The FAA proposed to amend 14 CFR part 39 with an AD for certain Boeing Model 747 airplanes. That action, published in the Federal Register on February 14, 2005 (70 FR 7446), proposed to require repetitive inspections of the dual side braces (DSBs), underwing midspar fittings, and associated parts; other specified actions; and corrective actions if necessary. That action also provides an optional terminating action for the inspections and other specified actions. \n\nComments \n\n\tWe provided the public the opportunity to participate in the development of this AD. We have considered the comments that have been submitted on the proposed AD. \n\nSupport for the Proposed AD \n\n\tOne commenter concurs with the content of the proposed AD. \n\nRequests to Refer to Revised Service Bulletin and Give Credit for Prior Issue \n\n\tOne commenter asks that the proposed AD reference Boeing Service Bulletin 747-54A2218, Revision 1, dated February 24, 2005. Boeing Alert Service Bulletin 747-54A2218, dated June 17, 2004, was referenced in the proposed AD as the appropriate source of service information for accomplishing the specified actions. The commenter states that Revision 1 specifies that no more work is necessary on airplanes changed per the original issue of the service bulletin. The commenter also asks that we give credit for actions done in accordance with the original issue of the service bulletin. The commenter notes that this will prevent additional work for the Civil Aviation Authorities that would necessitate approving Revision 1 as an alternative method of compliance. The commenter adds that the revised information specified in Revision 1 may be helpful for operators in accomplishing the actions required by the proposed AD. A second commenter asks that credit be given for the initial inspection done in accordance with the original issue of the service bulletin. \n\n\tWe agree with the commenters. We have reviewed Boeing Service Bulletin 747-54A2218, Revision 1, dated February 24, 2005. The instructions in Revision 1 are essentially the same as those in the original issue of the service bulletin. Accordingly, we have revised this AD to refer to Revision 1 of the service bulletin in the applicability section and as the applicable source of service information for accomplishing the actions required by this AD. We have also added a new paragraph (i) (and re-identified subsequent paragraphs accordingly) to give credit for actions accomplished before the effective date of this AD in accordance with the original issue of the service bulletin. \n\nRequests to Remove/Delay Check for an Insufficient Gap/Delay Corrective Actions \n\n\tOne commenter questions why the check for an insufficient gap between the underwing midspar fitting and the strut midspar fitting is necessary if no discrepancies are found during the proposed inspections of the dual side brace (DSB) bearings. The commenter states that it was both surprising and disappointing to learn of reported interference between the underwing midspar fitting and the adjacent strut midspar fitting. The commenter states that, while recognizing that corrective actions should be accomplished only if conditions warrant such actions, any future adopted rule should consider the inclusion of options that will enable corrective actions to occur during planned D-check visits to minimize unplanned out-of-service situations. The commenter notes that the proposed AD includes a check for an insufficient gap between those fittings within 24 months. The commenter concludes that the check for an insufficient gap between those fittings should only be required if discrepancies are found during the inspection of the DSB bearings per Parts 1 and 2 of the referenced service bulletin. \n\n\tA second commenter asks that paragraph (f) of the proposed AD be changed to postpone the requirement for accomplishing the corrective actions per Parts 3, 5, and 6 of the referenced service bulletin, if an insufficient gap is found per Part 4. The commenter states that those actions can be performed at its first FD-check, and until the actions are performed, the spring beam/wing fitting joint and DSB fitting can be inspected per the baseline inspection task specified in Boeing Service Bulletin 747-54A2182, Revision 1, dated January 8, 2004, but at a 3A interval. That service bulletin describes procedures for certain baseline inspections of the strut-to-wing attachment structure. The commenter adds that it has performed wing pylon modifications on more than 50 airplanes per Boeing Alert Service Bulletins 747-54A2156 (referenced in AD 95-13-06, amendment 39-9286, as the appropriate source of service information for modification of the nacelle strut and wing) and 747-54A2158 (referenced in AD 95-13-07, amendment 39-9287, as the appropriate source of service information for modification of the nacelle strut and wing), concurrently with Boeing Service Bulletin 747- 57-2246, Revision 5, dated July 17, 1997. Boeing Service Bulletin 747- 57-2246 describes procedures for modification of the nacelle strut attachment fittings. The commenter notes that Service Bulletin 747-57- 2246 also describes procedures for checking the surface wear on the underwing fittings of the outboard pylon midspar that were caused by interference with the spring beam flanged bushings, and removal of any damage by spotfacing. The commenter states that only four of its airplanes required the spotfaces to be larger than what was allowed in the service bulletin, and the larger spotfaces were approved by the FAA. The commenter adds that cracks were never found in the wear/ spotface area; however, several of the 50 airplanes must have had the insufficient gap condition for many years. The commenter concludes that if additional surface damage occurs on the underwing midspar fittings, it would be detected in a timely manner when performing the proposed inspections. \n\n\tA third commenter, the airplane manufacturer, states that it is concerned with the comments regarding a no-gap condition that may exist during inspection, and the actions specified in paragraph (f) of the proposed AD per Parts 4, 5, and 6 of the referenced service bulletin. The commenter adds that a deferral for these actions may be justified for a no-gap condition, provided that no damage is found during the Part 4 inspection. The commenter's position is based on fleet history data with similar conditions, as provided by other commenters. The commenter may consider a change to the referenced service bulletin upon a recommended course of action, and will advise us accordingly. The commenter adds that we may choose to approve an alternative method of compliance (AMOC) on a case-by-case basis, at our discretion. \n\n\tWe acknowledge the new information provided by the commenters. The airplane manufacturer has informed us that it is planning to revise the service bulletin to reflect this new information by the end of 2005.Delaying this action until after the release and approval of the manufacturer's planned service bulletin is not warranted. We have determined that the inspections must be conducted to ensure continued operational safety. When a new revision of the service bulletin has been developed, we will review that revision and consider approving it as an alternative method of compliance with the requirements of this AD. In light of this, we have determined that all the actions required by this AD are appropriate and warranted. No change is made to the AD in this regard.\n \n\tAdditionally, insufficient technical justification was provided by the commenters to justify delaying issuance of the AD; however, if sufficient technical justification is provided, we may approve an AMOC, in accordance with paragraph (j)(1) of the AD. \n\nRequests to Change Costs of Compliance Section/Extend Compliance Time \n\n\tOne commenter states that we should revise the Costs of Compliance section that is specified in the preamble of the proposed AD. The language in that section states, "The following table provides the estimated costs for U.S. operators to comply with this proposed AD." The commenter notes that the table provides the cost impact of the required inspections, but offers no estimate of the cost impact should an inspection detect the specific discrepancy that is the basis for the proposal. The commenter states that it is well aware that the FAA's policy for estimating the impact of proposed ADs does not include publishing the impact of aircraft re-routing, preparation, access, correction of discrepancies found, aircraft close-up, or return-to- flight tests and procedures, often categorizing them as "incidental" impacts. The commenter does not support that policy. The commenter states that, in this particular proposal, the impact of the man hours necessary for accomplishing the corrective action alone can be an order-of-magnitude greater than the per airplane cost published for comment.The commenter asks us to consider adopting a policy for proposed ADs that consistently states the per airplane impact of the prescribed corrective action in cases where that action is found necessary. \n\n\tA second commenter states that it will be subjected to a huge economic impact when accomplishing the actions specified in the proposed AD, per the referenced service bulletin, due to the mandatory status of the follow-up inspections and modification after an insufficient gap is found. The commenter adds that the follow-up inspections require engine and pylon removal. The commenter lists, and we respond to, the following factors that will make the economic impact of the proposed AD even greater: \n\n\t1. Experience with the modification specified in Part 3 of the referenced service bulletin shows that one of the DSB underwing fitting bolts may interfere with the modification tool. If a bolt interferes, it will have to be removed. Removal of a bolt requires removal of the WS 1140 rib togain access to the DSB underwing fitting bolt for modification, which is a very time-consuming job. \n\n\tSince we issued the proposed AD, this condition has not been reported by any other operators. In addition, accomplishing the modification is only necessary if damage or cracking is found, thus making it an on-condition action and not part of the inspections required by the AD. \n\n\t2. The tooling kit specified in the referenced service bulletin limits the operator to modifying only one fitting on one pylon at a time, and not two or more pylons simultaneously. This results in additional downtime when more than one pylon must be modified. \n\n\tAs we stated previously, accomplishing the modification is an on- condition action. Obtaining the tooling kits necessary for accomplishing the modification should be addressed by operators on a case-by-case basis. \n\n\t3. The airplane manufacturer does not seem