National Transportation Safety Board has issued an investigative update to the ongoing investigation of an Aug. 27, 2016, uncontained en...
National Transportation Safety Board has issued an investigative update to the ongoing investigation of an Aug. 27, 2016, uncontained engine failure on Southwest Airlines flight 3472 which resulted in loss of left engine inlet cowl.
The uncontained engine failure and cabin depressurization while climbing through flight level 310 happened at about 0930 central daylight time on a Boeing 737-700 enroute from New Orleans, Louisiana, to Orlando, Florida.
The airplane was diverted to Pensacola International Airport, Pensacola, Florida, and safely landed without further incident.
The investigative update details the NTSB’s initial findings from the examination of the airplane and the engine, and a metallurgical examination.
Initial findings from the examination of the airplane include:
- The left engine inlet separated from the engine during the flight. Debris from the engine inlet damaged the airplane fuselage, wing and empennage,
- A 5-inch by 16-inch hole was found in the left fuselage just above the left wing,
- No fan blade or inlet material was found in the hole and the passenger interior compartment was not penetrated, and
- During the accident sequence, the airplane experienced a cabin depressurization.
Initial findings from the engine examination include:
- One fan blade separated from the fan disk during the accident flight and
- The root of the separated fan blade remained in the fan hub; however, the remainder of the blade was not recovered.
Initial findings from the metallurgical examination conducted in the NTSB Materials Laboratory include:
- The fracture surface of the missing blade showed curving crack arrest lines consistent with fatigue crack growth. The fatigue crack region was 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, and
- The blades are manufactured of a titanium alloy and the root contact face is coated with a copper-nickel-indium alloy.
None of the 99 passengers and 5 crew members on board were injured and the airplane sustained substantial damage.
