We have received two reports indicating failure of the thrust reversers during takeoff on certain Boeing Model 777-200 and -300 series airplanes. Investigation of both incidents revealed that the composite inner wall of the thrust reverser collapsed as a result of the migration of hot engine core compartment air underneath the insulation blankets, which overheated the composite structure. In the second incident, the outer sleeve of the primary nozzle had detached from the airplane and impacted an automobile on the ground, causing significant damage. Investigation of the first incident revealed that debris from the right engine had departed the airplane and was left on the runway. The flightcrew was not aware of the failure until arrival at the destination airport. Extensive damage was found to the inner wall of the thrust reverser, with large sections of the composite structure missing. Both failures occurred on airplanes that had each accumulated more than 6,000 total flight cycles. Subsequent inspection of the thrust reversers on airplanes that had accumulated between 6,000 and 9,000 total flight cycles indicated areas of delamination and annealed compression pads of the inner wall. The cause of the delamination is exposure to hot engine core compartment air, which can also cause thermal damage to the compression and drag link fittings. These conditions, if not corrected, could result in a rejected takeoff (RTO) and cause asymmetric thrust and consequent loss of control of the airplane during reverse thrust operation. If an RTO does not occur, these separated components could cause structural damage to the airplane or damage to other airplanes and possible injury to people on the ground. \n\nRelevant Service Information \n\n\tWe have reviewed Boeing Alert Service Bulletin 777-78A0059, dated February 24, 2005. The service bulletin describes procedures for one- time detailed and special detailed inspections of the thrust reversers, as applicable, for damage of the insulation blankets, inner wall, and compression and drag link fittings; and repair if necessary. The compliance times for the inspections range from 3 months to 24 months, depending on the number of total flight cycles on the airplane. The damage includes over-temperature conditions such as brown to blackened scorching and disbonding. The repair includes repair or replacement of any damaged insulation blankets with new blankets, and replacement of any damaged fittings with new fittings. The service bulletin recommends reporting the inspection schedule and results to Boeing. \n\n\tThe service bulletin also recommends prior or concurrent accomplishment of Boeing Special Attention Service Bulletin 777-78- 0060, dated February 24, 2005. That service bulletin describes procedures for applying sealant to the seams of the thrust reverser insulation blankets and around the HP3 ducts, and insulating and sealing the compression pad fittings. \n\n\tAccomplishing the actions specified in the service information is intended to adequately address the unsafe condition. \n\nFAA's Determination and Requirements of This AD \n\n\tThe unsafe condition described previously is likely to exist or develop on other airplanes of the same type design. Therefore, we are issuing this AD to prevent failure of a thrust reverser and adjacent components and their consequent separation from the airplane, which could result in a rejected takeoff (RTO) and cause asymmetric thrust and consequent loss of control of the airplane during reverse thrust operation. If an RTO does not occur, these separated components could cause structural damage to the airplane or damage to other airplanes and possible injury to people on the ground. This AD requires accomplishing the actions specified in the service information described previously, except as discussed under "Differences Between the AD and the Service Information." \n\nDifferences Between the AD and the Service Information \n\n\tYou should note that, although Boeing Alert Service Bulletin 777- 78A0059 describes procedures for reporting information to the manufacturer, this AD will not require those actions. We do not need this information. \n\n\tBoeing Alert Service Bulletin 777-78A0059 recommends prior or concurrent accomplishment of Boeing Special Attention Service Bulletin 777-78-0060; however, this AD requires accomplishment of that service bulletin immediately after each inspection to prevent further damage. \n\n\tThe service bulletins specify that you may contact the manufacturer for repair or replacement instructions, but this AD requires you to repair or replace in one of the following ways: \n\n\tUsing a method that we approve; or \n\n\tUsing data that meet the certification basis of the airplane that have been approved by an Authorized Representative for the Boeing Delegation Option Authorization Organization who has been authorized by the FAA to make those findings. \n\nFAA's Determination of the Effective Date \n\n\tAn unsafe condition exists that requires the immediate adoption of this AD; therefore, providing notice and opportunity for public comment before the AD is issued is impracticable, and good cause exists to make this AD effective in less than 30 days. \n\nComments Invited \n\n\tThis AD is a final rule that involves requirements that affect flight safety and was not preceded by notice and an opportunity for public comment; however, we invite you to submit any relevant written data, views, or arguments regarding this AD. Send your comments to an address listed under ADDRESSES. Include "Docket No. FAA-2005-20885; Directorate Identifier 2005-NM-050-AD" at the beginning of your comments. We specifically invite comments on the overall regulatory, economic, environmental, and energy aspects of the AD. We will consider all comments received by the closing date and may amend the AD in light of those comments. \n\n\tWe will post all comments we receive, without change, to http://dms.dot.gov , including any personal information you provide. We will also post a report summarizing each substantive verbal contact with FAA personnel concerning this AD. Using the search function of our docket Web site, anyone can find and read the comments in any of our dockets, including the name of the individual who sent the comment (or signed the comment on behalf of an association, business, labor union, etc.). You can review the DOT's complete Privacy Act Statement in the Federal Register published on April 11, 2000 (65 FR 19477-78), or you can visit http://dms.dot.gov. \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 the regulation: \n\n\t1. Is not a "significant regulatory action" under Executive Order 12866; \n\n\t2. Is not a "significant rule" under the DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and \n\n\t3. 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. 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):