What was found
CYLINDER HEAD CRACKED, CAUSED AN ENGINE POWER REDUCTION ON TAKEOFF: A SUCCESSFUL RETURN TO AIRPORT AND LANDING WAS ACCOMPLISHED. VISIBLE IN COMBUSTION CHAMBER FROM .3750: BELOW INTAKE VALVE, CLOCKWISE THROUGH LOWER SPARK PLUG, AROUND OUTSIDE OF EXHAUST VALVE SEAT, THROUGH TOP SPARK PLUG TO BARREL INTERFACE. FROM EXTERIOR OF CYLINDER, CRACK IS VISIBLE FROM LOWER (INBD) EXHAUST STUD, UP AND AROUND THROUGH UPPER SPARK PLUG, TO BARREL JOINT AND AROUND TO JUST PAST INTAKE PORT. ENGINE APPROX 48 HOURS SINCE LAST 100 HOUR INSPECTION, WITH NO DEFECT NOTED AT THAT TIME. CYLINDER P/N IS SUBJECT IN AD 2007-04-19R1, SERIAL NUMBER IS NOT IN SUBJECT RANGE.