The US Federal Aviation Administration (FAA) and the European Aviation Safety Agency (EASA) issued emergency airworthiness directives on April 20, 2018, ordering airlines to conduct urgent safety inspections of some CFM International CFM56-7B engine units. The decisions follow a fatal incident of a Southwest Airlines B737-800 on April 17, 2018, in which one passenger was killed after a fan blade broke off mid-flight, producing debris which hit the fuselage and shattered one of the windows.
"The directive is based on a CFM International Service Bulletin issued today and on information gathered from the investigation of Tuesday’s Southwest Airlines engine failure. The inspection requirement applies to CFM56-7B engines. Specifically, engines with more than 30,000 total cycles from new must complete inspections within 20 days," the FAA said on April 20.
According to the American regulator, the directive affects some 352 engines in the US and 681 worldwide. The inspections have to be conducted within 20 days.
The order created delays and cancellations at Southwest, with some 40 flights (around 1% of all) cancelled and some 500 delayed on Sunday, April 22, 2018, the Washington Post has reported. The carrier has said in a statement that its maintenance and inspection procedures already exceed the minima set by FAA.
EASA's directive goes further as it orders checks of engine blades on all units with over 30,000 cycles within 20 days, on all units with between 20,000 and 30,000 fan blade cycles within 133 days, and all other CFM56-7B units upon reaching 20,000 total fan blade cycles.
Both regulators had already been aware of potential fatigue issues with CFM56-7B engines earlier. In August 2017, the FAA proposed an airworthiness directive which would impose an obligation to inspect CFM56-7B engines but it has since been stalled due to disagreements with the carriers in regard to the burden resulting from the timeline, costs, and scope of the checks.
For its part, EASA issued a directive on March 26, 2018, requiring the carriers to conduct inspections of the engines within nine months. This directive has now been replaced by the new rule.
CFM56-7B series engines are used exclusively for Boeing 737NG aircraft, including the BBJ and military variants. It is the sole power unit available for the type. According to the ch-aviation fleets module, there are currently 6,482 CFM56-7B-equipped Boeing twinjets active worldwide with a total of 296 operators. Some of the largest users of these engines include Southwest Airlines, Ryanair, American Airlines, United Airlines, Delta Air Lines, Alaska Airlines, Hainan Airlines, and Xiamen Airlines.
The airworthiness directives do not concern CFM56 units powering other types, such as the Airbus A320 Family.
