This article was originally published in German and has been automatically translated.
Boeing is changing the design of a Boeing 737 Max 9 fuselage section that was lost on a passenger flight in January. Accident investigators assume that four retaining bolts were forgotten during the assembly of the fuselage. With the design changes, this should no longer be possible, said Boeing's Vice President of Quality Assurance, Elizabeth Lund, at a hearing of the US National Transportation Safety Board (NTSB) on Tuesday.
On a domestic Alaska Airlines flight from Portland to Ontario (California) in January, part of the fuselage came loose from its anchorage shortly after take-off and was forced out by the cabin pressure. The Boeing 737 Max 9 aircraft was able to return safely to Portland Airport despite a large hole in the fuselage. The NTSB then launched an investigation into the incident.
Safety bolt missing
The lost component was a latch for a door frame. Depending on the number of seats, the Boeing 737 Max requires an additional door as an emergency exit. In the case of seating with fewer seats, as used by many US airlines, the door frame provided for this purpose in the fuselage is closed with a component with a normal window. A continuous row of windows can then be seen from the outside.
This component is held in the door frame by twelve fittings; the cabin pressure presses the fittings of the door panel against the retaining fittings of the frame. The construction is fastened and secured against slipping with four retaining bolts, two of which form the lower hinge of the door panel. According to previous investigation results , these four bolts were missing on the Alaska Airlines aircraft.
This design is now to be changed. "They're working on some design changes that will prevent the door panel from closing if there's any problem and it's not firmly anchored," Lund said at the NTSB hearing. The new design should be implemented later this year, he said, and will then be modified throughout the active fleet.
The door panel will be used in the assembly of the fuselage. The fuselage of the 737 is built by the supplier Spirit AeroSystems. Boeing sold its assembly plant in Wichita, Kansas, in 2005, which has been building parts for Boeing and other companies as Spirit AeroSystems ever since. At the beginning of July, Boeing announced that it would buy back Spirit AeroSystems for 4.7 billion US dollars (4.3 billion euros). Boeing has also had a new CEO since August.
Quality defects at Spirit and Boeing
Every fuselage delivered by Spirit is inspected before final assembly at the Boeing plant in Renton. If Boeing's quality management team finds a defect, it is documented and rectified. Spirit also sends employees to Boeing for this purpose, who then rectify faults directly on site at the factory in Renton. Boeing's own mechanics also work on the aircraft.
In the case of the Alaska Airlines aircraft, the door panel was apparently removed in order to carry out repairs to the riveting of the hull. Normally, meticulous records are kept of every component, every action and every tool in aircraft construction, no matter how small. However, it has not yet been possible to determine who is responsible for the loss of the four bolts. Apparently also because, according to the NTSB, documents are missing. Meanwhile, Boeing is said to have dismissed two employees in connection with the incident. The NTSB criticizes this because it hinders the investigation.
The NTSB had already counted Boeing out for lack of cooperation. During the hearing on Tuesday and Wednesday, NTSB head Jennifer Homendy criticized the safety culture at Boeing. The Alaska Airlines case was not the first time that unauthorized and undocumented work had occurred. "This incident should never have happened. It should have been stopped years ago," said Homendy.
Aviation authority criticized
The US Federal Aviation Administration (FAA), which is responsible for the operational monitoring of aircraft manufacturers and the certification of aircraft, components, software and technical procedures, has also come under fire. "We have a lot of questions - there was information that was known," said Homendy. Missing and incorrect documentation had been an issue for years: "This is not new."
Criticism of lax oversight is probably not new to the FAA either. The agency also played an inglorious role in the scandal surrounding the approval of poorly documented control software for the Boeing 737 Max 8, which led to the crashes of two passenger planes. During the NTSB hearing on the ripped-out door of the Alaska Airlines plane, an FAA representative said, "We believe we conducted effective oversight."
(vbr)
