Case Study 2 Southwest Airlines Flight 812

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National Transportation Safety Board Aviation Accident Data Summary

Location: Yuma, AZ Accident Number: DCA11MA039

Date & Time: 04/01/2011, 1557 MST Registration: N632SW

Aircraft: BOEING 737 Injuries: 1 Minor, 121 None

Flight Conducted Under: Part 121: Air Carrier - Scheduled

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.

Flight Events

Enroute-climb to cruise - Aircraft structural failure

Probable Cause The National Transportation Safety Board determines the probable cause(s) of this accident to be: 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

Aircraft-Aircraft structures-Fuselage-Fuselage main structure-Incorrect service/maintenance - C Personnel issues-Experience/knowledge-Knowledge-Knowledge of procedures-Cabin crew - F

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Aircraft and Owner/Operator Information

Aircraft Manufacturer: BOEING Registration: N632SW

Model/Series: 737 300 Engines: 2 Turbo Fan

Operator: SOUTHWEST AIRLINES CO Engine Manufacturer: CFM

Operating Certificate(s) Held:

Flag carrier (121) Engine Model/Series: 56

Flight Conducted Under: Part 121: Air Carrier - Scheduled

Meteorological Information and Flight Plan

Conditions at Accident Site: Visual Conditions Condition of Light: Day

Observation Facility, Elevation: Weather Information Source: Unknown

Lowest Ceiling: Wind Speed/Gusts, Direction:

Temperature: Visibility

Precipitation and Obscuration:

Departure Point: Phoenix, AZ (PHX) Destination: Sacramento, CA (SMF)

Airport Information

Airport: Yuma International Airport (NYL) Runway Surface Type: N/A

Runway Used: N/A Runway Surface Condition: Dry

Runway Length/Width:

Wreckage and Impact Information

Crew Injuries: 1 Minor, 4 None Aircraft Damage: Substantial

Passenger Injuries: 117 None Aircraft Fire: None

Ground Injuries: N/A Aircraft Explosion: None

Latitude, Longitude: 32.656667, -114.605833 (est)

Administrative Information

Investigator In Charge (IIC): William R English Adopted Date: 02/26/2014

Investigation Docket: http://dms.ntsb.gov/pubdms/search/dockList.cfm?mKey=78737 1

The National Transportation Safety Board (NTSB), established in 1967, is an independent federal agency mandated by Congress through the Independent Safety Board Act of 1974 to investigate transportation accidents, determine the probable causes of the accidents, issue safety recommendations, study transportation safety issues, and evaluate the safety effectiveness of government agencies involved in transportation. The NTSB makes public its actions and decisions through accident reports, safety studies, special investigation reports, safety recommendations, and statistical reviews.

The Independent Safety Board Act, as codified at 49 U.S.C. Section 1154(b), precludes the admission into evidence or use of any part of an NTSB report related to an incident or accident in a civil action for damages resulting from a matter mentioned in the report.