What was found
DURING CLIMB THROUGH 180, A CHIRPING NOISE HEARD FROM CABIN. STOPPED AFTER ABOUT 2 MINS. ON ARRIVAL, MAIN DOOR WAS DIFFICULT TO UNLOCK. MOVEMENT OF LOCKING HANDLE PRODUCES A GRINDING NOISE FROM INSIDE. TROUBLESHOT AND FOUND THE SOURCE OF THE GRINDING NOISE IS THE MED SUPPORT STRUT, ATTEMPTED TO LUBRICATE THE STRUT WITHOUT SUCCESS, REMOVED DEFECTIVE STRUT AND INSTALLED A NEW STRUT IAW MM 52-10-40 OP'S CK GOOD.