A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) by superseding AD 98-25-51, amendment 39-10952 (63 FR 70637, December 22, 1998), which is applicable to certain Airbus Model A300-600 and A310 series airplanes, was published in the Federal Register on April 14, 2003 (68 FR 17893). The action proposed to require deactivating both thrust reversers and revising the airplane flight manual (AFM) to ensure safe and appropriate performance during certain takeoff conditions. \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 Proposed AD \n\n\tOne commenter supports the AD as proposed. Air Transport Association (ATA) reports that its members generally support the intent of the rulemaking. \n\nRequest To Extend Compliance Time \n\n\tOne commenter, an operator, is concerned that the proposed 1-year compliance time would result in grounded airplanes, and requests that the compliance time be extended from 12 months to 3 years. The operator reports that no thrust reversers have deployed in flight, uncommanded, on its affected airplanes. The operator notes that all of its PW4000- powered A310/A300-600 airplanes and engine spares have been modified, but hardware changes were often needed for configuration compatability. Further, because the modification was done during the 180-day passenger-to-freighter conversion process, the hardware changes were handled within the scheduled time with no unscheduled downtime. However, unlike its PW4000-powered fleet, the operator states that all of its PW JT9D-7R4-powered airplanes are in operational service and are to be modified during a shorter maintenance visit. The operator concludes that a 3-year compliance time for the modification would minimize the economic impact on operators' without compromising safety, since the repetitive inspections required by AD 98-25-51 would still be in force until the modification is done. \n\n\tWe partially agree with the request. We have previously issued an alternative method of compliance (AMOC) for the requirements of AD 98- 25-51. The AMOC, based on a method developed cooperatively between the airframe and engine manufacturers, allows the thrust reversers to be reactivated in accordance with an FAA-approved program of parts replacement and repetitive inspections. However, because of the severe consequences associated with an in-flight thrust reverser deployment, we cannot increase the compliance time to 3 years, as the operator requests. Nonetheless, to avoid airplanes being grounded until the modification can be done, we agree to extend the compliance time for the modification from 1 year to 18 months. We have determined that this extension will not adversely affect safety. Paragraph (c) of this final rule has been changed accordingly. We have advised the Direction Generale de l'Aviation Civile (DGAC), which is the airworthiness authority for France, of this change. \n\nRequest To Ensure Compliance Time After a Certain Date \n\n\tOne commenter, the manufacturer, considers the proposed compliance time appropriate, but requests a deadline not earlier than June 30, 2004, to correspond to the compliance time mandated by French airworthiness directive 2001-523(B), dated October 31, 2001. In light of the compliance time discussion above, the new compliance time for this AD will not take effect until after June 30, 2004. \n\nRequest To Refer to AOTs \n\n\tOne commenter, the manufacturer, states that Airbus All Operators Telex (AOT) 78-09 (currently at Revision 3, dated June 29, 1999) has been considered as an approved AMOC for the requirements of AD 98-25-51 to allow the thrust reversers to be reactivated. The manufacturer notes that the proposed AD does not refer to Airbus AOT 78-09, or to AOT 78- 10, which is referenced in AOT 78-09 and provides details for an exhaustive checkof the thrust reverser electrical circuit as part of the reactivation control program/reinforcement against power supply loss. We infer that the manufacturer requests that we revise the proposed AD to refer to these AOTs and give credit for paragraphs (a) and (b) of the proposed AD for airplanes on which the actions specified in AOT 78-09 have been done. \n\n\tWe partially agree with the request; however, the actions specified in AOT 78-09 alone are insufficient to address the unsafe condition. We approved the AMOC to AD 98-25-51 to allow reactivation of the thrust reversers in accordance with Revision 3 of Airbus AOT 78-09, but the AOT does not contain all the AMOC requirements. The referenced AMOC involves certain tests, checks, maintenance actions, and parts changes to each individual thrust reverser. The AMOC is conditional on a stow- latching minimum-force check being done after the serialized selector solenoid valve is installed. That check is not specified in the AOT. We agree that most of the thrust reverser reactivation program is defined in Airbus AOT 