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Federal Register / Vol. 86, No. 119 / Thursday, June 24, 2021 / Rules and Regulations
Request To Correct the Date of the Service Information UAL commented that, in the toolbox on https www.myboeingfleet.com, there are two versions of Boeing Special Attention Service Bulletin 76725
0550, Revision 1: One version is dated December 4, 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 76725
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.
The 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.
Request for Correct Figure Reference DAL commented that figure 42A of Boeing Special Attention Service Bulletin 767250550, 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 34634446605.
The FAA agrees that the correct reference for figure 42A between stations 434 through 456 of Boeing Special Attention Service Bulletin 767
250550, Revision 1, dated December 4, 2019, is item 3. In addition, figure 42 is a RC step. The FAA has added paragraph h2 of this AD to identify the correct item number.

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Request To Correct Insulation Blanket Location DAL commented that in figure 51 of Boeing Special Attention Service Bulletin 767250550, 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 76725
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.
The FAA agrees with the commenters statement. The FAA has added paragraph h3 of this AD to specify that Boeing Special Attention Service
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Bulletin 767250550, 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.
Request To Allow Stoppage Options Due to the Pandemic For 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:
Airplanes that are currently undergoing storage, or airplanes that will enter storage during the compliance time of the proposed AD.
Airplanes that were preserved with instructions in close reference to the AMM procedures.
DAL 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:
Passenger Safety: The newly installed insulation blankets are meant to prevent smoke from migrating behind the cargo compartment 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.
Potential 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.
In 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.
The 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 Boeings concurrence. It is difficult to plan for every possible storage
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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 i1 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.
Conclusion The 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.
Related Service Information Under 1
CFR Part 51
The FAA reviewed Boeing Special Attention Service Bulletin 76725
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. Oncondition 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.
Costs of Compliance The FAA estimates that this AD
affects 329 airplanes of U.S. registry.
The FAA estimates the following costs to comply with this AD:

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