What was found
(CAN) ON APPROACH, FLT CREW NOTICED "FLAP DRIVE" CAUTION LIGHT ILLUMINATE. FLAPS HAD ALREADY BEEN EXTENDED, SO CREW CARRIED OUT A NORMAL LANDING. AFTER LANDING, MX CREW PERFORMED AN INSPECTION OF VISIBLE SECTIONS OF FLAP DRIVE TRAIN & DISCOVERED A SHEARED RT NR 4 TORQUE TUBE. IT APPEARS THAT THE TORQUE TUBE HAD BEEN CHAFING FOR SOME TIME AGAINST ONE OF THE FLAP SHROUD HANGERS, DUE TO EITHER AN UNBALANCED CONDITION, OR A SLIGHT BEND IN THE TORQUE TUBE. (TC# 20090929002)