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 Boeing Model 747-100, -200, -300, -400, and 747SR series airplanes was published in the Federal Register on April 24, 2000 (65 FR 21675). That action proposed to require repetitive inspections to detect cracks and corrosion around the lower bearing of the actuator attach fittings of the inboard and outboard flaps. That action also proposed to require repetitive overhauls for certain attach fittings or repetitive replacement of the attach fittings with new attach fittings, as applicable, which would constitute terminating action for certain repetitive actions. \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\nSupport for the Proposal \n\n\tOne commenter supports the proposed rule.Limit Applicability of AD \n\n\tOne commenter, the airplane manufacturer, requests that the FAA limit the applicability of the proposed rule to airplanes having line numbers up to and including 1265. The commenter states that new, improved actuator attach fittings will be installed during production on airplanes starting at line number 1266. The commenter explains that the new, improved actuator attach fittings in certain positions (i.e., actuator attach fittings number 2 and 7) have an increased cross-sectional area that reduces stress levels and, consequently, the possibility of stress corrosion cracking. Attach fittings in all other locations will have increased bushing interference, and BMS 5-26 sealant will be applied to the new fittings to prevent general corrosion. \n\n\tThe FAA concurs with the intent of the commenter's request to limit the applicability of this AD. However, since they submitted their comment, the airplane manufacturer has advised the FAA that new fittings havebeen incorporated on airplanes starting with line number 1264. This coincides with the effectivity listing of a new service bulletin related to this AD, Boeing Service Bulletin 747-57A2310, Revision 2, dated February 22, 2001 (which is described in the next section of this final rule). Therefore, the FAA has revised and clarified the applicability of this AD to apply only to Model 747 series airplanes listed in Boeing Service Bulletin 747-57A2310, Revision 2. (Operators may note that, while the applicability of this AD has been reduced, the estimated number of affected airplanes has been increased in the "Cost Impact" section of the preamble. The new estimate includes airplanes delivered after the preparation of the proposed rule.) \n\nReference New Terminating Action \n\n\tOne commenter notes that, in the preamble of the proposed AD, the FAA identifies the proposed AD as interim action, and states that, once a modification is developed, approved, and available, the FAA may consider additional rulemaking. The commenter states that it is very interested in this terminating modification. The commenter requests that, if release of the modification is imminent, the FAA delay release of this AD until the airplane manufacturer has developed the terminating modification. If the release is not imminent, the commenter requests that the FAA make the modification available as an alternative method of compliance (AMOC) to this AD or issue a superseding AD to include the terminating action as soon as possible. \n\n\tThe FAA partially concurs with the commenter's request. The FAA does not agree that issuance of the final rule should intentionally be delayed pending development of a terminating modification. The commenter provides no technical justification for such a delay. \n\n\tHowever, since the issuance of the proposed AD, the FAA has reviewed and approved Boeing Service Bulletin 747-57A2310, Revision 2. (The proposed AD references Boeing Service Bulletin 747-57A2310, Revision 1, dated November 23, 1999, as an appropriate source of service information for certain proposed actions.) Among other actions, Revision 2 of the service bulletin includes procedures for a new terminating action. The new terminating action involves rework of the numbers 1, 3, 4, 5, 6, and 8 actuator attach fittings on both the inboard and outboard flaps, or replacement of the attach fittings with improved attach fittings; and replacement of the number 2 and 7 attach fittings of the trailing edge flap actuators with new, improved attach fittings (of a new design). \n\n\tThe FAA has determined that, if accomplished, this terminating action would adequately address the unsafe condition. Therefore, the FAA has added subparagraphs to paragraph (e) of this final rule, including paragraph (e)(2) which provides the terminating action specified in Revision 2 of the service bulletin as an option that ends the requirements of this AD. Additionally, the FAA finds that Revision 2 is also an acceptable source of service information for the inspections required by paragraph (c) of this AD. Thus, paragraph (c) of this final rule has also been revised to reference Revision 2 of the service bulletin, in addition to Revision 1, as an acceptable source of service information. \n\nClarify References in Paragraphs (a) and (b) \n\n\tOne commenter requests that the FAA revise paragraphs (a) and (b) of the proposed rule to state, "Accomplish the actions in paragraphs (c), (d), or (e) of this AD * * *" instead of referring to paragraph (c) only. The commenter provides no justification for its request. \n\n\tThe