CEN24LA211

The pilot reported that about an hour and twenty minutes into the flight he smelled smoke and noticed that the oil pressure was decreasing. He diverted for a precautionary landing. By that time, the oil pressure had dropped to zero and the cabin was filling with smoke. He landed on a beach, and the nose landing gear dug into the sand and collapsed. The landing gear well structure sustained substantial damage during the precautionary landing. A postaccident examination determined that the oil pressure line from the engine to the firewall fitting had fractured due to fatigue. The line was bent about 360° near mid-span, and the line was fractured within the bent segment. Airplane maintenance records revealed that the engine was overhauled and reinstalled on the airframe about a month before the accident. The mechanic noted that the oil line was inspected and reinstalled after the overhaul. The airplane had accumulated 119 hours since the engine overhaul.

On May 22, 2024, about 0653 central daylight time, a Cessna 172RG airplane, N751DW, was substantially damaged when it was involved in an accident near Chandeleur Island, Louisiana. The pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 aerial observation flight. The pilot reported that about an hour and twenty minutes into the flight he smelled smoke and noticed that the oil pressure was decreasing. He diverted to Chandeleur Island for a precautionary landing. By that time, the oil pressure had dropped to zero and the cabin was filling with smoke. He landed on a beach, and the nose landing gear dug into the sand and collapsed. The landing gear well structure sustained substantial damage during the precautionary landing. A postaccident examination determined that the oil pressure line from the engine to the firewall fitting had fractured. The line was bent about 360° near mid-span, and the line was fractured within the bent segment. Metallurgical examination revealed that the fracture surface exhibited features consistent with fatigue. The origin was located at the exterior surface of the tube at the outside of the 360°bend. The crack progressed through the thickness of the tube wall and then circumferentially to final fracture at the opposite side of the tube. Airplane maintenance records revealed that the engine had been overhauled and was reinstalled on the airframe about one month before the accident. The mechanic noted that the oil line was visually inspected for condition, and there was no corrosion, worn areas, dents, or nicks on the line. As a result, the oil line was reinstalled on the airplane after the overhaul. The airplane had accumulated 119 hours since the engine overhaul.