Airworthiness Directives; Rolls-Royce RB211 Series Turbofan Engines

This amendment adopts a new airworthiness directive (AD), that is applicable to Rolls-Royce (RR) plc RB211-535E4-37, RB211-535E4-B-37, and RB211-535E4-B-75 series turbofan engines. This amendment requires introducing an alternative technique to ultrasonically inspect installed fan blades on-wing using a surface wave ultrasonic probe. This action also adds the application of Metco 58 blade root coating as an optional terminating action. This amendment is prompted by the discovery of cracks on LPC fan blade roots during an engine overhaul. The actions specified by this AD are intended to detect cracks in LPC fan blade roots, which if not detected, could lead to uncontained multiple fan blade failure, and damage to the airplane.