AD 2008-04-21

We are adopting a new airworthiness directive (AD) for certain Boeing Model 737-300, -400, and -500 series airplanes. This AD requires repetitive inspections for cracking of the body buttock line (BBL) 0.07 floor beam between body station (BS) 651 and BS 676 and between BS 698 and BS 717, and related investigative and corrective actions if necessary. This AD also provides an optional terminating action for the repetitive inspections. This AD results from reports of cracking in the BBL 0.07 floor beam. We are issuing this AD to prevent failure of the main deck floor beams at certain body stations due to fatigue cracking, which could result in rapid decompression of the airplane.

Final rule.

2008-04-21 Boeing: Amendment 39-15393. Docket No. FAA-2007-0226; Directorate Identifier 2007-NM-187-AD. \n\nEffective Date \n\n\t(a) This airworthiness directive (AD) is effective April 3, 2008. \n\nAffected ADs \n\n\t(b) None. \n\nApplicability \n\n\t(c) This AD applies to Boeing Model 737-300, -400, and -500 series airplanes, certificated in any category; as identified in Boeing Service Bulletin 737-57-1210, Revision 2, dated June 13, 2007. \n\nUnsafe Condition \n\n\t(d) This AD results from reports of cracking in the body buttock line (BBL) 0.07 floor beam. We are issuing this AD to prevent failure of the main deck floor beams at certain body stations due to fatigue cracking, which could result in rapid decompression of the airplane. \n\nCompliance \n\n\t(e) You are responsible for having the actions required by this AD performed within the compliance times specified, unless the actions have already been done. \n\nInspections and Related Investigative/Corrective Actions \n\n\t(f) Beforethe accumulation of 20,000 total flight hours, or within 7,000 flight cycles after the effective date of this AD, whichever occurs later: Do the detailed inspections for cracking of the BBL 0.07 floor beam between body station (BS) 651 and BS 676 and between BS 698 and BS 717, and do all the applicable related investigative and corrective actions before further flight, by accomplishing all of the applicable actions specified in paragraphs B.2. and B.4. of the Accomplishment Instructions of Boeing Service Bulletin 737-57-1210, excluding Appendix A, Revision 2, dated June 13, 2007, except as provided by paragraph (g) of this AD. Repeat the inspections thereafter at intervals not to exceed 7,000 flight cycles. Installing a repair in accordance with paragraphs B.2. and B.4. of the Accomplishment Instructions of the service bulletin, or doing the modification in accordance with paragraph (h) of this AD, terminates the repetitive inspections for the applicable area only. \n\nException to Corrective Action \n\n\t(g) If any cracking is found during any inspection required by this AD, and Boeing Service Bulletin 737-57-1210, excluding Appendix A, Revision 2, dated June 13, 2007, specifies to contact Boeing for appropriate action: Before further flight, repair the cracking using a method approved in accordance with the procedures specified in paragraph (i) of this AD. \n\nOptional Terminating Action \n\n\t(h) If no cracking is found during the detailed inspection and related investigative action required by paragraph (f) of this AD: Accomplishing the modification of the BBL 0.07 floor beam between BS 651 and BS 676 and between BS 698 and BS 717, as applicable, in accordance with paragraphs B.2. and B.4., as applicable, of the Accomplishment Instructions of Boeing Service Bulletin 737-57-1210, excluding Appendix A, Revision 2, dated June 13, 2007, terminates the repetitive inspections for the applicable area only. \n\nAlternative Methods of Compliance (AMOCs) \n\n\t(i)(1) The Manager, Seattle Aircraft Certification Office (ACO), FAA, has the authority to approve AMOCs for this AD, if requested in accordance with the procedures found in 14 CFR 39.19. \n\t(2) To request a different method of compliance or a different compliance time for this AD, follow the procedures in 14 CFR 39.19. Before using any approved AMOC on any airplane to which the AMOC applies, notify your appropriate principal inspector (PI) in the FAA Flight Standards District Office (FSDO), or lacking a PI, your local FSDO. \n\t(3) An AMOC that provides an acceptable level of safety may be used for any repair required by this AD, if it is approved by an Authorized Representative for the Boeing Commercial Airplanes Delegation Option Authorization Organization who has been authorized by the Manager, Seattle ACO, to make those findings. For a repair method to be approved, the repair must meet the certification basis of the airplane, and the approval must specifically refer to this AD. \n\nMaterial Incorporated by Reference \n\n\t(j) You must use Boeing Service Bulletin 737-57-1210, Revision 2, dated June 13, 2007, to do the actions required by this AD, unless the AD specifies otherwise. \n\t(1) The Director of the Federal Register approved the incorporation by reference of this service information under 5 U.S.C. 552(a) and 1 CFR part 51. \n\t(2) For service information identified in this AD, contact Boeing Commercial Airplanes, P.O. Box 3707, Seattle, Washington 98124-2207. \n\t(3) You may review copies of the service information incorporated by reference at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the National Archives and Records Administration (NARA). For information on the availability of this material at NARA, call 202-741-6030, or go to: http://www.archives.gov/federal_register/code_of_federal_ regulations/ibr_locations.html.

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 Boeing Model 737-300, -400, and -500 series airplanes. That NPRM was published in the Federal Register on November 26, 2007 (72 FR 65901). That NPRM proposed to require repetitive inspections for cracking of the body buttock line 0.07 floor beam between body station (BS) 651 and BS 676 and between BS 698 and BS 717, and related investigative 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. Boeing supports the NPRM. \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 as proposed. \n\nCosts of Compliance \n\n\tThere are 1,961 airplanes of the affected design in the worldwide fleet. This AD affects 599 airplanes of U.S. registry. The required inspections take about 4 work hours per airplane, at an average labor rate of $80 per work hour. Based on these figures, the estimated cost of the required AD for U.S. operators is $191,680, or $320 per airplane, per inspection cycle. \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 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\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. \n\tYou 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\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\n 1. 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: