Airworthiness Directives; Rolls-Royce Corporation Turboshaft Engines

We propose to supersede Airworthiness Directive (AD) 2015-02- 22, which applies to certain Rolls-Royce Corporation (RRC) model 250 turboprop and turboshaft engines. AD 2015-02-22 currently requires repetitive visual inspections and fluorescent-penetrant inspection (FPIs) on certain 3rd-stage and 4th-stage turbine wheels for cracks in the turbine wheel blades. Since we issued AD 2015-02-22, we determined that it is necessary to remove the 4th-stage wheels at the next inspection. We are also proposing to revise the applicability to remove all RRC turboprop engines and add additional turboshaft engines. This proposed AD would require repetitive visual inspections and FPIs of 3rd-stage turbine wheels while removing from service 4th-stage turbine wheels. We are proposing this AD to correct the unsafe condition on these products.