Airworthiness Directives; CFM International CFM56-7B and -7B/2 Series Turbofan Engines

This amendment adopts a new airworthiness directive (AD) that is applicable to CFM International CFM56-7B and -7B/2 series turbofan engines. This action requires initial and repetitive inspections of certain hydromechanical unit (HMU) overspeed governor (OSG) spool valves for out-of-specification conditions or the presence of heavy contact or galling on the spool valve, and optional installation of an improved HMU as a terminating action to the inspections. This amendment is prompted by a report of a flameout that occurred on a flight test engine due to a failed HMU OSG spool valve shaft. The actions specified in this AD are intended to prevent failure of the HMU OSG spool valve shaft, and subsequent engine flameout.