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Federal Register / Vol. 86, No. 136 / Tuesday, July 20, 2021 / Proposed Rules Proposed AD Requirements
could result in reduced structural integrity of the airplane.
Actions Since AD 20210303 Was Issued Since the FAA issued AD 202103
03, the FAA has determined that new or more restrictive airworthiness limitations are necessary.
EASA, which is the Technical Agent for the Member States of the European Union, has issued EASA AD 20210020, dated January 15, 2021 EASA AD
20210020 also referred to as the Mandatory Continuing Airworthiness Information, or the MCAI, to correct an unsafe condition for all ATRGIE
Avions de Transport Regional Model ATR72 airplanes. EASA AD 20200020
refers to ATR ATR72 Time Limits Document. Revision 18, dated October 9, 2020. Airplanes with an original airworthiness certificate or original export certificate of airworthiness issued after October 9, 2020, must comply with the airworthiness limitations specified as part of the approved type design and referenced on the type certificate data sheet; this AD
therefore does not include those airplanes in the applicability.
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 fatigue cracking and damage in principal structural elements, which could result in reduced structural integrity of the airplane. See the MCAI
for additional background information.

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Related Service Information Under 1
CFR Part 51
EASA AD 20210020 describes new or more restrictive airworthiness limitations for airplane structures and safe life limits.
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.
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 referenced above. The FAA is proposing this AD
because the FAA 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.

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This proposed AD would retain all of the requirements of AD 20210303.
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 20210020
described previously, as incorporated by reference. Any differences with EASA
AD 20210020 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 m1 of this proposed 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, EASA AD
20210020 will be incorporated by reference in the FAA final rule. This proposed AD would, therefore, require compliance with EASA AD 20210020
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 the EASA AD 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 the EASA AD.
Service information specified in EASA AD 20210020 that is required for compliance with EASA AD 20210020
will be available on the internet at https www.regulations.gov by searching for and locating Docket No.

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FAA20210508 after the FAA final rule is published.
Airworthiness Limitation ADs Using the New Process 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 and 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 action or interval.
Costs of Compliance The FAA estimates that this proposed AD affects 23 airplanes of U.S. registry.
The FAA estimates the following costs to comply with this proposed AD:
The FAA estimates the total cost per operator for the retained actions from AD 20210303 to be $7,650 90 workhours $85 per work-hour.
The FAA has determined that revising the existing maintenance or inspection program takes an average of 90 workhours per operator, although the agency recognizes that this number may vary from operator to operator. Since operators incorporate maintenance or inspection program changes for their affected fleets, the FAA has determined that a per-operator estimate is more accurate than a per-airplane estimate.

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