BOEING 737-9ALASKA AIRLINES INC
Portland, OR, USA · 2024-01-06·N704AL
What happened
NTSB summary, verbatimOn January 5, 2024, about 1713 Pacific standard time, Alaska Airlines flight 1282, a Boeing 737-9 airplane, N704AL, experienced an in-flight separation of the left mid exit door plug and rapid depressurization during climb after takeoff from Portland International Airport, Portland, Oregon. One flight attendant and 7 passengers received minor injuries; the captain, the first officer, 3 flight attendants, and 164 passengers were uninjured; and the airplane sustained substantial damage. The scheduled domestic passenger flight was operated under Title 14 Code of Federal Regulations Part 121 and departed PDX about 1707 with a planned destination of Ontario International Airport, Ontario, California.
Photographs
8the aircraft, and what the investigators foundPhotographs are NTSB docket attachments — works of the US government, in the public domain. Captions are the Board’s own.
Probable cause
the Board's determinationthe in-flight separation of the left mid exit door (MED) plug due to Boeing Commercial Airplanes’ failure to provide adequate training, guidance, and oversight necessary to ensure that manufacturing personnel could consistently and correctly comply with its parts removal process, which was intended to document and ensure that the securing bolts and hardware that were removed from the left MED plug to facilitate rework during the manufacturing process were reinstalled. Contributing to the accident was the Federal Aviation Administration’s ineffective compliance enforcement surveillance and audit planning activities, which failed to adequately identify and ensure that Boeing addressed the repetitive and systemic nonconformance issues associated with its parts removal process.
Occurrence sequence
1 stepsNTSB coding · CICTT taxonomy- 1 · Enroute-climb to cruisePart(s) separation from ACdefining event
Findings
5 causal · 0 contributing- CAUSEAircraft › Aircraft structures › Fuselage › Equip attach fittings (on fus) — Not installed/available
- CAUSEOrganizational issues › Support/oversight/monitoring › Training — Manufacturer
- CAUSEOrganizational issues › Support/oversight/monitoring › Oversight › Oversight of personnel — Manufacturer
- CAUSEOrganizational issues › Support/oversight/monitoring › Enforcement › Company/organization policy — FAA/Regulator
- CAUSEOrganizational issues › Support/oversight/monitoring › Safety programs › Adequacy of safety program — FAA/Regulator
Safety recommendations
19 issuedwhat changed because of this accidentTO THE FEDERAL AVIATION ADMINISTRATION: Once you complete the certification of Boeing Commercial Airplanes’ design enhancement for ensuring the complete closure of Boeing 737 mid exit door (MED) plugs following opening or removal, issue an airworthiness directive to require that all in-service MED plug-equipped airplanes be retrofitted with the design enhancement.
TO THE FEDERAL AVIATION ADMINISTRATION: Revise your compliance enforcement surveillance system to ensure that it provides the necessary functionality for Federal Aviation Administration managers and inspectors overseeing production approval holders to effectively identify, record, track, and resolve recurring and systemic discrepancies and nonconformance issues, including those related to specific manufacturing processes.
TO THE FEDERAL AVIATION ADMINISTRATION: Revise your audit planning activities to ensure that they provide the necessary functionality for Federal Aviation Administration managers and inspectors overseeing production approval holders to effectively identify, record, track, and resolve recurring and systemic discrepancies and nonconformance issues, including those related to specific manufacturing processes.
TO THE FEDERAL AVIATION ADMINISTRATION: Revise your records systems to ensure that they provide the necessary records for Federal Aviation Administration managers and inspectors overseeing production approval holders to effectively identify, record, track, and resolve recurring and systemic discrepancies and nonconformance issues, including those related to specific manufacturing processes.
TO THE FEDERAL AVIATION ADMINISTRATION: Once the actions in Safety Recommendations A-25-16 through 18 are completed, develop guidance for Federal Aviation Administration managers and inspectors who provide oversight of production approval holders on how to identify, record, track, and effectively address repetitive and systemic discrepancies and nonconformance issues, to include strategies for assessing the effectiveness of corrective actions taken by the production approval holder during the previous year when developing next year’s certificate management plan.
