WPR20LA097

The pilot reported that during a local flight, the engine started to knock and vibrate, and the oil pressure indication was low. He initiated a precautionary landing to an open field, and during the landing rollout, the airplane impacted a small ditch, which resulted in substantial damage to the left wing. A postaccident examination of the engine revealed that the No. 2 connecting rod was separated from the crankshaft. The No. 2 connecting rod journal exhibited thermal distress and mechanical damage. The remaining connecting rod journals and the crankshaft main bearings also exhibited thermal discoloration consistent with oil starvation. When the engine was rotated, no oil flow was observed through the crank journals and lifters. The oil filter screen was covered in dark thick oil and metallic debris and was collapsed. It is likely that the contaminated oil filter screen collapsed under pressure from the oil pump, which prevented the normal flow of oil through the engine; this resulted in the oil starvation of the No. 2 connecting rod bearing and subsequent separation of the connecting rod from the crankshaft.

On February 27, 2020, about 1500 mountain standard time, a Cessna 170, N5478C, was substantially damaged when it was involved in an accident near Baker City, Oregon. The pilot and one passenger were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot reported that the purpose of the flight was to warm up the oil before a scheduled annual inspection and oil change. About 15 minutes into the local flight, the engine started to “knock and vibrate badly,” and the oil pressure indication was low. The pilot initiated a precautionary landing to an open field, and during the landing rollout, the airplane impacted a small ditch. The left wing sustained substantial damage. A postaccident examination of the engine revealed that the No. 2 connecting rod was separated from the crankshaft. The No. 2 connecting rod journal exhibited thermal distress and mechanical damage. The remaining connecting rod journals also exhibited thermal discoloration. The crankshaft main bearings exhibited thermal discoloration and excessive wear. When the engine was rotated, no oil flow was observed through the crank journals and lifters. The oil sump contained metal fragments, and the oil filter screen was covered in dark thick oil and metallic debris and was collapsed. The engine contained about 6 quarts of oil before the examination. According to the pilot, who was the airplane owner, the engine had 465 hours of operation since the last overhaul.