New York - The fatal incident at Southwest Airlines concerns the US aviation authority about the safety of CFM56 engines. FAA wants to test certain engines within two weeks

We found a crack in a fan blade," reported Robert Sumwalt, the chief investigator of the NTSB.
We are very concerned about this incident.

At the same time, the FAA announced it would issue an airworthiness directive for CFM56-7B engines within the next two weeks.

The material fatigue of the fan blades is a potential weak point of the CFM56-7B engines, and it is not something new for the FAA. Since August 2017, the US civil aviation authority has been asking airlines for the ultrasonic inspection, which becomes now mandatory after the Southwest incident.

Pensacola, August 27, 2016: An engine failure with debris leakage forced Southwest Airlines Flight 3472 to land at Florida International Airport. The CFM56-7B was completely destroyed, and the Boeing 737-700 suffered significant damage.

A few weeks later, the experts of the NTSB declared material fatigue of a fan blade as the probable cause.

The processing of the 2016 forced landing by the FAA is not yet completed. Despite the findings of the NTSB, the FAA did not issue an emergency airworthiness directive.

In August 2017, one year after the incident, FAA considered mandatory ultrasonic inspections on CFM56-7B engines as a consequence of Flight 3472 incident. To conduct the tests, the authority put a period of 18 months.

Until October 2017, the FAA sought comments from affected companies regarding the intended regulation. The engine manufacturer CFM demanded a test window of only twelve months.

Southwest Airlines opposed the CFM's demand. The company did not want to reduce the compliance period to 12 months to file and execute the required ultrasound inspections.

Southwest Airlines referred to the need to review 732 of its own engines, significantly more than the FAA assumed for the entire US.

Other airlines demanded more flexibility. Ryanair proposed a deadline for 31 December 2018.

The European Aviation Safety Agency EASA no longer waited for an FAA decision and imposed its own regulation on CFM56-7B on 26 March 2018. The airworthiness directive EASA 2018-0071 requires operators to carry out ultrasonic checks of the CFM56-7B within nine months.