Several bolts supposed to block the door of a Boeing 737 MAX 9 which came loose in mid-flight in early January during a trip by the American company Alaska Airlines were missing, according to the preliminary investigation report of the Safety Agency of Transportation (NTSB), released Tuesday.
According to the NTSB, the lack of wear or deformation around some of the holes “indicates that four bolts intended to prevent the cap holder from moving upward were missing before it moved.”
The agency has collected written documents and photos that show Boeing employees removed four bolts at these locations during an inspection at the Renton, Wash., factory before delivery of the plane, in last October.
The operation was carried out to replace five damaged rivets in the cabin of the aircraft. Other photos taken after changing the rivets show that in at least three points, the bolts had not been reinstalled.
This door was used to block an exit and was not intended to be opened, this model already having enough emergency exits in this configuration.
On January 5, she took off during the ascent of the Alaska Airlines MAX 9 which was to connect Porland, Oregon to Ontario, California. The incident left only a few minor injuries.
Before the NTSB report was released, Alaska had already reported “loose equipment” after preliminary inspections.
Owner of the largest fleet of 737 MAX 9s (79 aircraft), United Airlines said it had discovered, during checks, “bolts that needed to be tightened”.
In recent months, Boeing has experienced other episodes of failure and in particular had to slow down its deliveries because of problems on the fuselage, in particular on the rear bulkhead of the aircraft.
Tuesday, during a Congressional hearing, the new boss of the American Civil Aviation Regulatory Agency (FAA), Mike Whitaker, considered it necessary to strengthen supervision of Boeing after the 737 MAX 9 incident.
“There were problems [avec Boeing] in the past and it appears that they have not been resolved,” said the new FAA administrator, who took office in October, during a hearing before the House of Representatives subcommittee on Aviation.
“So we feel like we need to raise the level of supervision to deal with this,” he continued.