FAA concurs with the commenter's request because adding references to paragraphs (d) and (e) will clarify the complete range of actions available to operators. Paragraphs (a) and (b) of this final rule have been revised accordingly. \n\nProvide for Previous Overhaul of Actuator Fittings \n\n\tOne commenter requests that the FAA provide for actuator attach fittings of the inboard flaps thathave been overhauled in accordance with a revision of Boeing 747 Overhaul Manual (OHM) 57-52-35 that is dated prior to June 10, 1999. The commenter specifically requests that, for airplanes previously overhauled, the FAA revise the compliance times in paragraph (a) of the proposed AD to 8 years or 8,000 flight cycles after overhaul of the actuator attach fittings for the inboard flaps. The commenter notes that this compliance time would agree with the compliance time for the actuator attach fittings of the outboard flaps, which are more critical. \n\n\tThe FAA concurs with the commenters request, and has revised paragraph (a) of this final rule to apply to: \n\n\tActuator attach fittings on the outboard flaps that have NOT been overhauled in accordance with revisions of OHM 57-52-55 dated prior to June 1, 1999, or replaced with a new fitting; and \n\n\tActuator attach fittings on the inboard flaps that have NOT been overhauled in accordance with revisions of OHM 57-52-35, dated prior toJune 10, 1999, or replaced with a new fitting.\n\n\tAlso, the FAA has revised paragraph (b) of this final rule to apply to: \n\n\tActuator attach fittings on the outboard flaps that HAVE been overhauled in accordance with revisions of OHM 57-52-55 dated prior to June 1, 1999, or replaced with a new fitting; and \n\n\tActuator attach fittings on the inboard flaps that HAVE been overhauled in accordance with revisions of OHM 57-52-35, dated prior to June 10, 1999, or replaced with a new fitting. \n\nAllow Use of Later Revisions of OHM \n\n\tOne commenter requests that the FAA revise paragraph (d) of the proposed rule to specify overhaul of the actuator attach fittings for the flaps in accordance with Boeing OHM 57-52-55, Temporary Revision 57-7, dated June 1, 1999, or Temporary Revision 57-9, dated May 14, 2000; and Boeing OHM 57-52-35, Temporary Revision 57-8, dated June 10, 1999, Temporary Revision 57-10, dated May 8, 2000, or Full Revision 57-10, dated July 1, 2000. The commenter also requests that the FAA refer to Boeing OHM 57-52-35, Temporary Revision 57-10, or Full Revision 57-10, in Note 4 of the proposed rule. The commenter states that these later revisions of the OHM chapters describe the same actions as those revisions referred to in the proposed rule but provide additional repair information. \n\n\tSimilarly, a second commenter requests that the FAA revise paragraph (d) of the proposed rule to specify overhaul of the actuator attach fittings in accordance with Boeing OHM 57-52-55, Temporary Revision 57-7, dated June 1, 1999, or later, and Boeing OHM 57-52-35, Temporary Revision 57-8, dated June 10, 1999, or later. The commenter states that this would allow use of the latest revision of the OHM when overhauling the fittings. \n\n\tThe FAA partially concurs with the commenters' requests. The FAA has reviewed the specific revisions referenced by the first commenter and finds them acceptable. The FAA has also reviewed Boeing OHM 57-52-55, Full Revision 57-9, dated July 1, 2000, and finds it acceptable. However, rather than revising paragraph (d) to cite all of these revisions, the FAA finds that paragraph (d) of this AD may be revised to refer to the accomplishment instructions of Boeing Service Bulletin 747-57A2310, Revision 1, dated November 23, 1999, or Revision 2, dated February 22, 2001, as acceptable sources of service information for the accomplishment of the overhaul required by that paragraph. The FAA finds that this change will clarify the requirements of paragraph (d) of this AD, and make it easier for operators to comply with that paragraph. The FAA has revised paragraph (d) accordingly. In addition, for the actuator attach fittings on the inboard flaps, the FAA has revised Note 4 of this AD to refer to specific OHM revisions referenced by the first commenter and reviewed and accepted by the FAA. \n\nAllow Approval of Repairs By Designated Engineer Representative (DER) \n\n\tOne commenter requests that the FAA revise the "Alternative Methods of Compliance" paragraph--paragraph (f) in the proposed rule--to allow repairs of corrosion or cracking that is outside the limits specified in the OHM in accordance with a method approved by a Boeing DER, in lieu of requiring replacement of the actuator attach fittings before further flight. The commenter states that this allowance is necessary to prevent unnecessary delays or grounding of airplanes if operators find conditions outside the rework limits in the OHM. \n\n\tThe FAA partially concurs with the commenter's request. The FAA does not concur with the commenter's request to revise the "Alternative Methods of Compliance" paragraph to allow the Boeing DER to approve repairs. However, the FAA finds that a new paragraph may be added to provide for repair of actuator attach fittings, in lieu of replacement. Therefore, the FAA has added paragraph (f) to this final rule (and reordered subsequent paragraphs accordingly), to