Background \n\n\n\tThe FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 by adding an AD that would apply to certain GE CF6-80C2A1, CF6-80C2A2, CF6-80C2A3, CF6-80C2A5, CF6-80C2A5F, CF6-80C2A8, CF6- 80C2B1, CF6-80C2B1F, CF6-80C2B2, CF6-80C2B2F, CF6-80C2B4, CF6-80C2B4F, CF6-80C2B5F, CF6-80C2B6, CF6-80C2B6F, CF6-80C2B6FA, CF6-80C2B7F, CF6- 80C2B8F, and CF6-80C2D1F model turbofan engines. The NPRM published in the Federal Register on April 10, 2020 (85 FR 20211). The NPRM was prompted by reports of incidents that resulted in a significant fuel loss during flight and an IFSD of the engine. The incidents resulted from inserts on the HMU/MEC idler adapter on the AGB assembly pulling out of the housing. An investigation by the manufacturer discovered improperly cut threads on the inserts and erroneous instructions in the maintenance manual, which contributed to poor thread engagement. In the NPRM, the FAA proposed to require initial and repetitive shim checks of the HMU/MEC idler adapter on the AGB assembly and, depending on the results of the shim check, possible replacement of the inserts on the HMU/MEC idler adapter. As a terminating action to the repetitive shim \n\n((Page 11114)) \n\nchecks, the NPRM proposed to require a protrusion check and a pull-out test, and the replacement of inserts on the HMU/MEC idler adapter that fail either test. The FAA is issuing this AD to address the unsafe condition on these products. \n\nDiscussion of Final Airworthiness Directive Comments \n\n\n\tThe FAA received comments from four commenters. The commenters were All Nippon Airways (ANA), Delta Air Lines, Inc. (DAL), FedEx Express (FedEx), and Japan Airlines (JAL). All commenters requested changes, some of which resulted in changes to this AD. The following presents the comments received on the NPRM and the FAA's response to each comment. \n\nRequest To Update the Applicability \n\n\n\tDAL requested that paragraph (c), Applicability,of this AD be updated to align with the effectivity in GE CF6-80C2 Service Bulletin (SB) 72-1577 R01, dated August 16, 2019 (GE CF6-80C2 SB 72-1577 R01), which includes the part numbers (P/Ns) of the affected HMU/MEC idler adapters. \n\tThe FAA agrees. The FAA confirmed with the manufacturer that only the P/Ns of the HMU/MEC idler adapter listed in GE CF6-80C2 SB 72-1577 R01 are affected. The FAA updated the applicability of this AD to include the P/Ns of the affected HMU/MEC idler adapter. The number of engines affected by this AD is unchanged from the NPRM. \n\nRequest To Update Terminating Action \n\n\n\tDAL requested that paragraph (h), Terminating Action, of this AD also terminate the initial shim check of the HMU/MEC idler adapter inserts required by paragraph (g)(1) of this AD. DAL reasoned that since the NPRM proposed to allow for terminating the repetitive shim checks of the HMU/MEC idler adapter inserts, that this AD should add a terminating action for the initial shim check of the HMU/MEC idler adapter inserts if the action was performed within 1,200 flight hours (FHs) after the effective date of this AD. \n\tThe FAA agrees. The FAA updated paragraph (h) of this AD to terminate the actions required by paragraph (g) of this AD. \n\nRequest To Remove the Shim Check \n\n\n\tDAL requested that the FAA remove the shim check of the HMU/MEC idler adapter inserts in paragraph (g)(3)(ii) of the NPRM. DAL reasoned that performing this shim check is not necessary because the (g)(3)(ii) shim check is already required by paragraph (g)(3)(i) of this AD. Additionally, DAL stated that referencing paragraph (g)(1) of this AD to perform the shim check may confuse operators as paragraph (g)(1) of this AD includes the requirement to perform the shim check within 1,200 FHs after the effective date of this AD. Therefore, DAL suggested that paragraph (g)(3)(ii) of this AD should only address the requirement to perform the terminating action if the shim check fails. \n\tThe FAA partially agrees. The FAA disagrees that paragraph (g)(3)(ii) of this AD should only address the requirement to perform the terminating action if the shim check of the HMU/MEC idler adapter inserts fails. After retorque of the bolts at each bolt location that failed the shim check, operators must perform the shim check again. If that shim check fails, then the terminating action is required. The FAA agrees that referencing paragraph (g)(1) of this AD may confuse operators whether to perform the shim check after the aircraft operated for some time or within 1,200 FHs after the effective date of this AD. The FAA updated paragraph (g)(3)(ii) of this AD to reference the service information when performing the shim check rather than paragraph (g)(1) of this AD. \n\nRequest To Update Credit for Previous Actions \n\n\n\tANA, DAL, FedEx, and JAL requested updates to paragraph (i), Credit for Previous Actions, of this AD. ANA requested adding credit for the repetitive shim checks of the HMU/MEC idler adapter inserts and terminating action. DAL and FedEx requested credit for the terminating action. JAL requested credit for the repetitive shim checks of the HMU/ MEC idler adapter inserts, retorque of the bolts that failed the shim check, and the terminating action. The commenters reasoned that GE CF6- 80C2 SB 72-1577 R00, dated October 31, 2018 (GE CF6-80C2 SB 72-1577 R00), instructs the operator to perform the same tasks required by GE CF6-80C2 SB 72-1577 R01. Therefore, credit should be allowed for initial and repetitive shim checks of the HMU/MEC idler adapter inserts and the terminating action. \n\tThe FAA agrees. The FAA reviewed GE CF6-80C2 SB 72-1577 R00, and determined that the instructions are consistent with GE CF6-80C2 SB 72- 1577 R01. The FAA updated this AD to