A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an airworthiness directive (AD) that is applicable to all Aerospatiale Model ATR42 series airplanes was published in the Federal Register on August 3, 1999 (64 FR 42052). That action proposed to require a revision to the Airworthiness Limitations Section of the Instructions for Continued Airworthiness to incorporate inspections to detect fatigue cracking in certain structure, inspection intervals, and life limits for certain items. \n\nComments \nInterested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received. \n\nNecessity for Rulemaking \nOne commenter, an operator, questions the need to issue the proposed AD. The commenter notes that a listing of airworthiness limitations is required for type certification, as specified by section 25.1529 of the Federal Aviation Regulations (14 CFR 25.1529) and Appendix H, paragraph H25.4. The commenter states that this listing is included in its Operations Specifications, and that such specifications would never be approved with any airworthiness limitations that were beyond the limits specified by the manufacturer. In light of this, the commenter considers the actions required by the proposed rule to be redundant. \n\nThe FAA infers that the commenter requests that the proposed AD be withdrawn. The FAA does not concur. As stated in the proposed AD, all products certificated to comply with the airworthiness standards requiring "damage tolerance assessments" must have Instructions for Continued Airworthiness (or, for some products, maintenance manuals), that include an Airworthiness Limitations Section (ALS). \n\nBased on in-service data or post-certification testing and evaluation, the manufacturer may revise the ALS to include new or more restrictive life limits and structural inspections, or it may become necessary for the FAA to impose new or more restrictive life limits and structural inspections, in order to ensure continued structural integrity and continued compliance with damage tolerance requirements. However, to require compliance with these new inspection requirements and life limits for previously certificated airplanes, the FAA must engage in rulemaking; namely, the issuance of an AD. Because loss of structural integrity would constitute an unsafe condition, it is appropriate to impose such requirements through the AD process. Although prudent operators already may have incorporated the latest revisions of the ALS, issuance of this AD ensures that all operators take appropriate action to correct the identified unsafe condition. \n\nThe practice of requiring a revision to the ALS, rather than requiring individual inspections, has been used for several years and is not a novel or unique procedure. The FAA finds that requiring ALS revisions is advantageous for operators becauseit allows them to record AD compliance status only once--at the time they make the revision--rather than after every inspection. It also has the advantage of keeping all airworthiness limitations, whether imposed by original certification or by the requirements of an AD, in one place within the operator's maintenance program, thereby reducing the risk of non-compliance because of oversight or confusion. In addition, for a large fleet of airplanes with several small operators, it is possible that operators may not receive revisions to the ALS documents. The AD process ensures that these operators are aware of the revisions to the ALS. No change is made to the final rule. \n\nRequest to Include Certification Maintenance Requirements Tasks \nOne commenter, the manufacturer, states that the "Time Limits" section of the Maintenance Planning Document (MPD) also includes Certification Maintenance Requirements (CMR) tasks that are applicable to the equipment and systems and are necessaryto maintain the certificated standard level of airworthiness. The commenter suggests that a paragraph be added to the proposed AD to require accomplishment of the CMR tasks. \n\nThe FAA does not concur. Although the FAA agrees that accomplishment of CMR tasks is necessary to maintain these airplanes in an airworthy condition, the necessity for those actions is based on statistical safety analyses of various airplane systems prior to issuance of an airplane Type Certificate (TC). Thus, CMR tasks are undertaken for a different purpose than are the actions required by this AD, and are intended to address a different unsafe condition than is addressed in this AD. However, if CMR tasks are added, or made more restrictive, following issuance of the TC, the FAA will consider separate rulemaking action to require accomplishment of those additional actions. No change to the final rule is necessary. \n\nRevisions to Service Information \nTwo commenters advise the FAA that the ATR42 MPD hasbeen reissued as two separate documents, one applicable to Model ATR42-200, -300, and -320 series airplanes, and the other applicable to Model ATR42-500 series airplanes. One commenter suggests that, since the "Time Limits" section of the MPD for ATR42-500 airplanes may be changed independently of the other document, the actions in the proposed AD should be separated to reflect the separate documents and revision levels. In addition, these commenters state that Revision 3 of each of these "Time Limits" sections was issued in February 1999. The manufacturer also advises that Revision 4 of the "Time Limits" section for Model ATR42-200, -300, and -320 series airplanes, dated July 1999, is in the process of review and approval by the appropriate airworthiness authorities. The manufacturer suggests that issuance of the final rule