What was found
DURING NORMAL CRUISE FLIGHT PILOT REPORTED ROUGH RUNNING ENGINE AND ASSUMED A SPARK PLUG HAD FAILED. MAINTENANCE INSPECTION DETERMINED THE NR 1 ENGINE CYLINDER, FUEL INJECTOR NOZZLE FAILED. THE INJECTOR LINE FAILED AT THE BRAZED PORTION CLOSEST TO THE FUEL NOZZLE. NO FIRE WAS REPORTED. THESE FUEL INJECTOR LINES ARE SUBJECT TO REPETITIVE INSPECTION REQUIRED BY AIRWORTHINESS DIRECTIVE AD 2015-19-07. THIS LINE HAD BEEN INSPECTED WITH SATISFACTORY RESULTS 27.6 FLIGHT HOURS PRIOR TO FAILURE. THE FAILED LINE HAD 429 HOURS TIME IN SERVICE (TIME SINCE NEW)