What was found
DURING REMOVAL AND REPLACEMENT OF THE P/N 15708-001 INDUCTION DUCT ASSY. IT WAS NOTED THAT THE INDUCTION DUCT WAS CRACKED IN AREA OF AN3-34 BOLT WHICH SERVES AS HINGE POINT FOR ALTERNATE AIR DOOR. AFTER REMOVING BOLT IT WAS FOUND TO HAVE A GROOVE WORN INTO BOLT SHANK ALL THE WAY AROUND (360 DEGREES). IT APPEARS THAT INDUCTION DUCT SUPPORT BRACKET P/N 15671-002, MADE OF STAINLESS STEEL, IS WEARING INTO BOLT. IT IS VERY DIFFICULT TO TELL IF THERE IS CRACKING ON DUCT (CRACKING LOCATED AT BOTTOM OF DUCT) WITHOUT REMOVING IT. THE CONDITION OF THE BOLT CANNOT BE VERIFIED UNLESS IT IS REMOVED. THIS MODEL AIRCRAFT, WITH THE PLASTIC TYPE INDUCTION DUCTS SHOULD BE INSPECTED FOR THIS CONDITION AS SOON AS POSSIBLE.