Background \n\n\n\tThe FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 to supersede AD 2016-24-08, Amendment 39-18725 (81 FR 86567, December 1, 2016) (AD 2016-24-08). AD 2016-24-08 applied to all RR RB211-Trent 875-17, RB211-Trent 877-17, RB211-Trent 884-17, RB211- Trent 884B-17, RB211-Trent 892-17, RB211-Trent 892B-17, and RB211-Trent 895-17 model turbofan engines. The NPRM published in the Federal Register on June 24, 2019 (84 FR 29423). The NPRM was prompted by RRD developing a modification of the engine upper bifurcation nose fairing assembly that terminates the need for repetitive inspections of this part. In the NPRM, the FAA proposed to retain the requirements to perform repetitive inspections of the engine upper bifurcation nose fairing assembly and repair or replacement of any fairing assembly that fails inspection. As a terminating action, in the NPRM the FAA also proposed to require modification of the engine upper bifurcation nose fairing assembly. The FAA is issuing this AD to address the unsafe condition of these products. \n\tThe European Aviation Safety Agency (EASA), which is the Technical Agent for the Member States of the European Community, has issued EASA AD 2018-0088, dated April 18, 2018 (referred to after this as ''the MCAI''), to address the unsafe condition on these products. The MCAI states: \n\n\n\n((Page 78216)) \n\n\n\n\n\tInspection of in-service Trent 800 engines identified cracking and/or material release from the upper bifurcation fairing, which mates to the aeroplane thrust reverser upper bifurcation forward fire seal. Both sets of hardware create the engine firewall to isolate the engine compartment fire zone, which is a firewall feature of the aeroplane type design. Damage (missing materials and holes/openings) to the upper bifurcation fairing creates a breach of the engine fire wall, which may decrease the effectiveness of the engine fire detection and suppression systems dueto excess fan air entering the engine compartment fire zone. This could delay or prevent the fire detection and suppression system from functioning properly, and can result in an increased risk of prolonged burning, potentially allowing a fire to reach unprotected areas of the engine, strut and wing. \n\tThis condition, if not detected and corrected, could lead to an uncontrolled fire, possibly resulting in damage to, or loss of, the aeroplane. \n\tTo address this potential unsafe condition, RR published the NMSB to provide inspection instructions. Consequently, EASA issued AD 2016-0084 to require repetitive inspections of the upper bifurcation fairing and, depending on findings, accomplishment of applicable corrective action(s). \n\tSince that (EASA) AD was issued, RR developed modification (mod) 72-J803, which introduces a revised upper bifurcation nose fairing assembly, featuring an additional support bracket assembly at the right hand seal land. RR also published the modification SBto provide instructions for in-service engines. This modification removes the need for repetitive inspections. \n\tFor the reasons described above, this (EASA) AD retains the requirements of EASA AD 2016-0084, which is superseded, and requires a modification, which constitutes terminating action for the repetitive inspections required by this (EASA) AD. \n\n\n\tYou may obtain further information by examining the MCAI in the AD docket at https://www.regulations.gov by searching for and locating Docket No. FAA-2019-0425. \n\nDiscussion of Final Airworthiness Directive \n\nComments \n\n\n\tThe FAA received comments from six commenters. The commenters were Rolls-Royce plc (RR); American Airlines (AAL); The Boeing Company (Boeing); Delta Air Lines, Inc. (DAL); and two individual commenters. Five commenters requested changes to this AD, which included adding or updating the unsafe condition, terminating action, installation prohibition, and credit for previous actions. One commenter requested clarification regarding on-wing rework. One commenter expressed support for the AD. The following presents the comments received on the NPRM and the FAA's response to each comment. \n\nRequest To Remove Statement Indicating the Unsafe Condition Could Cause a Fire \n\n\n\tBoeing requested that paragraph (e), Unsafe Condition, of this AD be revised to replace ''. . . could result in engine fire and damage to the airplane'' with ''. . . could result in reduced ability to detect and/or control an engine fire which could lead to damage to the airplane.'' Boeing reasoned that unsafe condition is not expected to cause an engine fire. Instead, when material is liberated from the engine upper bifurcation nose fairing assembly, the core zone fire detection and extinguishing may be less effective in the event of a fire. This is due to airflow that may be allowed to pass into the fire zone through an alternate path and at an unknown rate compared to the intended design. \n\tThe