Airworthiness Directives; Rolls-Royce plc RB211 Trent 800 Series Turbofan Engines

This amendment supersedes an existing airworthiness directive (AD), applicable to certain Rolls-Royce plc RB211 Trent 800 series turbofan engines, that currently requires initial and repetitive ultrasonic inspections of fan blade roots for cracks, and replacement, if necessary, with serviceable parts. This amendment requires the reduction of the initial cyclic compliance threshold and repetitive inspection intervals. This amendment also allows inspections to be accomplished within 100 cycles-in-service if the initial or repetitive thresholds are exceeded on the effective date of this AD. This amendment is prompted by an improved understanding of the crack propagation mechanism and the latest service operational data. The actions specified by this AD are intended to detect and prevent fan blade failure, which could result in multiple fan blade releases, uncontained engine failure, and possible damage to the airplane.