Summary
The FAA proposes to adopt a new airworthiness directive (AD) for CFM International, S.A. CFM56-7B Series Turbofan Engines. This proposed AD would require 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 proposed 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 proposing 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.