AD FAA-2008-1353

The FAA is superseding an existing airworthiness directive (AD) for CFM International, S.A. CFM56-5B series turbofan engines. That AD requires reviewing exhaust gas temperature (EGT) monitoring records to determine EGT margin deterioration, and for airplanes where both engines have greater than 80 [deg]centigrade (C) of EGT margin deterioration, borescope-inspecting the high-pressure compressor (HPC) of both engines. That AD also requires removing from service any engine that does not pass the borescope inspection and, if both engines pass, replacing one of the engines with an engine that has 80 [deg]C or less of EGT margin deterioration. That AD also requires continuous monitoring of EGT margin deterioration on engines in service to prevent two engines on an airplane from having greater than 80 [deg]C of EGT margin deterioration. This AD: <bullet> Reduces the number of engine models affected; <bullet> Continues to monitor EGT margin deterioration; <bullet> Lowers the EGT margin threshold from 80 [deg]C to 75 [deg]C; <bullet> Removes FADEC software version 5.B.Q and earlier versions from the engine as mandatory terminating action to the continuous EGT margin deterioration monitoring, for certain engine models; <bullet> Removes the requirement to borescope inspect; and <bullet> Removes the requirement to replace one of the engines with an engine that has 80 [deg]C or less deterioration of EGT margin as a corrective action. This AD results from a reduction of the affected engine models listed in AD 2009-01-01 from 25 to 19, a reduction in the engine EGT margin deterioration threshold from 80 [deg]C to 75 [deg]C, the introduction of terminating action to the continuous EGT monitoring for certain engines, and a change to the removal plan for the remaining engines if the EGT margin deterioration is greater than 75 [deg]C. We are issuing this AD to prevent HPC stalls, which could prevent continued safe flight or landing.