ERA25LA141

During the initial climb on an instructional flight, the airplane’s engine lost total power. The flight instructor then performed a forced, off-airport landing, during which the airplane impacted a tree, resulting in substantial damage to the right wing. Postaccident examination of the engine revealed that the crankshaft had fractured at the No. 3 main journal. Metallurgical analysis determined the fracture originated from a preexisting, thermally-induced crack at the aft side of the oil supply hole for the No. 3 connecting rod journal. A fatigue crack then initiated at the edge of the preexisting crack and propagated toward the No. 3 connecting rod journal, culminating in fracture of the crankshaft. The detailed metallurgical examination found that the features observed on the crankshaft showed evidence of three different fracture mechanisms associated with the crankshaft fracture. The region closest to the origin had intergranular features consistent with brittle overstress fracture. The next region showed evidence of mixed intergranular and transgranular features with dimple features consistent with ductile overstress fracture. The largest region showed features consistent with fatigue. It is likely that the final fracture region had features consistent with ductile overstress fracture, but the remaining overstress region was substantially obscured and obliterated by post-fracture contact damage. The intergranular region and part of the overstress region near the origin were oxidized, consistent with a different environmental exposure relative to the remainder of the overstress region and the fatigue region. Additionally, the bore of the No. 3 connecting rod oil supply hole was heat tinted in the area where the fracture surface was oxidized. This suggested that the No. 3 main journal likely experienced a high heat event, such as a bearing failure and/or inadequate lubrication. The high heat event then likely led to formation of the intergranular crack. Lead deposits consistent with the Babbitt layer on the interior surface of the main journal bearings were observed only in the intergranular region, including some deposits that ended precisely at the boundary. This suggested that Babbitt material migrated into the intergranular crack during the high heat event. While scoring and bearing damage was observed on the accident parts, the condition of the journals as found did not show evidence of a high heat event in the current installation. This indicated that the intergranular region likely formed during a previous period of service. Flakes and serrated chips of metallic debris were observed scattered throughout the intergranular and ductile overstress regions; however, similar debris was not observed in the fatigue region. The debris was consistent with material generated during journal grinding. Given the difference in oxidation across part of the overstress region and the presence of the debris across most of the overstress region, it islikely that the crack grew slightly during the grinding process, producing a comparatively short ductile overstress region. Once the cracked crankshaft was placed back in service, a fatigue crack initiated at the boundary of the ductile overstress crack. At the outer surface, the fatigue fracture intersected the ductile overstress crack behind the crack tip, further indicating that the fatigue crack was secondary to the overstress crack. The fatigue crack propagated aft along the oil supply hole for the No. 3 connecting rod journal and into the aft cheek until the remaining section could no longer support the load, resulting in fracture through the cheek at the aft end of the No 3. main journal. Review of the engine’s maintenance logbook showed that the engine was overhauled nearly 2 years before the accident and since that time, it had accumulated almost 2,400 flight hours. The maintenance records also indicated that the crankshaft was inspected by magnetic particle inspection during the last engine overhaul. The evidence observed on the crankshaft fracture surfaces indicated that the No. 3 main journal was likely cracked at the time of the inspection. The crack at the aft side of the oil supply hole for the No. 3 connecting rod journal likely had a total length of 0.147 inch at the No. 3 main journal surface at the time of inspection, which should have been detectable.

On March 12, 2025, about 1300 eastern daylight time, a Piper PA-28-181, N3055B, was substantially damaged when it was involved in an accident near Hollywood, Florida. The flight instructor was not injured, and the student pilot sustained minor injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 instructional flight. During the initial climb after takeoff, the engine lost power, and the flight instructor performed a forced landing to a field, during which the airplane struck a tree. The airplane came to rest upright, and no postaccident fire occurred. Postaccident examination of the wreckage revealed that the right outboard wing was buckled and crushed. Detailed examination of the engine revealed that the main bearings exhibited circumferential scoring, wear through the Babbitt layer, exposed copper, and localized material loss. All journals on the crankshaft had a mostly reflective gray color and did not show evidence of substantial heat damage. The crankshaft’s No 3. main journal had some circumferential gouges and light scoring damage, and the No. 4 journal had light circumferential scoring damage and isolated areas of rub marks. The remaining journals were relatively free of damage. A fatigue fracture was identified through the crankshaft cheek adjacent to the No. 3 main journal, originating at the journal surface near the oil supply hole for the No. 3 connecting rod journal. Multiple secondary cracks were observed emanating from oil supply holes in the No. 3 main journal. Metallurgical examination revealed oxidation and overstress at the crack origin, followed by fatigue crack propagation. No material defects were identified. Although the crankshaft’s No. 3 main journal surface showed scoring damage, the journal surface did not show evidence of high heating associated with bearing failure. However, heat tinting was observed on the interior surface of the No 3. connecting rod oil supply hole. Near the No. 3 main bearing journal surface, the hole bore was tinted dark gray, and deeper into the bore, the hole was tinted shades of blue and red. Additional details of the metallurgical examination can be found in the Material Laboratory Factual Report, in the public docket for this investigation. A review of the engine logbook records revealed that the engine was overhauled in April 2023 at a tachometer time of 2,413.1 hours. During the overhaul, the crankshaft underwent and passed a non-destructive magnetic particle inspection. The most recent annual inspection was recorded at a tachometer time of 4,787.1 hours. According to Lycoming Engines Service Instruction No. 1009BE, the recommended time between overhaul (TBO) for the IO-390-A, -C, and -D engine models was 2,000 hours. At the time of the accident, the engine had accumulated approximately 2,374 hours since the last overhaul.