Discussion \n\n\n\tWe issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 by adding an AD that would apply to all The Boeing Company Model 747-8 and 747-8F series airplanes. The NPRM published in the Federal Register on August 3, 2018 (83 FR 38096). The NPRM was prompted by reports of damaged vapor seals, block seals, and heat shield seals on the outboard pylons between the engine strut and aft fairing. The NPRM proposed to require installing new aft fairing vapor seals, heatshield seals, heatshield seal retainers, block seals, and outboard lateral restraint access panels. \n\tWe are issuing this AD to address heat damage to the vapor seals between the engine strut and aft fairing. Such damage could allow flammable fluid leakage out of the aft fairing, which could result in an uncontrolled fire in the engine strut. \n\nComments \n\n\n\tWe 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\nRequest To Review Airplane Maintenance Records in Lieu of an Inspection \n\n\n\tUnited Parcel Service (UPS) requested that operators be allowed to perform a records review to determine if the affected part number is installed in lieu of performing an inspection. UPS stated that the records review will provide an equivalent level of safety. UPS stated that in accordance with paragraph (g)(2) of the proposed AD, it would be required to inspect all Model 747-8F airplanes within 4 years or 4,800 flight cycles after the AD effective date, whichever occurs first. \n\tWe agree with the commenter's request that a review of the airplane maintenance records is acceptable in lieu of an inspection if the part number of the part can be conclusively determined from that review. We have revised paragraph (g)(2) of this AD accordingly. \n\nRequest To Revise the Line Numbers in the Applicability Paragraph \n\n\n\tBoeing requestedwe revise the proposed AD to address airplanes only specified in Boeing Alert Service Bulletin 747-54A2247, dated August 3, 2017, line numbers (L/Ns) 1420 through 1540, instead of all 747-8 and 747-8F series airplanes as specified in paragraph (c), ''Applicability,'' of the proposed AD. \n\tBoeing stated that airplanes not identified in Boeing Alert Service Bulletin 747-54A2247, dated August 3, 2017, L/Ns 1541 and on, were built and delivered from the Boeing factory with the correct parts. Boeing commented that the factory utilizes the approved Boeing Production System to maintain configuration control of the airplanes through delivery, and that the remainder of the Model 747-8 fleet is covered by Boeing Alert Service Bulletin 747-54A2247, dated August 3, 2017. \n\tWe disagree with the commenter's request. As we stated in the ''Differences Between this Proposed AD and the Service Information'' of the NPRM, the applicability in this AD does not refer to paragraph l. A., ''Effectivity,'' of Boeing Alert Service Bulletin 747-54A2247, dated August 3, 2017. The service information does not contain a comprehensive list of the airplanes affected by the identified unsafe condition because the spare parts identified in paragraph (j) of this AD have been determined to be rotable parts that are capable of being installed on all Model 747-8 and 747-8F series airplanes. Therefore, the applicability of this AD is all Model 747-8 and 747-8F series airplanes. \n\tAdditionally, there is the potential for previously delivered Model 747-8 and 747-8F airplanes having the affected spare parts installed during a repair of the aft fairing. Delivered airplanes with line numbers 1541 and on could have been exposed to the affected parts between delivery and as of the effective \n\n((Page 20243)) \n\ndate of this AD, which is why operators can either review airplane maintenance records to confirm whether the subject parts are not installed, or perform an inspection of the parts on the airplanes.We have been informed by operators that the practice of rotating interchangeable parts among airplanes is widespread and even a key part of their operations. In the absence of an AD or airworthiness limitation (AWL) that restricts the installation of the affected parts, we cannot be assured that the unsafe condition will not be introduced to Model 747-8 and 747-8F airplanes that are not identified in Boeing Alert Service Bulletin 747-54A2247, dated August 3, 2017. In addition, we cannot rely solely on the Boeing Production System to maintain configuration control of these airplanes until the AD has been published. In order to eliminate the unsafe condition, we must address all of the potentially exposed airplanes. We have not changed this AD in this regard. \n\nRequest To Remove the Parts Installation Prohibition Paragraph \n\n\n\tBoeing requested that we remove the ''Parts Installation Prohibition'' paragraph in the proposed AD. Boeing stated that some of the parts listed in paragraph (j), ''Parts Installation Prohibition,'' remain in use on all Model 747-8 airplanes and therefore cannot be prohibited. \n\tBoeing also commented that, regarding the seals, rotation of these parts from one airplane to another is not feasible due to their location and the effort required, as the aft fairings must be removed and reinstalled to gain access to the seals. In addition, Boeing stated that the lateral restraint access panels were revised to include an integral air scoop on one side, and if a panel is inadvertently installed in an incorrect location, the seal system would still operate with an acceptable level of safety. \n\tWe partially agree with the commenter's request. We agree the vapor seal-outboard aft fairing, part number (P/N) 323U8452-3, is a part that could be used as a part of the service information modification. Therefore, we have revised the ''Parts Installation Prohibition/ Limitation'' paragraph in this AD to specify that no person may install a vapor seal with P/N 323U8452-3, on any airplane, unless it is a new vapor seal that has been installed as specified in the Accomplishment Instructions of Boeing Alert Service Bulletin 747-54A2247, dated August 3, 2017. \n\tWe disagree with removing any other part numbers as they are subject to the heat damage that leads to the unsafe condition. However, we have revised the compliance time specified in paragraph (j) of this AD by removing ''as of the effective date of this AD'' and replacing it with either ''as of the determination that no affected part is installed'' or ''after accomplishing the required actions specified in paragraph (g) of this AD'', depending on whether the actions in the service information specified in paragraph (g) of this AD must be done. \n\tIn addition, for clarity, we revised paragraph (g)(2) of this AD by listing the affected part numbers instead of referring to paragraph (j) of this AD for the part numbers. \n\nRequest To Clarify the Requirements of the Parts InstallationProhibition Paragraph \n\n\n\tCathay