be delayed until approval of this latest revision is granted. \n\nThe FAA has received and reviewed the latest revisions of the service information. Revision2 of the "Time Limits" section, dated January 1997, was referenced in the proposed AD as the appropriate source of service information for all Model ATR42 series airplanes. Revision 4 of the "Time Limits" section for Model ATR42-200, -300, and -320 series airplanes, dated July 1999, differs from Revision 2 in that a life limit for certain equipment is removed, and a note is added to clarify the compliance threshold for a structural inspection. The FAA has determined that the actions required by this AD must be accomplished in accordance with Revision 4 of the "Time Limits" section of the MPD for these airplanes, and has revised the final rule accordingly. Since Revision 4 imposes no additional burden on operators of Model ATR42-200, -300, and -320 series airplanes beyond the action specified in Revision 2, additional notice and opportunity for public comment is not considered necessary. \n\nHowever, Revision 3 of the "Time Limits" section for Model ATR42-500 series airplanes, datedFebruary 1999, adds new inspections and life limits for those airplanes. \n\nTherefore, the FAA has determined that revision to the Airworthiness Limitations Section of the Instructions for Continued Airworthiness for Model ATR42-500 series airplanes should be addressed in separate rulemaking action, and has limited the applicability of this AD to Model ATR42-200, -300, and -320 series airplanes only. The Cost Impact paragraph, below, has also been revised to reflect the reduced number of airplanes affected by this AD. \n\nUse of Subsequent Service Information Revisions \nOne commenter requests that the FAA revise the proposed AD to refer to the current revision of the "Time Limits" section of the MPD, "or later approved revisions." The commenter suggests that only referring to the current revision in the AD may lead to confusion about the validity of subsequent revisions. \n\nThe FAA does not concur. To use the phrase "or later approved revisions" in an AD when referring to futurerevisions of service information violates Office of the Federal Register (OFR) regulations regarding approval of materials that are "incorporated by reference" in rules. The AD may only refer to the service information that was submitted and approved by the OFR for "incorporation by reference." For operators to use later revisions of the service information, either the FAA must revise the AD to reference the specific later revisions, or operators must request approval of any later revisions as alternative methods of compliance with this AD. No change to the AD is necessary in this regard. \n\nMPD Section Reference \nTwo commenters state that, although the "Time Limits" section of the MPD is incorrectly referenced in the proposed AD as Section 9, the correct reference is Section 13. The FAA acknowledges the correction. However, the FAA has removed the reference to the exact section of the "Time Limits" section of the MPD in paragraph (a) of this AD to avoid any confusion in case thesection number changes in the future. \n\nConclusion \nAfter careful review of the available data, including the comments noted above, the FAA has determined that air safety and the public interest require the adoption of the rule with the changes described previously. These changes will neither increase the economic burden on any operator nor increase the scope of the AD. \n\nCost Impact \nThe FAA estimates that 75 airplanes of U.S. registry will be affected by this AD, that it will take approximately 1 work hour per airplane to accomplish the required actions, and that the average labor rate is $60 per work hour. Based on these figures, the cost impact of the AD on U.S. operators is estimated to be $4,500, or $60 per airplane. \n\nThe cost impact figure discussed above is based on assumptions that no operator has yet accomplished any of the requirements of this AD action, and that no operator would accomplish those actions in the future if this AD were not adopted. \n\nRegulatory Impact \nThe regulations adopted herein will not have a substantial direct effect on the States, on the relationship between the national Government and the States, or on the distribution of power and responsibilities among the various levels of government. Therefore, it is determined that this final rule does not have federalism implications under Executive Order 13132. \n\nFor the reasons discussed above, I certify that this action (1) is not a "significant regulatory action" under Executive Order 12866; (2) is not a "significant rule" under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and (3) will not have a significant economic impact, positive or negative, on a substantial number of small entities under the criteria of the Regulatory Flexibility Act. A final evaluation has been prepared for this action and it is contained in the Rules Docket. A copy of it may be obtained from the Rules Docket at the location provided under the caption "ADDRESSES."List of Subjects in 14 CFR Part 39 \nAir transportation, Aircraft, Aviation safety, Incorporation by reference, Safety. \n\nAdoption of the Amendment \nAccordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends part 39 of the Federal Aviation Regulations (14 CFR part 39) as follows: \n\nPART 39 - AIRWORTHINESS DIRECTIVES \n\n1. The authority citation for part 39 continues to read as follows: Authority: 49 U.S.C. 106(g), 40113, 44701. § 39.13 (Amended) \n\n2. Section 39.13 is amended by adding the following new airworthiness directive: