Background \n\n\n\tThe FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 to supersede AD 2016-25-29, Amendment 39-18755 (81 FR 94956, December 27, 2016) (AD 2016-25-29). AD 2016-25-29 applied to certain The Boeing Company Model 767-200 and -300 series airplanes, and required replacing the cargo compartment insulation blankets on the left and right sides with new insulation blankets that incorporate fire stops. The NPRM published in the Federal Register on August 10, 2020 (85 FR 48122). The NPRM was prompted by a report of a fire in the bilge area of the cargo compartment that burned through the insulation blankets that were intended to prevent smoke from migrating behind the cargo compartment sidewall liners and upward into the main cabin. In the NPRM, the FAA proposed to continue to require the actions in AD 2016-25-29 for certain airplanes. The NPRM also proposed to add airplanes to the applicability and proposed to require a general visual inspection of the replacement insulation blankets to determine if the blankets are in serviceable condition and correctly installed, and applicable on-condition actions. For certain airplanes, the NPRM also proposed to require an inspection to determine the insulation blanket part number installed; replacement of additional insulation blankets; and applicable on-condition actions. The FAA is issuing this AD to address a fire in the bilge area of the cargo compartment, which if not contained could lead to a possible smoke and fire event in the passenger compartment. \n\nDiscussion of Final Airworthiness Directive \n\nComments \n\n\n\tThe FAA received comments from three commenters, including Aviation Partners Boeing, Delta Air Lines (DAL), and United Airlines (UAL). The following presents the comments received on the NPRM and the FAA's response to each comment. \n\nEffect of Winglets on Accomplishment of the Proposed Actions \n\n\n\tAviation Partners Boeing stated that the installation of winglets per Supplemental Type Certificate (STC) ST01920SE does not affect the accomplishment of the manufacturer's service instructions. \n\tThe FAA agrees with the commenter that STC ST01920SE does not affect the accomplishment of the manufacturer's service instructions. Therefore, the installation of STC ST01920SE does not affect the ability to accomplish the actions required by this AD. The FAA has not changed this AD in this regard. \n\nRequest To Delay Rule Pending Revised Referenced Service Information \n\n\n\tUAL concurs with the NPRM and requested that the FAA delay issuance of the final rule until the referenced Illustrated Parts Catalog (IPC) and airplane maintenance manual (AMM) specified in Boeing Service Bulletin 767-25-0550, Revision 1, dated December 4, 2019, are revised to ensure continued airworthiness and safety. UAL stated that the referenced service information will provide proper documentation support to maintain the insulation blanket changes specifiedin Boeing Service Bulletin 767-25-0550, Revision 1, dated December 4, 2019, prior to the release of the final rule. UAL also commented that the revised referenced service information can mitigate incorrect repairs and blanket installation, and minimize future alternative methods of compliance (AMOC) requests. \n\tThe FAA disagrees with delaying the final rule. Since the publication of the NPRM, the operator's existing IPC and AMM have been revised and provide accurate part numbers and corrective action procedures for missing insulation blankets. In addition, an operator unable to accomplish the actions in this AD for any reason may request approval of an AMOC under the provisions of paragraph (i)(1) of this AD, if sufficient data are submitted to substantiate that the change would provide an acceptable level of safety. The FAA has not changed this AD in this regard. \n\nRequest To Identify Proper Insulation Blankets \n\n\n\tUAL expressed concern about the post-compliance maintenance configuration using Boeing Service Bulletin 767-25-0550, Revision 1, dated December 4, 2019, in the absence of a revised Boeing 767 IPC (i.e., Boeing 767 IPC sections 25-21-05; 25-52-03; 25-52-52; 25-52-62; 25-55-01) to identify the proper insulation blankets with integrated fire stops. UAL described disagreements in the service information for the identity of the insulation blanket installations and corresponding part numbers in the aft and forward cargo compartment of post- modification airplanes and missing insulation blankets from certain appendixes and figures. UAL stated that it is essential to identify post-service bulletin configurations in certain Boeing 767 IPCs to ensure that AD compliance is maintained and to avoid inadvertent demodification by maintenance technicians. UAL commented that the configuration control for the airplane