Airworthiness Directives; Rolls-Royce Corporation (Formerly Allison Engine Company) 250-B17B, -B17C, -B17D, -B17E, -C20, -C20B, -C20F, -C20J, -C20S, and -C20W Turboprop and Turboshaft Engines

The FAA is adopting a new airworthiness directive (AD) for Rolls- Royce Corporation (RRC) (formerly Allison Engine Company) 250-B17B, - B17C, -B17D, -B17E, -C20, -C20B, -C20F, -C20J, -C20S, and -C20W turboprop and turboshaft engines that do not have turbine energy absorbing ring, RRC part number (P/N) 23035175, or an equivalent FAA- approved serviceable turbine energy absorbing ring, installed. This AD requires installation of a turbine energy absorbing ring in the plane of the 1st stage turbine wheel. This AD results from an unacceptable rate of uncontained 1st stage turbine wheel failures. We are issuing this AD to minimize the risk of uncontained 1st stage turbine wheel fragments from causing damage to the aircraft or damage to the second engine on twin-engine installations, which could lead to loss of control and loss of the aircraft.