FAA partially agrees.The FAA agrees that a cracked engine upper bifurcation nose fairing assembly and material release would not lead to an engine fire. The unsafe condition of this AD, however, is not the cracking of the engine upper bifurcation nose fairing assembly and material release, but the resulting failure of the engine fire control system. Since the engine fire control system would be inadequate to detect and control an engine fire, regardless of cause, the resulting hazard is the engine fire and consequent damage to the airplane. The FAA did not change this AD. \n\nRequest To Clarify Engine Upper Bifurcation Nose Fairing Assembly With FRSJ739 Repair \n\n\n\tDAL requested that Note 1 to paragraph (g)(3) of this AD be updated to clarify inspection if on-wing repair FRSJ739 was applied. DAL reasoned that RRD added a second sheet to Figure 1 when it published Revision 2 of RR Alert Non-Modification Service Bulletin (NMSB) RB.211- 72-AJ165, on August 21, 2018. This second sheet includes the entire length of the bracket in Zone A if on-wing repair FRSJ739 was applied. The proposed AD did not provide any distinctions for on-wing repair FRSJ739. \n\tThe FAA disagrees. As stated in Note 1 to paragraph (g)(3) of this AD, Figure 1 of RR Alert NMSB RB.211-72-AJ165, Revision 2, dated August 21, 2018, provides guidance on the engine upper bifurcation nose fairing assembly inspection locations. Operators are not required to use Figure 1 to comply with this AD. Therefore, this AD is not required to reference on-wing repair FRSJ739. \n\nRequest To Add Credit for Previous Actions Paragraph \n\n\n\tDAL requested that the FAA add a Credit for Previous Actions paragraph to this AD for previous initial and repetitive inspections completed using RR Alert NMSB RB.211-72-AJ165, Initial Issue, dated March 31, 2016, required by AD 2016-24-08. \n\tThe FAA disagrees. AD 2016-24-08 and this AD do not require use of RR Alert NMSB RB.211-72-AJ165 to perform the initial and repetitive inspections. RR Alert NMSBRB.211-72-AJ165 is provided as guidance on engine upper bifurcation nose fairing assembly inspection locations. Therefore, this AD does not need to provide credit for inspections performed using RR Alert NMSB RB.211-72-AJ165. The FAA did not change this AD. \n\nRequest To Update Terminating Action With the Latest Service Information \n\n\n\tAAL, Boeing, DAL, and an individual commenter requested that paragraph (h), Mandatory Terminating Action, of this AD be updated to include RR Service Bulletin (SB) RB.211-72-J803, Revision 2, dated April 1, 2019. The commenters reasoned that RR SB RB.211-72-J803, Revision 1, dated July 13, 2018, has been superseded by Revision 2, dated April 1, 2019. Boeing also suggested adding language that allows any later revisions of the service information to be equivalent action as RRD may publish further revisions. \n\tThe FAA agrees to revise the reference to RR SB RB.211-72-J803 in paragraph (h) of this AD from Revision 1, dated July 13, 2018, to Revision 2,dated April 1, 2019. The FAA disagrees with adding language that allows any later revisions of the service information. Since later revisions of the service information have not been published or reviewed by the agency, the FAA will not require their use. \n\tWith the update to RR SB RB.211-72-J803 in this AD from Revision 1, dated July 13, 2018, to Revision 2, dated April 1, 2019, the FAA determined the need to update the estimated costs to reflect the increase in labor hours from 2 work-hours to 8 work-hours for both on- wing and in-shop visits. \n\nRequest To Add On-Wing Mandatory Terminating Action \n\n\n\tDAL requested that the on-wing rework instructions introduced in the Accomplishment Instructions, paragraph 3.D., of RR SB RB.211-72- J803, Revision 2, dated April 1, 2019, be included as an option for the mandatory terminating action to the AD. DAL \n\n((Page 78217)) \n\nadded that paragraph (i), Installation Prohibition, will ensure that de-modification of the engine upper bifurcation nose fairing assembly will not be possible once the reworked engine upper bifurcation nose fairing assembly is installed. \n\tThe FAA agrees that the on-wing rework instructions should be added as an option to the mandatory terminating action in addition to the in- shop rework procedure. RR SB RB.211-72-J803, Revision 2, dated April 1, 2019, provides an option to perform the on-wing rework instructions. As a result, operators can perform the rework in-shop or on-wing. The FAA added the on-wing rework instructions to the mandatory terminating action section of this AD. \n\tThe FAA also agrees that de-modification of the engine upper bifurcation nose fairing assembly will not be possible once the reworked engine upper bifurcation nose fairing assembly is installed. As noted in the following comment response, the FAA removed the installation prohibition proposed in the NPRM as the mandatory