AD 2001-13-23

This amendment adopts a new airworthiness directive (AD), applicable to certain Boeing Model 737-700 and -800 series airplanes, that requires inspections of certain tension bolts at the attachment of the aft pressure bulkhead to the fuselage at body station 1016 to determine if the correct parts are installed, and corrective action, if necessary. The actions specified by this AD are intended to prevent fatigue cracking along the bulkhead-to-fuselage attachment, which could result in structural failure of the aft pressure bulkhead and consequent rapid decompression of the airplane. This action is intended to address the identified unsafe condition.

Final rule.

2001-13-23 Boeing: Amendment 39-12305. Docket 2000-NM-403-AD. \n\n\tApplicability: Model 737-700 and -800 series airplanes; line numbers 4, 6, 9 through 20 inclusive, 29, and 31 through 46 inclusive; certificated in any category. \n\n\tNote 1: This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been modified, altered, or repaired in the area subject to the requirements of this AD. For airplanes that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must request approval for an alternative method of compliance in accordance with paragraph (d) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it. \n\n\tCompliance: Required as indicated, unless accomplished previously. \n\n\tTo prevent fatigue cracking along the bulkhead-to-fuselage attachment, which could result in structural failure of the aft pressure bulkhead and consequent rapid decompression of the airplane, accomplish the following: \n\nInspections and Corrective Actions \n\n\t(a) Prior to the accumulation of 3,000 total flight cycles, or within 90 days after the effective date of this AD, whichever occurs later, do one-time special detailed inspections of tension bolts at the attachment of the aft pressure bulkhead to the fuselage at body station 1016 to determine whether the correct parts are installed, per the Accomplishment Instructions of Boeing Service Bulletin 737-53-1212, including Appendix A, dated August 13, 1998. \n\n\t\t(1) If any long bolt is found above the main deck floor, do paragraphs (a)(1)(i) and (a)(1)(ii) of this AD. \n\n\t\t\t(i) Before further flight, do a torque test of the nut on the long bolt to determine whether the bolt is properly clamped. \n\n\t\t\t(ii) Replace the bolt and nut, as applicable, with new parts, per the service bulletin, except as provided by paragraph (c) of this AD. The correct replacement parts are listed in Figure 4 of the service bulletin. Do the replacement no later than the compliance time specified in the compliance table in Section 1.D. ("Compliance") of the service bulletin. For the purposes of this AD, compliance times stated in flight cycles and years are to be counted from the time of the inspection per paragraph (a) of this AD. \n\n\t\t(2) For any long or short bolt other than those identified in paragraph (a)(1) of this AD, replace the bolt and nut, as applicable, with new parts, per the service bulletin, except as provided by paragraph (c) of this AD. The correct replacement parts are listed in Figure 4 of the service bulletin. Do the replacement no later than the compliance time specified in the compliance table in Section 1.D. ("Compliance") of the service bulletin. For the purposes of this AD, compliance times stated in flight cycles and years are to be counted from the time of the inspection per paragraph (a) of this AD. \n\n\tNote 2: For the purposes of this AD, a special detailed inspection is defined as: "An intensive examination of a specific item(s), installation, or assembly to detect damage, failure, or irregularity. The examination is likely to make extensive use of specialized inspection techniques and/or equipment. Intricate cleaning and substantial access or disassembly procedures may be required." \n\nRepetitive Inspections \n\n\t(b) Where short bolts are installed between two adjacent stringer end fittings or at stringer end fittings, doing repetitive inspections of the nuts to determine if bolts are properly clamped, per Boeing Service Bulletin 737-53-1212, including Appendix A, dated August 13, 1998, extends the compliance time for the replacement of bolts, per the compliance table in Section 1.D. ("Compliance") of the service bulletin. \n\nException for Certain Repair Conditions \n\n\t(c) Where Boeing Service Bulletin 737-53-1212, including Appendix A, dated August 13, 1998, specifies to contact Boeing for replacement instructions: Before further flight, replace per a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA; or per data meeting the type certification basis of the airplane approved by a Boeing Company Designated Engineering Representative who has been authorized by the Manager, Seattle ACO, to make such findings. For a repair method to be approved by the Manager, Seattle ACO, as required by this paragraph, the approval letter must specifically reference this AD. \n\nAlternative Methods of Compliance \n\n\t(d) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved by the Manager, Seattle ACO. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Seattle ACO. \n\n\tNote 3: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Seattle ACO. \n\nSpecial Flight Permits \n\n\t(e) Special flight permits may be issued in accordance with sections 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate the airplane to a location where the requirements of this AD can be accomplished. \n\nIncorporation by Reference \n\n\t(f) Except as provided by paragraph (c) of this AD, the actions shall be done in accordance with Boeing Service Bulletin 737-53-1212, including Appendix A, dated August 13, 1998. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124-2207. Copies may be inspected at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC. \n\nEffective Date \n\n\t(g) This amendment becomes effective on August 13, 2001.

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an airworthiness directive (AD) that is applicable to certain Boeing Model 737-700 and -800 series airplanes was published in the Federal Register on April 12, 2001 (66 FR 18880). That action proposed to require inspections of certain tension bolts at the attachment of the aft pressure bulkhead to the fuselage at body station 1016 to determine if the correct parts are installed, and corrective action, if necessary. \n\nComments \n\n\tInterested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comment received. \n\n\tThe Air Transport Association (ATA) of America, on behalf of one of its members, states that its member supports the proposed rule. \n\nConclusion \n\n\tAfter careful review of the available data, including the comment noted above, the FAA has determined that air safety and the public interest require the adoption of the rule as proposed. \n\nCost Impact \n\n\tThere are approximately 31 airplanes of the affected design in the worldwide fleet. The FAA estimates that 14 airplanes of U.S. registry will be affected by this AD, that it will take approximately 2 work hours per airplane to accomplish the required actions, and that the average labor rate is $60 per work hour. Based on these figures, the cost impact of the AD on U.S. operators is estimated to be $1,680, or $120 per airplane. \n\n\tThe cost impact figure discussed above is based on assumptions that no operator has yet accomplished any of the requirements of this AD action, and that no operator would accomplish those actions in the future if this AD were not adopted. The cost impact figures discussed in AD rulemaking actions represent only the time necessary to perform the specific actions actually required by the AD. These figures typically do not include incidental costs, such as the time required to gainaccess and close up, planning time, or time necessitated by other administrative actions. \n\nRegulatory Impact \n\n\tThe regulations adopted herein 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. Therefore, it is determined that this final rule does not have federalism implications under Executive Order 13132. \n\n\tFor the reasons discussed above, I certify that this action (1) is not a "significant regulatory action" under Executive Order 12866; (2) is not a "significant rule" under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and (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. A final evaluation has been prepared for this action and it is contained in the Rules Docket. Acopy of it may be obtained from the Rules Docket at the location provided under the caption ADDRESSES. \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\n\tAccordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends part 39 of the Federal Aviation Regulations (14 CFR part 39) as follows: \n\nPART 39--AIRWORTHINESS DIRECTIVES \n\n\t1. 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\n\t2. Section 39.13 is amended by adding the following new airworthiness directive: