Airworthiness Directives; CFM International, S. A. CFM56-5B Series Turbofan Engines

The FAA is adopting a new airworthiness directive (AD) for CFM International, S. A. CFM56-5B series turbofan engines. This AD requires reviewing exhaust gas temperature (EGT) monitoring records to determine EGT deterioration margin, and for airplanes where both engines have greater than 80[deg] centigrade (C) deterioration of EGT margin, borescope-inspecting the high-pressure compressor (HPC) of both engines. This AD also requires removing from service any engine that does not pass the borescope inspection, and if both engines pass, removing and replacing one of the engines with an engine that has 80 [deg]C or less deterioration of EGT margin. This AD also requires continuous monitoring of EGT margin on engines in service, to prevent two engines on an airplane from having greater than 80 [deg]C of deterioration of EGT margin. This AD results from an Airbus A321 airplane powered by CFM56-5B1/P turbofan engines experiencing HPC stalls during climb out after takeoff. We are issuing this AD to prevent HPC stalls, which could prevent continued safe flight or landing.