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Federal Register / Vol. 86, No. 154 / Friday, August 13, 2021 / Proposed Rules This proposed AD was prompted by a determination that new or more restrictive airworthiness limitations are necessary. The FAA is proposing this AD to address premature wear of the carbon friction disks on the NBB of the THSA, which could lead to reduced braking efficiency in certain load conditions, and, in conjunction with the inability of the power gear train to keep the ball screw in its last commanded position, could result in uncommanded movements of the trimmable horizontal stabilizer and loss of control of the airplane. See the MCAI for additional background information.
Model A320216 Airplanes The Airbus SAS Model A320216 was U.S. type certificated on December 19, 2016. Before that date, any EASA ADs that affected Model A320216 airplanes were included in the U.S. type certificate as part of the Required Airworthiness Actions List RAAL. One or more Model A320216 airplanes have subsequently been placed on the U.S.
Register, and will now be included in FAA AD actions. For Model A320216
airplanes, the requirements that correspond to AD 20161712 were mandated by the MCAI via the RAAL.
Although that RAAL requirement is still in effect, for continuity and clarity the FAA has identified Model A320216
airplanes in paragraph c of this proposed AD; the MCAI that is specified in paragraph l in this proposed AD
includes restated requirements, which would therefore apply to those airplanes.

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Related Service Information Under 1
CFR Part 51
EASA AD 20200270 describes new or more restrictive airworthiness limitations for airplane structures and safe life limits.
Airbus A318/A319/A320/A321
Airworthiness Limitations Section ALS Part 4 Variation 7.1, dated October 5, 2020, describes a task for removal from service and replacement of certain THSA NBB disks.
This proposed AD would also require Airbus Service Bulletin A320271242, Revision 01, dated February 4, 2016, which the Director of the Federal Register approved for incorporation by reference as of September 30, 2016 81
FR 58823, August 26, 2016.
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 the ADDRESSES section.

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FAAs Determination and Requirements of This Proposed AD
This product has been approved by the aviation authority of another country, and is approved for operation in the United States. Pursuant to the FAAs bilateral agreement with the State of Design Authority, the FAA has been notified of the unsafe condition described in the MCAI and service information referenced above. The FAA
is proposing this AD because the FAA
has evaluated all pertinent information and determined an unsafe condition exists and is likely to exist or develop on other products of the same type design.

Using common terms that are the same as the heading of a particular section in EASA AD 20200270 does not mean that operators need comply only with that section. For example, where the AD
requirement refers to all 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 20200270.
Service information required by EASA
AD 20200270 for compliance will be available at https www.regulations.gov by searching for and locating Docket No.
FAA20210663 after the FAA final rule is published.

Proposed AD Requirements This proposed AD would retain the requirements of AD 20161712. This proposed AD would also require revising the existing maintenance or inspection program, as applicable, to incorporate new or more restrictive airworthiness limitations, which are specified in EASA AD 20200270
described previously, as proposed for incorporation by reference. Any differences with EASA AD 20200270
are identified as exceptions in the regulatory text of this AD.
This proposed AD would require revisions to certain operator maintenance documents to include new actions e.g., inspections. Compliance with these actions is required by 14 CFR
91.403c. For airplanes that have been previously modified, altered, or repaired in the areas addressed by this proposed AD, the operator may not be able to accomplish the actions described in the revisions. In this situation, to comply with 14 CFR 91.403c, the operator must request approval for an alternative method of compliance according to paragraph p1 of this proposed AD.

Airworthiness Limitation ADs Using the New Process
Explanation of Required Compliance Information In the FAAs ongoing efforts to improve the efficiency of the AD
process, the FAA developed a process to use certain civil aviation authority CAA ADs as the primary source of information for compliance with requirements for corresponding FAA
ADs. The FAA has been coordinating this process with manufacturers and CAAs. As a result, the FAA proposes to incorporate EASA AD 20200270 by reference in the FAA final rule. This proposed AD would, therefore, require compliance with EASA AD 20200270
in its entirety through that incorporation, except for any differences identified as exceptions in the regulatory text of this proposed AD.

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The FAAs process of incorporating by reference MCAI ADs as the primary source of information for compliance with corresponding FAA ADs has been limited to certain MCAI ADs primarily those with service bulletins as the primary source of information for accomplishing the actions required by the FAA AD. However, the FAA is now expanding the process to include MCAI
ADs that require a change to airworthiness limitation documents, such as airworthiness limitation sections.
For these ADs that incorporate by reference an MCAI AD that changes airworthiness limitations, the FAA
requirements are unchanged. Operators must revise the existing maintenance or inspection program, as applicable, to incorporate the information specified in the new airworthiness limitation document. The airworthiness limitations must be followed according to 14 CFR 91.403c and 91.409e.
The previous format of the airworthiness limitation ADs included a paragraph that specified that no alternative actions e.g., inspections or intervals may be used unless the actions or intervals are approved as an alternative method of compliance AMOC in accordance with the procedures specified in the AMOCs paragraph under Other FAA
Provisions. This new format includes a New Provisions for Alternative Actions and Intervals paragraph that does not specifically refer to AMOCs, but operators may still request an AMOC to use an alternative actions or intervals.
Costs of Compliance The FAA estimates that this proposed AD affects 1,630 airplanes of U.S.
registry. The FAA estimates the following costs to comply with this proposed AD:

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