A proposal to amend part 39 of the Federal Aviation Regulations to include an airworthiness directive (AD) that is applicable to certain Boeing Model 727 series airplanes was published in the Federal Register on August 31, 1993 (58 FR 45863). That action proposed to require structural inspections of older airplanes. \n\n\tInterested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received. \n\n\tOne commenter supports the proposed rule. \n\n\tTwo commenters note errors in the Discussion section of the proposal in the description of Boeing Document Number D6-54860, "Aging Airplane Service Bulletin Structural Modification and Inspection Program - Model 727," Revision G, dated March 5, 1993. Although the Discussion section does not reappear in the preamble to the final rule, the FAA takes this opportunity to correct the number of service bulletins referenced by the Boeing Document. There is a total of 17 service bulletins referenced by the Boeing Document: five service bulletins that describe inspections of the wings, six service bulletins that describe inspections of the fuselage, one service bulletin that describes inspections of the main landing gear door support fitting, four service bulletins that describe inspections of the empennage, and one service bulletin that describes inspections of the attach fittings on the center engine inlet duct housing. \n\n\tOne commenter requests that the FAA issue one rulemaking action that would combine the requirements of this proposal, which proposes to require the structural inspections listed in the Boeing Document, with the proposal to require the structural modifications listed in that Boeing Document. That rulemaking action was proposed in AD Docket 93-NM-73-AD (58 FR 45861, August 31, 1993). This commenter requests that these two rulemaking actions be combined with AD 90-06-09, Amendment 39-6488 (55 FR8370, March 7, 1990), which references Revision C of the Boeing Document, dated December 11, 1989. Combining all of these actions into one AD would ease the operators' burden in tracking compliance and recordkeeping. \n\n\tThe FAA does not concur. The FAA's normal policy in this regard is that when an AD requires a substantive change, such as a change in the existing AD's requirements, the existing AD (90-06-09) is superseded by being removed from the system and a new AD added. However, to supersede the existing AD and replace it with a new one having a new AD number would serve no purpose in terms of the ability of affected operators to track compliance with the AD and maintain accurate records of compliance. In consideration of the consequent workload associated with revising maintenance records to enter new AD numbers to demonstrate compliance with requirements accomplished previously, the FAA has determined that a less burdensome approach is to issue a separate AD. This finalrule is issued as a separate AD action since combining these rulemaking actions would necessitate recordkeeping changes to reflect new AD numbers. Furthermore, the FAA's intent in keeping the requirement to accomplish the inspections listed in the Boeing Document separated from the requirement to accomplish the modifications listed in the Boeing Document was to minimize the recordkeeping burden to the operators; i.e., operators will not be required to make recordkeeping changes to their inspection entries whenever revisions are made to modification requirements and vice versa. \n\n\tOne commenter requests that the proposed compliance time for the repetitive inspections in paragraph (a) be revised to be consistent with those recommended in the Boeing Document. The FAA does not concur that any change is necessary. From this comment, the FAA concludes that this commenter may have mistakenly assumed that the proposal would have required that the repetitive inspections must be accomplishedat the times specified in the corresponding service bulletins. Consequently, paragraph (a) of the final rule remains unchanged and states that repetitive inspections are to be accomplished "thereafter at intervals not to exceed those specified in the Boeing Document for each inspection." Furthermore, since the corresponding service bulletins have been revised to be consistent with the Boeing Document, the compliance times for the repetitive inspections are consistently defined in the final rule, the Boeing Document, and the corresponding service bulletins. \n\n\tSeveral commenters request that proposed paragraphs (a) and (b) be revised to clarify that only the structural inspections listed in Section 4 and Appendices A.4 and B.4 of the Boeing Document must be accomplished. Since the proposal stated that the inspections were specified in "Section 4 and Appendices A. and B." of the Boeing Document, these commenters contend that the possibility exists for misinterpretation. The FAA concurs. The FAA finds that these commenters' proposal to reference the specific appendices of the Boeing Document (rather than the generalization cited in the proposal) would avoid any possibility for misinterpretation. Therefore, paragraphs (a) and (b) of the final rule have been revised accordingly. \n\n\tThe Air Transport Association of America, on behalf of one of its member operators, requests that the note following proposed paragraph (b)(2) be clarified. The commenter states that the term "phase-in period" was not adequately defined in the proposal and that it was not used in the Boeing Document, which was referenced in the proposal. Since some of the service bulletins that are referenced by the Boeing Document specify a "phase-in" time, while others do not, the commenter further requests that issuance of the final rule be