FAA issues an emergency airworthiness directive for PW4000-112 engines
Emilie Drab
 le 24/02/2021 , Maintenance aéronautique
Following the serious incident on a United Airlines 777-200 on February 20, the FAA issued an emergency airworthiness directive (AD) requiring thermal-imaging inspections of fan blades on Pratt & Whitney's PW4000-112 engines.
The FAA is asking that the titanium fan blades be sent to the engine manufacturer, who will carry out thermal-acoustic imaging (TAI) inspections to check that they do not show any cracks. The first observations of the NTSB, in charge of the investigation of the incident, revealed that two fan blades were fractured : one fan blade was fractured near the root and an adjacent fan blade was fractured about mid-span.
The FAA explained in a statement that "TAI technology can detect cracks on the interior surfaces of the hollow fan blades, or in areas that cannot be seen during a visual inspection."
The AD affects approximately 125 Boeing 777s (-200, -200ER and -300).
The FAA said it will revise its directive based on the results of the inspections and may set new inspection intervals. Initially, this interval was 6500 flight cycles.
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