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Federal Register / Vol. 86, No. 213 / Monday, November 8, 2021 / Rules and Regulations requires removal of an LLP prior to its approved life limit or within 90 days after the effective date of this AD, whichever occurs later. The FAA is issuing this AD to address the unsafe condition on these products.
DATES: This AD is effective December 13, 2021.
The Director of the Federal Register approved the incorporation by reference of a certain publication listed in this AD
as of December 13, 2021.
ADDRESSES: For service information identified in this final rule, contact Rolls-Royce Deutschland Ltd & Co KG, Eschenweg 11, Dahlewitz, 15827
Blankenfelde-Mahlow, Germany; phone:
+49 0 33 70864040; website: https
www.rolls-royce.com/contact-us.aspx.
You may view this service information at the FAA, Airworthiness Products Section, Operational Safety Branch, 1200 District Avenue, Burlington, MA
01803. For information on the availability of this material at the FAA, call 781 2387759. It is also available at https www.regulations.gov by searching for and locating Docket No.
FAA20210257.

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Examining the AD Docket You may examine the AD docket at https www.regulations.gov by searching for and locating Docket No.
FAA20210257; or in person at Docket Operations between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The AD docket contains this final rule, the mandatory continuing airworthiness information MCAI, any comments received, and other information. The address for Docket Operations is U.S. Department of Transportation, Docket Operations, M
30, West Building Ground Floor, Room W12140, 1200 New Jersey Avenue SE, Washington, DC 20590.
FOR FURTHER INFORMATION CONTACT:
Wego Wang, Aviation Safety Engineer, ECO Branch, FAA, 1200 District Avenue, Burlington, MA 01803; phone:
781 2387134; fax: 781 2387199;
email: Wego.Wang@faa.gov.
SUPPLEMENTARY INFORMATION:
Background The FAA issued a notice of proposed rulemaking NPRM to amend 14 CFR
part 39 by adding an AD that would apply to certain RRD BR700710A220
model turbofan engines. The NPRM
published in the Federal Register on April 2, 2021 86 FR 17326. The NPRM
was prompted by flight data obtained from airplanes equipped with certain Rockwell Collins avionics and autothrottle systems that demonstrated significant oscillation of the engine rotor
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revolution speed during flight. In the NPRM, the FAA proposed to require initial and repetitive recalculation of the consumed and remaining service life of certain LLPs. The NPRM also proposed to require removal of an LLP prior to its approved life limit or within 90 days after the effective date of this AD, whichever occurs later. The FAA is issuing this AD to address the unsafe condition on these products.
The European Union Aviation Safety Agency EASA, which is the Technical Agent for the Member States of the European Community, has issued EASA
AD 20180268, dated December 11, 2018 and corrected on February 20, 2019 referred to after this as the MCAI, to address the unsafe condition on these products. The MCAI states:
Flight data obtained from aeroplanes equipped with certain Rockwell Collins avionics and auto-throttle system demonstrated significant oscillation of the engine rotor revolution speed during cruise.
Analysis indicates that this affects the service life of the affected LLP.
This condition, if not corrected, may lead to failure of an affected LLP, possibly resulting in release of high-energy debris, with consequent damage to, and/or reduced control of, the aeroplane. To address this potentially unsafe condition, RRD issued the NMSB, providing instructions to recalculate the consumed and remaining service life of the affected LLP.
For the reasons described above, this EASA AD requires repetitive recalculation of the service life consumed and remaining of each affected LLP and, depending on the results, replacement of each affected LLP
before exceeding the life limit, taking the recalculated life consumption into account.

You may obtain further information by examining the MCAI in the AD
docket at https www.regulations.gov by searching for and locating Docket No.
FAA20210257.
Discussion of Final Airworthiness Directive Comments The FAA received comments from one commenter, NetJets Aviation NJA.
The following presents the comments received on the NPRM and the FAAs response to each comment.
Request To Confirm Compliance With Previous Action NJA asked if they are in compliance with this AD if they performed the required actions using Bombardier Service Bulletin SB 700345021 or Bombardier SB 700346021, revisions earlier than Revision 3, dated January 5, 2018, as applicable. NJA reasoned that paragraph c, Applicability, of the proposed AD references only Revision 3
of Bombardier SB 700345021 and
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Bombardier SB 700346021
Bombardier SBs. NJA states that it performed the required actions using Revision 2 of the Bombardier SBs before the effective date of this AD. NJA also referenced language from Revision 3 of the Bombardier SBs that indicates no further action is necessary if operators performed the action using earlier revisions of the Bombardier SBs.
The FAA notes that NJA would be in compliance with the required actions of this AD if they performed those actions using the earlier versions of the Bombardier SBs to meet the requirements of this AD. The FAA
updated paragraph h, Credit for Previous Actions, of this AD to give credit for using earlier revisions of the Bombardier SBs if the actions were performed before the effective date of this AD.
Request To Confirm Compliance for Simultaneous Actions NJA asked if they would be in compliance with the required actions of this AD, based on paragraph h, Credit for Previous Actions, if they complied with the Bombardier SBs and RRD Alert Non-Modification Service Bulletin SB
BR70072A900584, Revision 2, dated November 22, 2017 the NMSB, at the same time before the fleet accumulated 500 flight cycles. NJA indicated that the Accomplishment Instructions, paragraphs 3.A.1 and 2, of the NMSB
apply only to the low-pressure compressor LPC disk whereas this AD
applies to all LLPs.
The FAA notes that NJA would be in compliance with the replacement of the LPC disk required by paragraph g3 of this AD if they performed the action before the effective date of this AD.
Paragraph f of this AD mandates compliance with this AD within the compliance times specified, unless already done.
Update to Service Information The FAA determined the need to incorporate the latest service information in this AD. The FAA
revised the reference to Bombardier SB
700345021 in paragraph c of this AD
from Revision 03, dated January 5, 2018, to Revision 04, dated February 11, 2021, or earlier revision, and Bombardier SB
700346021 in paragraph c of this AD
from Revision 03, dated January 5, 2018, to Revision 04, dated February 11, 2021, or earlier revision. This change does not change the number of affected engines that the FAA estimated in the NPRM
and imposes no additional burden on operators who are required to comply with this AD.

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