terminating actions requiring the modification of the engine upper bifurcation nose fairing assembly makes this installation prohibition unnecessary. \n\nRequest To Revise Installation Prohibition \n\n\n\tRR and AAL requested that paragraph (i), Installation Prohibition, of the proposed AD be revised. Rolls-Royce was concerned if an upper bifurcation panel (upper bifurcation nose fairing assembly) is required to complete an on-wing repair, it will prevent the installation of the original panel without the part being modified to the later standard. AAL reasoned that a serviceable engine upper bifurcation nose fairing assembly that needs to be repaired or replaced per AD 2016-24-08, but has not been, may be removed during non-related maintenance. The FAA infers that RR's concern aligns with AAL reasoning that removal of a panel for on-wing activity, such as maintenance or repair unrelated to the rework, will make the part ineligible for installation. Therefore, AAL proposed that paragraph (i) of the proposed AD be revised to ''After the effective date of this AD, do not install anengine upper bifurcation nose fairing assembly, P/N FK25470, onto any engine that has or had an engine upper bifurcation nose fairing assembly, P/N KH75280, installed.'' \n\tThe FAA agrees that the installation prohibition would prevent the installation of the engine upper bifurcation nose fairing assembly, P/N FK25470, onto any engine after the effective date of this AD, even for work unrelated to this AD. The mandatory terminating action requires the modification of engine upper bifurcation nose fairing assembly, P/N FK25470 and, as such, the installation prohibition is not necessary. The FAA removed the installation prohibition from this AD. \n\nSupport for the AD \n\n\n\tAn individual commenter expressed support for the AD as written. \n\nConclusion \n\n\n\tThe FAA reviewed the relevant data, considered the comments received, and determined that air safety requires adopting the 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 RR SB RB.211-72-J803, Revision 2, dated April 1, 2019; Revision 1, dated July 13, 2018; and Initial Issue, dated December 7, 2017. The service information describes procedures for modification of the engine upper bifurcation nose fairing assembly. This service information is reasonably available because the interested parties have access to it through their normal course of business or by the means identified in ADDRESSES. \n\nOther Related Service Information \n\n\n\tThe FAA reviewed RR Alert NMSB RB.211-72-AJ165, Revision 2, dated August 21, 2018. The NMSB provides guidance on engine upper bifurcation nose fairing assembly inspection locations. The FAA also reviewed AMM TASK 70-20-02, Water Washable Fluorescent Penetrant Inspection (Maintenance Process 213), and OMat 632, high sensitivity fluorescent penetrant inspection. This service information provides guidance on performing a fluorescent penetrant inspection. \n\nCosts of Compliance \n\n\n\tThe FAA estimates that this AD affects 70 engines installed on airplanes of U.S. registry. Based on updated information since publication of the NPRM, the FAA revised the estimated number of engines installed on airplanes of U.S. registry from 125 in the NPRM to 70 in this final rule. \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 ---------------------------------------------------------------------------------------------------------------- Inspect engine upper bifurcation nose 3.25 work-hours x $85 $0 $276.25 $19,337.50 \n\tfairing assembly. per hour = $276.25. Modify engine upper bifurcation nose 8 work-hours x $85 per 50 730 51,100 \n\tfairing assembly. hour = $680. ---------------------------------------------------------------------------------------------------------------- \n\n\n\tThe FAA estimates the following costs to do any necessary repairs or replacements that would be required based on the results of the mandated inspections. The agency has no way of determining the number of engines that might need these repairs or replacements: \n\n\n\tOn-Condition Costs ---------------------------------------------------------------------------------------------------------------- \n\tCost per \n\tAction Labor cost Parts cost product ---------------------------------------------------------------------------------------------------------------- Repair engine upper bifurcation nose fairing 8 work-hours x $85 per hour = $500 $1,180 \n\tassembly. $680. \n\n((Page 78218)) \n\n\n\nReplace engine upper bifurcation nose fairing 30 work hours x $85 per hour = 500 3,050 \n\tassembly. $2,550. ---------------------------------------------------------------------------------------------------------------- \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\tThe FAA has determined that this AD will not have federalism implications under Executive Order 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.