What was found
WHILE APPROACHING INTENDED DESTINATION OF SSI, LEVEL AT 5,000 FEET, THE PLANE STARTED VIBRATING/SHAKING WITH A LOSS OF PERCENT POWER AND MANIFOLD PRESSURE, AMONG OTHER INDICATIONS. CYLINDER #6 EGT WENT OFFLINE, INDICATING A PROBLEM WITH THAT CYLINDER. TURNED AROUND TO CLOSEST AIRPORT FHB AND MADE AN EMERGENCY LANDING. UPON LANDING, DISCOVERED CYLINDER #6 HAD CRACKED AT THE HEAD BETWEEN THE ROCKER BOX COVERS. CYLINDER SERIAL NUMBER IS AC21IB171 BUT UNSURE OF THE PART NUMBER. THIS IS A FACTORY REMANUFACTURED ENGINE SERIAL NUMBER 1042372 FOR WHICH AD2020-16-11 DOES NOT APPEAR APPLICABLE; HOWEVER, AFTER THIS INCIDENT, IT WAS COMPLIED WITH ANYWAY, FOLLOWED IN JUNE 2025 BY ANOTHER CYLINDER (#5) CRACKING IN THE SAME FASHION.