Discussion \n\n\tThe FAA issued a second supplemental notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 to include an AD that would apply to certain Boeing Model 737-300, -400, -500, -600, -700, -700C, -800, and -900, and 747-400 series airplanes; and Model 757, 767, and 777 airplanes. That second supplemental NPRM was published in the Federal Register on January 12, 2009 (74 FR 1159). That second supplemental NPRM proposed to require modifying the static inverter by replacing resistor R170 with a new resistor and relocating the new resistor. \n\nActions Since Issuance of Second Supplemental NPRM \n\n\tSince issuance of the second supplemental NPRM, Boeing has issued the revised service bulletins listed in the following table: \n\nRevised Service Bulletins\n\nModel -\nBoeing -\n737-300, -400, -500 series airplanes\nAlert Service Bulletin 737-24A1166, Revision 4, dated May 21, 2009\n757-200, -200CB, -200PF series airplanes\nSpecial Attention Service Bulletin 757-24-0110, Revision 1, dated August 6, 2009\n757-300 series airplanes\nSpecial Attention Service Bulletin 757-24-0111, Revision 1, dated August 6, 2009\n\n\tNo additional work is necessary for airplanes on which the modification specified in Boeing Alert Service Bulletin 737-24A1166, Revision 3, dated July 25, 2007, has been done. Revision 4 clarifies certain sections, moves airplanes from Group 2 to Group 1 in the effectivity, and removes the Group 2 work instructions. \n\n\tBoeing Special Attention Service Bulletin 757-24-0110, Revision 1, dated August 6, 2009, adds an inspection of certain static inverter part numbers to make sure only approved part numbers are installed; however, the proposed modification requires modifying the static inverter by replacing the resistor with a new resistor having an approved part number. Revision 1 also moves airplanes from Group 2 to Group 1 in the effectivity, and the Group 2 work instructions were deleted. Therefore, no additional work is necessary for airplanes modified in accordance with Boeing Special Attention Service Bulletin 757-24-0110, dated April 28, 2005. \n\n\tBoeing Special Attention Service Bulletin 757-24-0111, Revision 1, dated August 6, 2009, also adds an inspection of certain static inverter part numbers to make sure only approved part numbers are installed; however, the proposed modification requires modifying the static inverter by replacing the resistor with a new resistor having an approved part number. Revision 1 also moves airplanes from Group 2 to Group 1 in the effectivity, and the Group 2 work instructions were deleted. No additional work is necessary for airplanes modified in accordance with Boeing Special Attention Service Bulletin 757-24-0111, dated April 28, 2005. \n\n\tWe have revised Table 1 of this AD to refer to the latest revisions of the service bulletins and added a new paragraph (h) to this AD to give credit for actions done in accordance with the earlier revisions that were referenced in Table 1 of the NPRM. \n\nComments \n\n\tWe provided the public the opportunity to participate in the development of this AD. We have considered the comments received on the second supplemental NPRM. \n\nSupport for the Second Supplemental NPRM \n\n\tNorthwest Airlines has no objection to the second supplemental NPRM; Boeing concurs with the content of the second supplemental NPRM. \n\nRequest To Permit Installation of Static Inverters Having Certain Part Numbers \n\n\tAmerican Airlines (AAL) and FedEx Express request that we allow installation of static inverters having certain part numbers. \n\n\tAAL asks that we permit installation of static inverters having part numbers (P/Ns) S282T004-2, -3, and -4. AAL states that those static inverters do not have an overheating safety concern, which is the unsafe condition addressed in the second supplemental NPRM. AAL adds that static inverters that have P/Ns S282T004-2, -3, and -4 are fully interchangeable on the Model 757 fleet. \n\n\tFedEx Express asks that Boeing Special Attention Service Bulletin 757-24-0110, dated April 28, 2005, be revised to include Avionics Instruments static inverters having P/Ns S282T004-28 and S282T004-30 as acceptable to remain on Model 757 airplanes. FedEx Express adds that since issuance of the original issue of Boeing Special Attention Service Bulletin 757-24-0110, those static inverters have been installed on some Model 757 airplanes and have been added to the Boeing Illustrated Parts Catalog. FedEx Express notes that P/Ns S282T004-2, - 3, -4, -28, and -30 should be the P/Ns for the static inverters installed in accordance with the requirements in the second supplemental NPRM. FedEx Express adds that combining Groups 1 and 2 into one group would accomplish this task. \n\n\tWe agree with the commenters' requests and provide the following explanation. As noted previously, Boeing has issued Special Attention Service Bulletin 757-24-0110, Revision 1, dated August 6, 2009. The effectivity specified in Revision 1 is changed to move airplanes from Group 2 to Group 1, and to remove the Group 2 work instructions by combining Group 2 work instructions with Group 1. The work instructions specified in Revision 1 also add an inspection for certain static inverter part numbers that allows for installation of static inverters having P/Ns S282T004-2, -3, -4, -25, -28, and -30. Inspection of the static inverter P/Ns will prevent unnecessary replacement of approved static inverters. We have changed the applicability in