Examining the Docket \n\n\tYou may examine the airworthiness directive (AD) docket on the Internet at http://dms.dot.gov or in person at the Docket Management Facility office between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The Docket Management Facility office (telephone (800) 647-5227) is located on the plaza level of the Nassif Building at the street address stated in the ADDRESSES section. \n\nDiscussion \n\n\tThe FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 to include an AD that would apply to certain Boeing Model 737-300, -400, -500, -600, -700, -800 and -900 series airplanes; and Model 757-200 and -300 series airplanes. That NPRM was published in the Federal Register on July 13, 2006 (71 FR 39593). That NPRM proposed to require modifying the activation mechanism in the chemical oxygen generator of each passenger service unit (PSU). \n\nComments \n\n\tWe provided the public the opportunity to participate in the development of this AD. We have considered the comments received. \n\nSupport for the NPRM \n\n\tBoeing and AirTran support the NPRM. \n\nRequest To Change Compliance Time \n\n\tThe Air Transport Association (ATA), on behalf of its member, Delta Airlines, asks that the compliance time for accomplishing the modification be changed from 60 months to 72 months. Delta states that this would better align with airplane heavy maintenance visits. \n\n\tWe do not agree with ATA and Delta. The commenters provided no technical justification for revising this compliance time. Chemical oxygen generators failing to activate during in-flight decompression events is a significant safety issue; therefore, we have determined that the proposed 60-month compliance time is warranted. This determination is based on the effectiveness of the modification and the fact that failure of the activation mechanism of the chemical oxygen generator could result in the unavailability of supplemental oxygen and possible incapacitation of passengers and cabin crew during an in- flight decompression. In developing an appropriate compliance time for this AD, we considered those safety issues, as well as the manufacturer recommendations, the availability of necessary repair parts, and the practical aspect of accomplishing the required modification within an interval of time that corresponds to the normal maintenance schedules of most affected operators. In light of these factors, we have determined that the 60-month initial compliance time, as proposed, is appropriate. We do not find it necessary to change the AD in this regard. \n\nRequest To Publish Service Information/Incorporate by Reference in NPRM \n\n\tThe Modification and Replacement Parts Association (MARPA) states that ADs are based on service information that originates from the type certificate holder or its suppliers. MARPA adds that manufacturers' service documents are privately authored instruments, generally having copyright protection against duplication and distribution. MARPA states that when a service document is incorporated by reference into a public document, such as an AD, pursuant to 5 U.S.C. 552(a) and 1 CFR part 51, it loses its private, protected status and becomes a public document. MARPA notes that if a service document is used as a mandatory element of compliance, it should not simply be referenced, but should be incorporated by reference. MARPA believes that \npublic laws, by definition, should be public, which means they cannot rely upon private writings for compliance. MARPA adds that the legal interpretation of a document is a question of law, not of fact; therefore, unless the service document is incorporated by reference, it cannot be considered. MARPA is concerned that failure to incorporate essential service information could result in a court decision invalidating the AD. \n\n\tMARPA also states that service documents incorporated by reference should be made available to the public by publication in the Docket Management System (DMS), keyed to the action that incorporates those documents. MARPA notes that the stated purpose of the incorporation by reference method is brevity, to keep from expanding the Federal Register needlessly by publishing documents already in the hands of the affected individuals. MARPA adds that, traditionally, "affected individuals'' means aircraft owners and operators, who are generally provided service information by the manufacturer. MARPA adds that a new class of affected individuals has emerged, since the majority of aircraft maintenance is now performed by specialty shops instead of aircraft owners and operators. MARPA notes that this new class includes maintenance and repair organizations, component servicing, and/or