Airworthiness Directive · Amendment 39-10761 · CFM International CFM56-7B and -7B/2 Series Turbofan Engines
CFM International CFM56-7B and -7B/2 Series Turbofan Engines
CFM International CFM56-7B and -7B/2 series turbofan engines, with hydromechanical unit (HMU), Part Number (P/N) 1853M56P04 (AlliedSignal P/N 442008) or 1853M56P05 (Allied Signal P/ N 442026), installed. These engines are installed on, but not limited to Boeing 737-600/-700/-800 series aircraft.
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.
The aircraft, engines and makers this AD names, by the model designations in its text. A model listed here may still be outside the AD's serial ranges.
