ERA23LA264

About 20 to 25 minutes into the flight the engine lost power and began to run rough. The pilot described the power loss as if the engine was firing on two cylinders. He reported that the airframe began shaking and the airplane began losing altitude. Attempts to restore power were unsuccessful. Unable to make it to the nearest airport, the pilot chose a field in which to land. He notified air traffic control of the loss of engine power and performed a forced landing in a field. At touchdown, the nose landing gear collapsed and the engine mount was substantially damaged. Postaccident examination of the engine revealed the No. 2 cylinder exhaust valve stem fractured due to fatigue that initiated on the outer surface. The resulting separation of the valve head resulted in the reported partial loss of engine power and rough running engine. Review of the engine maintenance records revealed it had been 39 years since the No. 2 exhaust valve was replaced, and 34 years since the valve guides were replaced. Although engine manufacturer service instructions are not mandatory for Part 91 operators, the engine manufacturer recommended engine overhaul within 12 years of either being put in service or last overhaul. The most recent engine overhaul had been 45 years earlier.

On May 21, 2023, about 1435 central daylight time, a Piper PA-28-180, N9139J, was substantially damaged when it was involved in an accident near Lancaster, Tennessee. The private pilot and one passenger sustained minor injuries. The airplane was operated as a Title 14 Code of Federal Regulations part 91 personal flight. The pilot stated that after arrival at John C Tune Airport, Nashville, Tennessee, he had the fuel tanks topped off then performed a preflight inspection that included a check of the wing tank sump drains. He reported no issues, and departed to return to Seymour Air Park, Seymour, Tennessee. About 20 to 25 minutes into the flight, while flying at 3,500 ft mean sea level with visual flight rules flight following, the engine exhibited a loss of power; it began to run rough, which the pilot described as like it were running on 2 cylinders. He reported that the airframe was shaking and the airplane began losing altitude. He turned on the auxiliary fuel pump, switched fuel tanks, checked the magnetos, and turned on carburetor heat but none of those actions restored engine power. The nearest airport was 17 nautical miles south of his position and he noticed several large fields in his vicinity. He informed the controller of the loss of engine power and, ultimately, that he would be landing in a field. He performed a forced landing in a field with full flaps; at touchdown, the nose landing gear collapsed, and the airplane pitched nose-down. The airplane came to rest upright in a nose-down attitude and incurred substantial damage to the engine mount. According to the recovery personnel, the nose landing gear was collapsed aft, and about 45 gallons of uncontaminated fuel were drained from the airplane’s fuel tanks. Examination of the engine following recovery of the airplane revealed that the exhaust valve for the No. 2 cylinder was fractured, and the head was missing with damage to several areas of the top of the piston. The No. 2 cylinder, with the fractured exhaust valve stem, was shipped to the National Transportation Safety Board Materials Laboratory for examination. The examination revealed the valve fractured from fatigue cracking, which initiated at multiple locations along the stem exterior surface. Once the cracking progressed through most of the valve stem cross-section, the head separated and the resulting damage was consistent with the loose fragment having been repeatedly battered against the cylinder and piston surfaces. The valve exhibited thick lead oxide deposits, surface oxidation, and coarsened microstructure, indicating an elevated temperature exposure to the valve. Review of the engine maintenance records revealed that the engine had accrued about 1,915 hours and 45 years since engine overhaul, 1,635 hours and 39 years since the No. 2 exhaust valve was replaced, and 1,218 hours and 34 years since the valve guides were replaced. According to Lycoming Service Instruction No. 1009BE, Time Between Overhaul Schedules,which is not mandatory for Part 91 operators, all engine models are to be overhauled within 12 calendar years of the date first entered service or of last overhaul.