Discussion \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 The Boeing Company Model 787-8 and 787-9 airplanes. The NPRM published in the Federal Register on January 10, 2020 (85 FR 1295). The NPRM was prompted by reports that the CAC outlet check valve failed due to fatigue of the aluminum flappers, and exposed the Y-duct to temperatures above its design limit. The NPRM proposed to require installing new inboard and outboard CAC outlet check valves on the left-side and right-side CACTCS packs. \n\tThe FAA is issuing this AD to address failed CAC outlet check valves, which could expose the flight deck and passenger cabin to smoke and fumes, and lead to reduced crew performance or produce passenger discomfort. Off-gassed compounds could cause respiratory distress and could cause serious injury for an individual with a compromised respiratory system. \n\nComments \n\n\n\tThe FAA gave the public the opportunity to participate in developing this final rule. The following presents the comments received on the NPRM and the FAA's response to each comment. \n\nSupport for the NPRM \n\n\n\tThe Air Line Pilots Association, International, stated that it supports the NPRM. \n\nRequest to Reference Part Number for Parts Installation Prohibition Within the AD \n\n\n\tAll Nippon Airways (ANA) requested that the FAA reference CAC outlet check valve, part number (P/N) 7010105H01, directly in paragraph (i) of the proposed AD. ANA noted that paragraph (i) of the proposed AD stated that ''no person may install a CAC outlet check valve, with a part number listed in paragraph 1.B, 'Spares Affected' of Boeing Service Bulletin B787-81205-SB210108-00, Issue 002, dated October 15, 2019, on any airplane.'' ANA pointed out that only CACTCS Pack P/Ns are listed in paragraph 1.B, ''Spares Affected'' of Boeing Service Bulletin B787-81205-SB210108-00, Issue 002, dated October 15, 2019 (''SB B787- 81205-SB210108-00, Issue 002''), and the part number of the CAC outlet check valve that is of concern is not listed. \n\tThe FAA agrees with the request for the reasons provided. Although SB B787-81205-SB210108-00, Issue 002, does list CAC outlet check valves part numbers in paragraph 1.B of the service bulletin, the CAC outlet check valve part number that is of concern, P/N 7010105H01, is not listed in paragraph 1.B of the service bulletin. The CAC outlet check valve part number of concern, P/N 7010105H01, was intended to be a part prohibited from installation. The Accomplishment Instructions of SB B787-81205-SB210108-00, Issue 002, Note 9 of the General Information section states, among other things, that any CAC outlet check valve having P/N 7010105H01 cannot be installed again and must be made unserviceable. Additionally, supplier service information UTC Aerospace Systems Service Bulletin 7110097/098/188/189-21-4, dated May 3, 2018; and UTC Aerospace Systems Service Bulletin 7010097/098/188/189-21-9, dated May 3, 2018, which are referenced in SB B787-81205-SB210108-00, Issue 001; dated May 25, 2018 (''SB B787-81205-SB210108-00, Issue 001''), and SB B787-81205-SB210108-00, Issue 002, also state that all replaced CAC outlet check valves having P/N 7010105H01 cannot be installed again and must be made unserviceable. The FAA has revised paragraph (i) of this AD to specify that no person may install a CAC outlet check valve with a part number listed in paragraph 1.B of SB B787-81205-SB210108-00, Issue 002, or P/N 7010105H01 on any airplane as of the effective date of this AD. \n\nRequest To Clarify Part Marking Requirements \n\n\n\tAmerican Airlines (AA) and United Airlines (UA) requested that the FAA clarify the requirements for marking the MOD DOT number on the CACTCS pack identification plate. Both commenters noted that paragraphs 2.A.(2), 2.A.(3), 2.B.(2), and 2.B.(3) of the Accomplishment Instructions of SB B787-81205-SB210108-00, Issue 002, are listed as ''RC'' (Required for Compliance) and specify to replace the CAC outlet check valve and mark the MOD DOT number on the CACTCS pack identification plate. The commenters pointed out that paragraph (j) of the proposed AD provides credit for actions accomplished in accordance with Boeing Service Bulletin B787-81205-SB210108-00, Issue 001, which does not have instructions for marking the MOD DOT number on the CACTCS pack identification plate. Because SB B787-81205-SB210108-00, Issue 002, specifies to mark the MOD DOT number on the CACTCS pack identification plate, but SB B787-81205-SB210108-00, Issue 001, does not, the commenters requested clarification on this requirement. \n\tThe FAA agrees to clarify. SB B787-81205-SB210108-00, Issue 001, specifies to do actions ''in accordance with'' the supplier service information, which included instructions for part marking. Therefore, operators that accomplished this issue of the service bulletin should have also marked the MOD DOT number on the CACTCSpack identification plate. However, the FAA acknowledges that SB B787-81205-SB210108-00, Issue 001 specified only replacing the parts, not marking them. If operators otherwise complied with SB B787-81205-SB210108-00, Issue 001, but did not mark the MOD DOT number on the CACTCS pack identification plate, they cannot claim credit for part marking and must mark the part as specified in SB B787-81205-SB210108-00, Issue 002. The FAA has not changed this AD in this regard. \n\nRequest To Clarify Part Marking of an ''X'' on the CACTCS Pack Identification Plate \n\n\n\tUA requested that the FAA clarify the requirement to part mark an ''X'' on the CACTCS pack identification plate. UA pointed out that paragraphs 2.A.(2), 2.A.(3), 2.B.(2), and 2.B.(3) of the Work Instructions of SB B787-81205-SB210108-00, Issue 002, specify to mark the MOD DOT number on the CACTCS pack identification plate. In \n\n((Page 54887)) \n\nthe associated tables, footnote (1) specifies to ''also part mark an 'X' on the applicable number in the MOD DOT area of the identification plate . . .'' UA stated that the result is that MOD DOT markings are required in two places, which UA maintains is redundant and not consistent. \n\tThe FAA agrees to clarify. Footnote (1) of Tables 1 through 8 of the Work Instructions of SB B787-81205-SB210108-00, Issue 002, specifies to mark an ''X'' on the identification plate for the appropriate MOD DOT for CACTCS pack configuration H05 and H09 only, which is a separate action from marking the MOD DOT number on the CACTCS pack identification plate. The FAA has not changed this AD in this regard. \n\nRequests To Update Supplier Warranty Information \n\n\n\tBoeing requested that the FAA update the Costs of Compliance section of the NPRM to reflect a name change for the supplier warranty information from UTC Aerospace Systems to Collins Aerospace. The FAA has revised the Costs of Compliance section of this AD accordingly. \n\nRequest To Clarify Discussion \n\n\n\tBoeing requestedthat the FAA modify portions of the Discussion of the NPRM to clarify the cause of failing CAC outlet check valves and more clearly explain the sequence of events leading to the unsafe condition. Whereas the NPRM described the cause of the flapper fatigue as ''increasing open/close cycles,'' Boeing stated that the flapper fatigue was due to ''open/close cycles exceeding design requirements.'' Boeing also requested that the FAA modify the Discussion of the NPRM to clarify that ''This (open/close cycles exceeding design requirements) can cause reverse flow through the broken check valve during times of single CAC operation. With repeated exposure to temperatures in excess of the Y-Duct design limit, the duct may degrade and this can lead to failure of the Y-Duct if not addressed. Dual CAC operation with a failed Y-Duct may lead to high temperatures that can result in off gassing from the duct material.'' \n\tThe FAA agrees that the description in the NPRM was inaccurate and is clarified in the previous paragraph. Since that section of the preamble does not reappear in the final rule, no change to the final rule is necessary. \n\nConclusion \n\n\n\tThe FAA reviewed the relevant data, considered the comments received, and determined that air safety and the public interest require adopting this final rule with the changes described previously and minor editorial changes. The FAA has determined that these changes: \n\tAre consistent with the intent that was proposed in the NPRM for addressing the unsafe condition; and \n\tDo not add any additional burden upon the public than was already proposed in the NPRM. \n\tThe FAA also determined that these changes will not increase the economic burden on any operator or increase the scope of this final rule. \n\nRelated Service Information Under 1 CFR Part 51 \n\n\n\tThe FAA reviewed Boeing Service Bulletin B787-81205-SB210108-00, Issue 002, dated October 15, 2019. The service information describes procedures for installing new inboard and outboard CAC outlet check valves on the left-side and right-side CACTCS packs. 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 the ADDRESSES section. \n\nCosts of Compliance \n\n\n\tThe FAA estimates that this AD affects 90 airplanes of U.S. registry. The FAA estimates the following costs to comply with this AD: \n\n\n\tEstimated Costs for Required Actions ---------------------------------------------------------------------------------------------------------------- \n\tCost on U.S. \n\tAction Labor cost Parts cost Cost per product operators ---------------------------------------------------------------------------------------------------------------- Replace CAC outlet check valves.. 3 work-hours x $85 $0 $255 per check $22,950 per check \n\tper hour = $255 valve. valve.per check valve. ---------------------------------------------------------------------------------------------------------------- \n\n\n\tAccording to the manufacturer, some or all of the costs of this AD may be covered under warranty by Collins Aerospace, thereby reducing the cost impact on affected individuals. The FAA does not control warranty coverage for affected individuals. As a result, the FAA has included all known costs in the cost estimate. \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 aircraftin 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 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.