TO THE FEDERAL AVIATION ADMINISTRATION: Once the actions in Safety Recommendation A-25-19 are completed, provide Federal Aviation Administration managers and inspectors who provide oversight of production approval holders with recurrent training on how to identify, record, track, and effectively address repetitive and systemic discrepancies and nonconformance issues, to include strategies for assessing the effectiveness of corrective actions taken by the production approval holder during the previous year when developing next year’s certificate management plan.
TO THE FEDERAL AVIATION ADMINISTRATION: Retain historical compliance enforcement surveillance and audit records older than 5 years and provide Federal Aviation Administration managers and inspectors access to these records to enhance their oversight planning for production approval holders.
TO THE FEDERAL AVIATION ADMINISTRATION: Convene an independent panel to conduct a comprehensive review of Boeing Commercial Airplanes’ safety culture. The findings should be used to enhance the ongoing development of Boeing’s regulatory safety management system (SMS) and the integration of its SMS into its broader quality management system.
TO THE FEDERAL AVIATION ADMINISTRATION: Notify operators of the circumstances of the accident involving Alaska Airlines flight 1282, and encourage them to review their flight crew training programs and ensure that they include hands-on, aircraft specific training and procedures for each type of oxygen system in the operators’ fleet, to include establishing and maintaining communications when the oxygen masks are donned and removed while participating in realistic emergency procedures training scenarios.
TO THE FEDERAL AVIATION ADMINISTRATION: Review and revise, as necessary, the design standards that apply to portable oxygen bottle design to ensure that they adequately address ease of use and quick donning in an emergency situation, including considerations for the effort needed to remove the mask from its packaging.
TO THE FEDERAL AVIATION ADMINISTRATION: Require operators of airplanes equipped with a cockpit voice recorder (CVR) to incorporate guidance into company standard operating procedures, emergency protocols, and postincident and postaccident checklists—applicable to both flight crew and non-flight crew personnel—detailing actions to preserve CVR recordings as soon as practical after completion of a flight with a reportable event.
TO THE BOEING COMPANY: Continue the certification process for the design enhancement for mid exit door plugs to ensure that, once the design enhancement is certified, all applicable newly manufactured airplanes are equipped with the enhancement.
TO THE BOEING COMPANY: Once the design enhancement for mid exit door (MED) plugs is certified, issue a service bulletin to address retrofitting in-service MED plug equipped airplanes with the design enhancement.
TO THE BOEING COMPANY: Apply your updated safety risk management process to current and future revisions to Business Process Instruction “Perform Part or Assembly Removal” to ensure that it provides clear and concise guidance for determining when a removal record is needed.
TO THE BOEING COMPANY: Develop recurrent training on Business Process Instruction “Perform Part or Assembly Removal” for Boeing manufacturing personnel that emphasizes the importance of removal records for product safety, prepares personnel to consistently and correctly determine when a removal record is needed, and ensures that a removal record is generated when required.
TO BOEING COMPANY: Develop a structured on-the-job training program that identifies and defines tasks necessary for manufacturing personnel to be considered fully qualified in their job series and includes a grading system for trainers and trainees to track progress and determine competence.
TO THE BOEING COMPANY: Document and archive the results of training provided and received as part of the program recommended in Safety Recommendation A 25-30 to support future data analysis.
TO THE BOEING COMPANY: Revise your safety risk management process to ensure that it 1) identifies the root causes of manufacturing process compliance issues, like the persistent deficiencies with Business Process Instruction “Perform Part or Assembly Removal” and other production process inconsistencies identified in this investigation, and 2) evaluates the effectiveness of corrective actions.
TO THE BOEING COMPANY: As you integrate your quality management system and safety management system, develop a process that can identify escapes that result from human error, assess them using a system specifically designed to identify factors that contribute to such errors, and implement effective mitigation strategies.
Sequence of events
24 timed eventsfrom the FDR factual report · claude-sonnet-5- 17:06:47 PSTTakeoffp.7The aircraft departed runway 28L at Portland International Airport (PDX).
- 17:12:33 PSTClimbp.7The recorded cabin pressure dropped from 14.09 to 11.64 psi when the aircraft was at 14,830 ft and 271 kts. The "Cabin Altitude Greater than (>) 10k ft Warning" activated.
