B747 Captain reported a malfunction with the main cabin door during climb. The aircraft diverted to an alternate airport and landed safely.
Synopsis
B747 Captain reported a malfunction with the main cabin door during climb. The aircraft diverted to an alternate airport and landed safely.
Narrative
'With all paperwork complete and ready for departure the ops agent asked if a crewmember could come down to close the door since they claimed it was difficult to close from the outside. I went down to the main deck to close the door and found it difficult to close but on the third try the door closed smoothly and normally.On the first officer's before start flow all doors indicated closed. After takeoff around 2500 feet we received the EICAS message 'DOOR ENTRY' the door also showed open on the doors page. Soon after that; we heard a boom from the main deck similar to a cargo container 'oil canning'. I ran the QRH to its completion and since the aircraft was pressurizing normally with no other indications of any abnormalities the crew agreed to continue ops normal to ZZZZ1. A climb to a higher altitude was given but around 8500 feet a second much louder boom came from the main deck that was felt in the cockpit floor and seats. Coordinating with air traffic control we stopped the climb at 8500 feet entered an orbiting holding pattern and contacted the company via SatCom. At this point I communicated with the dispatcher I had no intentions of continuing to a higher altitude and wanted to return the aircraft to the ground for an inspection either in ZZZZ or ZZZZ2. It was determined ZZZZ2 was the best option due to maintenance availability. The flight continued to ZZZZ2 at 9000 feet and 250 kts eventually entering a holding pattern to burn gas to get below maximum landing weight and landed without incident. At the parking stand when the door was opened the top two locking mechanisms fell to the floor.Cause: Failure of top locking mechanisms
Second reporter narrative
'In ZZZZ the ops agent asked us to assist him with closing the door from the inside since he was having difficulty from the outside. Person A; the captain went down and assisted the ops Manager and closed the door. The door was closed on the doors page as well as the EICAS. Takeoff was normal; as I was hand flying at approximately 1500' the Door Entry EICAS message appeared; followed by the first loud bang. I engaged autopilot and we had a brief discussion to continue the climb to a safe altitude before we assessed the door message. On the published SID; at approximately 8500 ft we heard a second much louder bang that reverberated through the aircraft. I pushed altitude hold and we asked ATC for a location to present position hold while we assessed. We completed the QRH and called the company and determined the best course would be to remain low altitude and continue for a precautionary landing at ZZZZ2. To note we did not declare a pan or mayday since the aircraft was pressurizing. We remained under 250 kts the whole flight since we were not sure of the extent of the damage and held south of ZZZZ2 to get below max landing weight. My landing was smooth and uneventful.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.