delayed until such time that the 727 Structures Working Group of the Airworthiness Assurance Task Force has reconvened to resolve this issue. The FAA concursthat clarification is warranted; however, the FAA does not concur that delaying issuance of the final rule is necessary, since the following discussion, as well as the revised final rule, adequately defines "phase-in period." The FAA's intent in using the term "phase-in period" was to grant a "grace period" of 15 months to operators having airplanes that will soon exceed or that have already exceeded the threshold specified in the Boeing Document. \n\n\tIn light of this comment, the FAA has revised paragraph (b) of the final rule to clarify that, in those instances when a "phase-in period" is specified in any of the service bulletins referenced by the Boeing Document, the maximum initial inspection time is to be calculated using the "phase-in period" specified in the service bulletin and adding a date 15 months after the effective date of the AD. An example of this, although not specifically referred to as a "phase-in period", can be found in the Accomplishment Instructions of BoeingService Bulletin 727-53-0041, Revision 6, dated September 5, 1991, which states, in part, that "airplanes having accumulated more than 16,000 flight cycles should be inspected within 3,000 flight cycles..." The "phase-in period" in this example is "within 3,000 flight cycles." Therefore, for the purposes of this AD, the maximum initial inspection time in this instance is 3,000 flight cycles measured from a date 15 months after the effective date of this AD. \n\n\tHowever, in those instances when a "phase-in period" is not specified in any of the service bulletins referenced by the Boeing Document, the FAA's intent is to allow operators 15 months for planning purposes. In these instances, the maximum initial inspection time is 15 months after the effective date of this AD. \n\n\tOne commenter requests that the proposal be revised to permit deviations to the corrective actions required by proposed paragraph (c), and suggests that these be permitted to be accomplished in accordance withother FAA-approved methods, e.g., Structural Repair Manuals; Statement of Compliance with the Federal Aviation Regulations, FAA Form 8110-3; etc. The commenter's intent for requesting this change is to gain authorization to make minor deviations, such as oversizing fasteners and substituting materials, without obtaining approval for an alternative method of compliance for each deviation. The commenter states that safety could be ensured with repetitive inspections until such time that the corrective action specified in the corresponding service bulletin referenced by the Boeing Document could be accomplished during regularly scheduled maintenance, so as to minimize the impact to operators' revenue bearing passenger service. The FAA does not concur. The FAA has determined that the Manager, Seattle Aircraft Certification Office, should approve any such deviations to the AD's requirements. Given that possible new relevant issues might be revealed during this process, it is imperative that the FAA, at this level, have such feedback. Only by reviewing deviation approvals can the FAA be assured of this feedback and of the adequacy of the repair methods. However, when the FAA has obtained an adequate sampling of the quality, type, and extent of repairs being made as a result of this AD, the FAA anticipates that it will, at some future date, authorize manufacturer's Designated Engineering Representatives to approve minor deviations to the modifications required by this final rule, as it has done in the past regarding the requirements of AD 90-06-09, and other aging fleet AD's. Furthermore, affected operators may request approval to use an alternative method of compliance to the corrective actions specified in the corresponding service bulletins, under the provisions of paragraph (e) of the final rule. \n\n\tAfter 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 previously described. The FAA has determined that these changes will neither increase the economic burden on any operator nor increase the scope of the AD. \n\n\tThere are approximately 1,635 Model 727 series airplanes of the affected design in the worldwide fleet. The FAA estimates that 688 airplanes of U.S. registry will be affected by this AD, that it will take approximately 512 work hours per airplane to accomplish the required actions, and that the average labor rate is $55 per work hour. Based on these figures, the total cost impact of the AD on U.S. operators is estimated to be $19,374,080, or $28,160 per airplane. \n\n\tThe total 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\n\tThe regulations adopted herein will not have substantial direct effects 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, in accordance with Executive Order 12612, it is determined that this final rule does not have sufficient federalism implications to warrant the preparation of a Federalism Assessment. \n\n\tFor 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." \n\nList of Subjects in 14 CFR Part 39 \n\nAir transportation, Aircraft, Aviation safety, Incorporation by reference, Safety. \n\nAdoption of the Amendment \n\nAccordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends 14 CFR part 39 of the Federal Aviation Regulations as follows: \n\nPART 39 - AIRWORTHINESS DIRECTIVES \n\n1.\tThe authority citation for part 39 continues to read as follows: Authority: 49 U.S.C. App. 1354(a), 1421 and 1423; 49 U.S.C. 106(g); and 14 CFR 11.89. § 39.13 - (Amended) \n\n2.\tSection 39.13 is amended by adding the following new airworthiness directive: