Summary
The FAA proposes to adopt a new airworthiness directive (AD) for Rolls-Royce plc (RR) RB211 Trent 875-17, Trent 877-17, Trent 884-17, Trent 892-17, Trent 892B-17, and Trent 895-17 turbofan engines with intermediate pressure (IP) turbine discs, part numbers (P/Ns) FK21117 and FK33083 installed. This proposed AD would require removal from service of these IP turbine discs in accordance with newly established reduced turbine disc life limits. This proposed AD is prompted by reports of two IP turbine blade release incidents as a result of dust caps separating from the blades, and subsequent improved modeling analysis. The actions specified in this proposed AD are intended to prevent uncontained IP turbine disc failure and damage to the airplane.