NTSB: four bolts missing from flight 1282 door plug

The National Transportation Safety Board (NTSB) has released a preliminary report into the in-flight structural failure aboard Alaska Airlines flight 1282, indicating four missing bolts from the door plug assembly were removed by Boeing during a rivet repair. The mid-exit door plug (which was lost in the rapid decompression of the 737 MAX 9) was manufactured by Spirit AeroSystems Malaysia on March 24 2023 before being received at Spirit AeroSystems Wichita on May 10. It was then installed and rigged on the fuselage before being shipped to Boeing’s Renton, Washington facility, where it arrived on August 31 2023. After being located in the backyard of a private residence, the recovered door plug and associated hardware were shipped to the NTSB’s Materials Laboratory for further examination. The plug was ‘mostly intact with some damage from the event and appeared to be manufactured in accordance with the engineering drawings,’ confirmed the NTSB, who also added that ‘the two vertical movement arrestor bolts, two upper guide track bolts, forward lower hinge guide fitting, and forward lift assist spring were missing and have not been recovered’. ‘Overall, the observed damage patterns and absence of contact damage or deformation around holes… indicate that the four bolts that prevent upward movement of the MED plug were missing before the MED plug moved upward off the stop pads,’ added the NTSB. When the fuselage arrived at Boeing’s Washington facility, a non-conformance report indicating five damaged rivets necessitated the opening of the door plug to rectify the rivets. To open the plug, ‘the two vertical movement arrestor bolts and two upper guide track bolts had to be removed’. The NTSB ‘continues to determine what manufacturing documents were used to authorize the opening and closing of the left MED plug during rivet rework’.