Accident Summary
On April 19, 2024, at approximately 1230 mountain standard time, a Piper PA-28 airplane (registration N4399X) was substantially damaged after an engine failure and forced landing near Marana, Arizona. The aircraft was conducting a Title 14 Code of Federal Regulations Part 91 instructional flight, having departed Coolidge Municipal Airport (P08) in Coolidge, Arizona, about 1210. Both the flight instructor and student pilot were not injured.
According to the pilot's report, during cruise flight at approximately 4,500 feet mean sea level, the engine began to run rough and emit grinding noises. The engine subsequently 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 both wings sustained substantial damage.
Engine Examination
Post-accident examination of the engine found no impact-related damage and no evidence of fire. A crack extended from above the No. 3 intake valve tappet casing 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 a pre-accident oil leak. Both the engine oil filter media and oil suction screen were coated in shiny metallic particles.
Disassembly revealed catastrophic damage to the No. 4 cylinder and piston assembly, while the remaining cylinders and valvetrain components exhibited no significant damage. 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. Despite this, all four connecting rods remained attached to the crankshaft and moved smoothly around the journal. No internal components showed signs of heat distress. Camshaft lobes were worn, with 10% to 50% of the contact face material missing. Metal burrs were present on the edges of the cam lobe remnants, and the associated tappet heads were either shattered or showed spalling and cupping deformation on their cam lobe contact faces.
The No. 4 piston and pin, along with fragments, were examined at the NTSB Materials Laboratory. The piston skirt sustained the most damage, with approximately half of the skirt material missing; the fracture demarcation was along the bore containing the pin. The lower third of the piston fracture surfaces showed discernible features, while the rest had reflective lusters with erratic streaks consistent with post-fracture smearing damage. 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 piston remnants.
Maintenance Records
Lycoming Engine Service Instruction No. 1009BE specified a time between overhaul (TBO) of 2,200 hours of operation or 12 years, whichever occurred first, for the O-360 engine. It noted that the published TBO does not guarantee that every engine will operate for that duration without requiring component replacement or unscheduled maintenance; noncompliance with instructions for continued airworthiness and operational or environmental factors may necessitate earlier repair or replacement.
According to the maintenance records, the engine was overhauled by the manufacturer on March 5, 2003. The most recent 100-hour inspection was completed on April 9, 2024, at which time the engine had accrued approximately 2,189.9 hours since overhaul. There was no record of engine oil analysis having been performed.