KUALA LUMPUR – The panel or door plug manufactured by Spirit AeroSystems Malaysia and which blew out mid-flight of a Boeing 737 MAX 9 Alaska Airlines plane last month cleared manufacturing processes, a preliminary investigation by a US body has found.
The door plug received one quality notification (QN) that a “seal flushness was out of tolerance by 0.01 inches”, but “no manufacturing rework was required”, the National Transportation Safety Board (NTSB) said in its early investigation report into the January 5 incident.
“Spirit AeroSystems Engineering determined the condition was structurally and functionally acceptable and did not adversely affect the form, fit, or function of the installation.
“There were no other QNs for the left mid-exit door (MED) plug before leaving Spirit AeroSystems. (The) fuselage (was) shipped to Boeing on August 20, 2023,” it said in the report released yesterday.
The board’s full investigation is to take up to a year before final conclusions are reached into the January 5 incident.
NSTB said the door plug had been manufactured by Spirit AeroSystems Malaysia on March 24, 2023.
It reached the United States, at the manufacturer’s plant in Wichita, Kansas, on May 10 the same year, where the door plug was installed on the fuselage and where the QN regarding seal flushness was reported.
After determining that no manufacturing rework was required, the fuselage was shipped to Boeing on August 20, 2023, and arrived at the Renton facility in Washington on August 31.
It was at Boeing where investigators determined that four bolts for securing the door plug to the fuselage were missing.
NSTB said it found indication the four bolts had been removed as there was lack of “contact damage” in the parts where they were supposed to be.
Written and photographic evidence collected for the investigation showed that Boeing employees had removed the bolts during an inspection prior to delivery of the aircraft to the airline, and had not reinstalled them. The inspection, last October, was to replace other damaged rivets in the aircraft cabin.
Other damage marks found were consistent with the door plug blowing out of the fuselage in an upward direction with great force. It was later found in the backyard of a Portland resident.
The blown-out door plug had sparked Malaysians’ interest as handwritten information in marker pen on the piece stated it was made in Malaysia.
The incident occurred after the plane took off from Portland for Ontario in California. It caused the cabin to depressurise and forced the plane to turn back for an emergency landing. There were no fatalities and only minor injuries were reported.
Responding to NTSB’s preliminary report, Boeing CEO Dave Calhoun said the company would review the findings but acknowledged that “whatever final conclusions are reached, Boeing is accountable for what happened”. – February 7, 2024