CEN24LA342

During the landing flare, the airplane encountered a gust of wind, climbed about 3 ft, and landed on the runway centerline. The pilot described the landing as firm, but not hard. The airplane was refueled and returned to the hangar with no issues. The next day, the pilot’s son flew the airplane. The pilot’s son performed a preflight inspection with no anomalies noted. After the takeoff, he retracted the landing gear, and he noticed that the “gear in transit” light stayed illuminated. He extended the landing gear, and all three green landing gear lights were illuminated. The pilot’s son landed back at the airport and taxied back to the hangar with no issues. The following day, the pilot’s son flew the airplane to another airport to have a mechanic inspect it. A postflight inspection by the mechanic revealed that the engine mount had fractured at the nose gear attachment point. The airplane’s engine mount sustained substantial damage. Postaccident examination revealed that the engine mount likely failed under normal operating loads due to the fracture of a vertical tube that was weakened by corrosion and fatigue cracks. The corrosion occurred on the interior surface of the vertical tube, likely due to the presence of water and greasy deposits at the lower end of the tube. Although the corrosion damage had likely been developing for an extended time, it would not have been detectable by visual inspection. The corrosion damage included a loss of wall thickness that increased the average stress in the remaining cross-section, and local stresses were further increased by rough surfaces and pits that formed during the corrosion process. As a result, fatigue cracks initiated and grew from multiple origins at the corroded surface. Although the total extent of fatigue cracking could not be determined due to post-fracture damage, it is likely that the tube was weakened sufficiently from the combination of wall thickness loss and fatigue crack growth to cause failure under normal loading conditions. The corrosion and fatigue cracks at the lower end of the tube were secondary to another failure that could not be determined from the examined pieces. Although an incomplete weld or service damage such as a crack or hole in the tube could have allowed water to seep into the tube bore, causing the tube to corrode from the inside out, no such anomalies or cracks were observed below the cut location.

On September 4, 2024, about 1950 central daylight time, a Piper PA-28R-200 airplane, N4081S, sustained substantial damage when it was involved in an accident near Crystal, Minnesota. The pilot was uninjured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot performed a preflight inspection on the airplane with no anomalies noted. The airplane departed from the Crystal Airport (MIC), Crystal, Minnesota, for a local area flight. As the pilot returned to MIC, he completed the before-landing checklist and was cleared to land by air traffic control. During the landing flare, the airplane encountered a gust of wind, climbed about 3 ft, and landed on the runway centerline. The pilot described the landing as firm, but not hard. The airplane was refueled and returned to the hangar with no issues. The next day, the pilot’s son flew the airplane. He performed a preflight inspection with no anomalies noted. After takeoff, he retracted the landing gear and noticed that the “gear in transit” light stayed illuminated. He extended the landing gear, and all three green landing gear lights were illuminated. The pilot’s son landed back to MIC and taxied back to the hangar with no issues. The following day, the pilot’s son flew the airplane from MIC to the Rochester International Airport (RST), Rochester, Minnesota, to have a mechanic inspect it. The pilot’s son flew the airplane from MIC to RST with the landing gear extended the whole flight and landed and taxied at RST without incident. A post-flight inspection by the mechanic revealed a fractured engine mount at the nose gear attachment point. The airplane’s engine mount, Piper part number 67119-57, sustained substantial damage. The engine mount was not serialized. Postaccident examination of the engine mount revealed that the fracture surface generally showed substantial damage from oxidation and post-fracture contact. Greasy deposits were observed covering the black painted surfaces over most of the fractured tube’s exterior surface. On the interior of the fractured tube, an accumulation of greasy, mostly black deposits of corrosion products and other debris was observed inside the tube piece. Areas with relatively flat features in planes perpendicular to the tube axis were observed in several locations, mostly on the left half of the fracture. Additional features including radial lines and ratchet marks were also observed in these areas emanating from the interior edge of the fracture. These fracture features were consistent with fatigue initiating from corrosion pits at the interior surface of the tube. Each fatigue region had multiple origins. The fatigue regions appeared to extend through the wall thickness on the aft left and forward left portions of the fracture. At the forward right side of the fracture, the fatigue region extended part way through the thickness. An area on the left side of the fracture was smeared from post-fracture damage, so thefracture mechanism was undetermined in that area. The remainder of the fracture surface outside of the fatigue boundary and to the right of the fatigue regions had rough features on slant angles consistent with ductile overstress fracture. At the time of the accident, the airframe, which was manufactured in 1974, had accumulated 3,711 hours. The most recent annual inspection on the airframe was completed on November 8, 2023.