What was found
MAINTENANCE FOUND THE NR 3 ENGINE LEFT CORE COWL MISSING AND EGT STRAKES DAMAGED. THE EGT STRAKES, LEFT AND RIGHT CORE COWLING WERE REPLACED. IN ADDITION, THE NR 4 AND NR 5 CAP STRUTS, LOWER VENT SYSTEM MANIFOLD AND NR 3 ENGINE EXHAUST NOZZLE WERE REPLACED. *S/D* ONLY THE NR 3 ENGINE RT CORE COWL DEPARTED THE AIRCRAFT. INVESTIGATION BY ENGINEERING CONCLUDED THAT ONE OF THE BOLTS HOLDING THE HINGE FITTING ONTO THE PYLON HAD DEVELOPED A CRACK WHICH SLOWLY PROGRESSED UNTIL BOLT SEPARATED. THE REMAINING BOLTS EVENTUALLY SEPARATED DUE TO THE INCREASED LOAD.