On April 20, three days after a Southwest Airlines Boeing 737-700 experienced an engine failure due to a fractured fan blade, resulting in the death of a passenger, the U.S. Federal Aviation Administration issued an emergency airworthiness directive that requires operators of CFM56-7B engines with more than 30,000 flight cycles to perform a one-time ultrasonic inspection of all 24 fan blades to detect cracking.
It was the second failure of a CFM56-7B engine fan blade on a Southwest flight: a similar episode occurred in August 2016 when a fan blade broke at the engine hub and debris caused a 5-inch by 16-inch gash in the fuselage. Following that incident, the engine’s manufacturer, CFM International, recommended ultrasonic inspections of fan blades on CFM56-7B engines with 20,000 cycles be completed before the end of August 2018.