paragraph (c) of this AD to identify Revision 1 of Boeing Special Attention Service Bulletin 757-24-0110. \n\nRequest To Include Revised Service Information \n\n\tAAL states that it found a discrepancy in Figure 1 of Boeing Special Attention Service Bulletin 767-24-0160, dated June 30, 2005 (referred to in the second supplemental NPRM), and asks that this service bulletin be revised to correct the discrepancy. AAL adds that the discrepancy is in Figure 1, which specifiesan inspection of the static inverter on Groups 1 and 3 airplanes. Figure 2 also contains an error which specifies the actions are applicable to Group 3 airplanes. However, Group 2 airplanes are not identified in either of these figures. AAL also notes that in Boeing Service Message 1-1156909141-2, Boeing specifies that static inverters having P/Ns S282T004-2, -3, -4 are acceptable for installation across the Model 757 airplane fleet since the Model 767 airplane fleet uses the same static inverter. \n\n\tWe acknowledge the commenter's concern and agree that the error in Figure 1 of Boeing Special Attention Service Bulletin 767-24-0160, dated June 30, 2005, should be corrected in a revision; but we do not consider that delaying the final rule until after the release of a future revision is warranted. The original issue of Boeing Special Attention Service Bulletin 767-24-0160 includes sufficient information to accomplish the modification of the static inverter. However, we have added new paragraph (g) to this AD to exclude Group 2 airplanes that have a static inverter with part number S282T004-2, S282T004-3, or S282T004-4, from the modification requirement. We have re-identified subsequent paragraphs accordingly. \n\nRequest To Change Cost Impact Section \n\n\tAAL states that the cost estimate for material and labor necessary for accomplishing the modification on its airplanes is more than the estimate in the second supplemental NPRM. \n\n\tWe infer that AAL is asking that the work hours and cost specified in the Cost Impact section of the AD be increased. We do not agree. The cost information below describes only the direct costs of the specific actions required by this AD. Based on the best data available, the manufacturer provided the number of work hours (up to 2 hours, depending on airplane configuration) necessary to do the required actions. This number represents the time necessary to perform only the actions actually required by this AD. We recognize that, in doing the actions required by an AD, operators might 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, time necessary for planning, or time necessitated by other administrative actions. Those incidental costs, which might vary significantly among operators, are almost impossible to calculate. We have not changed the AD in this regard. \n\nRequest for Clarification \n\n\tCargolux Airlines International S.A. states that it has followed the history of the proposed rule since 2003, and is not aware of any new event reported on the static inverters since that time. Cargolux asks for clarification that only one airplane was affected prior to 2003, and no airplanes were affected after 2003. Cargolux also asks for the number of occurrences of R170 resistors overheating, and the number of units manufactured. \n\n\tWe acknowledge the commenter'srequest and provide the following clarification. Prior to 2003 there were 39 static inverter failures on 39 airplanes; since 2003 there have been 15 inverters on 15 airplanes that failed due to the R170 resistor overheating, and approximately 9,400 units have been manufactured. \n\nExplanation of Additional Paragraph in the Final Rule \n\n\tWe have added a new paragraph (d) to this AD to provide the Air Transport Association (ATA) of America code 24: Electrical power. This code is added to make this AD parallel with other new AD actions. We have reidentified subsequent paragraphs accordingly. \n\nConclusion \n\n\tWe have carefully reviewed the available data, including the comments received, and determined that air safety and the public interest require adopting the AD with the changes described previously. We have determined that 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 approximately3,856 airplanes of the affected design in the worldwide fleet. The FAA estimates that 1,882 airplanes of U.S. registry will be affected by this AD. The following table provides the estimated costs for U.S. operators to comply with this AD. \n\nEstimated Costs\n\nAction\nWork hours\nAverage labor rate per hour\nParts\nCost per airplane\nNumber of U.S.-registered airplanes\nFleet cost\nModification\nUp to 2 hours, depending on airplane configuration\n$80\n$0\nBetween $80 and $160\n1,882\nUp to $301,120\n\n\tThe cost impact figure discussed above is based on assumptions that no operator has yet accomplished any of the proposed requirements of this AD action, and that no operator would accomplish those actions in the future if the AD were not adopted. The cost impact figures discussed in AD rulemaking actions represent only the \ntime 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\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 Regulatory Flexibility Act. \n\n\tWe prepared a regulatory evaluation of the estimated costs to comply with this AD and placed it in the AD docket. 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 Federal Aviation Administration (FAA) amends Sec. 39.13 by adding the following new airworthiness directive (AD):