What was found
DURING ROUTINE 500-HOUR INSPECTION, FLAPS WERE OPERATED TO VERIFY PROPER FUNCTION. DURING OPERATION, A 'POP' WAS HEARD AND THE LEFT OUTBOARD FLAP WAS NO LONGER MOVING. INSPECTION REVEALED THE FLEX CABLE INNER SHAFT HAD FAILED. CABLE WAS INSTALLED 2-8-88, AD 87-04-03, PERFORMED AT 4,113.0 HRS. BOTH LEFT AND RIGHT CABLES REPLACED WITH NEW AT THIS TIME.