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Missing bolts in door plug installation of Alaska flight 1282 led to blowout, NTSB finds

WASHINGTON D.C.—The National Transportation Safety Board (NTSB), on February 6, released its preliminary findings in the Alaska Airlines Flight 1282 incident involving a mid-cabin door blowing off mid-flight on January 5, 2024. In that report it was found that four key bolts were missing from the cabin door, which prevent upward movement to the aircraft’s mid exit door (MED) plug, that led to the MED plug moving upwards off the stop pad leading to rapid decompression of the aircraft with almost 180 passengers and crew on board.

Photo showing the left MED plug immediately before interior restoration and the
circles show the three locations without the retaining bolts, two vertical movement arrestor bolts and the forward upper guide track bolt. The aft upper guide track is covered with insulation and cannot be seen in the photo. (Source: Boeing. Image Copyright © Boeing. Reproduced with permission.). SOURCE: NTSB Preliminary findings report of Alaska Airline flight 1282.

“The separation of the MED plug from the airplane adversely affected the pressurization performance of the airplane and the damage to the MED plug adversely affected its structural strength, requiring replacement of the MED plug, resulting in in a classification of substantial damage in accordance with TItle 49 CFR Part 830”, the investigation report reads.

Overall view of the MED plug and associated components removed from the accident airplane as received at the NTSB Materials Laboratory. SOURCE: NTSB Preliminary findings report of Alaska Airline flight 1282.
Contact damage was noted on the lower sides of the 12 stop pins and fittings on the MED plug. Witness mark matching between upper forward MED plug stop pin fitting and stop pad fitting as received in the NTSB Materials Laboratory. SOURCE: NTSB Preliminary findings of Alaska Airline flight 1282.

Two weeks ago, the NTSB held a press conference in Portland, Oregon, where Jennifer Homendy, Chair of the NTSB, briefed the media on key preliminary findings of the investigation. The following is a summary of their findings:

  • At approximately 5:06 p.m.PST Alaska Airlines flight 1282 left the runway at Portland International Airport. Just six minutes later the recorded cabin pressure of the aircraft dropped from 14.09 to 11.64 PBS per square inch when the aircraft was at approximately 14,830 feet and 271 knots. The cabin altitude greater than 1,000 feet warning activated.
  • At 5:12 the master caution activated. The cabin pressure dropped to 9.08 psi at approximately 14,850 feet and 271 knots. Just twenty seconds later the master caution deactivated.
  • At 5:13 the aircraft continued to climb and reached a maximum altitude of 16,320 feet and began to descend. The air speed was 276 knots. The selected altitude changed from 23,000 feet to 10,000 feet.
  • At 5:14 p.m. the master caution activated for three seconds.
  • At 5:16 the aircraft began a left turn from 121 degrees. The altitude was approximately 10,120 feet.
  • At 5:17 the aircraft descended below 10,000 feet.
  • At 5:18 the altitude was approximately 9,050 feet and the air speed was 271 knots. The cabin altitude greater than 10,000 feet warning deactivated. The cabin pressure was 10.48 PSI.
  • At 5:26 the aircraft landed on Runway 28 left at Portland International Airport.

The NTSB found that the cockpit door was designed to open during rapid decompression, which none of the flight crew knew. Boeing has announced it will update its manual which the NTSB hopes will translate into procedures and information for the flight attendants and crew. The oxygen masks did deploy during the incident, Homendy added.

Location of the mid-cabin doors. SOURCE: NTSB preliminary findings report of Alaska Airline flight 1282.

The NTSB Systems Group focused on the cabin pressure control system aboard the aircraft, because the auto-pressurization light illuminated during the incident. This is designed as a triple redundant system with one primary cabin pressure controller, Homendy said, with one primary cabin pressure controller (a computer system). There is a secondary cabin pressure controller, and a manual controller. The system is designed so that if the first system fails the flight controller switches to the second controller and, if that fails, they can switch to manual.

“Any one of these systems is fully capable of maintaining safe cabin pressurization,” said Homendy. “In fact, if either one of the computer systems is inoperative the FAA allows the operator to continue flying the aircraft. We have verified from the maintenance logs that the redundant system operated as designed on December 7, January 3, and January 4. At this time, we have no indications whatsoever that this correlated in any way to the expulsion of the door plug and the rapid decompression.”

Maria Cantwell

Just hours after the NTSB released the report, U.S. Senator Maria Cantwell (D-WA), chair of the Senate Committee on Commerce, Science, and Transportation, issued the following statement:

“This morning, NTSB gave Committee leaders an up-close look at the plug door that flew off Alaska Airlines flight 1282 and its initial finding that bolts securing it to the fuselage were missing. The NTSB’s preliminary report on the Alaska Airlines flight 1282 accident underscores how important quality assurance is from manufacturers and how important quality control inspections from both manufacturers and the FAA are to the safety process. We look forward to NTSB’s final report highlighting the importance of these safety practices,” wrote Sen. Cantwell. “The Commerce Committee will be holding oversight hearings on these issues and the NTSB findings.”

The U.S. Transportation and Infrastructure Committee held a meeting on the state of Aviation and the Federal Aviation Administration (FAA) that same morning where FAA Administrator Mike Whitaker testified.

The three-hour meeting discussed the 2018 FAA reauthorization which expired last December, the passage of the comprehensive long-ranged 2023 FAA reauthorization which passed the House last July and examined the recent problems the Boeing 737-9 MAX exposed when a door blew off mid-flight on January 5.

“Safety has always been this committee’s top priority and the aviation system here in the U.S. is responsible for safely transporting hundreds of millions of passengers each year without fear of harm or injury,” said Representative Rick Larsen, ranking member of the committee, at yesterday’s hearing. “Americans have to have the full confidence for our aviation system and that confidence must be justified. This committee must ensure the FAA has the resources and tools to effectively conduct its investigations, audits, and enforcement actions. And as always, we remain vigilant to ensure the likelihood of this accident is decreased substantially.”

Subcommittee Hearing on “The State of American Aviation and the Federal Aviation Administration” | House Transportation & Infrastructure Committee

During Whitaker’s testimony, he highlighted the FAA’s commitment to reducing close calls to zero since March of last year holding over 100 runway safety meetings at airports with control towers to identify and address airport-specific risks. The FAA also tasked the Investigative Technologies Aviation Rulemaking Committee (ARC) to recommend new technologies, such as cockpit alerting systems to reduce runway safety events. The ARC is expected to submit an interim recommendation report later this year.

Additionally, Whitaker defended the FAA’s commitment to enhancing safety by focusing on infrastructure improvements (namely airfield geometry issues which he says are a significant contributor to runway incursions) and evaluating runway safety areas.

Since the beginning of the Fiscal Year 2023, the FAA has awarded 57 grants for runway safety projects under the Bipartisan Infrastructure Law and 154 runway safety projects under the Airport Improvement Program, totaling more than $1 billion. These projects will install airfield lighting, signage, and markings, as well as reconfigure and construct new taxiways to enhance safety on the airfield, Whitaker said.

“Overall, our data shows a recent downward trend in the rate of runway incursions. We are optimistic that our recent and ongoing work and collaboration with industry will lead to continued safety improvements,” said Whitaker during his testimony Tuesday. “But to drive the number of runway incursions to zero, we must continue to focus on and invest in this priority.”

The FAA’s response to Alaska Airlines Flight 1282 was immediate, calling for the grounding of the Boeing 737-9 MAX under an emergency airworthiness directive the very next day. Before the 737-9 MAX was approved to resume flights last week, the FAA further approved a thorough inspection and maintenance process that was performed on each grounded aircraft prior to resuming flight. The findings during that inspection found that the quality system issues at Boeing were “unacceptable”, said Whitaker, and “require further scrutiny.”

As a response the FAA increased oversight activities of Boeing which includes capping expanded production of new 737-9 MAX aircrafts, launching an investigation scrutinizing Boeing’s compliance with manufacturing requirements, aggressively expanding oversight of new aircrafts with increased floor presence at all Boeing facilities, closely monitoring data to identify and mitigate safety trends and risks in the system, and launching an analysis of potential safety-focused reforms around quality control and delegation.

“We will follow the data and take appropriate and necessary action. The safety of

the flying public will continue to inform our decision-making,” said Whitaker. “We will continue to implement the Aircraft Certification, Safety, and Accountability Act as recent events underscore the importance of continuously looking for ways to improve and refine safety oversight activities.

Alaska Airlines resumed its 737-9 MAX service on Friday, January 26, with Flight 1146 from Seattle to San Diego

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