# NTSB DCA11MA039: Boeing 737, N632SW, Yuma, AZ, April 1, 2011

- Type: NTSB accident investigation
- Classification: Accident · Minor injuries · Major investigation · Final report
- Date: April 1, 2011, 15:57 local (22:57 UTC)
- Place: Yuma, AZ
- Coordinates: 32.656665, -114.605834 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=32.6567&lon=-114.6058&mi=10
- Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping)
- Defining event: [Enroute-climb to cruise: Aircraft structural failure](https://openairdocs.org/ntsb-events/337)
- Highest injury: Minor injuries
- Injuries: 2 minor, 120 uninjured
- Status: Completed, report February 26, 2014
- Report: Approved by Office Director
- NTSB office: Major Investigations Division
- NTSB case key (mKey): 78737
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=DCA11MA039
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/78737/pdf
- NTSB docket: https://data.ntsb.gov/Docket?ProjectID=78737
- Page: https://openairdocs.org/ntsb/DCA11MA039

## Probable cause

the improper installation of the fuselage crown skin panel at the S-4L lap joint during the manufacturing process, which resulted in multiple site damage fatigue cracking and eventual failure of the lower skin panel. Contributing to the injuries was flight attendant A's incorrect assessment of his time of useful consciousness, which led to his failure to follow procedures requiring immediate donning of an oxygen mask when cabin pressure is lost.

## Findings

NTSB's coded findings; those marked are part of the probable cause.

- [Knowledge: knowledge of procedures](https://openairdocs.org/ntsb-findings/02032010): Personnel issues › Experience/knowledge · Cabin crew (probable cause); cases with it: [All aircraft, 41 cases](https://openairdocs.org/ntsb-findings/02032010/cases.md)
- [Fuselage: fuselage main structure](https://openairdocs.org/ntsb-findings/01035310): Aircraft › Aircraft structures · Incorrect service/maintenance (probable cause); cases with it: [All aircraft, 24 cases](https://openairdocs.org/ntsb-findings/01035310/cases.md)

## Sequence of events

The events NTSB coded, in order, by phase of flight. The defining event best describes what happened.

- [Enroute-climb to cruise: Aircraft structural failure](https://openairdocs.org/ntsb-events/337) (defining event); cases with it: [All aircraft, 290 cases](https://openairdocs.org/ntsb-events/337/sequence.md)

## Analysis

The Safety Board's full report is available at http://www.ntsb.gov/investigations/reports_aviation.html. The Aircraft Accident Brief number is NTSB/AAB-13/02. On April 1, 2011, about 1558 mountain standard time (MST), a Boeing 737-3H4, N632SW, operating as Southwest Airlines flight 812 experienced a rapid decompression while climbing through flight level 340. The flight crew conducted an emergency descent and diverted to Yuma International Airport (NYL), Yuma, Arizona. Of the 5 crewmembers and 117 passengers on board, one crewmember and one nonrevenue off-duty airline employee passenger sustained minor injuries. The airplane sustained substantial damage; postaccident inspection revealed that a section of fuselage skin about 60 inches long by 8 inches wide had fractured and flapped open on the upper left side above the wing. The flight was conducted under the provisions of 14 Code of Federal Regulations (CFR) Part 121 as a regularly scheduled domestic passenger flight from Phoenix Sky Harbor International Airport, Phoenix, Arizona, to Sacramento International Airport, Sacramento, California.

## Factual narrative

The Safety Board's full report is available at http://www.ntsb.gov/investigations/reports_aviation.html. The Aircraft Accident Brief number is NTSB/AAB-13/02. On April 1, 2011, about 1558 mountain standard time (MST), a Boeing 737-3H4, N632SW, operating as Southwest Airlines flight 812 experienced a rapid decompression while climbing through flight level 340. The flight crew conducted an emergency descent and diverted to Yuma International Airport (NYL), Yuma, Arizona. Of the 5 crewmembers and 117 passengers on board, one crewmember and one nonrevenue off-duty airline employee passenger sustained minor injuries. The airplane sustained substantial damage; postaccident inspection revealed that a section of fuselage skin about 60 inches long by 8 inches wide had fractured and flapped open on the upper left side above the wing. The flight was conducted under the provisions of 14 Code of Federal Regulations (CFR) Part 121 as a regularly scheduled domestic passenger flight from Phoenix Sky Harbor International Airport, Phoenix, Arizona, to Sacramento International Airport, Sacramento, California.

