The investigation into the incident that saw a door plug blown out of a 737 MAX 9 aircraft mid-flight has found that the panel was missing four bolts when it left a Boeing factory in its preliminary report on the causes of the event.
The National Transportation Safety Board’s (NTSB) report found the bolts were removed during the manufacturing process to fix an issue with damaged rivets and did not appear to be re-fitted when the plug fell out of the plane soon after take-off.
The report said observed damage from the recovered plug and associated parts “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.”
The investigation recovered an image sent between Boeing employees during the manufacturing process that showed the door plug refitted after the damaged rivets were fixed. At least three of the bolts in question were missing in the image, with the fourth covered by insulation.
In response to the release of the report, Boeing CEO Dave Calhoun, who recently told investors that Boeing “caused the problem” said: “Whatever final conclusions are reached, Boeing is accountable for what happened. An event like this must not happen on an aeroplane that leaves our factory. We simply must do better for our customers and their passengers.
“We are implementing a comprehensive plan to strengthen quality and the confidence of our stakeholders. It will take significant, demonstrated action and transparency at every turn – and that is where we are squarely focused.”
While Boeing has already stepped up its production inspections in response to the incident, which saw more than 170 planes grounded by the FAA pending additional inspections, the NTSB’s findings will likely raise further questions about quality control at the manufacturer’s factories.
The door plug supplier Spirit AeroSystems will also likely have to face further scrutiny as the NTSB report found that its staff were responsible for completing the Non-Conformance Order documenting the rivet replacements that possibly led to the bolts not being replaced.
While nobody was reported as injured during the incident on an Alaska Airlines flight, the plane, carrying 171 passengers, was forced to return to Portland airport.
