We have received reports of two separate incidents in which a Boeing Model 747-200 airplane equipped with a performance management system (PMS) had an unexpected autopilot disconnect induced by the passing of another airplane within 1,000 feet below the airplane while operating in reduced vertical separation minimum (RVSM) airspace. In both incidents, the PMS-equipped airplane lost 300 to 400 feet of altitude, causing it to come within approximately 650 feet of the other, lower aircraft (starting at 1,000 feet separation), and received a traffic collision and avoidance system (TCAS) resolution advisory (RA) with instructions to "climb, climb." \n\n\tThe PMS installed in certain Boeing Model 747 airplanes has an interlock that is activated with radar altitude. This interlock disconnects the autopilot upon receipt of a valid radar altitude signal of less than 2,500 feet. Because there is no means to accurately determine how the airplane is trimmed then using thePMS, it cannot be predicted which direction the airplane will fly or how far it will depart from an assigned altitude. Unexpected disconnect of the autopilot during operation in RVSM airspace, if not corrected or if manual control is not promptly established, may result in altitude deviation, and consequently, could lead to a possible mid-air collision or a near miss with aggressive evasive action (by either or both airplanes). Aggressive maneuvering at cruise altitudes and airspeeds could result in loss of control of the airplane and/or injury to passengers and crew. \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 unexpected disconnect of the autopilot during operation in RVSM airspace, which could result in altitude deviation causing a mid-air collision or a near miss with aggressive evasive action (by either or both airplanes). Aggressive maneuvering at cruise altitudes and airspeeds could cause the airplane to exceed its structural limits, which could result in loss of control of the airplane and/or injury to passengers and crew. This AD requires revising the airplane flight manual to prohibit operation of the autopilot/flight director in command mode with performance management system selected on the speed mode switch during cruise in RVSM airspace. \n\nInterim Action \n\n\tWe consider this AD interim action. If final action is later identified, we may consider further rulemaking then. \n\nChanges to 14 CFR Part 39/Effect on the AD Relating to Special Flight Permits \n\n\tOn July 10, 2002, we 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 alternative methods of compliance (AMOC). This material is included in part 39, except that the office authorized to approve AMOCs is identified in each individual AD. However, as amended, part 39 provides for the FAA to add special requirements for operating an airplane to a repair facility to do the work required by an airworthiness directive. For purposes of this AD, we have determined that such a special flight permit is prohibited. \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-2004-19815; Directorate Identifier 2004-NM-215-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\n\tWe are reviewing the writing style we currently use in regulatory documents. We are interested in your comments on whether the style of this document is clear, and your suggestions to improve the clarity of our communications with you. You can get more information about plain language at http://www/faa.gov/language and http://www.plainlanguage.gov.\n\nAuthority for This Rulemaking \n\n\tThe FAA's authority to issue rules regarding aviation safety is found in Title 49 of the United States Code. 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\tThis rulemaking is promulgated under the authority described in Subtitle VII, Part A, Subpart III, Section 44701, "General requirements." Under that section, the FAA is charged 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 AD. \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, 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\n§ 39.13 (Amended) \n\n2. The FAA amends § 39.13 by adding the following new airworthiness directive (AD):