What was found
(CAN)HOLE NOTED ON LEFT SIDE OF FORE RUDDER. APPROXIMATELY 1 INCH FROM TOP OF RUDDER ALONG TOP RIB. IT SEEMS A CRACK HAD STARTED ALONG THE ROW OF RIVETS ON THE RIB AND THE AIRFLOW TORE THE SKIN BACK LEAVIN G A 6 INCH HOLE. CRACK APPEARS TO BE FATIGUE RELATED CAUSED BY OIL CANNING.CRACKING DUE TO STIFFENE R. GENERIC REPAIR RD 8-55-335 DEVELOPED FEBRUARY 1996. LIKELY PROBLEM CAUSED BY VIBRATION BUFFETING. SERIES 400 AIRCRAFT TO BE MODIFIED.