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 certain Boeing Model 747 series airplanes was published in the Federal Register on May 30, 2002 (67 FR 37734). That action proposed to require repetitive inspections to detect evidence of wear damage in the area at the interface between the vertical stabilizer and fuselage skin, and corrective actions, if necessary. That action also proposed to provide for an optional terminating action for the repetitive inspections. \n\nComments \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\nRequest To Change Cost Impact \n\n\tOne commenter states that the work hours cited in the cost impact section of the proposed AD are significantly understated. The commenter notes that the hours for access and restoration have been omitted from the cost figures, so the true cost impact is not specified. The commenter states that access and restoration tasks do not routinely occur during scheduled maintenance visits in this instance. The commenter adds that 18 hours are necessary to gain access, perform the inspection and terminating action, and restore the airplane. The commenter asks that the cost impact section be changed to 18 hours for these actions. \n\n\tThe FAA agrees that access to the area under the vertical seal is not a task normally accomplished during routine maintenance, and the work hours required for access and closeup should be added. We have changed the work hours for the inspection specified in the cost impact section to 12 work hours; the optional terminating action will remain at 6 work hours, as it can be done immediately following the inspection, before closeup. \n\nRequest To Change Limits for Allowable Wear Damage \n\n\tOne commenter states that the definition for the limits for allowable skin damage as specified in the structural repair manual (SRM) was recently revised, and the damage limits have been reduced. The commenter adds that Section 3 of the referenced service bulletin specifies these new allowable damage limits in the Accomplishment Instructions. The commenter asks that the proposed AD be changed to refer to the service bulletin or list the revision date of the appropriate SRM to assure operators use the new limits for allowable damage. \n\n\tWe do not agree with the commenter. Operators should use the new allowable damage limits cited in the service bulletin or they may not be evaluating existing blendouts against the proper limits. However, we have determined that evaluation of existing blendouts against the old damage limits will not compromise an acceptable level of safety. Regarding new repairs, paragraph (a)(2) of the proposed AD requires that operators repair and refinish the skin per the service bulletin. In order to comply with this requirement, operators must use the allowable limits specified in the service bulletin. No change to the final rule is necessary in this regard. \n\nRequest Credit for Previous Inspections and Terminating Action \n\n\tOne commenter asks that credit be given for the inspections and terminating action required by the proposed AD, if done before the effective date of the proposed AD per Boeing Service Bulletin 747-53- 2192, dated July 21, 1981. The commenter states that the service bulletin referenced in the proposed AD includes a provision that specifies such credit. \n\n\tWe agree that credit can be given under certain explicit conditions. Service Bulletin 747-53-2192 specifies that, for airplanes having line numbers 0001 through 0414 inclusive, there is an option of using enamel coating or BMS 10-86 Teflon-filled coating. If operators can confirm that BMS 10-86 Teflon-filled coating was used, and the new allowable damage limits specified in Boeing Alert Service Bulletin 747- 53A2478 (referenced inthe proposed AD as the appropriate source of service information for accomplishment of the actions specified) are met, then no more work is necessary. A new paragraph (c) has been added to this final rule to provide credit if the conditions are met. \n\nRequest Credit for Inspections Done per Certain Maintenance Procedures \n\n\tOne commenter states that the Boeing Model 747 Maintenance Planning Document (MPD) recommends inspections of the affected areas of the fuselage skin at no greater than "D" check intervals. The commenter adds that the Corrosion Prevention and Control Program (CPCP) recommends inspections of the exterior surface of the fuselage skin for corrosion and other discrepancies at 5-year intervals. Based on these requirements, the commenter does the inspections required by the proposed AD earlier than the 6,000-flight-cycle compliance time specified for the repetitive inspections. The commenter also adds that, since the existing inspection programs already require inspections more frequently, there is no additional safety to be gained from promulgation of the proposed AD. The commenter asks that credit be given for the repetitive inspections required by paragraph (a)(1) of the proposed AD if done as part of these maintenance programs. \n\n\tBased on operator reports of wear damage of the fuselage skin at the interface area of the vertical stabilizer seal and fuselage skin, we do not agree with the commenter that existing maintenance programs are providing acceptable levels of safety. Additionally, this area is not accessed by all operators during scheduled maintenance visits, as specified previously under "Request to Change Cost Impact," so no change to the final rule is necessary in this regard. However, under the provisions of paragraph (d) of the final rule, we may approve requests for alternate inspections if data are submitted to substantiate that the inspections are equivalent and that repairs and any existing wear meet the allowable damage limits specified in the referenced service bulletin. \n\nRequest To Change Paragraphs (a)(2) and (b) \n\n\tOne commenter states that paragraph (b) of the proposed AD allows refinishing of the fuselage skin with BMS 10-86 Teflon-filled coating as terminating action for the proposed inspections. The commenter notes that there are other Teflon-filled coatings that are equivalent or better than BMS 10-86, and operators may already be using these "equivalent" coatings in their paint specifications. The commenter asks that, if the proposed AD is deemed necessary, paragraphs (a)(2) and (b) be changed to allow the use of other Teflon-filled coatings with equivalent abrasion resistant properties. \n\n\tWe do not agree with the commenter's request, as no supporting data were provided to us to substantiate the request. However, under the provisions of paragraph (d) of the final rule, we may approve requests for the use of other Teflon-filled coatings if data are submitted to substantiate that such coatings would provide an acceptable level of safety. \n\nRequest To Reconsider Terminating Action \n\n\tOne commenter states that paragraphs (a)(2) and (b) of the proposed AD allow the one-time application of Teflon-filled paint coating as terminating action for the repetitive inspections required by paragraph (a)(1) of the proposed AD. The commenter states that the proposed AD seems to indicate that the external paint will never again be removed and replaced, but is reapplied on an irregular basis. The commenter adds that, if this problem is as serious as alleged, a one-time application of a Teflon-filled paint coating to the exterior of the airplane would not provide a realistic terminating action. The paint will have to be reapplied whenever the external paint is stripped and refinished. \n\n\tWe do not agree with the commenter. If the external paint is stripped, refinishing the skin with BMS 10-86 Teflon-filled coating is required to remain in compliance with paragraph (a)(2) of this AD.Therefore, no change to the final rule is necessary in this regard. \n\nConclusion \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\nCost Impact \n\n\tThere are approximately 1,104 Boeing Model 747 series airplanes of the affected design in the worldwide fleet. The FAA estimates that 253 airplanes of U.S. registry will be affected by this AD, that it will take approximately 12 work hours per airplane (including time required to gain access and to close up) to accomplish the required inspection, 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 $182,160, or $720 per airplane, per inspection cycle. \n\n\tThe 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. The cost impact figures discussed in AD rulemaking actions represent only the time necessary to perform the specific actions actually required by the AD. These figures typically do not include incidental costs, such as the time required to gain access and close up, planning time, or time necessitated by other administrative actions. \n\n\tShould an operator elect to accomplish the proposed optional terminating action per paragraph (b) of this AD, it would take approximately 6 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the optional termination action would be $360 per airplane. \n\nRegulatory Impact \n\n\tThe 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\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\n\tAir transportation, Aircraft, Aviation safety, Incorporation by reference, Safety. \n\nAdoption of the Amendment \n\n\tAccordingly, 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\n\t1. The authority citation for part 39 continues to read as follows: \n\n\tAuthority: 49 U.S.C. 106(g), 40113, 44701. \n\n§ 39.13 (Amended) \n\n\t2. Section 39.13 is amended by adding the following new airworthiness directive: