A report by the National Transportation Safety Board cites shoddy workmanship as the cause of a 5-foot-long gash that opened in the fuselage of Southwest Airlines plane on April 1, 2011, forcing it to make an emergency landing in Yuma.
The airliner, a Boeing 737-300, was en route from Phoenix to Sacramento when the gaping hole opened in the ceiling of the cabin, causing immediate depressurization. Air rushed in, oxygen masks dropped from the ceiling and a flight attendant fainted, breaking his nose, as the pilots made a rapid descent from a cruising altitude of 36,000 feet to land at Yuma International Airport. An off-duty airline employee was also injured.
Southwest Airlines flight 812 was carrying 118 passengers. The plane landed safely in Yuma at about 4:07 p.m., less than an hour after takeoff from Phoenix. Passengers on the plane were later placed on a second plane which arrived in Sacramento without incident.
The NTSB's findings, released Friday and first reported by The Seattle Times, say that when the jet was assembled in 1996, two panels appeared to have been misaligned, and many rivet holes were drilled incorrectly. The agency said it showed "a lack of attention to detail and extremely poor manufacturing technique."
Hidden cracks began emanating from the rivet holes soon after the plane entered service and had been growing slowly ever since, the NTSB said.
It isn't clear whether the work was done during initial fuselage assembly at Boeing's plant in Wichita, Kan., which is now Spirit Aero Systems, or during final assembly in Renton, Wash., the report said. At the time, Boeing only kept manufacturing records for up to seven years.
The 737-300 is the oldest plane in Southwest's fleet, and the company is retiring 300s as it takes deliveries of new models.
In 2011, Southwest Airlines officials stated the plane had undergone all inspections required by the FAA, including a routine examination on March 29. The plane had received its last "heavy check," a more costly and extensive overhaul, in March 2010.
An Associated Press review of FAA records of maintenance problems for the plane revealed that in March 2010 at least eight instances were found of cracking in the aircraft frame, which is part of the fuselage. Those cracks were repaired, the records indicate.
It's not uncommon for fuselage cracks to be found during inspections of planes that age, especially during scheduled heavy maintenance checks in which they are taken apart so that inspectors can see into areas not normally visible.
In an emailed statement Saturday, Boeing officials stated the company is dedicated to the safety of its planes and that it provided technical assistance to the NTSB investigators. The company pointed out that inspections on other 737s found no similar damage -- suggesting the problem was isolated.
The NTSB said it couldn't determine why Boeing's quality-assurance protocols failed to discover the shoddy work, but concluded that in light of the one-off nature of the problem, it is "unlikely that there was a systemic (quality assurance) error at the Boeing facilities."
At the time, the incident raised questions about whether aging jets might be more susceptible to metal fatigue earlier than previously thought. As a result of the emergency, Southwest Airlines grounded about 80 similar planes for inspection.
But Hans Weber, an aviation technical expert and president of Tecop International in San Diego, told The Seattle Times the NTSB analysis dispels that concern.
"The workmanship was just terrible," Weber said. "This has nothing to do with a typical fatigue fracture due to aging."
The NTSB report also addressed the injury suffered by the flight attendant, who told investigators that despite being trained to put on his oxygen mask immediately, he thought he "could get a lot more done" before putting on the mask. Instead, he tried to make a call or a public announcement to the passengers first, quickly passed out and broke his nose.
An off-duty airline employee flying as a passenger also passed out while trying to help the flight attendant and suffered a cut above his eye.
The NTSB report notes that people can lose consciousness in as little as six seconds in the event of a rapid de-pressurization of an airplane cabin.
An NTSB "Go Team" was sent to Yuma immediately following the incident to investigate the incident. The team collected the plane's black boxes and transported them to Washington, D.C., for inspection. A team from Boeing was also in Yuma to aid the Go Team with technical matters.
Structural experts and metallurgical experts documented the damaged areas of the aircraft, looking for signs of the initial crack formation and crack propagation. After documentation, the damaged area was cut out of the fuselage and transported to the NTSB materials lab in Washington, D.C.
A second NTSB Go Team was sent to the Southwest Airlines maintenance facilities in Dallas to look at the maintenance history of the aircraft.
The aircraft remained parked at the Yuma International Airport for several days during the initial investigation and for repairs.
Original headline: NTSB: Southwest plane forced down by shoddy workmanship
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