Airworthiness Directives; Rolls-Royce Corporation Turboprop and Turboshaft Engines

요약

We propose to supersede airworthiness directive (AD) 2012-14- 06, which applies to certain Rolls-Royce Corporation (RRC) 250-C20, - C20B, and -C20R/2 turboshaft engines. AD 2012-14-06 currently requires a one-time visual inspection and fluorescent-penetrant inspection (FPI) on certain 3rd-stage and 4th-stage turbine wheels for cracks in the turbine blades. Since we issued AD 2012-14-06, we determined that the one-time inspection required by AD 2012-14-06 should be changed to repetitive inspections and that we should add an inspection after any engine hot start. We also identified additional engine models subject to the unsafe condition. This proposed AD would replace the one-time visual inspection and FPI with repetitive visual inspections and FPIs, and would also require inspection and FPI after any engine hot start. This proposed AD would also add certain engine models to the applicability. We are proposing this AD to prevent failure of 3rd-stage and 4th-stage turbine wheel blades, which could cause engine failure and damage to the aircraft.