AD 2004-23-10

The FAA is adopting a new airworthiness directive (AD) for certain Boeing Model 737-700 and -800 series airplanes. This AD requires doing an initial inspection for pitting and cracks of the lower skin panel at the lap joint; trimming the inner skin; installing exterior doublers; replacing the fuselage skin assembly; doing repetitive supplemental inspections; and repairing if necessary; as applicable. This AD is prompted by a report indicating that localized pitting in the lower skin panels was found during production on a limited number of airplanes. We are issuing this AD to detect and correct premature fatigue cracking at certain lap splice locations and consequent rapid decompression of the airplane.

Final rule.

Adoption of the Amendment \n\n\tAccordingly, 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\t1. The authority citation for part 39 continues to read as follows: \n\n\tAuthority: 49 U.S.C. 106(g), 40113, 44701. \n\n§ 39.13 (Amended) \n\n\t2. The FAA amends Sec. 39.13 by adding the following new airworthiness directive (AD): \n\n2004-23-10 Boeing: Amendment 39-13865. Docket No. FAA-2004-18996; Directorate Identifier 2004-NM-40-AD. \n\nEffective Date \n\n\t(a) This AD becomes effective December 20, 2004. \n\nAffected ADs \n\n\t(b) None. \n\nApplicability \n\n\t(c) This AD applies to Boeing Model 737-700 and -800 series airplanes, certificated in any category; having variable and serial numbers listed in Table 1 of this AD. \n\nTable 1.-Applicable Variable and Serial Numbers.\n\n\nVariable number\nSerial number\nGroup\nYA004\n27837\n1\nYA005\n27836\n2\nYA201\n28004\n4\nYC003\n27977\n3\n\nUnsafe Condition \n\n\t(d) This AD was prompted by a report indicating that localized pitting in the lower skin panels was found during production on a limited number of airplanes. We are issuing this AD to detect and correct premature fatigue cracking at certain lap splice locations and consequent 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\nInitial Inspection and/or Repair \n\n\t(f) At the applicable times specified in Table 1 of paragraph 1.E., "Compliance," of Boeing Special Attention Service Bulletin 737-53-1256, dated September 18, 2003, do the applicable actions specified in Table 2 of this AD in accordance with the Accomplishment Instructions of the service bulletin. \n\nTable 2.-Initial Inspection and/or Repair\n\n\nFor airplanes identified in the service bulletin as-\nRequirements-\n(1) Groups 1, 2, and 3\nDo an external ultrasonic inspection for pitting and cracks of the lower skin panel at the lap joint.\n(2) Groups 1 and 2\nTrim the inner skin and install two exterior doublers (including related investigative actions).\n(3) Group 3\nInstall three exterior doublers.\n(4) Group 4\nReplace the fuselage skin assembly with a new assembly.\n\nRepetitive Inspections \n\n\t(g) For Groups 1, 2, and 3 airplanes identified in Boeing Special Attention Service Bulletin 737-53-1256, dated September 18, 2003: At the applicable times specified in Table 2 of paragraph 1.E., "Compliance," of the service bulletin, do the repetitive supplemental inspections of the lower skins and external doublers for discrepancies in accordance with the Accomplishment Instructions of the service bulletin. \n\nCorrective Action \n\n\t(h) If any discrepancy is found during any action required by this AD, before further flight, repair 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 (DER) who has been authorized by the Manager, Seattle ACO, to make such findings. For a repair method to be approved, the approval must specifically reference this AD. \n\nAlternative Methods of Compliance (AMOCs) \n\n\t(i)(1) The Manager, Seattle 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 a Boeing Company DER who has been authorized by the Manager, Seattle ACO, to make those findings. For a repair method to be approved, the approval must specifically refer to this AD. \n\nMaterial Incorporated by Reference \n\n\t(j) You must use Boeing Special Attention Service Bulletin 737-53-1256, dated September 18, 2003, to perform the actions that are required by this AD,unless the AD specifies otherwise. The Director of the Federal Register approves the incorporation by reference of this document in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. For copies of the service information, contact Boeing Commercial Airplanes, P.O. Box 3707, Seattle, Washington 98124-2207. For information on the availability of this material at the National Archives and Records Administration (NARA), call (202) 741-6030, or go to http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html. You may view the AD docket at the Docket Management Facility, U.S. Department of Transportation, 400 Seventh Street SW, room PL-401, Nassif Building, Washington, DC.

The FAA proposed to amend 14 CFR Part 39 with an AD for certain Boeing Model 737-700 and -800 series airplanes. That action, published in the Federal Register on September 3, 2004 (69 FR 53855), proposed to require doing an initial inspection for pitting and cracks of the lower skin panel at the lap joint; trimming the inner skin; installing exterior doublers; replacing the fuselage skin assembly; doing repetitive supplemental inspections; and repairing if necessary; as applicable. \n\nComments \n\n\tWe provided the public the opportunity to participate in the development of this AD. No comments have been submitted on the proposed AD or on the determination of the cost to the public. \n\nConclusion \n\n\tWe have carefully reviewed the available data and determined that air safety and the public interest require adopting the AD as proposed. \n\nCosts of Compliance \n\n\tThis AD will affect about 4 airplanes worldwide and 2 airplanes of U.S. registry. The following table provides the estimated costs to comply with this AD. \n\n\tThe average labor rate is $65 per work hour. The cost impact of the AD on U.S. operators is estimated to be $83,855. \n\nTable.-Cost Impact\n\n\nFor airplanes listed in the referenced service bulletin as group\nWork hours\nParts cost\nPer airplane cost\n1\nInspection: 2 \nModification: 38\nNone \n105\n$130 \n2,575\n2\nInspection: 2 \nModification: 30\nNone \n104\n130 \n2,054\n3\nInspection: 2 \nModification: 42\nNone \n106\n130 \n2,836\n4\nRepair: 920\n16,200\n76,000\n\nRegulatory Findings \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\n\tFor the reasons discussed above, I certify that this AD: \n\n\t(1) Is not a "significant regulatory action" under Executive Order 12866; \n\n\t(2) Is not a "significant rule" under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and \n\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\n\tWe prepared a regulatory evaluation of the estimated costs to comply with this AD. See the ADDRESSES section for a location to examine the regulatory evaluation. \n\nList of Subjects in 14 CFR Part 39 \n\n\tAir transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.