servicing alternatively certified parts under section 21.303 ("Replacement and modification parts'') of the Federal Aviation Regulations (14 CFR 21.303). MARPA notes that the concept of brevity is now nearly archaic as documents exist more frequently in electronic format than on paper. Therefore, MARPA asks that the service documents deemed essential to the accomplishment of the NPRM be incorporated by reference into the regulatory instrument and published in DMS. \n\n\tWe acknowledge MARPA's requests. The Office of the Federal Register (OFR) requires that documents that are necessary to accomplish the requirements of the AD be incorporated by reference during the final rule phase of rulemaking. This final rule incorporates by reference the documents necessary for the accomplishment of the requirements mandated by this AD. Further, we point out that while documents that are incorporated by reference do become public information, as noted by the commenter, they do not lose their copyright protection. For that reason, we advise the public to contact the manufacturer to obtain copies of the referenced service information. \n\n\tIn regard to MARPA's request to post service bulletins on the Department of Transportation's DMS, we are currently in the process of reviewing issues surrounding the posting of service bulletins on the DMS as part of an AD docket. Once we have thoroughly examined all aspects of this issue and have made a final determination, we will consider whether our current practice needs to be revised. No change to the AD is necessary in response to these comments. \n\nRequest To Change Costs of Compliance Section \n\n\tATA, on behalf of its member, Delta Airlines, states that since the NPRM is written against airplanes and not individual PSUs, it should reflect the cost per airplane. Delta states that its approximate cost per Model 757 airplane is over $10,000; the total cost for its Model 757 fleet is in excess of $350,000. Delta adds that for its Model 737- 800 fleet, 71 airplanes are affected, each currently having 54 PSUs installed. Delta states that the approximate cost per Model 737-800 airplane is over $6,000; the total cost for its Model 737-800 fleet is over $440,000.We agree with the commenters. We have provided the approximate number of PSUs per airplane that are necessary to do the modification in the Costs of Compliance section below. \n\nClarify Availability of Parts \n\n\tContinental Airlines has concerns regarding the availability of Boeing's material stock (i.e., service bulletin kits), as well as those ancillary PSU parts which may be needed during the modification. \n\n\tWe infer that Continental wants verification of available parts. We have confirmed with Boeing that an ample number of required parts will be available to modify the U.S. fleet within the proposed compliance time. In light of this fact, we do not find it necessary to change the AD in this regard. \n\nConclusion \n\n\tWe have carefully reviewed the available data, including the comments received, and determined that air safety and the public interest require adopting the AD as proposed. \n\nCosts of Compliance \n\n\tThere are about 3,283 airplanes of the affected design in the worldwide fleet. This AD affects about 815 airplanes of U.S. registry. The following table provides the estimated costs for U.S. operators to comply with this AD. The cost of the modification depends on the number of PSUs per airplane. The cost to modify all airplanes ranges from $4,342,320 up to $12,506,175. \n\n\tEstimated Costs \n\n\nAirplane Model\nWork hours\nNumber of PSUs \nAverage labor rate per hour\nParts cost per PSU\nCost per airplane\n737-500 and -600\n1 per PSU\nBetween 36 and 40\n$80\nBetween $68 and $75\nBetween $5,328 and $6,200\n737-300 and -700\n1 per PSU\nBetween 40 and 50\n$80\nBetween $68 and $75\nBetween $5,920 and $7,750\n737-400 and -800\n1 per PSU\nBetween 43 and 63\n$80\nBetween $68 and $75\nBetween $6,364 and $9,765\n737-900\n1 per PSU\nBetween 58 and 63\n$80\nBetween $68 and $75\nBetween $8,584 and $9,765\n757-200\n1 per PSU\nBetween 60 and 80\n$80\nBetween $68 and $75\nBetween $8,880 and $12,400\n757-300\n1 per PSU\nBetween 70 and 99\n$80\nBetween $68and $75\nBetween $10,360 and $15,345\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 this AD: \n\n\t(1) Is not a "significant regulatory action'' 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\tWe prepared a regulatory evaluation of the estimated costs to comply with this AD and placed it in the AD docket. 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 Federal Aviation Administration (FAA) amends Sec. 39.13 by adding the following new airworthiness directive (AD):