Pacific Airways Limited (Cathay) requested clarification of the requirements in the ''Parts Installation Prohibition'' paragraph of the proposed AD. Cathay stated that the paragraph should only be applicable to airplanes that have been modified in accordance with Boeing Alert Service Bulletin 747-54A2247, dated August 3, 2017, instead of being applicable to any airplane modified as of the effective date of the AD. Cathay stated that if the intention is indeed for any airplane, then it asked the FAA to clarify the following: \n\tWhether the intent of the proposed AD is to fulfill this paragraph requirement as of the compliance time of the proposed AD instead of as of the effective date of this proposed AD; \n\tWhether this paragraph affects the already installed parts or only the new parts to be installed in accordance with Boeing Alert Service Bulletin 747-54A2247, dated August 3, 2017. Cathay stated that on the effective date of the proposed AD, someof the airplanes are still in pre-mod configuration and are installing the pre-mod parts; \n\tWhether after the effective date of the proposed AD, do operators need to accomplish Boeing Alert Service Bulletin 747-54A2247, dated August 3, 2017, immediately and install the post-modification parts if the related parts are found damaged at line maintenance as a non-routine findings; and \n\tWhether after the effective date of the proposed AD, do operators need to accomplish Boeing Alert Service Bulletin 747-54A2247, dated August 3, 2017, immediately and install the post-modification parts if the related parts are found damaged during the Boeing Alert Service Bulletin 747-54A2246, dated February 5, 2016, inspections. \n\tWe agree to provide clarification for the commenter. Paragraph (g)(1) of this AD requires operators to complete the requirements in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 747-54A2247, dated August 3, 2017, within 4 years or 4,800 flight cycles after the effective date of this AD. Paragraph (g)(2) of this AD requires operators to determine if any affected part is installed and if so, to complete the applicable replacement in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 747-54A2247, dated August 3, 2017, within 4 years or 4,800 flight cycles after the effective date of this AD. \n\tWithin that time period, operators of airplanes that have any affected parts may use the existing/pre-modification parts that are subject to the repetitive inspections of AD 2017-04-13, Amendment 39- 18808 (82 FR 11795, February 27, 2017) (''AD 2017-04-13''). If it is discovered during line maintenance that the subject parts are damaged, the operator has the option to replace the parts that are damaged using either Boeing Alert Service Bulletin 747-54A2247, dated August 3, 2017, or Boeing Alert Service Bulletin 747-54A2246, dated February 5, 2016. Thus, operators are able to continue to conduct the repetitive inspections as well as accomplish the repairs using Boeing Alert Service Bulletin 747-54A2246, dated February 5, 2016, while using the older parts, for up to 4 years or 4,800 flight cycles from the effective date of this AD. \n\tHowever, operators are required to accomplish Boeing Alert Service Bulletin 747-54A2247, dated August 3, 2017, within the same compliance time specified in this AD. The FAA encourages operators to install the newer parts to eliminate the unsafe condition and terminate the inspections required by AD 2017-04-13. \n\tFor airplanes that do not have any affected parts, we have determined that in order to address the unsafe condition, we cannot allow that condition to be introduced into additional airplanes in the fleet. Therefore, paragraph (j)(1) of this AD is applicable to those airplanes and the prohibition and limitation specified in paragraphs (j)(1)(i) and (j)(1)(ii) of this AD must be complied with as of the determination that no affected part is installed. \n\tParagraph (j)(2) of this AD is only applicable to the airplanes that have incorporated the actions specified in Boeing Alert Service Bulletin 747-54A2247, dated August 3, 2017. Once an operator incorporates the new parts in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 747-54A2247, dated August 3, 2017, operators must comply with the \n\n((Page 20244)) \n\nprohibition and limitation specified in paragraphs (j)(2)(i) and (j)(2)(ii) of this AD. \n\nConclusion \n\n\n\tWe 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. We have determined that these minor 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\tWe 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\tWe reviewed Boeing Alert Service Bulletin 747-54A2247, dated August 3, 2017. This service information describes procedures for installing new aft fairing vapor seals, heatshield seals, heatshield seal retainers, block seals, and outboard lateral restraint access panels. 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\tWe estimate that this AD affects 13 airplanes of U.S. registry. We estimate the following costs to comply with this AD: \n\n\n\tEstimated Costs for Required Actions ---------------------------------------------------------------------------------------------------------------- \n\tCost per Cost on U.S. \n\tActionLabor cost Parts cost product operators ---------------------------------------------------------------------------------------------------------------- Installation of vapor seals, 136 work-hours x $85 per $21,910 $33,470 $435,110 \n\theatshield seals, heatshield seal hour = $11,560. \n\tretainers, block seals, and outboard \n\tlateral restraint access panels. ---------------------------------------------------------------------------------------------------------------- \n\n\n\tAccording to the manufacturer, some or all of the costs of this AD may be covered under warranty, thereby reducing the cost impact on affected individuals. We do not control warranty coverage for affected individuals. As a result, we have included all available costs in our 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\tWe are 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\tThis AD is issued in accordance with authority delegated by the Executive Director, Aircraft Certification Service, as authorized by FAA Order 8000.51C. In accordance with that order, issuance of ADs is normally a function of the Compliance and Airworthiness Division, but during this transition period, the Executive Director has delegated the authority to issue ADs applicable to transport category airplanes and associated appliances to the Director of the System Oversight Division. \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) Is not a ''significant rule'' under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979), \n\t(3) Will not affect intrastate aviation in Alaska, and \n\t(4) 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.