What was found
PILOT REPORTED ACFT NOT PRESSURIZING IN FLIGHT. THE LOWER FWD DOOR CORNER FRAME WAS FOUND TO BE CRACKED ALONG FWD END OF DOOR HINGE ATTACH RIVETS. THIS WAS THE THIRD FAILURE OF THIS THIS TYPE FOUND IN OUR FLEET. THE DOOR FRAME CORNER AND INTERCOSTAL WERE REPLACED TO CORRECT THE PROBLEM. M7 PROVIDES A LIGHT AND HEAVY VERSION OF THE DOOR CORNERS, THE PART REMOVED WAS THE LIGHT VERSION. IT IS BELIEVED THAT THE ADDED STRESS OF THE DOOR SNUBBER ATTACHED AT THIS LOCATION TO BE THE CAUSE OF THE FAILURE.