Fan blade broke off Southwest Airlines engine in mid-flight, NTSB says
A fan blade on a jet engine snapped off a Southwest Airlines plane last month in a violent failure that sent debris slamming into the plane, according to a preliminary investigative report released Monday.
Investigators with the National Transportation Safety Board found evidence of a crack “consistent” with metal fatigue in the titanium-alloy blade, it said in a statement released on the agency’s website.
The Boeing 737-700 was forced to make an emergency landing in Pensacola, Fla., on Aug. 27 after parts of the left engine broke apart, damaging the fuselage, wing and tail. The plane lost cabin pressure, and passengers tweeted pictures of themselves with oxygen masks on.
While no one was hurt on the flight from New Orleans to Orlando, some of the 99 passengers aboard reported on social media that the diversion was harrowing as they looked outside and saw the air intake, known as a cowling, had been ripped loose, exposing the front of the engine. The five crew members also weren’t hurt.
The CFM56 engine was built by CFM International, a joint venture between General Electric Co. and Safran SA. The NTSB has not determined the cause of the failure.
A shard put a 5-by-16-inch gash in the side of the plane above the wing, according to investigators. The cabin leaked air and lost pressure after the failure, though the NTSB said no metal from the engine pierced the cabin and no debris was found inside the plane.
NTSB investigators view so-called “uncontained” failures seriously because they can fling heavy metal parts into fuel lines, electronics and the passenger compartment. And under requirements in the U.S. and other nations, it’s never supposed to happen.
Regulations hold that jet engines must be built with a strong enough exterior casing to prevent fan blades and other debris from breaking through in the event of a failure. Tests must be conducted simulating a fan-blade breakup to prove that the metal shards can’t escape.
Modern jet engines contain a series of spinning fans, and if one of them breaks apart 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. Investigators did not say why they suspect the fan blade broke loose.
The last maintenance check on the Southwest plane was on Aug. 21, according to Brandy King, an airline spokeswoman.
While increasingly rare, engine failures that propel shrapnel into the fuselage of a plane have proved fatal. A mother and child seated in a Delta Air Lines plane were killed on July 6, 1996, in Pensacola when the left power plant on a Boeing MD-88 broke apart while accelerating for takeoff. sending metal shards flying into the plane.
This story was originally published September 12, 2016 at 3:48 PM with the headline "Fan blade broke off Southwest Airlines engine in mid-flight, NTSB says."