AD 2000-23-25

This amendment adopts a new airworthiness directive (AD) that is applicable to certain Boeing Model 747-100, 747-200, 747-300, 747SP, and 747SR series airplanes powered by Pratt & Whitney JT9D-3 or JT9D-7 series engines. This action requires inspections of the vertical chords of the aft torque bulkhead of the outboard nacelle struts, and corrective action, if necessary. This action also provides optional terminating action for the inspections. This action is necessary to detect and correct cracking of the vertical chords adjacent to the lower spar fitting, which could result in separation of the diagonal brace load path. Continued operation with a separated diagonal brace load path increases loads on the upper link, midspar fitting, and dual side links, which could result in separation of the strut and engine from the airplane. This action is intended to address the identified unsafe condition.

Final rule; request for comments

2000-23-25 BOEING: Amendment 39-11998. Docket 2000-NM-353-AD. \n\n\tApplicability: Model 747-100, 747-200, 747-300, 747SP, and 747SR series airplanes powered by Pratt & Whitney JT9D-3 or JT9D-7 series engines; listed in Boeing Alert Service Bulletin 747-54A2201, dated September 28, 2000; certificated in any category. \n\n\tNote 1: This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been modified, altered, or repaired in the area subject to the requirements of this AD. For airplanes that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must request approval for an alternative method of compliance in accordance with paragraph (e) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it. \n\n\tCompliance: Required as indicated, unless accomplished previously. \n\n\tTo detect and correct cracking of the vertical chords adjacent to the lower spar fitting, which could result in separation of the diagonal brace load path and lead to separation of the strut and engine from the airplane, accomplish the following: \n\nInspections \n\t(a) Except as provided by paragraph (b) of this AD, prior to the accumulation of 14,000 total flight cycles, or within 90 days after the effective date of this AD, whichever occurs later: Accomplish paragraphs (a)(1) and (a)(2) of this AD. \n\n\t\t(1) Perform a detailed visual inspection to detect cracking of the vertical chords of the aft torque bulkhead of the outboard nacelle struts, in accordance with Part 2 of the Accomplishment Instructions of Boeing Alert Service Bulletin 747-54A2201, dated September 28, 2000. Thereafter, repeat this inspection at intervals not to exceed 600 flight cycles until paragraph (d) of this AD is accomplished. \n\n\t\t(2) Perform surface eddy current and ultrasonic inspections to detect cracking of the vertical chords of the aft torque bulkhead of the outboard nacelle struts, in accordance with Part 3 of the Accomplishment Instructions of Boeing Alert Service Bulletin 747-54A2201, dated September 28, 2000. Thereafter, repeat these inspections at intervals not to exceed 1,200 flight cycles until paragraph (d) of this AD is accomplished. \n\nOptional Compliance Time \n\t(b) If Boeing Service Letter 747-54-055, dated April 24, 1998, was accomplished on the airplane during the modification of the nacelle strut in accordance with AD 95-10-16, amendment 39-9233: Accomplishment of the initial inspection in paragraph (a) of this AD may be deferred until 3,000 flight cycles after accomplishment of the service letter. \n\nRepair \n\t(c) If any cracking is detected during any inspection required by this AD: Prior to further flight, repair inaccordance 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 who has been authorized by the Manager, Seattle ACO, to make such findings. For a repair method to be approved by the Manager, Seattle ACO, as required by this paragraph, the approval letter must specifically reference this AD. \n\nOptional Terminating Action \n\t(d) Accomplishment of the modification specified in Part 4 of Boeing Alert Service Bulletin 747-54A2201, dated September 28, 2000, constitutes terminating action for the repetitive inspections required by paragraph (a) of this AD. \n\nAlternative Methods of Compliance \n\t(e) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved by the Manager, Seattle ACO. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Seattle ACO. \n\n\tNote 2: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Seattle ACO. \n\nSpecial Flight Permits \n\t(f) Special flight permits may be issued in accordance with sections 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate the airplane to a location where the requirements of this AD can be accomplished. \n\nIncorporation by Reference \n\t(g) Except as provided by paragraph (c) of this AD, the actions shall be done in accordance with Boeing Alert Service Bulletin 747-54A2201, dated September 28, 2000. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124-2207. Copies may be inspected at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC. \n\nEffective Date \n\t(h) This amendment becomes effective on December 13, 2000.

