What was found
(CAN) DURING HARD MANEUVERING WITH FLAPS DOWN, A LOUD BANG WAS HEARD BY THE PILOTS WHO NOTICED THE LT FLAP BEING PUSHED BACK AT A STRANGE ANGLE. THE FLAPS WERE LEFT IN THE DOWN POSITION AND THE AIRCRAFT WAS RETURNED WITHOUT INCIDENT. UPON INVESTIGATION THE LT IB FLAP TRACK WAS FOUND SEPARATED AND CRACKED FROM THE AIRFRAME AT THE LOWER FLANGE. THE CAUSE APPEARS TO BE THE CHERRYMAX RIVETS ATTACHING THE LOWER FLANGE OF THE WING RIB FRETTING, BECOMING WORN, AND WEARING THE RIVET HOLES IN THE WING SPAR UNTIL THE HIGHER STRESSES OF MANEUVERING TORE THEM FREE. THE FLAPS AND TRACKS WERE REMOVED, SPAR INSPECTED WITH NO DAMAGE NOTED. THE FLAP TRACK RIB ASSY`S WERE REPLACED, USING STRUCTURAL SCREWS AND NUTS TO ATTAC