2005-20-01: Stiffeners at left buttock line (LBL) and right buttock line (RBL)

2005-20-01 Boeing: Amendment 39-14294. Docket No. FAA-2005-20356; Directorate Identifier 2004-NM-115-AD. \n\nEffective Date \n\n\t(a) This AD becomes effective November 1, 2005. \n\nAffected ADs \n\n\t(b) None. \n\nApplicability \n\n\t(c) This AD applies to all Boeing Model 737-100, -200, -200C, - 300, -400, and -500 series airplanes, certificated in any category. \n\nUnsafe Condition \n\n\t(d) This AD was prompted by cracks in the stiffeners at left buttock line (LBL) and right buttock line (RBL) 6.15 on the rear spar of the wing center section. We are issuing this AD to detect and correct cracks in the stiffeners at LBL and RBL 6.15, which could result in damage to the keel beam structure and consequently reduce the capability of the airplane to sustain flight loads. \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\nService Bulletin Reference \n\n\t(f) Theterm "service bulletin," as used in this AD, means the Accomplishment Instructions of Boeing Alert Service Bulletin 737- 57A1269, Revision 1, dated September 16, 2004. \n\nInitial and Repetitive Inspections \n\n\t(g) Before accumulating 15,000 total flight cycles, or within 180 days after the effective date of this AD, whichever occurs later: Do a detailed inspection of the stiffeners at LBL and RBL 6.15 for cracks, in accordance with Part I of the service bulletin. Thereafter at intervals not to exceed 4,500 flight cycles, repeat the detailed inspection until the stiffeners at LBL and RBL 6.15 have been replaced with new, improved stiffeners, in accordance with paragraph (h) or (i) of this AD. \n\n\tNote 1: For the purposes of this AD, a detailed inspection is: "An intensive examination of a specific item, installation, or assembly to detect damage, failure, or irregularity. Available lighting is normally supplemented with a direct source of good lighting at an intensity deemed appropriate. Inspection aids such as mirror, magnifying lenses, etc., may be necessary. Surface cleaning and elaborate procedures may be required." \n\nReplacement of Cracked Stiffeners \n\n\t(h) If any crack is found during any inspection required by this AD, before further flight, replace both stiffeners with new, improved stiffeners by doing all of the applicable actions in Part IV through Part IX, as applicable, of the service bulletin; except where the service bulletin specifies to contact Boeing for appropriate action: Before further flight, repair using a method approved in accordance with the procedures specified in paragraph (l) of this AD. Accomplishing the replacement terminates the repetitive inspections required by paragraph (g) of this AD. \n\nOptional Terminating Action \n\n\t(i) Replacement of both stiffeners at LBL and RBL 6.15 with new, improved stiffeners in accordance with paragraph (h) of this AD terminates the repetitive inspections required by this AD. \n\nCredit for Previous Service Bulletin \n\n\t(j) The actions done before the effective date of this AD in accordance with Boeing Alert Service Bulletin 737-57A1269, dated December 4, 2003, are acceptable for compliance with the corresponding actions required by this AD. \n\nCredit for Previous Inspections \n\n\t(k) Inspections done before the effective date of this AD in accordance with Boeing All Operator Telex M-7200-01-00426, dated February 19, 2001, are acceptable for compliance with the requirements of paragraph (g) of this AD. \n\nAlternative Methods of Compliance (AMOCs) \n\n\t(l)(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\n\t(2) 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(m) You must use Boeing Alert Service Bulletin 737-57A1269, Revision 1, dated September 16, 2004, to perform the actions that are required by this AD, unless the AD specifies otherwise. The Director of the Federal Register approved the incorporation by reference of this document in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Contact Boeing Commercial Airplanes, P.O. Box 3707, Seattle, Washington 98124-2207, for a copy of this service information. You may review copies at the Docket Management Facility, U.S. Department of Transportation, 400 Seventh Street, SW., room PL-401, Nassif Building, Washington, DC; on the Internet at http://dms.dot.gov; or at the National Archives and Records Administration (NARA). For information on the availability of this material at the NARA, call (202) 741-6030, or go to http://www.archives.gov/federal-register/cfr/ibr-locations.html .