What was found
DURING A PREFLIGHT, THE EXHAUST NOZZLE, MIXER, WAS NOTICED TO HAVE CRACKS THROUGHOUT. THE ACFT WAS GNDED & PUT INTO MX. THROUGH FURTHER INSPECTION WE HAD TO PERFORM A BORESCOPE INSPECTION & A VIBRATION SURVEY TO THE ENG & IT WAS OUT OF LIMITS. THE BORESCOPE INSPECTION DID NOT FIND ANY DEFECTS. THEY TRIED TO BALANCE THE FAN SECTION & IT WOULD NOT COME WITHIN LIMITS. THE LPT SECTION WAS REMOVED & IT WAS DETERMINED TO HAVE BLADE SHIFT. THE LOW PRESS TURBINE SECTION WAS REPAIRED, REINSTALLED WITH A NEWLY BALANCED FAN. A VIBRATION SURVEY WAS AGAIN PERFORMED & IT WAS WITHIN LIMITS. ALL OPERATIONAL CHECKS, ENG PERFORMANCE RUNS WERE PERFORMED & A CHECK FLIGHT TO VERIFY OPERATION.