Airworthiness Directives; Rolls-Royce plc RB211-524 Series Turbofan Engines

The FAA is adopting a new airworthiness directive (AD) for Rolls Royce plc (RR) RB211-524 series turbofan engines with certain part number (P/N) intermediate pressure (IP) compressor stage 5 disks installed. This AD requires new reduced IP compressor stage 5 disk cyclic limits. This AD also requires removing from service affected disks that already exceed the new reduced cyclic limit, and removing other affected disks before exceeding their cyclic limits, using a drawdown schedule. This AD results from the discovery of cracks in the cooling air hole areas of the disk front spacer arm. We are issuing this AD to prevent IP compressor stage 5 disk failure, which could result in uncontained engine failure and possible damage to the airplane.