is the IPC, which maintenance technicians use for proper part replacement, and would alert maintenance personnel of insulation blankets having the integrated fire stops to ensure continued airworthiness. \n\tAs the FAA stated previously, since the NPRM was issued, relevant sections of the IPC have been revised. The operator's existing IPC contains the accurate part numbers and corrects missing insulation blankets. For clarification, the part numbers for the insulation blankets specified in Boeing Special Attention Service Bulletin 767-25- 0550, dated January 15, 2015, and Boeing Special Attention Service Bulletin 767-25-0550, Revision 1, dated December 4, 2019, are acceptable for installation; the new part numbers requires less work to install. The FAA has revised paragraph (h)(4) of this AD accordingly. \n\tIn addition, Boeing found that the insulation blankets at certain locations were not affected by the integrated fire stop issue that are addressed in Boeing Special Attention Service Bulletin 767-25-0550, Revision 1, dated December 4, 2019. Therefore, these insulation blankets were removed from Boeing Special Attention Service Bulletin 767-25-0550, Revision 1, dated December 4, 2019. Boeing Special Attention Service Bulletin 767-25-0550, Revision 1, dated December 4, 2019, includes work to re-inspect the installation of the insulation blankets that were installed in Boeing Special Attention Service Bulletin 767-25-0550, dated January 15, 2015. Since those insulation blankets that are not affected by the fire stop issue were removed from Boeing Special Attention Service Bulletin 767-25-0550, Revision 1, dated December 4, 2019, there is no need for instructions in Revision 1 to inspect the work that was performed in Boeing Special Attention Service Bulletin 767-25-0550, dated January 15, 2015. The FAA has not changed this AD in this regard. \n\n((Page 33114)) \n\nRequest To Correct the Date of the Service Information \n\n\n\tUAL commented that, in the toolbox on https://www.myboeingfleet.com, there are two versions of Boeing Special Attention Service Bulletin 767-25-0550, Revision 1: One version is dated December4, 2019, and one version is dated December 5, 2019. UAL also commented that the header of the toolbox states that Boeing Special Attention Service Bulletin 767-25-0550, Revision 1, dated December 4, 2019, is not the current version. UAL stated that the proper service information date needs to be addressed in the NPRM. \n\tThe FAA has confirmed that the correct date of the service information is December 4, 2019, and that there is currently only one version of the service information cited on https://www.myboeingfleet.com. The FAA has not changed this AD in this regard. \n\nRequest for Correct Figure Reference \n\n\n\tDAL commented that figure 42-A of Boeing Special Attention Service Bulletin 767-25-0550, Revision 1, dated December 4, 2019, refers to item 4 between stations 434 through 456, but it should be item 3. DAL stated this citation has been confirmed by Boeing in Service Request 3- 4634446605. \n\tThe FAA agrees that the correct reference for figure 42-A between stations 434 through 456 of Boeing Special Attention Service Bulletin 767-25-0550, Revision 1, dated December 4, 2019, is item 3. In addition, figure 42 is a RC step. The FAA has added paragraph (h)(2) of this AD to identify the correct item number. \n\nRequest To Correct Insulation Blanket Location \n\n\n\tDAL commented that in figure 51 of Boeing Special Attention Service Bulletin 767-25-0550, Revision 1, dated December 4, 2019, there should be an insulation blanket depicted between station (STA) 1395 and STA 1417. DAL also commented that appendixes D, E, F, G, H, and I of Boeing Special Attention Service Bulletin 767-25-0550, Revision 1, dated December 4, 2019, show the insulation blanket part numbers between STA 1395 and STA 1417. DAL reported that Boeing confirmed that the insulation blanket was missing from that figure. \n\tThe FAA agrees with the commenter's statement. The FAA has added paragraph (h)(3) of this AD to specify that Boeing Special Attention Service Bulletin 767-25-0550, Revision 1, dated December 4, 2019, figures 49, 50, and 51, between STA 1395 and STA 1417, should indicate that an insulation blanket is installed. \n\nRequest To Allow Stoppage Options Due to the Pandemic \n\n\n\tFor airplanes that have been in mass parking due to the worldwide pandemic, DAL requested clock stoppage options such as those offered to operators by the manufacturer for scheduled maintenance program tasks. DAL stated that this request is for airplanes that meet the following conditions: \n\tAirplanes that are currently undergoing storage, or airplanes that will enter storage during the compliance time of the proposed AD. \n\tAirplanes that