allow for repair of the actuator attach fittings on theinboard and outboard flaps in accordance with a method approved by the FAA or data approved by a Boeing Company DER who has been authorized to make such findings. \n\nRevise Cost Impact Estimate \n\n\tOne commenter requests that the FAA revise the estimate of the cost impact in the proposed rule. The commenter states that the estimate of 5 work hours per airplane for overhaul of the actuator attach fittings is extremely low. The commenter notes that the procedures for each actuator attach fitting include cleaning, removing sleeves, machining, performing non-destructive tests, and manufacturing and installing new sleeves. The commenter also submits estimates from several vendors as well as their own estimate of 192 work hours per airplane. \n\n\tThe FAA partially concurs with the commenter's request. The FAA does not concur that the commenter's estimate of 192 work hours is appropriate for use in this AD. The cost impact information in AD actions includes only the "direct" costs of the specific actions required by the AD. The FAA recognizes that, in accomplishing the requirements of any AD, operators may incur "incidental" costs in addition to the "direct" costs. The cost analysis in AD rulemaking actions, however, typically does not include incidental costs, such as the time required to gain access and close up; planning time; or time necessitated by other administrative actions. Because incidental costs may vary significantly from operator to operator, they are almost impossible to calculate. \n\n\tHowever, the FAA does concur that the estimated number of work hours can be adjusted somewhat. The estimate of 5 work hours included only the time necessary specifically for the overhaul, based on the data included in the manufacturer's service bulletin. The FAA finds it appropriate to include the estimate of work hours needed for removal, inspection, and re-installation, as well as overhaul, of the subject parts. Based on the data provided in the airplane manufacturer's service bulletin, the FAA estimates the number of work hours for these actions to be 37 work hours per airplane. Similarly, the FAA finds that the cost estimate for replacement of the actuators should include time for the inspection that is included in the procedures for the replacement. Thus, the number of work hours for the replacement has been increased from 2 to 4 work hours per airplane. The FAA has revised the cost impact estimate in this final rule accordingly. \n\nReduce Compliance Time for Actions on Attach Fittings on Outboard Flap \n\n\tOne commenter, an operator, requests that the FAA reduce the proposed initial compliance time for actions on the actuator attach fittings on the outboard flap that have been overhauled per OHM 57-52-55. The commenter requests a compliance time of 6 years or 6,000 flight cycles, whichever occurs first, after the attach fitting was overhauled, for the accomplishment of paragraph (c), (d), or (e) of this AD. The commenter states that the earlier of6 years or 6,000 flight cycles is its "hard time" interval between overhauls. \n\n\tThe FAA does not concur. The compliance time of 8 years or 8,000 flight cycles, whichever occurs first, is based on when cracking of actuator attach fittings has been found, and the manufacturer's recommendation in the service bulletin. However, an operator may choose to accomplish the actions in this AD prior to the 8-year-or-8,000-flight-cycle threshold. 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 1,111 Model 747 series airplanes of the affected design in the worldwide fleet. The FAA estimates that 237 airplanes of U.S. registry will be affected by this AD. \n\n\tIt will take approximately 2 work hours per airplane to accomplish the required inspection, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of this inspection on U.S. operators is estimated to be $28,440, or $120 per airplane, per inspection cycle. \n\n\tThe overhaul of actuator attach fittings, which is offered as one alternative for compliance with this AD action, will take approximately 37 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of this overhaul is estimated to be $2,220 per airplane, per overhaul cycle. \n\n\tIn lieu of the overhaul, this AD provides for a replacement of actuator attach fittings, which would take approximately 4 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Required parts will cost approximately $6,623 (for the four attach fittings on the outboard flaps) and $7,566 (for the four attach fittings on the inboard flaps). Based on these figures, the cost impact of this replacement is estimated to be $14,429, per airplane, per replacement cycle. \n\n\tThe cost impact figures discussed above are 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 optional replacement with improved attach fittings, which terminates the requirements of this AD, it would take approximately 16 work hours to accomplish, at an average labor rate of $60 per work hour. The cost of required parts would be approximately $15,322 per airplane. Based on these figures, the cost impact of the optional terminating action would be $16,282 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\nSec. 39.13 (Amended) \n\n\t2. Section 39.13 is amended by adding the following new airworthiness directive: