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Federal Register / Vol. 86, No. 218 / Tuesday, November 16, 2021 / Proposed Rules
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 Nicholas Paine, Aviation Safety Engineer, ECO Branch, FAA, 1200 District Avenue, Burlington, MA 01803. Any commentary that the FAA receives that is not specifically designated as CBI will be placed in the public docket for this rulemaking.
Background EASA, which is the Technical Agent for the Member States of the European Union, has issued EASA AD 20210114, dated April 23, 2021 EASA AD 2021
0114, to correct an unsafe condition for certain RRD RB211 Trent 87517, 877
17, 88417, 884B17, 89217, 892B17, and 89517 model turbofan engines.
This proposed AD was prompted by findings during engine overhaul of corrosion on the LPC front case assembly caused by excessive movement between the Kevlar wrap and the fan case, which resulted in the anticorrosion paint fretting away. The FAA
is proposing this AD to address corrosion on the LPC front case assembly. This condition, if not addressed, could affect the containment integrity of the LPC front case assembly during a fan blade release event, resulting in damage to the airplane, or reduced control of the airplane.
See EASA AD 20210114 for additional background information.

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FAAs Determination These engines have been approved by the aviation authority of another country and are approved for operation in the United States. Pursuant to the FAAs bilateral agreement with the State of Design Authority, the FAA has been notified about the unsafe condition described in the EASA AD referenced in this AD. 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.

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Related Service Information Under 1
CFR Part 51
The FAA reviewed EASA AD 2021
0114. EASA AD 20210114 specifies actions for inspecting the LPC front case assembly and, depending on the result of the inspection, corrective action. This material is reasonably available because the interested parties have access to it through their normal course of business or by the means identified in ADDRESSES.
Other Related Service Information The FAA reviewed Rolls-Royce RB211 Trent 800 Series Propulsion Systems Alert Non-Modification Service Bulletin RB.21172AG774, Revision 4, dated October 13, 2020 the NMSB. The NMSB specifies procedures for inspecting the LPC front case assembly for corrosion and taking corrective action.
Proposed AD Requirements in This NPRM
This proposed AD would require accomplishing the actions specified in EASA AD 20210114, described previously, as incorporated by reference, except for any differences identified as exceptions in the regulatory text of this proposed AD and except as discussed under Differences Between this Proposed AD and the EASA AD.
Explanation of Required Compliance Information In the FAAs ongoing efforts to improve the efficiency of the AD
process, the FAA initially worked with Airbus and EASA to develop a process to use certain EASA ADs as the primary source of information for compliance with requirements for corresponding FAA ADs. The FAA has since coordinated with other manufacturers and civil aviation authorities CAAs to use this process. As a result, the FAA
proposes to incorporate EASA AD
20210114 in the FAA final rule. This proposed AD would require compliance with EASA AD 20210114 in its entirety through that incorporation, except for any differences identified as exceptions in the regulatory text of this proposed AD. Using common terms that are the same as the heading of a particular section in EASA AD 20210114 does not mean that operators need comply only with that section. For example, where the AD requirement refers to all
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required actions and compliance times, compliance with this AD requirement is not limited to the section titled Required Actions and Compliance Times in EASA AD 20210114.
Service information specified by EASA
AD 20210114 that is required for compliance with it will be available at https www.regulations.gov by searching for and locating Docket No.
FAA20211004 after the FAA final rule is published.
Differences Between This Proposed AD
and the EASA AD
Qualified Shop Visit EASA AD 20210114 defines a qualified shop visit as any scheduled shop visit where the affected part is exposed and substantial rebuild has not yet started, except shop visits for serviceability only. This proposed AD
defines a qualified shop visit as the induction of an engine into the shop after the effective date of this AD for maintenance involving the separation of pairs of major mating engine flanges, with the exception of the separation of engine flanges solely for the purposes of transportation of the engine without subsequent engine maintenance.
Effective Date Where EASA AD 20210114 requires compliance from its effective date, this proposed AD would require using the effective date of this AD.
Compliance Where the service information referred to in EASA AD 20210114
specifies to inspect the affected part and contact the manufacturer for repair instructions if any corrosion is found exceeding the criteria as specified in the NMSB, this AD requires the removal of the affected LPC front case assembly from service if corrosion is found that exceeds the criteria specified in Appendix 2 of the NMSB.
Remarks This AD does not mandate compliance with the Remarks section of EASA AD 20200114.
Costs of Compliance The FAA estimates that this AD, if adopted as proposed, would affect 98
engines installed on airplanes of U.S.
Registry.
The FAA estimates the following costs to comply with this proposed AD:

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