N4399X

On April 19, 2024, about 1230 mountain standard time, a Piper PA-28 airplane, N4399X, was substantially damaged when it was involved in an accident near Marana, Arizona. The flight instructor and student pilot were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 instructional flight.

The flight departed Coolidge Municipal Airport (P08), Coolidge, Arizona, about 1210. The pilot reported that, during cruise flight at about 4,500 ft mean sea level, the engine began to run rough and make grinding noises. The engine stopped producing power and the propeller would not windmill. The flight instructor attempted to restart the engine and performed a forced landing to a field, during which the airplane sustained substantial damage to both wings.

Examination of the engine revealed no impact related damage and no evidence of fire. A crack was observed beginning above the No. 3 intake valve tappet casing that propagated through the engine crankcase into the oil sump. The right magneto was detached from its mounting flange. The oil cap was in place and there was no evidence of pre-accident oil leak. Both the engine oil filter media and oil suction screen were coated in shiny metallic particles.

Disassembly of the engine revealed catastrophic damage to the No. 4 cylinder and piston assembly, with no significant damage to the remaining cylinders or their associated valvetrain components. The No. 4 cylinder connecting rod was bent 45° at the piston pin end and the piston pin had detached and become embedded in the lower section of the crankcase. Even with this damage, all four connecting rods remained connected to the crankshaft and could be moved smoothly around the crankshaft journal. None of the internal components exhibited evidence of heat distress. The camshaft lobes were worn such that between 10% and 50% of the contact face material had worn away. Metal burrs were present on the edges of the cam lobe remnants, and the associated tappet heads were either shattered or exhibited spalling and cupping deformation to their cam lobe contact faces.

The No. 4 piston and pin, along with associated fragments, were examined by a specialist in the NTSB Materials Laboratory. The skirt on the piston underside exhibited the most damage. Approximately half of the skirt material was missing, with the demarcation of fracture located along the bore containing the pin. The lower third of the fracture surfaces of the piston exhibited discernible fracture features, while the rest exhibited reflective lusters with erratic streaks consistent with post-fracture smearing damage from impact or rubbing against adjacent parts. In addition, circular impact witness marks were present on the interior surface of the piston remnant.

No pre-existing or progressive cracking features were found on the pin or remnants of the piston.

Lycoming Engine Service Instruction No. 1009BE stated that the time between overhaul (TBO) for the O-360 engine was 2,200 hours of operation or 12 years (whichever occurred first) and that an engine’s published TBO does not mean that every engine will operate the number of hours or years listed without requiring component replacement and/or unscheduled maintenance events. Noncompliance with instructions for continued airworthiness, operational and/or environmental factors may necessitate repair or replacement of the engine, engine components and accessories earlier than the published TBO.

According to the maintenance records, the engine was overhauled by the manufacturer on March 5, 2003.

The airplane’s most recent 100-hour inspection was completed on April 9, 2024. At the time of the inspection, the engine had accrued approximately 2,189.9 hours of operation since the overhaul in 2003. There was no record in the maintenance logbooks of engine oil analysis having been performed.