were preserved with instructions in close reference to the AMM procedures. \n\tDAL also commented that an airplane in a preserved state does not experience the following risk factors that are taken into consideration for the proposed AD: \n\tPassenger Safety: The newly installed insulation blankets are meant to prevent smoke from migrating behind the cargocompartment sidewall liners and upward into the main cabin, where it could affect passengers. If the airplane does not have passengers during the time in which it is preserved, there is no increased risk to the public. \n\tPotential fire in the cargo compartments: Since the airplane is not in operation, there is no cargo being stored in the cargo compartments, meaning it is highly unlikely that there will be a fire initiated to cause smoke. \n\tIn addition, DAL asserted that the safety risk associated with the inferior insulation blankets installed on the airplane is either a small consideration or not a consideration at all in the calculation of overall fleet risk because the concern is not with degradation of insulation blanket material, or any other factor in which an increase in compliance time would increase the risk. \n\tThe FAA disagrees with having stoppage options due to the unsafe condition. In developing an appropriate compliance time, the FAA considered the safety implications, parts availability, and normal maintenance schedules for timely accomplishment of the actions in this AD. Further, the FAA arrived at the proposed compliance time with Boeing's concurrence. It is difficult to plan for every possible storage scenario, and currently, the FAA does not have procedures that would address every possible scenario to ensure that all airplanes will be addressed in a timely manner once the airplanes are back in service. If an operator is unable to accomplish the actions in this AD for whatever reason or has the airplane in storage, it may request approval of an AMOC under the provisions of paragraph (i)(1) of this AD, if sufficient data are submitted to substantiate that the change would provide an acceptable level of safety. The FAA has not changed this AD in this regard. \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. 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 Boeing Special Attention Service Bulletin 767-25- 0550, Revision 1, dated December 4, 2019. The service information describes procedures for replacement of cargo compartment insulation blankets between stringers 29 and 33, on the left and right sides, with new insulation blankets that incorporate fire stops; an inspection to determine the insulation blanket part number installed between stringers 29 and 33, on the left and right sides; a general visual inspection of the replacement insulation blankets between stringers 29 and 33, on the left and right sides to determine if the insulation blankets are in serviceable condition and correctly installed; and applicable on-condition actions. On-condition actions include repair, replacement, and correction of insulation blanket installations. 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\nCosts of Compliance \n\n\n\tThe FAA estimates that this AD affects 329 airplanes of U.S. registry. The FAA estimates the following costs to comply with this AD: \n\n((Page 33115)) \n\n\n\n\n\n\n\tEstimated Costs for Required Actions ---------------------------------------------------------------------------------------------------------------- \n\tCost on U.S. \n\tAction Labor cost Parts cost Cost per product operators ---------------------------------------------------------------------------------------------------------------- Replacement (retained actions Up to 54 work-hours (\*\) Up to $4,590....... Up to $1,510,110. \n\tfrom AD 2016(dash)25(dash)29). x $85 per hour = \n\tUp to $4,590. Inspections and replacements Up to 62 work-hour Up to $35,900 Up to $41,170...... Up to $13,944,530. \n\t(new proposed action). x $85 per hour = \n\tUp to $5,270. ---------------------------------------------------------------------------------------------------------------- \n* The FAA has received no definitive data that would enable providing parts cost estimates for the retained\n\n\tactions specified in this AD. \n\n\n\tThe FAA has received no definitive data that would enable us to provide cost estimates for the on-condition actions specified in this AD. \n\tAccording to the manufacturer, some of the costs of this AD may be covered under warranty, thereby reducing the cost impact on affected operators. The FAA does not control warranty coverage for affected operators. As a result, the FAA has 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\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 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.