## Aircraft

- Registration: N632SW (not matched to a registry record)
- Reported make and model: BOEING 737 (300)
- Category: Airplane
- Serial number: 27707
- Engines: CFM 56 turbo fan; CFM 56 turbo fan
- Damage: Substantial damage
- Flight: Part 121
- Operator: Southwest Airlines Co
- Registered owner: Southwest Airlines Co
- Airworthiness certificate: Standard, Transport
- Departed: PHX, Phoenix, AZ
- Destination: SMF, Sacramento, CA
- Flight plan: IFR
- Airport: NYL, Yuma International Airport

## Weather

- Conditions: Visual (VMC), Day

## FAA reports on this event (1)

The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs).

- [Accident 20110401007039A](https://openairdocs.org/incident/20110401007039A), Apr 1, 2011: Boeing 737-3H4, Yuma, AZ, Substantial damage. On April 1, 2011, at about 1557 mountain standard time (MST), southwest airlines flight 812, a Boeing 737-300, registration N632SW, experienced rapid…

## Docket (30 files)

The files NTSB released with the investigation on March 7, 2012, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=78737. 70.3 MB in all.

- Materials Laboratory Factual Report 11-092 (contains 18 pages of figures) (item 1, .PDF, 9.5 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40358590&FileExtension=.PDF&FileName=Materials%20Laboratory%20Factual%20Report%2011-092%20(contains%2018%20pages%20of%20figures)-Master.PDF
- Materials Laboratory Factual Report 11-070 (contains 3 pages of figures) (item 2, .PDF, 418 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40358591&FileExtension=.PDF&FileName=Materials%20Laboratory%20Factual%20Report%2011-070%20(contains%203%20pages%20of%20figures)-Master.PDF
- Materials Laboratory Factual Report 12-010 (item 3, .PDF, 222 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40365735&FileExtension=.PDF&FileName=Materials%20Laboratory%20Factual%20Report%2012-010-Master.PDF
- Materials Laboratory Factual Report 12-011 (with 2 figures) (item 4, .PDF, 709 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40365747&FileExtension=.PDF&FileName=Materials%20Laboratory%20Factual%20Report%2012-011%20(with%202%20figures)-Master.PDF
- Materials Laboratory Factual Report 12-033 (with 1 figure) (item 5, .PDF, 553 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40365761&FileExtension=.PDF&FileName=Materials%20Laboratory%20Factual%20Report%2012-033%20(with%201%20figure)-Master.PDF
- Materials Laboratory Factual Report 12-012 (with 10 figures) (item 6, .PDF, 2.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40365773&FileExtension=.PDF&FileName=Materials%20Laboratory%20Factual%20Report%2012-012%20(with%2010%20figures)-Master.PDF
- Survival Factors 6 - Factual Report of Group Chairman (item 7, .PDF, 1.0 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40367431&FileExtension=.PDF&FileName=Survival%20Factors%206%20-%20Factual%20Report%20of%20Group%20Chairman-Master.PDF
- Operations 2 - Flight Crew Statements (item 8, .PDF, 185 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40391494&FileExtension=.PDF&FileName=Operations%202%20-%20Flight%20Crew%20Statements-Master.PDF
- Survival Factors 6 - Attachment 1 - Flight Attendant Statements (item 9, .PDF, 185 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40365875&FileExtension=.PDF&FileName=Survival%20Factors%206%20-%20Attachment%201%20-%20Flight%20Attendant%20Statements-Redacted.PDF
- Survival Factors 6 - Attachment 2 - Passenger Questionnaires (item 10, .PDF, 10.3 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40365878&FileExtension=.PDF&FileName=Survival%20Factors%206%20-%20Attachment%202%20-%20Passenger%20Questionnaires-Redacted.PDF
- Structures 7 - Factual Report of Group Chairman (item 11, .PDF, 67 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40364019&FileExtension=.PDF&FileName=Structures%207%20-%20Factual%20Report%20of%20Group%20Chairman-Master.PDF
- Structures 7 - Appendix A - Figures (item 12, .PDF, 326 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40364020&FileExtension=.PDF&FileName=Structures%207%20-%20Appendix%20A%20-%20Figures-Master.PDF
- Structures 7 - Addendum 1 - Skin Panel Information (3 embedded photos) (item 13, .PDF, 418 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40378682&FileExtension=.PDF&FileName=Structures%207%20-%20Addendum%201%20-%20Skin%20Panel%20Information%20(3%20embedded%20photos)-Master.PDF
- Flight Data Recorder 10 - Specialist's Factual Report (item 14, .PDF, 2 photos, 100 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40346535&FileExtension=.PDF&FileName=Flight%20Data%20Recorder%2010%20-%20Specialist%27s%20Factual%20Report-Master.PDF
