AD 2004-22-05

The FAA is adopting a new airworthiness directive (AD) for all Boeing Model 737-300, -400, and -500 series airplanes. This AD requires inspecting for discrepancies of the fuselage skin under the dorsal fin assembly, and repairing if necessary. This AD is prompted by a report of an 18-inch crack found in the fuselage skin area under the blade seals of the nose cap of the dorsal fin due to previous wear damage. We are issuing this AD to find and fix discrepancies of the fuselage skin, which could result in fatigue cracking due to cabin pressurization, and consequent rapid in-flight decompression of the airplane fuselage.

Final rule; request for comments.

2004-22-05 Boeing: Amendment 39-13833. Docket No. FAA-2004-19461; Directorate Identifier 2004-NM-169-AD. \n\nEffective Date \n\n\t(a) This AD becomes effective November 12, 2004. \n\nAffected ADs \n\n\t(b) None. \n\nApplicability \n\n\t(c) This AD applies to all Boeing Model 737-300, -400, and -500 series airplanes; certificated in any category. \n\nUnsafe Condition \n\n\t(d) This AD was prompted by a report of an 18-inch crack found in the fuselage skin area under the blade seals of the nose cap of the dorsal fin due to previous wear damage. We are issuing this AD to find and fix discrepancies of the fuselage skin, which could result in fatigue cracking due to cabin pressurization, and consequent rapid in-flight decompression of the airplane fuselage. \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\nRepetitive Detailed Inspections \n\n\t(f) For airplanes specified in either paragraph (f)(1), (f)(2), (f)(3), or (f)(4) of this AD: Accomplish a detailed inspection for discrepancies (wear or cracking) of the fuselage skin under the dorsal fin assembly by doing all the actions specified in Boeing Message Number 1-QXO35, dated October 13, 2004. Repeat the inspection thereafter at intervals not to exceed 9,000 flight cycles. \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\n\t(1) For airplanes with line numbers 1001 through 2828 inclusive that have not been inspected as of the effective date of this AD, in accordance with Boeing Service Bulletin 737-55-1057, dated December 12, 1996; or Revision 1, dated July 22, 1999: Inspect before the accumulation of 18,000 total flight cycles, or within 90 days after the effective date of this AD, whichever is later. \n\n\t(2) For airplanes with line numbers 2829 through 3132 inclusive that are not included in the effectivity of Boeing Service Bulletin 737-55-1057, dated December 12, 1996; or Revision 1, dated July 22, 1999: Inspect before the accumulation of 18,000 total flight cycles, or within 90 days after the effective date of this AD, whichever is later. \n\n\t(3) For airplanes with line numbers 1001 through 2828 inclusive that have been inspected, but not repaired or modified as of the effective date of this AD, in accordance with Boeing Service Bulletin 737-55-1057, dated December 12, 1996; or Revision 1, dated July 22, 1999: Inspect within 9,000 flight cycles after accomplishing the inspection, or within 90 days after the effective date of this AD, whichever is later. \n\n\t(4) For airplanes with line numbers 1001 through 2828 inclusive that have been inspected and repaired or modified as of the effective date of this AD, in accordance with Boeing Service Bulletin 737-55-1057, dated December 12, 1996; or Revision 1, dated July 22, 1999: Inspect within 18,000 flight cycles after accomplishing the repair or modification, or within 90 days after the effective date of this AD, whichever is later; and if a repair doubler is installed, before further flight, inspect the repair doubler for discrepancies (wear or cracking). \n\n\tNote 2: Boeing Message Number 1-QXO35, dated October 13, 2004, references Part I of Boeing Service Bulletin 737-55-1057, Revision 1, dated July 22, 1999; as an additional source of service information for accomplishing the actions required by paragraph (f) of this AD. \n\nRepair \n\n\t(g) If any discrepancy (wear or cracking) is found during any inspection required by this AD, before further flight, repair in accordance with a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA; or in accordance with 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 refer to this AD. \n\n\tNote 3: No terminating action is currently available for the repetitive inspections required by this AD. \n\nReporting Not Required \n\n\t(h) Although Boeing Message Number 1-QXO35, dated October 13, 2004, specifies to report any fuselage skin cracking found during the detailed inspections, this AD does not include that requirement. \n\nAlternative Methods of Compliance (AMOCs) \n\n\t(i)(1) The Manager, Seattle ACO, 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 bythis 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 Message Number 1-QXO35, dated October 13, 2004, 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. You can review copies at the Docket Management Facility, U.S. Department of Transportation, 400 Seventh Street SW, room PL-401, Nassif Building, Washington, DC; or at the National Archives and Records Administration (NARA). For information on the availability of this material at NARA, call (202) 741-6030, or goto \nhttp://www. archives. gov/federal_register/code_of_federal_regulations/ibr_locations. html.

We have recently received a report indicating that wear of the fuselage skin was found between body stations 860 and 1006 on a Boeing Model 737-300 series airplane. Subsequently, an 18-inch crack developed in the area of the wear. Fuselage skin wear is attributed to the movement of the blade seals, which provide an aerodynamic seal between the dorsal fin fairing and the fuselage skin. Wear damage of the fuselage skin, if not found and fixed, could result in fatigue cracking due to cabin pressurization, and consequent rapid in-flight decompression of the airplane fuselage. \n\nRelevant Service Information \n\n\tWe have reviewed Boeing Message Number 1-QXO35, dated October 13, 2004. The message describes procedures for repetitive detailed inspections of the fuselage skin under the dorsal fin assembly for discrepancies (i.e., wear or cracking), and contacting Boeing for repair instructions. The message also describes procedures for accomplishing a detailed inspection for discrepancies if any repair doubler is installed. \n\n\tWe have also reviewed Boeing Service Bulletin 737-55-1057, Revision 1, dated July 22, 1999; specified in the Boeing message as an additional source of service information for accomplishing the actions. Part I of the Accomplishment Instructions of the service bulletin describes procedures for inspecting for discrepancies of the fuselage skin under the dorsal fin assembly. The discrepancies include chafing, wear damage, and lack of abrasion-resistant coating. \n\nFAA's Determination and Requirements of This AD \n\n\tThe unsafe condition described previously is likely to exist or develop on other airplanes of the same type design. Therefore, we are issuing this AD to find and fix discrepancies of the fuselage skin, which could result in fatigue cracking due to cabin pressurization, and consequent rapid in-flight decompression of the airplane fuselage. This AD requires accomplishing the actions specified in Boeing MessageNumber 1-QXO35, described previously, except as discussed under "Difference Between the AD and Boeing Message Number 1-QXO35." \n\nDifference Between the AD and Boeing Message Number 1-QXO35 \n\n\tThe message specifies that operators may contact the manufacturer for repair instructions, but this AD requires you to repair cracking in one of the following ways: \n\n\tUsing a method that we approve; or \n\n\tUsing data that meet the type certification basis of the airplane, and that have been approved by a Boeing Company Designated Engineering Representative who has been authorized by the FAA to make those findings. \n\n\tAlthough the message recommends reporting any fuselage skin cracking found during the detailed inspections, this AD does not require that action. \n\nFAA's Determination of the Effective Date \n\n\tAn unsafe condition exists that requires the immediate adoption of this AD; therefore, providing notice and opportunity for public comment before the AD is issued is impracticable,and good cause exists to make this AD effective in less than 30 days. \n\nComments Invited \n\n\tThis AD is a final rule that involves requirements that affect flight safety and was not preceded by notice and an opportunity for public comment; however, we invite you to submit any relevant written data, views, or arguments regarding this AD. Send your comments to an address listed under ADDRESSES. Include "Docket No. FAA-2004-19461; Directorate Identifier 2004-NM-169-AD" at the beginning of your comments. We specifically invite comments on the overall regulatory, economic, environmental, and energy aspects of the AD. We will consider all comments received by the closing date and may amend the AD in light of those comments. \n\n\tWe will post all comments we receive, without change, to http://dms.dot.gov , including any personal information you provide. We will also post a report summarizing each substantive verbal contact with FAA personnel concerning this AD. Using the search function of our docket Web site, anyone can find and read the comments in any of our dockets, including the name of the individual who sent the comment (or signed the comment on behalf of an association, business, labor union, etc.). You can review the DOT's complete Privacy Act Statement in the Federal Register published on April 11, 2000 (65 FR 19477-78), or you can visit http://dms.dot.gov. \n\n\tWe are reviewing the writing style we currently use in regulatory documents. We are interested in your comments on whether the style of this document is clear, and your suggestions to improve the clarity of our communications with you. You can get more information about plain language at http://www/faa.gov/language and http://www.plainlanguage.gov\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 the regulation: \n\n\t1. Is not a "significant regulatory action" under Executive Order 12866; \n\n\t2. Is not a "significant rule" under the DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and \n\n\t3. 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. \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\n1. 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\n2. The FAA amends § 39.13 by adding the following new airworthiness directive (AD):