- 17:12:34 PSTClimbp.7The master caution activated. The cabin pressure continued decreasing and was 9.08 psi at 14,850 ft and 271 kts. The aircraft magnetic heading was 123 deg.
- 17:12:52 PSTClimbp.7The master caution deactivated.
- 17:13:36 PSTClimbp.7The cabin pressure was 7.89 psi and was at the lowest value recorded. The aircraft was at 16,293 ft and 278 kts.
- 17:13:41 PSTClimb/Descentp.7The aircraft continued to climb and reached a maximum altitude of 16,320 ft and began to descend. The airspeed was 276 kts on a magnetic heading of 120 deg.
- 17:13:48 PSTDescentp.7The cabin pressure began to increase from 7.89 psi to 7.91 psi. The aircraft was at 16,266 ft and was descending.
- 17:13:56 PSTDescentp.8The selected altitude changed from 23,000 ft to 10,000 ft. The cabin pressure was 7.95 psi and continued to increase for the remainder of the flight.
- 17:14:35 PSTDescentp.9The master caution activated for 3 seconds.
- 17:16:56 PSTDescentp.9The aircraft began a left turn from 121 deg. The altitude was approximately 10,120 ft.
- 17:17:00 PSTDescentp.9The aircraft descended below 10,000 ft.
- 17:18:05 PSTDescentp.9The aircraft altitude was approximately 9,050 ft and the airspeed was 271 kts. The "Cabin Altitude Greater than (>) 10k ft Warning" deactivated. The cabin pressure was 10.48 psi.
- 17:26:46 PSTLandingp.9The aircraft landed on runway 28L at PDX.
- 17:06:48 QAR PSTTakeoffp.9The aircraft departed runway 28L at PDX. Cabin pressure controller (CPC) 1 was in automatic control.
- 17:12:33 QAR PSTClimbp.9The cabin differential pressure dropped from 5.72 psi to 3.28 psi and 2.48 psi for CPC1 and CPC2, respectively.
- 17:12:34 QAR PSTClimbp.9The recorded cabin pressure dropped from 14.09 to 10.67 psi for CPC1 when the aircraft was at 14,859 ft and 271 kts. CPC2 did not record a change in pressure.
- 17:12:35 QAR PSTClimbp.9The "Cabin Altitude Greater than (>) 10k ft Warning" activated. The cabin pressure dropped to 9.43 psi and 10.67 psi for CPC1 and CPC2, respectively, at 14,883 ft and 271 kts. The aircraft magnetic heading was 122 deg. The differential pressure was 0.22 psi and 0.17 psi for CPC1 and CPC2, respectively.
- 17:12:40 QAR PSTClimbp.9The outflow valve (OFV) switch was activated.
- 17:14:28 QAR PSTDescentp.9The OFV switch was deactivated. The OFV position began to increase from 1.06 deg and -0.63 deg to 8.19 deg and 1.69 deg for CPC1 and CPC2, respectively.
- 17:14:37 QAR PSTDescentp.9The OFV position reached a maximum 109.50 deg and 108.69 deg for CPC1 and CPC2, respectively.
- 17:15:05 QAR PSTDescentp.9The OPMODE for CPC1 changed from auto to manual.
- 17:15:06 QAR PSTDescentp.9The automatic CPC1 in control changed from operational to standby. The OPMODE for CPC2 changed from auto to manual.
- 17:17:00 QAR PSTDescentp.9The aircraft descended below 10,000 ft. The "Cabin Altitude Greater than (>) 10k ft Warning" deactivated.
- 17:26:47 QAR PSTLandingp.9The aircraft landed on runway 28L at PDX.
NTSB analysis
from the final reportOn January 5, 2024, about 1713 Pacific standard time, Alaska Airlines flight 1282, a Boeing 737-9 airplane, N704AL, experienced an in-flight separation of the left mid exit door plug and rapid depressurization during climb after takeoff from Portland International Airport, Portland, Oregon. One flight attendant and 7 passengers received minor injuries; the captain, the first officer, 3 flight attendants, and 164 passengers were uninjured; and the airplane sustained substantial damage. The scheduled domestic passenger flight was operated under Title 14 Code of Federal Regulations Part 121 and departed PDX about 1707 with a planned destination of Ontario International Airport, Ontario, California.