A proposal to amend part 39 of the Federal Aviation Regulations to include an airworthiness directive (AD) that is applicable to Boeing Model 707 series airplanes was published in the Federal Register on September 7, 1993 (58 FR 47085). That action proposed to require incorporation of a certain structural modification of the wing front spar lower chord. \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 proposal. \n\n\tAnother commenter requests that the structural inspections and modifications referenced in Sections A.3 and A.4 of Appendix A of Boeing Document Number D6-54996, "Aging Airplane Service Bulletin Structural Modification and Inspection Program - Model 707/720," Revision D, dated January 23, 1992, be addressed in a single AD action, rather than in two different actions, as presently proposed by the FAA.This commenter points out that the FAA has issued a separate proposed AD, Docket 93-NM-80-AD (58 FR 53678, October 18, 1993), which would require the accomplishment of certain actions listed in Section 4 and Appendix A.4 of the Boeing Document, while this proposal (93-NM-82-AD) would require the accomplishment of actions referenced in Appendix A, Section A.3. The commenter contends that by issuing a single AD to cover both sections of the Boeing Document, the FAA will contribute to reducing the cost and complexity of publishing and tracking multiple AD's, while maintaining the same level of safety. \n\n\tThe FAA does not concur with the commenter's request, specifically because of the nature of the requirements of the currently proposed rules. The actions proposed in Docket 93-NM- 80-AD address structural inspections of both the Model 707 and Model 720, which are listed in Section 4 and Appendix A.4 of the Boeing Document. Those inspection actions entail various compliance times for implementation and a specified "phase-in" period for repetitive inspection intervals. On the other hand, the action proposed by this AD addresses a single modification of only Model 707 series airplanes, which is listed in Appendix A.3. of the Boeing Document. The modification action entails a specific compliance time for implementation based on either a flight cycle count or a calendar time limit. The FAA considers that to have combined the requirements for these dissimilar actions into one complex AD, would have created unnecessary confusion for affected operators. Therefore, as issued, there will be one AD addressing "inspections only" and another AD addressing the modification. This method of issuance will also ensure easier tracking of and proper compliance with the requirements of the AD's. \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 as proposed. \n\n\tThere are approximately 374 Model 707 series airplanes of the affected design in the worldwide fleet. The FAA estimates that 70 airplanes of U.S. registry will be affected by this AD within the initial threshold of 4 years. Approximately 194 work hours will be required to accomplish the modification, at an average labor charge of $55 per work hour. (This figure does not include downtime, planning, set up, familiarization, or tool acquisition costs.) The cost of the required modification kit is approximately $3,500 per airplane. Based on these figures, the total cost impact of this AD on U.S. operators within the initial threshold of 4 years is estimated to be $991,900, or $14,170 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 adoptedherein 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\n\t1.\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. \n\n§ 39.13 - (Amended) \n\t2.\tSection 39.13 is amended by adding the following new airworthiness directive: