What was found
DURING A ROUTINE INSPECTION, A PART THAT FORMS THE FORWARD FRAME OF THE CABIN DOOR SILL WAS FOUND CRACKED. CRACKING WAS THROUGH RIVET HOLES THAT CONTAINED LOOSE, WORKING RIVETS. STRESS TO THIS AREA OF STRUCTURE IS SUSPECTED TO BE CAUSED BY THE CABIN DOOR WHICH IS MOUNTED ADJACENT; CABIN DOOR IS USED AS A HANDHOLD BY PILOTS ENTERING/EXITING CABIN.