Airworthiness Directives; CFM International, S.A. CFM56-7B Series Turbofan Engines

The FAA is adopting a new airworthiness directive (AD) for CFM International, S.A. CFM56-7B series turbofan engines. This AD requires revising the Airworthiness Limitations Section (ALS) in the Engine Shop Manual (ESM) and the air carrier's approved continuous airworthiness maintenance program (CAMP) to add mandatory inspections of certain low pressure turbine rear frames (TRFs) to the ALS or CAMP. This AD results from a refined lifing analysis by the engine manufacturer that shows the need to identify an initial threshold for inspecting certain TRFs. We are issuing this AD to prevent failure of the TRF from low-cycle fatigue cracks. Failure of the TRF could result in engine separation from the airplane, which could lead to loss of control of the airplane.