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Federal Register / Vol. 86, No. 150 / Monday, August 9, 2021 / Proposed Rules
NPRM, any comments received, and other information. The street address for Docket Operations is listed above.
FOR FURTHER INFORMATION CONTACT: Tak Kobayashi, Aerospace Engineer, Propulsion Section, FAA, Seattle ACO
Branch, 2200 South 216th St., Des Moines, WA 98198; phone and fax: 206
2313553; email: takahisa.kobayashi@
faa.gov.
SUPPLEMENTARY INFORMATION:

Comments Invited The FAA invites you to send any written relevant data, views, or arguments about this proposal. Send your comments to an address listed under ADDRESSES. Include Docket No.
FAA20210571; Project Identifier AD
202100101T at the beginning of your comments. The most helpful comments reference a specific portion of the proposal, explain the reason for any recommended change, and include supporting data. The FAA will consider all comments received by the closing date and may amend this proposal because of those comments.
Except for Confidential Business Information CBI as described in the following paragraph, and other information as described in 14 CFR
11.35, the FAA will post all comments received, without change, to https
www.regulations.gov, including any personal information you provide. The agency will also post a report summarizing each substantive verbal contact received about this NPRM.

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Confidential Business Information CBI is commercial or financial information that is both customarily and actually treated as private by its owner.
Under the Freedom of Information Act FOIA 5 U.S.C. 552, CBI is exempt from public disclosure. If your comments responsive to this NPRM
contain commercial or financial information that is customarily treated as private, that you actually treat as private, and that is relevant or responsive to this NPRM, it is important that you clearly designate the submitted comments as CBI. Please mark each page of your submission containing CBI
as PROPIN. The FAA will treat such marked submissions as confidential under the FOIA, and they will not be placed in the public docket of this NPRM. Submissions containing CBI
should be sent to Tak Kobayashi, Aerospace Engineer, Propulsion Section, FAA, Seattle ACO Branch, 2200
South 216th St., Des Moines, WA 98198;
phone and fax: 2062313553; email:
takahisa.kobayashi@faa.gov. Any commentary that the FAA receives
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which is not specifically designated as CBI will be placed in the public docket for this rulemaking.
Background The FAA has received reports of damage to the TR translating sleeve secondary sliders. Gouging damage to the slider end and grooving damage along the length of the slider occurred due to contact between the slider and the slider track liner. This damage was found only on TR sleeves installed on Rolls-Royce engines with mission improvement configuration thrust reversers. This damage, if not addressed, could result in failure of the TR
translating sleeve secondary slider and possible detachment of the outer cowl, which could strike the fuselage causing damage to the airplane, and could result in reduced control or performance of the airplane.
FAAs Determination The FAA is issuing this NPRM after determining that the unsafe condition described previously is likely to exist or develop on other products of the same type design.
Related Service Information Under 1
CFR Part 51
The FAA reviewed Boeing Alert Requirements Bulletin B78781205
SB78004300 RB, Issue 001, dated January 15, 2021. This service information specifies procedures for determining the serial number of the TR, and applicable on-condition actions; or replacing the TR with a serviceable TR. On-condition actions include reworking affected TR slider track liners; determining the serial number of the TR translating sleeves;
checking to determine if certain TR
translating sleeves have been installed on certain TRs; performing a detailed inspection of the secondary sliders of affected TR translating sleeves for cracking, grooving, gouging damage, and any existing repair; performing a dye penetrant inspection on any cracking, grooving or gouging damage, and any existing repair for cracking; and repairing any discrepancy found.
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.
Proposed AD Requirements in This NPRM
This proposed AD would require accomplishing the actions specified in the service information already described, except for any differences identified as exceptions in the
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regulatory text of this proposed AD. For information on the procedures and compliance times, see this service information at https
www.regulations.gov by searching for and locating Docket No. FAA2021
0571.
Explanation of Requirements Bulletin The FAA worked in conjunction with industry, under the Airworthiness Directive Implementation Aviation Rulemaking Committee AD ARC, to enhance the AD system. One enhancement is a process for annotating which steps in the service information are required for compliance RC with an AD. Boeing has implemented this RC
concept into Boeing service bulletins.
In an effort to further improve the quality of ADs and AD-related Boeing service information, a joint process improvement initiative was worked between the FAA and Boeing. The initiative resulted in the development of a new process in which the service information more clearly identifies the actions needed to address the unsafe condition in the Accomplishment Instructions. The new process results in a Boeing Requirements Bulletin, which contains only the actions needed to address the unsafe condition i.e., only the RC actions.
Differences Between This Proposed AD
and the Service Information The effectivity of Boeing Alert Requirements Bulletin B78781205
SB78004300 RB, Issue 001, dated January 15, 2021, includes all Model 7878, 7879, and 78710 airplanes equipped with Rolls-Royce engines.
This proposed AD would only require accomplishing the actions specified in Boeing Alert Requirements Bulletin B78781205SB78004300 RB, Issue 001, dated January 15, 2021, on airplanes with an original airworthiness certificate or original export certificate of airworthiness issued on or before the effective date of this AD. Airplanes certificated after the effective date of this AD will not be delivered with affected TRs or TR translating sleeves.
However, because the affected TRs and TR translating sleeves are rotable parts, the FAA has determined that these parts could later be installed on airplanes delivered with acceptable parts, thereby subjecting those airplanes to the unsafe condition. This proposed AD would therefore include a parts installation prohibition applicable to all Model 787
8, 7879, and 78710 airplanes equipped with Rolls-Royce engines.
Furthermore, the FAA has determined that a parts installation prohibition needs to be specified for airplanes on
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