WPR24LA076

The loss of engine power due to the failure of the No. 2 piston pin plug, which resulted in oil starvation and subsequent failure of the No. 3 connecting rod. Contributing to the accident was the inadequate engine inspections by maintenance personnel.

The pilot reported that, while the airplane ascended through about 8,000 ft to 8,200 ft mean sea level (msl), the engine started vibrating and producing a loud “clunking” noise. He assumed that the engine had been subjected to carburetor icing and applied carburetor heat, but the condition worsened. He performed an emergency engine shutdown, configured the airplane to maintain the best glide airspeed, and selected the nearest suitable landing area. During the landing roll, the nose landing gear sheared off, and the left wing struck the ground resulting in damage to the aileron. Postaccident examination of the engine revealed heat tinting and scoring damage on three of four connecting rod journals, which is consistent with insufficient lubrication. Pitting was observed on the tappet body faces and corrosion observed on two of the tappet body faces had corresponding wear on the camshaft lobes. Additionally, material deformation was observed on the No. 2 cylinder piston skirt. The No. 2 piston pin bushing was worn into a small aluminum ball within the bore where it was normally situated. The wear signatures appeared consistent with long-term abnormal wear. The piston pin bore was elongated to the point of material deformation observed to the oil control ring, the second compression ring, and their respective lands. The oil suction screen contained an excessive quantity of metallic material that likely restricted oil flow throughout the engine. The engine was last overhauled about 28 years before the accident and had accumulated about 1,683 hours since. The manufacturer’s recommended overhaul time is 12 years or 2,000 hours, whichever occurs first. While closely monitored and frequently operated engines may be able to safely operate beyond the manufacturer’s recommended schedule, the damage observed on the No. 2 piston, the tappets and the camshaft suggest a likelihood that either the engine was not adequately monitored for signs of deterioration, or signs of deterioration were observed but ignored. For example, the wear on the No. 2 piston skirt, piston rings and their lands, camshaft lobe and pitted tappet body faces would have produced excessive metal for some time and was detected by oil trend analysis. An unspecified amount of ferrous metal flakes in the oil filter was recorded in the engine logbook about 15 months (about 65.5 engine hours) before the accident, no metal was observed during subsequent oil filter and oil screen inspections performed 12 months and 2 months before the accident. The engine’s logbook indicated that oil analysis was performed at intervals four times in the 19 months before the accident. Since the inception of the oil analysis, an increase in iron content quantity to the “reportable” range was documented; however, a subsequent oil analysis performed 7 days (about 5 engine hours) before the accident showed a decrease in the iron content, back into the “normal” range. Additionally, a consistent increase in aluminum and chromium along with increased reported oil consumption was observed in each of the reported oil samples. Components in this engine with a material composition comprised of aluminum, iron, or chromium include pistons, piston pin plugs, piston rings, valve stems, bearings, and rotating shafts within the valve train. It’s likely that more in depth analysis of the oil analysis coupled with additional engine inspections by maintenance personnel may have resulted in the detection of the failed No. 2 piston plug and associated damage to the No. 2 piston. The excessive quantity of metallic debris captured by the oil suction screen would have restricted oil flow throughout the engine. It is likely that the loss of engine power was ultimately due to insufficient lubrication to the connecting rod bearings that resulted in the No. 3 connecting rod bearing failure and subsequent fracture of the No. 3 connecting rod bolts.

