Safety Recommendation A-19-017

This report discusses the April 17, 2018, accident involving a Boeing 737-7H4, N772SW, operated by Southwest Airlines as flight 1380, that experienced a failure of its left CFM International CFM56-7B turbofan engine while climbing through flight level 320 en route to the flight’s assigned cruise altitude (the flight had departed from LaGuardia Airport, Queens, New York, about 30 minutes earlier). Portions of the left engine inlet and fan cowl separated from the airplane; one fan cowl fragment impacted the left-side fuselage near a cabin window, and the window departed the airplane, which resulted in a rapid depressurization.

As a result of the engine failure, the flight crew conducted an emergency descent and diverted to Philadelphia International Airport (PHL), Philadelphia, Pennsylvania. The airplane landed safely at PHL about 17 minutes after the engine failure occurred. Of the 144 passengers and 5 crewmembers aboard the airplane, 1 passenger received fatal injuries, and 8 passengers received minor injuries.

Safety issues identified in this report include the need to ensure the structural integrity of the fan cowl on Boeing 737 next-generation-series airplanes after a fan-blade-out event involving CFM56 7B engines, the need to determine whether other airframe/engine combinations have any critical fan blade impact locations and how an impact at those locations could affect nacelle components, the need to emphasize the importance of having flight attendants secured in a jumpseat during emergency landings, and the need to mitigate hazards to passengers affected by an in-flight loss of seating capacity.

As a result of this investigation, the National Transportation Safety Board makes five new safety recommendations to the Federal Aviation Administration and one new recommendation each to Southwest Airlines and the European Aviation Safety Agency.