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

This amendment supersedes an existing airworthiness directive (AD) that is applicable to Rolls-Royce plc (RR) RB211-524G and -524H series turbofan engines. That AD currently requires initial and repetitive ultrasonic inspections for cracks in fan blade dovetail roots, and, if necessary, replacement with serviceable parts. That action also provides the options of installing improved design fan blades or reworking current fan blades to the improved configuration as terminating action for the inspections. This amendment requires initial inspection at lower thresholds, using either the blade root probe method or the surface wave probe method. This amendment also removes the option of reworking blades as terminating action for the inspections. Lastly, this amendment adds the model RB211-524H-T-36 engine to the applicability of this AD. This amendment is prompted by two additional reports of fan blade cracks found during inspections performed in accordance with the current AD. The actions specified in this AD are intended to detect cracked fan blades, which could result in an uncontained engine failure and damage to the airplane.