Summary
The FAA proposes to adopt 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, part number (P/N) 23035175, installed. This proposed AD would require installation of a turbine energy absorbing ring in the plane of the 1st stage turbine wheel. This proposed AD may also require installation of 1st stage turbine nozzles, 2nd stage turbine nozzles, and a gas producer support assembly, all modified to allow for installation of the turbine energy absorbing ring. This proposed AD results from an unacceptable rate of uncontained 1st stage turbine wheel failures. We are proposing 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.