- Flight Data Recorder 10 - Incident Flight Tabular Data (item 15, .CSV, 3.7 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40354313&FileExtension=.csv&FileName=Flight%20Data%20Recorder%2010%20-%20Incident%20Flight%20Tabular%20Data-Master.csv
- Maintenance Records 11 - Factual Report of Group Chairman (item 16, .PDF, 270 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40364036&FileExtension=.PDF&FileName=Maintenance%20Records%2011%20-%20Factual%20Report%20of%20Group%20Chairman-Master.PDF
- Maintenance Records 11 - Attachment 1 - Air Carrier Certificate (item 17, .PDF, 67 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40364037&FileExtension=.PDF&FileName=Maintenance%20Records%2011%20-%20Attachment%201%20-%20Air%20Carrier%20Certificate-Redacted.PDF
- Maintenance Records 11 - Attachment 2 - Supplemental Type Certificates (item 18, .PDF, 400 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40364038&FileExtension=.PDF&FileName=Maintenance%20Records%2011%20-%20Attachment%202%20-%20Supplemental%20Type%20Certificates-Master.PDF
- Maintenance Records 11 - Attachment 3 - Airworthiness Directives and Service Bulletin Listing (item 19, .PDF, 3.6 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40364039&FileExtension=.PDF&FileName=Maintenance%20Records%2011%20-%20Attachment%203%20-%20Airworthiness%20Directives%20and%20Service%20Bulletin%20Listing-Master.PDF
- Maintenance Records 11 - Attachment 4 - Aircraft Flight Logs (item 20, .PDF, 21.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40364040&FileExtension=.PDF&FileName=Maintenance%20Records%2011%20-%20Attachment%204%20-%20Aircraft%20Flight%20Logs-Redacted.PDF
- Maintenance Records 11 - Attachment 5 - Weight and Balance (item 21, .PDF, 219 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40364041&FileExtension=.PDF&FileName=Maintenance%20Records%2011%20-%20Attachment%205%20-%20Weight%20and%20Balance-Master.PDF
- Maintenance Records 11 - Attachment 6 - Service Difficulty Report and Mechanical Interruption Summary Report (item 22, .PDF, 66 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40364042&FileExtension=.PDF&FileName=Maintenance%20Records%2011%20-%20Attachment%206%20-%20Service%20Difficulty%20Report%20and%20Mechanical%20Interruption%20Summary%20Report-Master.PDF
- Maintenance Records 11 - Attachment 7 - Major Repairs and Alterations (item 23, .PDF, 508 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40364133&FileExtension=.PDF&FileName=Maintenance%20Records%2011%20-%20Attachment%207%20-%20Major%20Repairs%20and%20Alterations-Master.PDF
- Maintenance Records 11 - Attachment 8 - Time Limit Component Listing (item 24, .PDF, 416 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40364134&FileExtension=.PDF&FileName=Maintenance%20Records%2011%20-%20Attachment%208%20-%20Time%20Limit%20Component%20Listing-Master.PDF
- Maintenance Records 11 - Attachment 9 - Spirit Aerosystems (item 25, .PDF, 7.6 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40364135&FileExtension=.PDF&FileName=Maintenance%20Records%2011%20-%20Attachment%209%20-%20Spirit%20Aerosystems-Redacted.PDF
- Cockpit Voice Recorder 12 - Specialist's Factual Report (item 26, .PDF, 82 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40364254&FileExtension=.PDF&FileName=Cockpit%20Voice%20Recorder%2012%20-%20Specialist%27s%20Factual%20Report-Master.PDF
- Cockpit Voice Recorder 12 - Errata 1 (item 27, .PDF, 95 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40378583&FileExtension=.PDF&FileName=Cockpit%20Voice%20Recorder%2012%20-%20Errata%201-Master.PDF
- Exterior and interior views of the skin showing fracture along the lower row of rivets. (item 28, .PDF, 2.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40346917&FileExtension=.PDF&FileName=Exterior%20and%20interior%20views%20of%20the%20skin%20showing%20fracture%20along%20the%20lower%20row%20of%20rivets.-Master.PDF
- Release of Aircraft Wreckage, NTSB Form 6120.15 (item 29, .PDF, 177 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40391493&FileExtension=.PDF&FileName=Release%20of%20Aircraft%20Wreckage,%20NTSB%20Form%206120.15-Redacted.PDF
- Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 30, .PDF, 3.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40391492&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF

From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model.

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