The FAA has received numerous reports of fatigue cracking of the vertical chords of the aft torque bulkhead of the outboard nacelle struts on certain Boeing Model 747-100, 747-200, 747-300, 747SR, and 747SP series airplanes powered by Pratt & Whitney JT9D-3 or JT9D-7 series engines. The cracks have been found adjacent to the lower spar fitting. Such cracking of the vertical chords adjacent to the lower spar fitting could result in separation of the diagonal brace load path. Continued operation with a separated diagonal brace load path, if not corrected, increases loads on the upper link, midspar fitting, and dual side links, which could result in separation of the strut and engine from the airplane. \n\nExplanation of Relevant Service Information \nThe FAA has reviewed and approved Boeing Alert Service Bulletin 747-54A2201, dated September 28, 2000, which describes procedures for repetitive detailed visual, ultrasonic, and surface eddy current inspections to detect cracking of the vertical chords of the aft torque bulkhead of the outboard nacelle struts. The service bulletin also describes procedures for a modification that involves installation of doublers on the vertical chords, which constitutes terminating action for the repetitive inspections. \n\n\tThe service bulletin provides for deferment of the initial inspections if Boeing Service Letter 747-SL-54-055, dated April 24, 1998, has been accomplished. That service letter recommends accomplishment of detailed visual and high frequency eddy current inspections of the chords of the aft torque bulkhead during modification of the nacelle strut. The FAA finds that, if the inspections recommended in Boeing Service Letter 747-SL-54-055 were accomplished during the modification of the nacelle strut and wing in accordance with AD 95-10-16, amendment 39-9233 (60 FR 27008, May 22, 1995), the initial inspections required by this AD may be deferred until 3,000 flight cycles after accomplishment of Boeing Service Letter 747-SL-54-055. \n\nExplanation of the Requirements of the Rule \nSince an unsafe condition has been identified that is likely to exist or develop on other airplanes of the same type design, this AD is being issued to detect and correct cracking of the vertical chords adjacent to the lower spar fitting, which could result in separation of the diagonal brace load path. This AD requires accomplishment of the inspections specified in the service bulletin described previously, except as discussed below. \n\nInterim Action \nThis is considered to be interim action. The FAA is currently considering requiring the modification specified in the service bulletin, which will constitute terminating action for the repetitive inspections required by this AD action. However, the planned compliance time for the installation of the modification is sufficiently long so that notice and opportunity for prior public comment will be practicable. \n\nDifference Between ServiceBulletin and This AD \nOperators should note that, although the service bulletin specifies that the manufacturer may be contacted for disposition of certain repair conditions, this AD requires the repair of those conditions to be accomplished in accordance with a method approved by the FAA, or in accordance with data meeting the type certification basis of the airplane approved by a Boeing Company Designated Engineering Representative who has been authorized by the FAA to make such findings. \n\nDetermination of Rule's Effective Date \nSince a situation exists that requires the immediate adoption of this regulation, it is found that notice and opportunity for prior public comment hereon are impracticable, and that good cause exists for making this amendment effective in less than 30 days. \n\nComments Invited \nAlthough this action is in the form of a final rule that involves requirements affecting flight safety and, thus, was not preceded by notice and an opportunity for public comment, comments are invited on this rule. Interested persons are invited to comment on this rule by submitting such written data, views, or arguments as they may desire. Communications shall identify the Rules Docket number and be submitted in triplicate to the address specified under the caption "ADDRESSES." All communications received on or before the closing date for comments will be considered, and this rule may be amended in light of the comments received. Factual information that supports the commenter's ideas and suggestions is extremely helpful in evaluating the effectiveness of the AD action and determining whether additional rulemaking action would be needed. \n\n\tSubmit comments using the following format: ? Organize comments issue-by-issue. For example, discuss a request to change the compliance time and a request to change the service bulletin reference as two separate issues. ? For each issue, state what specific change to the AD is being requested. ? Include justification (e.g., reasons or data) for each request. \n\n\tComments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the rule that might suggest a need to modify the rule. All comments submitted will be available, both before and after the closing date for comments, in the Rules Docket for examination by interested persons. A report that summarizes each FAA-public contact concerned with the substance of this AD will be filed in the Rules Docket. \n\n\tCommenters wishing the FAA to acknowledge receipt of their comments submitted in response to this rule must submit a self-addressed, stamped postcard on which the following statement is made: "Comments to Docket Number 2000-NM-353-AD." The postcard will be date stamped and returned to the commenter. \n\nRegulatory Impact \nThe regulations adopted herein 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. Therefore, it is determined that this final rule does not have federalism implications under Executive Order 13132. \n\n\tThe FAA has determined that this regulation is an emergency regulation that must be issued immediately to correct an unsafe condition in aircraft, and that it is not a "significant regulatory action" under Executive Order 12866. It has been determined further that this action involves an emergency regulation under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979). If it is determined that this emergency regulation otherwise would be significant under DOT Regulatory Policies and Procedures, a final regulatory evaluation will be prepared and placed in the Rules Docket. A copy of it, if filed, may be obtained from the Rules Docket at the location provided under the caption "ADDRESSES." \n\nList of Subjects in 14 CFR Part 39 \n\tAir transportation, Aircraft, Aviation safety, Incorporation by reference, Safety. \n\nAdoption of the Amendment \nAccordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends part 39 of the Federal Aviation Regulations (14 CFR part 39) as follows: \n\nPART 39 - AIRWORTHINESS DIRECTIVES \n1. The authority citation for part 39 continues to read as follows: \n\tAuthority: 49 U.S.C. 106(g), 40113, 44701. \n\n§ 39.13 (Amended) \n2. Section 39.13 is amended by adding the following new airworthiness directive: