NTSB Examining Uncontained Engine Failure on Southwest Plane

So far, NTSB's initial findings from the examination of the airplane and the engine and a metallurgical examination show that the the left engine inlet separated from the engine during the flight, and debris from the inlet damaged the airplane fuselage and wing, gashing a 5-inch by 16-inch hole in the left fuselage just above the left wing.

The National Transportation Safety Board provided an update Sept.12 on its investigation of an Aug. 27, 2016, uncontained engine failure on Southwest Airlines flight 3472 as the Boeing 737-700 was flying from New Orleans to Orlando. The aircraft was diverted to Pensacola International Airport and safely landed without further incident.

So far, NTSB's initial findings from the examination of the airplane and the engine and a metallurgical examination show that the the left engine inlet separated from the engine during the flight, and debris from the inlet damaged the airplane fuselage and wing, gashing a 5-inch by 16-inch hole in the left fuselage just above the left wing. But no fan blade or inlet material was found in the hole, and the passenger interior compartment was not penetrated.

The airplane did experience a cabin depressurization.

According to NSTB, the aircraft's maintenance records are being reviewed.

A fan blade separated from the fan disk during the flight, and the root of that blade remained in the fan hub. Analysis showed curving crack arrest lines consistent with fatigue crack growth, with a fatigue crack region measuring 1.14 inches long and 0.217 inch deep. "The center of the fatigue origin area was about 2.1 inches aft of the forward face of the blade root. No surface or material anomalies were noted during an examination of the fatigue crack origin using scanning electron microscopy and energy-dispersive x-ray spectroscopy," according to NTSB, which added that the blades are made of a titanium alloy and the root contact face is coated with a copper-nickel-indium alloy.

The aircraft's flight data recorder and cockpit voice recorder were shipped to the NTSB Recorder Laboratory and the data from both have been downloaded. Parties to the investigation include FAA, Southwest Airlines, the Southwest Airlines Pilots Association, and CFM International.

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