(Bloomberg) -- Southwest Airlines Co. is stepping up engine inspections as the discount carrier known for its quirky cheerfulness and strong safety record grapples with its first accident to result in a passenger’s death.
Ultrasonic examinations of the fan blades on its CFM56 engines will be completed within 30 days, Southwest said. The airline, which operates the world’s largest fleet of Boeing Co. 737 jetliners, relies on the turbofan to power its more than 700 planes.
The National Transportation Safety Board found indications of metal fatigue caused by repeated bending where a fan blade on the engine was missing, NTSB Chairman Robert Sumwalt said in a briefing late Tuesday. One woman died after shrapnel from the blown engine tore through a window about 20 minutes into Flight 1380 from New York to Dallas, partially sucking her out before passengers pulled her back in.
“This is a very sad day, and on behalf of the entire Southwest family I want to extend deepest sympathies for the family and loved ones of the deceased customer,” Southwest Chief Executive Officer Gary Kelly told reporters at the airline’s headquarters in Dallas. “We will do all we can to support them.”
The death was the first in-flight fatality caused by an accident in the 47-year history of Southwest. That doesn’t include a 2005 episode in which one of its jets skidded off a snowy runway onto a Chicago road and killed a six-year-old boy in a car.
Federal investigators along with teams of technical experts from Boeing and engine maker CFM International, a venture of General Electric Co. and France‘s Safran SA, are gathering clues about what caused the accident.
“Our specialists immediately focused on a missing fan blade,” Sumwalt said in his briefing. “This fan blade was broken right at the hub. Our preliminary examination is that there was evidence of metal fatigue where the blade separated.”
Technicians from both companies are also being sent to support Southwest’s inspections, according to an emailed statement from GE.
The CFM turbofan, one of the most widely used jet engines, has amassed more than 350 million flight hours on 6,700 aircraft since entering the market in 1997.
There have been “only a handful” of failures with the engine, Kelly said. It would be “premature to even link it to other engine failures that have occurred.”
Southwest has more than 500 of Boeing’s 737-700 jets, the version involved in Tuesday’s incident. While the average length of Southwest’s flights has increased as it has grown into the No. 4 U.S. carrier, the company is still known for doing more of the shorter trips than full-service airlines with flights that cross oceans. The relatively high number of takeoffs and landings puts added stress on the planes and engines.
“Anytime you run an engine like that to maximum power and hold it there for a couple of minutes on takeoff, you are putting maximum stress on all the rotating parts,” said John Nance, a former airline and military pilot. “You can’t deny that the more you run an engine up to full power on takeoff, the more you stress those blades.”
The stress those operations put on the aluminum frames of Southwest’s 737 jetliners has been raised before, notably after an aircraft’s roof tore midflight in 2011. The metal fatigue was later linked to the technique Boeing workers used to assemble the aircraft family, which Southwest retired last year.
Metal fatigue was also blamed for a hole opened atop a 737-300 in 2009, depressurizing the cabin and forcing an emergency landing. No one was injured. The incident prompted regulators to require checks on 135 Boeing 737-300s, -400s and -500s in the U.S.
In March 2009, Southwest agreed to pay a $7.5 million fine for flying jets in 2006 and 2007 without some required fuselage inspections. It was the Federal Aviation Administration’s largest fine against an airline at the time.
Investigators will also want to know if there is any relation between Tuesday’s engine blowout and an uncontained engine failure that spewed shrapnel on a Southwest airplane cruising above the Gulf of Mexico in 2016, according to Sumwalt, the NTSB chairman.
On that plane, also a 737-700, a fan blade on a jet engine snapped off and sent debris slamming into the fuselage, safety-board investigators determined. They found evidence of a crack “consistent” with metal fatigue in the titanium-alloy blade. The jet was forced to make an emergency landing in Pensacola, Florida, after the plane lost cabin pressure and passengers tweeted pictures of themselves with oxygen masks on.
Modern jet engines contain a series of spinning fans and if one of them breaks it can eject blades and other metal debris at high speeds. Engine manufacturers and airlines conduct periodic inspections on planes designed to spot any evidence of cracks or weakening of the metal due to fatigue.
After the latest accident, Kelly said Southwest would work “with the NTSB to make sure we understand the root cause, and any further actions we need to take in terms of maintenance or inspections we’ll want to add to our program.”
The airline’s shares rose 3.8 percent to $56.33 at 12:55 p.m. Wednesday after strong earnings from United Continental Holdings Inc. spurred an industry rally. Southwest fell 1.1 percent on Tuesday after the fatality was announced.
“Southwest is a close-knit and attentive company,” said David Greenberg, founder of Compass Group Aviation Consulting. “They’ll first focus on the needs of the survivors, both the uninjured and those that lost a family member. The internal people take that very, very seriously.”
The latest incident marks a tragic milestone for an airline that has had a strong track record of safety, said Bob Mann, a former airline executive who now heads aviation consultant R.W. Mann & Co.
While the situation may not have a long-term impact on Southwest’s business, the company faces a critical test with its handling of the situation, he said.
“They’ve responded to it very well,” Mann said, citing Kelly’s initial comments. “I think they’ve approached it very professionally -- not clinically, but with an eye toward the sort of personalized relationship they’d like to have with their customers.”
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