ready to support so many modifications with tooling and material kits. Currently, the airplane manufacturer does not have enough tooling and material kits available to support all operators in the 24-month timeframe allowed for the modification. \n\n\tWe have no way of estimating how many operators will be accomplishing the on-condition modifications. The airplane manufacturer has confirmed that it will have the necessary tooling and material kits available to complete the on-condition actions required by the AD. \n\n\tA third commenter states that the maintenance and economic impact of the proposed AD could be significantly greater than that specified in the "Costs of Compliance" section. The commenter notes that a review of labor estimates in the referenced service bulletin revealed that over 500 labor hours per airplane may be required to perform the necessary corrective actions if problems exist at all four engine strut to wing attachment locations. The commenter adds that this would raise the labor cost for compliance to over $30K per airplane; additionally, material costs total over $21K per airplane, plus tooling rental charges in excess of $1K per day are expected. \n\n\tWe do not agree with the commenters that request changing the work hours in this AD, because the AD reflects only the direct costs of the specific required actions based on the best data available from the manufacturer. We recognize that operators may incur incidental costs (such as the time for planning and associated administrative actions) in addition to the direct costs. The cost analysis in ADs, however, typically does not include incidental costs. \n\n\tThe 24-month compliance time for the initial inspection required by this AD should allow ample time for the majority of affected operators to do the required actions at the same time as scheduled major airplane inspection and maintenance activities, which would reduce the additional time and costs associated with special scheduling. We note that the 24-month compliance time is consistent with the compliance time specifiedin the referenced service bulletin. However, operators may submit a request for approval of an AMOC, as specified in paragraph (j)(1) of this AD. The request must include data substantiating that an acceptable level of safety would be maintained by extending the compliance time. No change is made to the AD in this regard. \n\nConclusion \n\n\tWe have carefully reviewed the available data, including the comments that have been submitted, and determined that air safety and the public interest require adopting the AD with the changes described previously. These changes will neither increase the economic burden on any operator nor increase the scope of the AD. \n\nCosts of Compliance \n\n\tThere are about 1,091 airplanes of the affected design in the worldwide fleet. The following table provides the estimated costs for U.S. operators to comply with this AD. \n\n\tEstimated Costs \n\n\nAction \nWork hours \nAverage labor rate per hour \nParts \nCost per airplane \nNumber of U.S.-\nregistered airplanes \nFleet cost \nPart 1 Inspections, per inspection \n8\n$65\nNone \n$520\n229\n$119,080, per inspection \n\n\n\n\n\n\n\nPart 2 Inspections, per inspection \ncycle. \n 48 \n 65 \nNone\n 3,120 \n 229 \n714,480, per inspection \ncycle. \n\n\n\n\n\n\n\nPart 4 Inspections, per inspection \ncycle. \n4 \n65 \nNone \n260 \n229 \n59,540, per inspection \ncycle. \n\nAuthority for This Rulemaking \n\n\tTitle 49 of the United States Code specifies the FAA's authority to issue rules on aviation safety. Subtitle I, section 106, describes the authority of the FAA Administrator. Subtitle VII, Aviation Programs, describes in more detail the scope of the Agency's authority. \n\n\tWe are issuing this rulemaking under the authority described in subtitle VII, part A, subpart III, section 44701, "General requirements." Under that section, Congress charges the FAA with promoting safe flight of civil aircraft in air commerce by prescribing regulations for practices, methods, and procedures the Administrator finds necessary for safety in air commerce. This regulation is within the scope of that authority because it addresses an unsafe condition that is likely to exist or develop on products identified in this rulemaking action. \n\nRegulatory Findings \n\n\tWe have determined that this AD will not have federalism implications under Executive Order 13132. This AD 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. \n\n\tFor the reasons discussed above, I certify that this AD: \n\n\t(1) Is not a "significant regulatory action" under Executive Order 12866; \n\n\t(2) Is not a "significant rule" under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and \n\n\t(3) Will not have a significant economic impact, positive or negative, on a substantial number of small entities under the criteria of the RegulatoryFlexibility Act. \n\n\tWe prepared a regulatory evaluation of the estimated costs to comply with this AD. See the ADDRESSES section for a location to examine the regulatory evaluation. \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\nAccordingly, under the authority delegated to me by the Administrator, the FAA amends 14 CFR part 39 as follows: \n\nPART 39--AIRWORTHINESS DIRECTIVES \n\n1. 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\n2. The FAA amends Sec. 39.13 by adding the following new airworthiness directive (AD):