Discussion \n\n\n\tPATS Aircraft (holder of Supplemental Type Certificates (STC) SA83NE, SA1078NE, SA725NE, ST00040NY, and ST01337NY) notified us that it has determined that Boeing Model 737-200, -300, -400, and -500 series airplanes equipped with an auxiliary fuel tank system installed by STC SA83NE, SA1078NE, SA725NE, ST00040NY, or ST01337NY, have insufficient structural strength in the auxiliary fuel tank support structure. The STC holder has also determined that the cargo barriers have insufficient structural strength if subjected to emergency landing loads with the cargo load weights listed in the existing airplane flight manual (AFM) supplements. These determinations were based on a new structural analysis resulting from a re-evaluation of the floor structure and cargo barriers conducted by the STC holder. Structural overload of the auxiliary fuel tank support structure could cause the floor beams to fail, resulting in damage to the primary flight controls and the auxiliary power unit (APU) fuel lines that pass through the floor beams, and consequent loss of control of the airplane. Structural overload of the cargo barriers could cause the barriers to fail, allowing the cargo to shift, resulting in possible damage to the auxiliary fuel tanks, residual fuel leakage, and consequent increased risk of a fire. \n\nRelevant Service Information \n\n\n\tWe have reviewed the PATS Aircraft service bulletins listed in the table below. These service bulletins describe procedures for deactivating the auxiliary fuel system, which, for certain airplanes, includes installing new cargo loading weight limit and "INOP" placards, depending on the airplane configuration. The service bulletins also describe procedures for venting any residual air pressure from the auxiliary fuel tanks following each flight. For certain airplanes, paragraph I.D. ("Description") of the service bulletins describes limiting the maximum cargo weight (as specified on the newcargo weight placards) in the forward and aft cargo compartments, as applicable, depending on the STC configuration of the airplane. \n\n\n\t\t\t\tTable - Applicable Service Bulletins\n\nFor Model -\nHaving serial number(s) (S/N) -\nSTC -\nUse PATS Aircraft Service Bulletin -\n737-200 series airplanes\n22431 and 22628\nSA83NE\nSA83NE-28-SB-002_IR, dated June 7, 2006\n737-200 series airplanes\n22600\nSA1078NE\nSA1078NE-28-SB-005_A, Revision A, dated June 21, 2006\n737-200, -300, -400, and -500 series airplanes\n23800, 22620, 23124, 23468, 26333, 26307, 27456, 27426, and 27906\nSA725NE\nSA725NE-28-SB-007_B, Revision B, dated July 27, 2006\n737-500 series airplanes\n24970\nST00040NY\nST00040NY-28-SB-003_IR, dated June 7, 2006\n737-500 series airplanes\n28866\nST01337NY\nST01337NY-28-SB-002_IR, dated June 7, 2006\n\n\n\tWe have also reviewed the PATS Aircraft AFM supplements to the Limitations section of the applicable Boeing AFMs, which are listed in the following table. These AFM supplementsprovide revised maximum cargo weight limits. \n\n\t\tTable - AFM Supplements for Revised Maximum Cargo Weight Limits\n\nFor Model -\nHaving S/N(s) -\nSTC -\nSTC configuration(s) - \nUse PATS Aircraft AFM Supplement - \n737-200 series airplanes\n23124\nSA725NE\n2\n148, dated May 31, 2006\n737-200 series airplanes\n22620 and 23468\nSA725NE\n3 and 8\n149, Revision A, dated August 11, 2006\n737-200 series airplanes\n22600\nSA1078NE\n3 Tank forward\n152, dated May 31, 2006\n737-200 series airplanes\n22431 and 22628\nSA83NE\n2\n155, dated May 31, 2006\n737-300 series airplanes\n27456, 26307, and 26333 \nSA725NE\n1 and 6\n147, dated May 31, 2006\n737-300 series airplanes\n23800\nSA725NE\n7\n151, dated May 31, 2006\n737-400 and -500 series airplanes\n27906 and 27426\nSA725NE\n4 and 5\n150, dated May 31, 2006\n737-500 series airplanes\n28866\nST01337NY\nAft 3-tank\n153, Revision A, dated August 3, 2006\n737-500 series airplanes\n24970\nST00040NY\n7\n154, dated May 31, 2006\n\n\nFAA's Determination and Requirements of This AD \n\n\n\tThe unsafe condition described previously is likely to exist or develop on other airplanes of the same type design. For this reason, we are issuing this AD to prevent structural overload of the auxiliary fuel tank support structure, which could cause the floor beams to fail and resultant damage to the primary flight controls and the APU fuel lines that pass through the floor beams, and consequent loss of control of the airplane. We are also issuing this AD to prevent structural overload of the cargo barriers, which could cause the barriers to fail, allowing the cargo to shift, resulting in possible damage to the auxiliary fuel tanks, residual fuel leakage, and consequent increased risk of a fire. This AD requires accomplishing the actions specified in the service information described previously, except as discussed under "Difference Between the AD and the Service Bulletins." \n\nDifference Between the AD and the Service Bulletins \n\n\n\tThe PATS Aircraft service bulletins do not specify a compliance time for deactivating the auxiliary fuel system or implementing the new cargo weight limits. In developing an appropriate compliance time for those actions in this AD, we considered the degree of urgency associated with the subject unsafe condition, the average utilization of the affected fleet, and the time necessary to perform the deactivation (3 work hours) and AFM revision. In light of all of these factors, we find that a 30-day compliance time represents an appropriate interval of time for affected airplanes to continue to operate without compromising safety. \n\nInterim Action \n\n\n\tWe consider this AD interim action. If final action is later identified, we may consider further rulemaking then. \n\nFAA's Determination of the Effective Date \n\n\n\tSince an unsafe condition exists that requires the immediate adoption of this AD, we have found that notice and opportunity for public comment before issuing this AD are impracticable, and that good cause exists to make this AD effective in less than 30 days. \n\nComments Invited \n\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 in the ADDRESSES section. Include "Docket No. FAA-2006- 25746; Directorate Identifier 2006-NM-151-AD" at the beginning of your comments. We specifically invite comments on the overall regulatory, economic, environmental, and energy aspects of the AD that might suggest a need to modify it. \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 that 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 may review the DOT's complete Privacy Act Statement in the Federal Register published on April 11, 2000 (65 FR 19477-78), or you may visit http://dms.dot.gov. \n\n\n\nExamining the Docket \n\n\n\tYou may examine the 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 DOT street address stated in the ADDRESSES section. Comments will be available in the AD docket shortly after the Docket Management System receives them. \n\nAuthority for This Rulemaking \n\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 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\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\tFor the reasons discussed above, I certify that the regulation: \n\t1. Is not a "significant regulatory action" under Executive Order 12866; \n\t2. Is not a "significant rule" under the DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and \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\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\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\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):