What was found
DURING A 100-HOUR INSPECTION, A RIVET WAS FOUND MISSING ON THE BOTTOM OF THE RUDDER WHERE THE TORQUE TUBE IS RIVETED TO THE BOTTOM RIB. CLOSER INSPECTION REVEALED HOLE WAS CORRODED. DRILLED AND PEELED BACK SKIN. FOUND STEEL TORQUE TUBE RUSTED AND BOTTOM RIB HEAVILY CORRODED. REMOVED AND REPLACED AFFECTED PARTS WITH NEW. SUBMITTER STATED PROBLEM COULD BE CAUSED BY PLUGGED DRAIN HOLES OR DISSIMILAR METALS. RECOMMEND CLOSE INSPECTION OF THIS AREA AND TO ENSURE DRAIN HOLES ARE CLEAR.