CEN13LA233

While in cruise flight, the engine lost power and oil immediately covered the windscreen. The pilot initiated a forced landing to a field. During the forced landing, the airplane impacted terrain and sustained substantial damage to the right wing. Disassembly of the engine showed multiple failures of the connecting rod assemblies. Metallurgical examination of the connecting rod assemblies revealed that the connecting rods likely failed due to insufficient clamping force at the split lines at the crankshaft end of the connecting rods. The pieces showed evidence of the nuts backing off from at least 3 of the connecting rod bolts. Fatigue of the connecting rod bolt and connecting rod straps was secondary to the loss of clamping force at the split lines. It is likely that the connecting rod bolts were not installed properly during the last overhaul.

On April 19, 2013, approximately 1200 central daylight time, a Piper PA-32-301 single-engine airplane, N82723, impacted terrain following a loss of engine power during cruise flight near Paris, Texas. The commercial pilot was not injured. The airplane was registered to Galaxy Travellaire Inc, and operated by the pilot under the provisions of 14 Code of Federal Regulations Part 91 as a personal flight. Visual meteorological conditions prevailed for the flight, which was on a visual flight rules flight plan. The flight originated from Parsons, Kansas, at 1030. According to the pilot, while in cruise flight at 7,500 mean sea level, the engine lost power and oil immediately covered the windscreen. The pilot initiated a forced landing to a field. During the forced landing, the airplane impacted terrain and came to rest upright. Examination of the airplane showed substantial damage to the right wing, firewall, and the nose gear was separated. A review of the maintenance records showed that the Lycoming IO-540-K1G5 engine (serial number L-15708-48A) had accumulated 4,683 total hours and 1,086 hours since major overhaul at the time of the accident. The engine's major overhaul was completed on November 3, 2008. The most recent annual inspection was completed on April 4, 2013, at an engine time of 1,080.7 hours since overhaul. On November 14, 2013, at the facilities of Air Salvage of Dallas (ASOD), Lancaster, Texas, the engine was disassembled under the supervision of a Federal Aviation Administration inspector and ASOD mechanics. Visual examination showed the crankcase sustained an uncontained failure near the number 2, 4, and 6 cylinders. The right side of the crankcase was cracked near the number 1 cylinder. Disassembly of the engine showed metal debris throughout the engine. The oil pickup tube was 3/4 full of metal debris. The oil sump contained metal debris and sections of connecting rod bolts, bearings, and connecting rods. Sections of all 6 connecting rods were retained and submitted to the NTSB Materials Laboratory for further metallurgical examination.The number 3 connecting rod was bent adjacent to the fracture surface, and the fracture features were irregular and rough, consistent with overstress failure. One of the strap fractures on the number 2 connecting rod showed flat features with curving crack arrest lines, features consistent with fatigue. The fatigue features emanated from origin areas at the connecting rod bolt head cut out and from the bearing face. The fatigue regions were relatively rough with multiple origins and step features, consistent with low cycle fatigue. Fracture surfaces on the opposite strap for the number 2 connecting rod and one of the fractures in the strap for connecting rod number 4 also showed crack arrest features consistent with fatigue. The nuts on two of the connecting rod bolt pieces were displaced toward the end of the bolt, and thread peaks between the nut and the grip were flattened. One nut was receivedseparated from the bolt, and the final 2 threads on the nut were damaged consistent with bolt pullout, and the remaining threads were intact. The fracture surfaces on one bolt showed curving crack arrest lines consistent with fatigue and were emanating from one side of the bolt.