AD 2020-24-08 Airworthiness Directives; Rolls-Royce Deutschland Ltd & Co KG (Type Certificate Previously Held by Rolls-Royce plc) Turbofan Engines

This AD applies to Rolls-Royce Deutschland Ltd & Co KG (Type Certificate Previously Held by Rolls-Royce plc) (RRD) RB211 Trent 768-60, 772-60, 772B-60, and 772C-60 model turbofan engines with an engine serial number (ESN) identified in Table 1 or Table 2 of Appendix 1 of Rolls-Royce (RR) RB211 Trent 700 Series Alert Non-Modification Service Bulletin RB.211-72-AK165, dated November 26, 2018 (the NMSB).

Comply with this AD within the compliance times specified, unless already done.

(1) For engines with an ESN listed in Table 1 of Appendix 1 of the NMSB, prior to each HPT blade accumulating 3,500 flight cycles since new, or before further flight after the effective date of this AD, whichever occurs later, remove the HPT blade from service and replace with a part eligible for installation. (2) For engines with an ESN listed in Table 2 of Appendix 1 of the NMSB, prior to each HPT blade accumulating 5,800 flight cycles since new, or before further flight after the effective date of this AD, whichever occurs later, remove the HPT blade from service and replace with a part eligible for installation. (3) If the flight cycles since new of an HPT blade are unable to be determined, use the flight cycles since new, flight cycles since refurbishment, or flight cycles since overhaul of the HPT module.

This AD was prompted by a determination by the manufacturer that high-pressure turbine (HPT) blades on several RB211 Trent 700 model turbofan engines have been subject to high levels of corrosion fatigue, leading to HPT blade cracking and eventual release. The FAA is issuing this AD to prevent failure of the HPT blades. The unsafe condition, if not addressed, could result in blade failure and subsequent release of high-energy debris, possibly resulting in damage to, and reduced control of, the airplane.

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