LUV Southwest Airlines Co

The U.S. aviation-safety watchdog on Monday linked a cracked jet-engine fan blade to the emergency landing of a Southwest Airlines Co. plane last month, as part of its preliminary investigation to identify the cause of the unusual incident.

The National Transportation Safety Board has yet to conclude the root cause of what happened but said it found cracking consistent with metal fatigue on a remaining piece of one of the engine's broken fan blades. The engine was made by General Electric Co.'s joint venture CFM International with France's Safran SA.

None of the 99 passengers or five crew aboard were injured during the flight from New Orleans to Orlando, Fla., which was forced to land in Pensacola, Fla., on Aug. 27 after the rare engine failure, which caused major engine damage and led to depressurization of the cabin.

The failure of a fan blade is a rare event, and engines are designed to contain them inside the engine casing or to eject any debris safely out of the back. The failure aboard the Southwest jet was characterized as uncontained by the NTSB, meaning debris was ejected out of the sides of the engine, an extremely unusual event.

The failure of one of the engine's 38 front fan blades appeared to precede the significant damage sustained by the CFM engine nacelle, according to an industry official, followed by the complete separation of the forward inlet. The NTSB said debris from the inlet damaged the Boeing Co. 737-700 jet's fuselage, wing and tail stabilizers.

The CFM56-7 series engine involved in the accident was one of the oldest in service, according to the official. However, the age of an engine and its internal components aren't necessarily related as parts are refurbished or replaced during the life of an engine.

An NTSB spokesman said the agency's investigation is ongoing and a sequence of events wasn't included in its preliminary findings. A Southwest Airlines spokesman said repairs to the jet have begun and the company continues "to work closely with the NTSB on the investigation of this unique and extremely rare event."

Aircraft and their engines are subjected to repeated stresses during their life in service and cracks are a normal part of their aging, but if left unchecked, they can cause major damage to an aircraft. Regulators, airlines and manufacturers have developed inspection regimes to identify and remedy cracks before they become safety issues.

The source of the cracking on the titanium alloy blade was still under investigation, and the NTSB said it was continuing to review the engine's maintenance records and test the remaining blades.

CFM is the biggest engine manufacturer in the world for single-aisle aircraft, such as the workhorse Boeing 737.

Write to Jon Ostrower at jon.ostrower@wsj.com

(END) Dow Jones Newswires

September 12, 2016 18:05 ET (22:05 GMT)

Southwest Airlines (NYSE:LUV)
Historical Stock Chart
From Mar 2024 to Apr 2024

Southwest Airlines (NYSE:LUV)
Historical Stock Chart
From Apr 2023 to Apr 2024