Discussion \n\n\tWe issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 to include an airworthiness directive (AD) that would apply to certain Boeing Model 777-200 series airplanes. That NPRM was published in the Federal Register on May 7, 2009 (74 FR 21284). That NPRM proposed to require installing a new insulation blanket on the latch beam firewall of each thrust reverser (T/R) half. \n\nRelevant Service Information \n\n\tSince we issued the NPRM, we have reviewed Boeing Alert Service Bulletin 777-78A0066, Revision 2, dated April 8, 2010. Boeing Service Bulletin 777-78A0066, Revision 1, dated March 12, 2009, was referred to in the original NPRM as the appropriate source of service information for accomplishing the proposed actions. No more work is necessary for airplanes on which Revision 1 of this service bulletin was used for doing the actions. Boeing Alert Service Bulletin 777-78A0066, Revision 2, dated April 8, 2010, moves certain airplanes to Group 1, and contains minor editorial changes. \n\n\tWe have revised paragraphs (c) and (g) of this AD to refer to Revision 2 of Boeing Alert Service Bulletin 777-78A0066, Revision 2, dated April 8, 2010, and paragraph (h) to add credit for accomplishing the specified actions in accordance with Boeing Service Bulletin 777- 78A0066, Revision 1, dated March 12, 2009. \n\nComments \n\n\tWe gave the public the opportunity to participate in developing this AD. We considered the comments received. \n\nRequest To Clarify Description of Unsafe Condition \n\n\tBoeing asked that we clarify the description of the unsafe condition by removing the words "or strut'' from the identified description. Boeing stated that the unsafe condition, as currently written, is not correct. Boeing did not provide the reason that the description is not correct. \n\n\tWe disagree that the description of the unsafe condition should be clarified by removing "or strut'' from the description. A fire in the lowerlatch beam area that burns through an inadequate firewall may propagate into the strut. We have made no change to the AD in this regard. \n\nRequest To Clarify Applicability \n\n\tJapan Airlines International (JALI) asked for clarification of the applicability specified in the NPRM. JALI stated that the applicability specifies Model 777-200 series airplanes identified in Boeing Service Bulletin 777-78A0066, Revision 1, dated March 12, 2009. JALI noted that the service bulletin specifies its effectivity as delivered condition, and the proposed rule is considered to be applicable to each T/R half that has been installed on airplanes with the applicable serial numbers. JALI added that the T/R half is a replaceable line unit and the installed airplane and/or engine position will be changed from the delivered condition in the future; the T/R half that is not necessary for doing the requirements in the NPRM may be installed on an airplane identified in the applicability. \n\n\tJALI stated that, in light of these factors, it is not clear whether compliance with the specified actions has been met. JALI asked that we clarify the applicability either to note that the NPRM does not apply to airplanes on which a T/R is installed with a design change known as "Commonality T/R,'' which is common to Model 777-300 series airplanes, or to change the airplane serial numbers to T/R part numbers or serial numbers. \n\n\tWe do not agree that the effectivity specified in Boeing Service Bulletin 777-78A0066, Revision 1, dated March 12, 2009, could apply to an airplane that has an incorrect T/R configuration because the T/R is a line replaceable unit and is not identified in the effectivity. The manufacturer has informed us that for airplanes not identified in Revision 1 or Revision 2 of this service bulletin, the specified T/R configuration is not an approved configuration. We have determined that it is not possible to install the T/R with the unsafe condition on airplanes that were manufactured after line number 413; therefore, the AD does not apply to those airplanes. We have made no change to the AD in this regard. \n\nRequest To Include Part Number and Compliance Status for T/R Halves \n\n\tJALI asked that we include the applicable part numbers of each T/R half and add a procedure in the NPRM to reidentify the parts as the part numbers change. JALI added that this change to the NPRM would include indicating the service bulletin number or adding a suffix to the serial number on the ID plate for each T/R so operators can easily track the applicable part number and compliance status for each T/R half. JALI noted that there is nothing identified in the service bulletin, and the only way for operators to identify the applicable part number and compliance status of each T/R half is by reviewing the maintenance record. JALI added that this would be burdensome for operators. \n\n\tWe agree that the part numbers of each T/R half should be included in the service information anda procedure should be added to reidentify the parts as the part numbers change. Boeing Alert Service Bulletin 777-78A0066, Revision 2, dated April 8, 2010, includes the part marking provision. As stated previously, we have revised paragraph (c) of this AD (i.e., the AD applicability) to refer to Revision 2 of this service bulletin. Therefore, we have made no further change to the AD in this regard. \n\nExplanation of Changes Made to This AD \n\n\tWe have revised this AD to identify the legal name of the manufacturer as published in the most recent type certificate data sheet for the affected airplane models. \n\nConclusion \n\n\tWe reviewed the relevant data, considered the comments received, and determined that air safety and the public interest require adopting the AD with the changes described previously. We also determined that these changes will not increase the economic burden on any operator or increase the scope of the AD. \n\nExplanation of Change to Costs of Compliance \n\n\tSince issuance of the original NPRM, we have increased the labor rate used in the Costs of Compliance from $80 per work-hour to $85 per work-hour. The Costs of Compliance information, below, reflects this increase in the specified hourly labor rate. \n\nCosts of Compliance \n\n\tWe estimate that this AD affects 25 airplanes of U.S. registry. We also estimate that it will take about 7 work-hours per product to comply with this AD. The average labor rate is $85 per work-hour. Required parts will cost between $3,546 and $5,253 per product. Based on these figures, we estimate the cost of this AD to the U.S. operators to be between $103,525 and $146,200, or between $4,141 and $5,848 per product. \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\tThis 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 regulatoryaction'' 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\tYou can find our regulatory evaluation and the estimated costs of compliance in the AD Docket. \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 AD: