A proposed Federal Aviation Administration (FAA) Airworthiness Directive (AD) has recommended a redesign of all Boeing 737NG engine cowlings.
The AD was prompted by what the FAA describes as ‘two engine fan blade-out events that resulted in the separation of engine inlet cowl and fan cowl parts from the airplane’. During a fatal event in 2018, a fractured fan blade and subsequent engine failure on board a Southwest Airlines 737-700 resulted in the death of a passenger, injuring eight others. In a separate Southwest Airlines incident, fan cowl parts punctured the fuselage and caused a loss of pressurisation; necessitating an emergency descent.
The FAA had previously imposed a deadline of July 31 for Boeing to submit design changes to the FAA and release service bulletins, with the manufacturer maintaining the issue was entirely mitigated by satisfactory fan blade inspections.
The proposed AD “would require replacing the fasteners on the fan cowl support beam hinge fitting for certain airplanes and, for all airplanes, would require modifying the radial restraint assembly and installing an external doubler at the starter vent, or as an option, installing a serviceable fan cowl,” clarifies the FAA.
Comments on the proposed change are open until 26 January 2024.