Summary
The Federal Aviation Administration (FAA) proposes to adopt a new airworthiness directive (AD) that is applicable to Rolls-Royce plc (RR) model RB211-22B turbofan engines with intermediate pressure (IP) compressor stage 6 to 7 rotor shaft assembly part number (P/N) UL37094 installed. This proposal would require removal from service of IP compressor stage 6 to 7 rotor shaft assemblies P/N UL37094 before reaching newly reduced life limits. This proposal is prompted by the discovery of corrosion during inspection and analysis of IP compressor stage 6 to 7 rotor shaft assemblies returned from the field. The actions specified by the proposed AD are intended to prevent corrosion- induced cracking of the IP compressor stage 6 to 7 rotor shaft assembly, resulting in an uncontained engine failure and damage to the airplane.