Airworthiness Directives; Rolls-Royce Corporation Turboshaft Engines

The FAA is superseding Airworthiness Directive (AD) 2017-18- 14, which applied to certain Rolls-Royce Corporation (RRC) 250 model turboshaft engines. AD 2017-18-14 required repetitive visual inspections and fluorescent penetrant inspections (FPIs) of the 3rd- stage turbine wheel and removal from service of the 4th-stage turbine wheel. This AD was prompted by in-service turbine blade failures that resulted in the loss of power and engine in-flight shutdowns. This AD requires replacement of the 3rd-stage and 4th-stage turbine wheels. This AD also revises the applicability to include an additional turboshaft engine model. The FAA is issuing this AD to address the unsafe condition on these products.