AD 2008-04-21 Airworthiness Directives; Boeing Model 737-300, -400, and -500 Series Airplanes

Models named: 737-300, -400, -500 series. Read the applicability below — it usually turns on serial or part numbers too.

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.

You are responsible for having the actions required by this AD performed within the compliance times specified, unless the actions have already been done. Inspections and Related Investigative/Corrective Actions (f) Before the 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. Exception to Corrective Action (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. Optional Terminating Action (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. Alternative Methods of Compliance (AMOCs) (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. (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. (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. Material Incorporated by Reference (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. (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. (2) For service information identified in this AD, contact Boeing Commercial Airplanes, P.O. Box 3707, Seattle, Washington 98124-2207. (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 . Issued in Renton, Washington, on February 15, 2008. Ali Bahrami, Manager, Transport Airplane Directorate, Aircraft Certification Service. [FR Doc. E8-3461 Filed 2-27-08; 8:45 am] BILLING CODE 4910-13-P

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.