On January 13, 2024, about 1300 mountain standard time, a Piper PA 28-181, N2886X, sustained substantial damage when it was in an accident near Colorado City, Arizona. The pilot and pilot-rated passenger were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. According to the pilot, after departing Colorado City Municipal Airport (AZC), Colorado City, (AZC), he conducted a practice RNAV instrument approach to the Kanab Municipal Airport (KNB), Kanab, Utah, and executed the published missed approach. While the airplane ascended through about 8,000 ft to 8,200 ft msl, the engine started vibrating and producing a loud “clunking” noise. As an attempt to troubleshoot the rough running engine, the pilot applied carburetor heat, which made the engine run more erratically. He turned the carburetor heat off and smoke entered the cockpit; he decided to shut down the engine by pulling the mixture control to idle cutoff and moving the throttle to idle. The pilot established best glide airspeed, initiated a turn to the northwest, and began to select the best place to land. During the landing roll on a sandy dirt surface, the nose landing gear sheared off, and the left wingtip struck the ground, resulting in substantial damage. Postaccident examination of the airplane’s engine revealed a hole in the crankcase aligned with the No. 3 connecting rod’s plane of rotation. The propeller was not able to rotate through when turned by hand. Examination of the internal engine components using a borescope (inserted via access holes drilled into the top of the crankcase) revealed that the No. 3 cylinder connecting rod was not connected to the crankshaft. Subsequently, the accessories were removed from the accessory case, and each of the cylinders and pistons were removed except for the No. 3 cylinder and piston, which sustained internal mechanical damage preventing their removal. The crankcase halves were separated and revealed severe heat distress consistent with lubrication depravation on the Nos. 2, 3, and 4 connecting rod journals. The heat gradient signatures were the most severe at the rear of the engine and became less prominent moving toward the front of the engine. (During engine operation, the lubricating oil flows from the back of the engine toward the front.) The crankcase and its installed tappet bodies and attached No. 3 cylinder, piston, and connecting rod assembly; camshaft and crankshaft; Nos. 1 and 2 main bearings, connecting rod pieces, and crankcase pieces were sent to the NTSB Materials Laboratory, Washington, DC, for examination. Examination of the No. 1 cylinder revealed signatures consistent with normal operation. The No. 2 cylinder connecting rod remained attached to the journal and showed localized heat distress. The bearing material surface was beginning to “wipe” and transfer material to the journal surface. The forward-facing piston pin bushing had worn itself into a small aluminum ball within the bore where it was normally situated. The wear signatures appeared consistent with long-term abnormal wear. The piston pin bore hole was elongated to the point of interfering with the ring lands of the oil control and second compression ring; corresponding cylinder wall scoring was observed. The No. 3 connecting rod was found separated from the crankshaft journal at the journal end of the rod. The No. 3 piston was seized within the cylinder. The No. 4 connecting rod end exhibited severe heat distress signatures on the rod journal end, and the bearing material was extruded from the rod end and cap. The combined signatures were consistent with lubrication depravation at the bearing. The camshaft lobes and tappets exhibited evidence of significant spalling. The tappet faces all had varying degrees of pitting. Pitting damage was most extensive on the tappet bodies for the intake valvetrains for the Nos. 1 and 2 cylinders. The camshaft lobe associated with the intake valvetrain for the Nos. 1 and 2 cylinders was substantially worn. At the lobe peak, the worn lobe measured 1.319 inches across the diameter, whereas the same measurement on other lobes showed a dimension of about 1.47 inches at the lobe peak. On the crankshaft, the Nos. 2, 3, and 4 connecting rod journals showed dark tinting and circumferential scoring. Additionally, the No. 3 connecting rod journal was damaged with relatively deep gouges. The No. 1 connecting rod journal and each of the main bearing journals showed some light circumferential scoring with some signs of slight brown heat tinting to the mostly light gray journal surfaces. The Nos. 1 and 2 main bearings did not have a Babbitt layer and were worn more substantially at the forward and aft ends on the upper and lower sides. The remaining main bearings had a blotchy appearance with areas of shallow spalling damage and embedded particles, and the Babbitt layer on each of the bearing halves was worn to a greater extent at the forward and aft sides. The camshaft lobe associated with the exhaust valve train for the No. 1 and No. 2 cylinders was substantially worn. At the lobe peak, the worn lobe measured 1.319 inches across the diameter, whereas the same measurement on other lobes showed a dimension of approximately 1.47 inch at the lobe peak. Lycoming Engines Mandatory Service Bulletin (SB) 301B, dated February 18, 1977, provided guidance for maintenance procedures and service limitations for valves. In particular, Paragraph 1(b), which provided instructions for a valve inspection to be performed at 400-hour engine maintenance check intervals, stated, “Rotate the engine by hand and check to determine that all cylinders have normal valve lift and that rocker arms operate freely.” Additionally, Lycoming Operator’s Manual for the O-360, dated October 2005, indicated in section 4, “Periodic Inspections,” that a valve inspection is required during the 400-hour inspection. The logbooks did not contain any record of a camshaft lobe inspection, camshaft replacement, compliance with SB 301B, or completion of any 400-hour inspection. Examination of the engine maintenance logbook indicated that the engine was overhauled April 2, 1997, at the tachometer time of 2,485.0 hours. According to the logbook, before 2022, four entries documented oil filter inspections, which were performed on August 8, 1998; August 21, 2007; August 23, 2008; and February 2, 2020. The logbook’s first reference of an oil sample being submitted to a laboratory for analysis was reflected in a July 30, 2018, entry that did not record the results of the analysis. Subsequent entries related to oil filter inspections and laboratory analyses of oil samples from the engine began in 2022, as follows: · A logbook entry dated October 5, 2022, at an engine total time since overhaul of 1,616.49 hours, stated that inspection of the oil filter revealed a “small amount of ferrous and other metal contamination.” The entry stated that an oil sample analysis was performed and indicated “wear results normal.” (Note: The laboratory’s oil analysis report reflected that the oil sample was taken on June 15, 2022.) The entry recommended that the next oil filter inspection and oil sample analysis be performed in 25 hours. · A logbook entry dated January 12, 2023, at an engine total time since overhaul of 1,640.88 hours, stated that an oil filter inspection revealed no contaminants and that an oil sample analysis indicated “wear results normal.” The entry recommended that the next oil sample analysis and oil filter inspection be performed in 15 to 20 hours. · A logbook entry dated November 8, 2023, at an engine total time since overhaul 1,662.27 hours, stated that an oil filter inspection revealed no contaminants and that an oil sample analysis indicated “wear results reportable for increased iron content.” The entry recommended that the next oil sample analysis be performed withi