Southwest Airlines Flight 812
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The Boeing 737–300 involved in the incident pictured in 2007.
|Date||April 1, 2011|
|Summary||In-flight structural failure leading to
|Site||near Yuma, Arizona|
|Injuries (non-fatal)||2 (minor)|
|Aircraft type||Boeing 737-3H4|
|Flight origin||Phoenix Sky Harbor Int'l Airport (KPHX)|
|Destination||Sacramento Int'l Airport (KSMF)|
Southwest Airlines Flight 812 (SWA812, WN812) was a passenger flight which suffered rapid depressurization at 34,400 ft (10,485 m) near Yuma, Arizona, leading to an emergency landing at Yuma International Airport, on April 1, 2011. The incident caused minor injuries to two of the 123 aboard. The aircraft involved, a Boeing 737–300, was operating Southwest Airlines' domestic scheduled service from Phoenix Sky Harbor International Airport, Phoenix, Arizona, to Sacramento International Airport, Sacramento, California. The depressurization occurred after a 6 ft (2 m) hole appeared in the top of the airplane's fuselage above the cabin, necessitating an emergency descent. An investigation revealed evidence of pre-existing fatigue, and led to the FAA increasing the inspection rate of certain airframes. The incident followed a similar one, Southwest Airlines Flight 2294, in 2009.
The aircraft involved was Boeing 737-3H4 N632SW, msn 27707, line number 2799.  It was built in 1996 and delivered to Southwest on June 13 of that year. At the time of the accident, the aircraft had completed 48,748 hours and 39,786 cycles.
Flight 812 was a domestic scheduled passenger flight from Phoenix, Arizona to Sacramento, California. On April 1, 2011, it was carrying five crew and 117 passengers. At 15:57 local time (22:57 UTC), while climbing through FL344 to reach FL360, a loud bang was heard and one of the ceiling tiles dislodged. A flight attendant and a passenger received minor injuries, but were both treated at the airport. Oxygen masks deployed and the pilots performed a rapid descent to 11,000 ft (3,353 m). An emergency landing was made at the joint Marine Corps Air Station Yuma / Yuma International Airport. The aircraft landed at 16:23. A spare aircraft with maintenance technicians, ground crew, and customer service agents was dispatched from Phoenix to take the passengers to Sacramento. The replacement aircraft was expected to reach Sacramento with a 4-hour delay to the passengers on board Flight 812.
This was the second structural failure, rapid decompression, and emergency landing for Southwest Airlines in two years. Southwest Airlines Flight 2294, also a 737–300, had a football-sized hole appear in its fuselage on July 13, 2009. That aircraft also made a safe emergency landing.
Inspection of the aircraft at Yuma revealed a tear in the fuselage, reported as being between 3 feet (0.91 m) wide and 6 feet (1.8 m) long. Southwest grounded 80 of its Boeing 737-300s for inspection following the incident. The grounded aircraft were those that had not had the skin on their fuselage replaced. Five aircraft were discovered to have cracks. The aircraft were to be repaired and returned to service. As of April 3, 2011, Boeing was developing a Service Bulletin for the inspection of similar aircraft.
On April 5, 2011, the FAA issued an emergency Airworthiness Directive (AD) requiring operators of 737 series 300, 400 and 500 aircraft to increase the frequency of inspections of lap joints on high flight cycle airframes. The AD requires that aircraft with over 30,000 cycles be inspected within 20 days of receipt of the AD, or upon reaching 30,000 cycles. For aircraft with over 35,000 cycles, the inspection is required within 5 days. The AD also requires periodic inspections of the same joints at every 500 cycles for aircraft with over 30,000 cycles. The AD refers to a range of airframes, line numbers 2553–3132 inclusive, totaling 580 aircraft. Of the total of 580 aircraft, only 175 aircraft currently meet the 30,000 cycle requirement, with 80 of those operating in the United States. The FAA AD is effective to only the portion of those that are registered in the United States, since the FAA can only mandate such changes in the United States. Countries with reciprocity airworthiness agreements will also follow the AD, but other nations are not required to adhere to the ruling. As a result of the incident, the FAA investigated Boeing's manufacturing techniques to discover whether or not they had any bearing on the cause of the failure. The incident aircraft was not considered to have a high number of cycles. Boeing co-operated with the FAA in the investigation.
Air New Zealand inspected all fifteen of their 737-300s and Qantas inspected four of their 21 737-400s. Several of the thirty-seven 737-400s operated by Malaysia Airlines were also to be inspected.
The Federal Aviation Administration sent an inspector to Yuma. The National Transportation Safety Board opened an investigation into the incident. A Go Team was sent to Yuma on April 2. Inspection of the 5 feet (1.5 m) long tear revealed evidence of pre-existing fatigue. The tear was along a lap joint. In March 2010, cracks had been found and repaired in the same place on the accident aircraft. The cause was determined to have been a manufacturing error dating from when the aircraft was built.
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- Yeo, Ghil-Lay (April 8, 2011). "MAS carries out preliminary inspections on 737s". Flight International. Retrieved April 9, 2011.
- "Passengers Of Damaged Southwest Flight Arrive In Sacramento". CBS. April 1, 2011. Retrieved April 2, 2011.
|Photos of the aircraft involved at airliners.net|
- "Southwest Airlines Responds to Loss of Pressurization Event on Flight From Phoenix to Sacramento." Southwest Airlines.
- Full list of operators affected by the AD