Accident Narrative
On January 13, 2024, at approximately 1300 mountain standard time, a Piper PA-28-181, registration N2886X, sustained substantial damage following an engine failure near Colorado City, Arizona. The flight was conducted as a personal flight under Title 14 Code of Federal Regulations Part 91. The pilot and a pilot-rated passenger were not injured.
The pilot reported that after departing Colorado City Municipal Airport (AZC), he conducted a practice RNAV instrument approach to Kanab Municipal Airport (KNB) in Kanab, Utah, and executed the published missed approach. As the airplane climbed through about 8,000 to 8,200 feet mean sea level, the engine began vibrating and producing a loud clunking noise. The pilot applied carburetor heat in an attempt to troubleshoot the rough-running engine, but the engine ran more erratically. He then turned the carburetor heat off, and smoke entered the cockpit. The pilot shut down the engine by pulling the mixture control to idle cutoff and moving the throttle to idle. He established best glide airspeed, turned to the northwest, and selected a landing area. During the landing roll on a sandy dirt surface, the nose landing gear sheared off, and the left wingtip struck the ground, causing substantial damage.
Examination Findings
Postaccident examination of the engine revealed a hole in the crankcase aligned with the No. 3 connecting rod's plane of rotation. The propeller could not be rotated by hand. Using a borescope, investigators found that the No. 3 cylinder connecting rod was not connected to the crankshaft. Subsequent disassembly showed that the No. 3 cylinder and piston could not be removed due to internal mechanical damage. The crankcase halves were separated, revealing severe heat distress consistent with lubrication deprivation on the Nos. 2, 3, and 4 connecting rod journals. The heat gradient signatures were most severe at the rear of the engine and diminished toward the front.
The engine components were sent to the NTSB Materials Laboratory for further examination. The No. 1 cylinder showed normal operation signatures. The No. 2 cylinder connecting rod remained attached to the journal but exhibited localized heat distress and bearing material wiping. The forward-facing piston pin bushing had worn into a small aluminum ball, and the piston pin bore hole was elongated, interfering with ring lands and causing cylinder wall scoring. The No. 3 connecting rod was separated from the crankshaft journal, and the No. 3 piston was seized within the cylinder. The No. 4 connecting rod end showed severe heat distress with extruded bearing material. Camshaft lobes and tappets exhibited significant spalling and pitting, with the most extensive damage on the intake valvetrain for the Nos. 1 and 2 cylinders. One camshaft lobe measured 1.319 inches at the peak, compared to approximately 1.47 inches on other lobes. The crankshaft journals showed dark tinting, circumferential scoring, and deep gouges on the No. 3 journal. Main bearings exhibited wear, with the Nos. 1 and 2 bearings lacking a Babbitt layer and worn more substantially at the ends.
Maintenance History
The engine was overhauled on April 2, 1997, at a tachometer time of 2,485.0 hours. Before 2022, four oil filter inspections were documented (August 1998, 2007, 2008, and February 2020). The first recorded oil sample analysis was July 30, 2018, but results were not recorded. From 2022 onward, several oil filter inspections and oil sample analyses were performed. On October 5, 2022, an oil filter inspection revealed small amounts of ferrous and other metal contamination, though an oil sample analysis indicated normal wear. On January 12, 2023, no contaminants were found, and wear was normal. On November 8, 2023, no contaminants were found, but the oil analysis showed reportable increased iron content (169 parts per million). On January 6, 2024, an oil sample was taken but the filter was not inspected; the sample showed decreased iron (56 ppm), reported as improved. The logbooks contained no record of camshaft lobe inspection, camshaft replacement, compliance with Lycoming Service Bulletin 301B, or completion of any 400-hour inspection.
Lycoming Service Bulletin 301B (dated February 18, 1977) and the Lycoming Operator's Manual for the O-360 engine specify valve inspections at 400-hour intervals, including checking valve lift and rocker arm operation. The engine's maintenance logbooks did not document any such inspections.