AD 2004-25-05

The FAA is adopting a new airworthiness directive (AD) for certain Boeing Model 747-100, 747-100B, 747-100B SUD, 747-200B, 747- 200C, 747-200F, 747-300, 747SP, and 747SR series airplanes. This AD requires repetitive inspections to detect cracks and fractures of the strut front spar chord assembly at each strut location, and repair if necessary. This AD is prompted by a report of a fractured front spar chord assembly for strut No. 3, which resulted in the loss of the strut upper link load path. We are issuing this AD to prevent loss of the strut upper link load path and consequent fracture of the diagonal brace, which could result in in-flight separation of the strut and engine from the airplane.

Final rule; request for comments.

2004-25-05 Boeing: Amendment 39-13893. Docket No. FAA-2004-19811; Directorate Identifier 2004-NM-201-AD. \n\nEffective Date \n\n\t(a) This AD becomes effective December 27, 2004. \n\nApplicability \n\n\t(b) This AD applies to Boeing 747-100, 747-100B, 747-100B SUD, 747-200B, 747-200C, 747-200F, 747-300, 747SP, and 747SR series airplanes; as listed in Boeing Alert Service Bulletin (ASB) 747- 54A2224, dated September 30, 2004; certificated in any category. \n\nUnsafe Condition \n\n\t(c) This AD was prompted by a report of a fractured front spar chord assembly for strut No. 3, which resulted in the loss of the strut upper link load path. The FAA is issuing this AD to prevent loss of the strut upper link load path and consequent fracture of the diagonal brace, which could result in in-flight separation of the strut and engine. \n\nCompliance \n\n\t(d) 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\nDetailed and High Frequency Eddy Current (HFEC) Inspections \n\n\t(e) Within 90 days after the effective date of this AD, perform detailed and HFEC inspections to detect any cracks or fractures of the front spar chord assembly for struts Number 1 through 4 inclusive, in accordance with Boeing ASB 747-54A2224, dated September 30, 2004. \n\n\t(f) Accomplishment of the detailed and HFEC inspections in accordance with Boeing 747 Fleet Team Digest 747-FTD-54-04002, dated April 15, 2004, May 4, 2004, June 1, 2004, July 12, 2004, or July 28, 2004; or Boeing Message 1-C6ELC (Service Request ID No.: 218724992), dated April 14, 2004; before the effective date of this AD, is considered acceptable for compliance with the requirements of paragraph (e) of this AD. \n\nRepetitive Inspections \n\n\t(g) For airplanes on which no crack or fracture is detected: At the times specified in Table 1--Repetitive Intervals of this AD, perform the detailed and HFEC inspections required by paragraph(e) of this AD at the intervals specified in Table 1. \n\n\tTable 1.--Repetitive Intervals \n\n\n\nFor Airplanes identified in Boeing ASB \t747-54A2224, dated September 30, 2004, as--\nAt intervals not to exceed-- \nGroup 1\nGroup 2 and Group 3\nGroup 4 and Group 6\nGroup 5\n1,000 flight cycles or 18 months, whichever occurs first. \n1,200 flight cycles or 18 months, whichever occurs first.\n1,500 flight cycles or 18 months, whichever occurs first. \n2,000 flight cycles or 18 months, whichever occurs first.\n \nCorrective Action \n\n\t(h) If any crack or fracture is found during any inspection required by this AD, and the bulletin specifies contacting Boeing for appropriate action: Before further flight, repair the crack or fracture according to 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 authorizedby the Manager, Seattle ACO, to make those 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 Alert Service Bulletin 747-54A2224, dated September 30, 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, PO 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 go to http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html .

We have received a report indicating that the front spar chord assembly for strut No. 3 fractured on a Boeing Model 747-200B series airplane that had accumulated a total of 16,604 flight cycles and 79,013 flight hours. The front spar chord assembly fractured 4.37 inches forward of the upper link attach lug. The manufacturer's analysis showed that the fitting fractured as the result of fatigue at a critical stress area. Fracture of the front spar chord assembly will result in the loss of the strut upper link load path. Loss of the upper link load path would result in the transfer of additional loads to the diagonal brace load path, which could result in fracture of the diagonal brace. This condition, if not corrected, could result in in-flight separation of the strut and engine from the airplane. \n\nRelevant Service Information \n\n\tWe have reviewed Boeing Alert Service Bulletin (ASB) 747-54A2224, dated September 30, 2004. The ASB describes procedures for accomplishing detailed and high frequency eddy current (HFEC) inspections of the strut front spar chord assembly for cracks and fractures at each strut location. The ASB also specifies, if any crack or fracture is found, to contact the manufacturer for additional instructions and repair. Accomplishing the actions specified in the service information is intended to adequately address the unsafe condition. \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 prevent loss of the strut upper link load path and consequent fracture \nof the diagonal brace, which could result in in-flight separation of the strut and engine from the airplane. This AD requires accomplishing the actions specified in the service information described previously, except as discussed under "Difference Between the AD and the ASB." \n\nDifference Between the AD andthe ASB \n\n\tThe ASB specifies that you may contact the manufacturer for instructions on how to repair certain conditions, but this AD requires you to repair those conditions 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\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-2004-19811; Directorate Identifier 2004-NM-201-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\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 airworthiness directive (AD):