Airworthiness Directives; The Boeing Company Airplanes

The FAA is adopting a new airworthiness directive (AD) for all The Boeing Company Model 737 series airplanes. This AD was prompted by a report that structural fatigue cracks can develop in certain aluminum pressure module check valves prior to the design limit. This AD requires an inspection to determine the part numbers of the four hydraulic systems A and B pressure module check valves and applicable on-condition actions. The FAA is issuing this AD to address the unsafe condition on these products.