WPR24LA076 · Piper PA-28-181

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.

Verbatim NTSB analysis and probable cause from the NTSB dataset