78-09, Revision 3; however, additional actions are included in the complete AMOC, so the accomplishment of the AOT actions alone cannot be considered an approved AMOC to this AD. In addition, the reference to AOT 78-10--through AOT 78-09--is sufficient for purposes of this AD. However, we have added a new Note 3 in this final rule to clarify the purpose of the AMOC and its relationship to the AOT, and reidentified subsequent notes. \n\nRequest To Revise Description of Unsafe Condition \n\n\tOne commenter, the manufacturer, finds that the term "unsafe condition" is inappropriately used in the preamble to the proposed AD. The manufacturer takes exception to the characterization of the modification as being necessary to address the unsafe condition. The manufacturer asserts that the reactivation program restores the level of safety required to satisfy the original design requirements for the thrust reverser sytem, and adds that the modification was developed to add a supplementary level of protection against inadvertent deployment of the thrust reversers.\n \n\tWe do not agree that the term "unsafe condition" is inappropriate as it is used in the proposed AD. The requirements of AD 98-25-51 (deactivating both thrust reversers and revising the airplane flight manual) are intended to prevent in-flight deployment of the thrust reversers and consequent reduced controllability of the airplane. The subsequently issued AMOC (discussed previously) was intended as an interim action only. Although we recognize the improved reliability provided to the thrust reverser system by the reactivation program, we have determined that the basic two-line-of-defense architecture does not adequately address the system's vulnerability to damage and long- term maintainability. Therefore, the modification is necessary to prevent the identified unsafe condition. No change to the final rule is necessary regarding this issue. \n\nRequest To Revise Estimated Costs \n\n\tAirbus reports that the estimated costs associated with the proposed modification have been revised. We have revised the Cost Impact section accordingly in this final rule. \n\nRequest To Include Certain Parts Costs \n\n\tOne commenter, an operator, states that the proposed AD understates the estimated costs associated with the modification because certain parts specified in Pratt & Whitney Service Bulletins PW7R4 A78-179 and JT9D-7R4-A73-80 were not considered. The operator asserts that the proposed AD accounts only for the labor hours, not the parts costs, associated with the actions specified in those service bulletins. The commenter provides its actual costs incurred to modify one of its airplanes, and compares those costs to the cost estimates of the proposed AD. \n\n\tWe agree that the parts costs may be underestimated in the proposed AD. While the commenter's total parts cost was $114,622 with Pratt & Whitney Service Bulletin PW7R4A78-179 included, we estimate that the parts costs could be as high as $120,000, depending on the airplane configuration. We have revised the Cost Impact section accordingly in this final rule. \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\nChanges to 14 CFR Part 39/Effect on the AD \n\n\tOn July 10, 2002, the FAA issued a new version of 14 CFR part 39 (67 FR 47997, July 22, 2002), which governs the FAA's airworthiness directives system. The regulation now includes material that relates to altered products, special flight permits, and AMOCs. However, for clarity and consistency in this final rule, we have retained the language of the proposed AD regarding that material.Change in Labor Rate \n\n\tWe have reviewed the figures we have used over the past several years to calculate AD costs to operators. To account for various inflationary costs in the airline industry, we find it necessary to increase the labor rate used in these calculations from $60 per work hour to $65 per work hour. The cost impact information, below, reflects this increase in the specified hourly labor rate. \n\nCost Impact \n\n\tThis AD affects about 38 airplanes of U.S. registry. The FAA provides the following cost estimates for the actions specified in this AD: \n\n\n\n\tOperators should note that, if the actions specified in Pratt & Whitney Service Bulletins PW7R4 A78-179 and JT9D-7R4-A73-80 have not been previously accomplished, the total parts costs associated with the required modification could be as high as $120,000 per airplane. \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\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.\nAdoption of the Amendment \n\nAccordingly, 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\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. Section39.13 is amended by removing amendment 39-10952 (63 FR 70637, December 22, 1998), and by adding a new airworthiness directive (AD), amendment 39-13726, to read as follows: