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 Model DC-9-30, DC-9-40, and DC-9-50 series airplanes. That NPRM was published in the Federal Register on August 12, 2009 (74 FR 40525). That NPRM proposed to require inspecting to determine the part numbers of the forward and aft auxiliary tank fuel boost and transfer pump conduit/conduit assembly and conduit assembly electrical connector, as applicable, and corrective actions if necessary. \n\nComments \n\n\tWe gave the public the opportunity to participate in developing this AD. We considered the comment received from the commenter. Northwest Airlines (NWA) concurs with the intent of the NPRM. \n\nRequest To Delay Issuance of the Final Rule Until the Revised Service Bulletin Is Issued, Reviewed, and Commented On by Operators \n\n\tNWA states that operators should have the opportunity to review andcomment on the revised service bulletin prior to any final rule decision. NWA explains that there are omissions regarding airplane effectivity and part number discrepancies in Boeing Service Bulletin DC9-28-227, dated April 23, 2009. NWA notes that Boeing was notified of these issues, and that Boeing concurs with the effectivity problems and noted the differences in the associated wiring diagrams and drawings that affect the part numbers. NWA asserts that Boeing has acknowledged that Boeing Service Bulletin DC9-28-227, dated April 23, 2009, needs to be revised. \n\tNWA believes that certain airplanes were delivered with a 780 gallon forward fuselage supplemental tank but without a 780 gallon aft fuselage supplemental tank, and that these airplanes may not be addressed as a group in Boeing Service Bulletin DC9-28-227, dated April 23, 2009. \n\tNWA also believes that certain airplanes identified as Group 1 in Boeing Service Bulletin DC9-28-227, dated April 23, 2009, have the same conduit assembly part number as other airplanes. NWA believes that these airplanes cannot use the same conduit assembly because conduit assemblies have specified wire numbers as per certain drawings. \n\tFrom these statements, we infer that NWA requests that we delay issuing the AD until Boeing Service Bulletin DC9-28-227, dated April 23, 2009, is revised and released. We do not agree to delay issuing the final rule until a revised service bulletin is reviewed and commented on by operators. The airplanes that NWA believes were delivered with a 780 gallon forward fuselage supplemental tank but without a 780 gallon aft supplemental fuselage tank, and that may not be addressed as a group in Boeing Service Bulletin DC9-28-227, dated April 23, 2009, are not included in the effectivity of that service bulletin because they already had the acceptable conduit assembly installed prior to the time of delivery. Also, Boeing Service Bulletin DC9-28-227, dated April 23, 2009, reflects the correct conduit part numbers installed prior to the time of airplane delivery; therefore, the content in Boeing Service Bulletin DC9-28-227, dated April 23, 2009, is correct. We have confirmed with Boeing that Boeing Service Bulletin DC9-28-227, dated April 23, 2009, does not need to be revised regarding these issues. We have not changed the AD in this regard. \n\tIf a new revision to the service information is published, under the provisions of paragraph (h) of the final rule, we will consider requests for alternative methods of compliance (AMOCs) if sufficient data are submitted to substantiate that the change would provide an acceptable level of safety. We have not changed the AD in this regard. \n\nRequest for a Clarification Statement Acknowledging Post-Production Removal of Auxiliary Fuel Tank(s) \n\n\tNWA states that the final rule should include a clarification statement for paragraph (g) of the NPRM that acknowledges post- production removal of an auxiliary fuel tank, which releases the operator from those requirements of Boeing Service Bulletin DC9-28-227, dated April 23, 2009, that are no longer applicable. NWA explains that Boeing Service Bulletin DC9-28-227, dated April 23, 2009, does not address the issue of a removed auxiliary fuel tank and that the equipment effectivity list quantifies airplane groups at the time of production and does not address post-production modifications to the airplane. NWA acknowledges that an auxiliary fuel tank, which was installed at the time of production, may have been removed by operators for a variety of reasons. NWA asserts that the removal of the auxiliary fuel tank and thereby the fuel boost or transfer pump conduit assembly connectors removes the unsafe condition specified in paragraph (e) of the NPRM, although the language specified in paragraph (g) of the NPRM will still require operators to request an AMOC for removed auxiliary fuel tanks. \n\tWe agree. If the auxiliary fuel tank(s) has been removed, thereby removing the fuel boost or transfer fuel pump conduit assembly connectors, the unsafe condition is removed as well. We have revised paragraph (g) of the final rule to account for auxiliary fuel tank(s) that have been removed. \n\nExplanation of Change 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 comment 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 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 137 airplanes of U.S. registry. We also estimate that it takes up to 8 work-hours per product to comply with this AD. The average labor rate is $85 per work-hour. Based on these figures, we estimate the cost of this AD to the U.S. operators to be $93,160, or $680 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\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 proceduresthe 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\tFor the reasons discussed above, I certify that this AD: \n\t(1) Is not a "significant regulatory action'' under Executive Order 12866, \n\t(2) Is not a "significant rule'' under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979), and \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.You 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\t\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: