife egressed with minor injuries.
The pilot held a commercial pilot certificate with ratings for airplane single-engine land and instrument airplane. He reported 960 total hours of flight experience, with 60 hours in the accident airplane make and model.
Aircraft Information
The airplane, manufactured in 1967, was a Cessna 150G. A review of the maintenance records by a Federal Aviation Administration (FAA) maintenance inspector showed that the most recent annual inspection was completed on April 12, 2012, at 3,968 total aircraft hours. A major overhaul of the engine was completed on November 12, 1986, and the engine was installed in the airplane on July 22, 1988. The engine had accrued 643 total hours since that date, with 5 hours since the annual inspection.
Examination Findings
On October 17, the engine was examined by an FAA inspector. The examination revealed that the crankshaft gear bolt locking tab washer and the alignment dowel for the gear mounting flange were fractured. The gear bolt and associated components were further examined at the NTSB Materials Laboratory in Washington, DC. The examination concluded that the locking tab and alignment dowel displayed fracture surfaces consistent with fatigue. The bolt, gear, and gear mounting flange all showed evidence of working and impact marks consistent with movement between the parts, indicative of insufficient clamping or pressure force at installation.
According to Lycoming Service Bulletin 475C, "Damage to the crankshaft gear and the counterbored recess in the rear of the crankshaft, as well as badly worn or broken gear alignment dowels are the result of improper assembly techniques or the reuse of worn or damaged parts during reassembly. Since a failure of the gear or the gear attaching parts would result in complete engine stoppage, the proper inspection and reassembly of these parts is very important."
According to Lycoming Service Instruction 1009AU, the recommended time between overhaul for the O-320 series engines was 2,000 hours. It further stated that engines not accumulating the hourly period between overhauls specified in the publication were recommended to be overhauled in the twelfth year.