We have received a report indicating an unsafe condition may exist on all McDonnell Douglas Model MD-10-10F, MD-10-30F, MD-11F, DC-10-10F, and DC-10-30F airplanes. Testing indicated a design discrepancy involving the operation of cargo smoke detectors manufactured by Meggitt Safety Systems Inc. (formerly Whittaker). During a test on Model MD-11F airplanes, 31 of 33 smoke detectors "locked up"--with no indication to the flightcrew--when the power was interrupted during power transfer from the auxiliary power unit (APU) to the engines. Investigation revealed that the smoke detector circuit does not meet power interrupt requirements during a power transfer between ground power, APU power, or main engine power sources on the airplane. The flightcrew is unaware of the inoperative smoke detector unless they test the smoke detection system. The smoke detector remains inoperative until power to the unit is cycled off and on. Under these conditions, the flightcrew would not be alerted in the event of a cargo compartment fire. \n\n\tThis lock-up condition may be produced by electrical power transfer on McDonnell Douglas Model MD-10-10F, MD-10-30F, MD-11F, DC-10-10F, and DC-10-30F airplanes. Therefore, all these airplanes may be subject to the identified unsafe condition. \n\nRelevant Service Information \n\n\tThe Boeing interim operating procedures (IOPs) listed in the following table advise the flightcrew of procedures for testing the smoke detection system after the last engine is started, if any Meggitt Model 602 smoke detector, part number (P/N) 8930, is installed. We have approved these procedures. \n\n\tService Information \n\n\nIOP- \nDated- \nTo the- \n2-212.1 \nNovember 9, 2004 \nBoeing MD-11 Flight Crew Operations Manual. \n2-34.1\nNovember 9, 2004 \nBoeing MD-10 Flight Crew Operations Manual. \n2-70 \nNovember 24, 2004 \nBoeing DC-10 Flight Crew Operating Manual. \n\n\n\tWe have reviewed Meggitt Safety Systems Service Information Letter (SIL)8930-26-01, dated November 8, 2004. The SIL provides procedures for replacing the P/N 8930 smoke detectors with modified smoke detectors. \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 identify and provide corrective action for a potentially inoperative smoke detector in the cargo compartment and ensure that the flightcrew is alerted in the event of a cargo compartment fire. This AD requires determining the part number(s) of the cargo smoke detectors and, if necessary, revising the Limitations section of the applicable airplane flight manual (AFM) to include the information in the IOPs described above. This AD also provides for the optional replacement of P/N 8930 smoke detectors with modified smoke detectors, which would terminate the AFM operational limitation. \n\nInterim Action \n\n\tWe consider this AD interim action because we may later require installation of the modified smoke detectors, which would terminate the operational limitation required by this AD. However, the planned compliance time for this action would allow enough time to provide notice and opportunity for prior public comment on the merits of the modification. \n\n\tIn addition, we are investigating potential problems with the subject smoke detectors on other transport category airplanes. We might consider further rulemaking to require modified smoke detectors on airplanes in addition to those affected by this AD. \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 bynotice 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-2005-20117; Directorate Identifier 2004-NM-248-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. Comments will be available in the AD docket shortly after the DMS receives them. 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 thatauthority 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, 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):