Airworthiness Directives; CFM International S.A. Turbofan Engines

We are adopting a new airworthiness directive (AD) for certain CFM International S.A. (CFM) CFM56-7B and CFM56-3 turbofan engines. This AD was prompted by a report of an uncommanded in-flight shutdown (IFSD) on a CFM CFM56-7B engine following rupture of the 73-tooth gearshaft located in the engine accessory gearbox (AGB). This AD requires AGB/transfer gearbox (TGB) magnetic chip detector (MCD) inspection of the affected gearshafts until removal. We are issuing this AD to prevent failure of certain engine AGB gearshafts, which could lead to failure of one or more engines, loss of thrust control, and damage to the airplane.