Southwest 812 Hole IN The Fuselage Rapid decompression and Emergency descent (2011)

Southwest 812 Suffers Rapid Decompression and Lands at Yuma With a Hole in the Fuselage

Southwest Flight 812 was climbing through FL340 when the cabin suddenly depressurized. The crew initiated an emergency descent, diverted to Yuma and landed after a section of the upper fuselage skin fractured open.

On 1 April 2011 at about 1558 MST, N632SW was operating from Phoenix to Sacramento when the rapid decompression occurred. The cockpit recording captured an unidentified sound followed almost immediately by the captain's recognition that cabin pressurization had been lost.

The crew ordered oxygen masks and declared an emergency. Controllers rapidly cleared the aircraft downward. Within about five minutes the aircraft had descended to 11,000 feet. Cabin crew then reported the size and location of the fuselage opening and an injury.

The captain requested the nearest suitable airport and was vectored to Yuma International. The aircraft landed on Runway 21R at about 1629 MST and the passengers deplaned using airstairs.

The NTSB determined that the accident resulted from improper installation of the fuselage crown skin panel at the S-4L lap joint, which allowed fatigue cracking and eventual structural failure. One flight attendant and one off-duty airline employee passenger sustained minor injuries.

The NTSB found that the fuselage crown skin panel at the S-4L lap joint had been improperly installed during manufacturing. The resulting multiple-site-damage fatigue cracking led to failure of the lower skin panel. The damaged section measured about 60 inches by eight inches.

The investigation also examined the injury sequence. A flight attendant suffered a broken nose, and an off-duty airline employee passenger sustained a minor injury. The NTSB identified the flight attendant's incorrect assessment of useful consciousness as a contributing factor to the injury because oxygen-mask procedures were not followed immediately.

The accident docket contains maintenance records, materials-laboratory reports, cockpit voice recorder material and aircraft records. This is therefore an unusually well-documented event in which the radio recording, physical damage and final engineering finding can be connected directly.

The final investigation also examined manufacturing and maintenance records, including service information and materials-laboratory work. The docket preserves the engineering evidence behind the probable-cause finding, making this more than a radio-audio reconstruction: the sequence can be followed from the initial sound in the cockpit through the emergency descent, the physical rupture and the later metallurgical examination.

“lost cabin pressurization”

Accident Facts

Sources

• Video source (ATC/audio reconstruction)
• NTSB, DCA11MA039, “Rapid Decompression Due to Fuselage Rupture.”
• NTSB AAB-13-02, final report, adopted 24 September 2013.
• Video/ATC recording