allow credit for the initial and repetitive shim checks of the HMU/MEC idler adapter inserts, retorque of the bolts that failed the shim check, and the terminating action, if performed before the effective date ofthis AD using GE CF6-80C2 SB 72- 1577 R00. \n\nRequest for an Alternate Marking Area \n\n\n\tANA requested that the FAA approve an alternate marking area to show compliance with performing the terminating action of this AD. ANA stated that the marking areas indicated in GE CF6-80C2 SB 72-1577 R01, are difficult to access because many components are installed to AGB assembly. \n\tThe FAA disagrees with approving an alternate marking area. The manufacturer provided two possible marking areas in GE CF6-80C2 SB 72- 1577 R01, and confirmed the suitability of the areas. \n\nRequest To Not Mandate the Marking Requirement \n\n\n\tDAL requested that the FAA not mandate the provision in GE CF6-80C2 SB 72-1577 R01 to mark the HMU/MEC idler adapter to show compliance with the terminating actions of this AD. DAL reasoned that the NPRM did not propose to apply to all engines and therefore should not be required. \n\tThe FAA disagrees. Marking the HMU/MEC idler adapter identifies if the terminating action of this AD has been completed. As noted in a previous comment response, the FAA revised the applicability of this AD to limit applicability to affected engines with certain HMU/MEC idler adapter P/Ns installed. Operators who determine that their engines are not applicable to this AD do not need to perform the terminating action or mark the HMU/MEC idler adapter. \n\nConclusion \n\n\n\tThe FAA reviewed the relevant data, considered any comments received, and determined that air safety requires adopting this AD as proposed. Accordingly, the FAA is issuing this AD to address the unsafe condition on these products. Except for minor editorial changes and any other changes described previously, this AD is adopted as proposed in the NPRM. None of the changes will increase the economic burden on any operator. \n\nRelated Service Information Under 1 CFR Part 51 \n\n\n\tThe FAA reviewed GE CF6-80C2 SB 72-1577 R01, dated August 16, 2019. The SB describes procedures for performing shim checks ofthe HMU/MEC idler adapter and for replacing the HMU/MEC idler adapter inserts. This service information is reasonably available because the interested parties have access to it through their normal \n\n((Page 11115)) \n\ncourse of business or by the means identified in ADDRESSES. \n\nCosts of Compliance \n\n\n\tThe FAA estimates that this AD affects 555 engines installed on airplanes of U.S. registry. \n\tThe FAA estimates the following costs to comply with this AD: \n\n\n\tEstimated Costs ---------------------------------------------------------------------------------------------------------------- \n\tCost per Cost on U.S. \n\tAction Labor cost Parts cost product operators ---------------------------------------------------------------------------------------------------------------- Shim check............................ 1 work-hour x $85 per $0 $85 $47,175 \n\thour = $85. Protrusion check/pull-outtest........ 4 work-hours x $85 per 0 340 188,700 \n\thour = $340. ---------------------------------------------------------------------------------------------------------------- \n\n\n\tThe FAA estimates the following costs to do any necessary replacements that are required based on the results of the shim check. The agency has no way of determining the number of aircraft that might need these replacements: \n\n\n\tOn-Condition Costs ---------------------------------------------------------------------------------------------------------------- \n\tCost per \n\tAction Labor cost Parts cost product ---------------------------------------------------------------------------------------------------------------- Replace HMU/MEC idler adapter insert.......... 4 work-hours x $85 per hour = $50 $390 \n\t$340. ---------------------------------------------------------------------------------------------------------------- \n\nAuthority for This Rulemaking \n\n\n\tTitle 49 of the United States Code specifies the FAA's authority to issue rules on aviation safety. Subtitle I, section 106, describes the authority of the FAA Administrator. Subtitle VII: Aviation Programs, describes in more detail the scope of the Agency's authority. \n\tThe FAA is issuing this rulemaking under the authority described in Subtitle VII, Part A, Subpart III, Section 44701: General requirements. Under that section, Congress charges the FAA with promoting safe flight of civil aircraft in air commerce by prescribing regulations for practices, methods, and procedures the Administrator finds necessary for safety in air commerce. This regulation is within the scope of that authority because it addresses an unsafe condition that is likely to exist or develop on products identified in this rulemaking action. \n\nRegulatory Findings \n\n\n\tThis AD will not have federalism implications under ExecutiveOrder 13132. This AD will not have a substantial direct effect on the States, on the relationship between the national government and the States, or on the distribution of power and responsibilities among the various levels of government. \n\tFor the reasons discussed above, I certify that this AD: \n\t(1) Is not a ''significant regulatory action'' under Executive Order 12866, \n\t(2) Will not affect intrastate aviation in Alaska, and \n\t(3) Will not have a significant economic impact, positive or negative, on a substantial number of small entities under the criteria of the Regulatory Flexibility Act. \n\nList of Subjects in 14 CFR Part 39 \n\n\n\tAir transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.