AD 99-09-11 SUPERSEDED

This amendment adopts a new airworthiness directive (AD) that is applicable to certain Boeing Model 747 series airplanes and all 747-E4B (military) airplanes. This action requires repetitive inspections to detect cracking or fracture of the steel attachment fittings of the diagonal brace to the nacelle struts; and replacement of the attachment fittings with new steel fittings, if necessary. This amendment is prompted by a report indicating a fractured steel attachment fitting of a diagonal brace to the number 2 nacelle strut; such fracture has been attributed to fatigue cracking. The actions specified in this AD are intended to detect and correct such fatigue cracking, which could result in failure of a nacelle strut diagonal brace load path and possible separation of the nacelle from the wing.

Final rule; request for comments

99-09-11 BOEING: Amendment 39-11144. Docket 99-NM-49-AD. \n\n\tApplicability: Model 747 series airplanes equipped with General Electric Model CF6-45 or -50 series engines, or Pratt & Whitney Model JT9D-3, -7, or -70 series engines, and all 747-E4B (military) airplanes, having steel attachment fittings of the diagonal brace to the nacelle struts; certificated in any category. \n\n\tNOTE 1: This AD excludes those airplanes that are included in the applicability of AD 97-20-01 R1, amendment 39-10982 (64 FR 985, January 7, 1999). Those airplanes have aluminum attachment fittings. \n\n\tNOTE 2: 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 (c) 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 fatigue cracking or fracture of the steel attachment fittings of the diagonal brace to the nacelle struts, which could result in failure of a nacelle strut diagonal brace load path and possible separation of the nacelle from the wing; accomplish the following: \n\nInitial Inspection \n\n\t(a)\tGain access to the attachment fittings of the diagonal brace to the inboard and outboard nacelle struts through the aft fairing doors, and perform a detailed visual inspection to detect cracking or fracture of the steel attachment fittings of the diagonal brace to the inboard and outboard nacelle struts, at the applicable time specified in paragraph (a)(1) or (a)(2) of this AD. \n\n\t\t(1)\tFor airplanes on which the strut and wing modification required by AD 95-10-16, amendment 39-9233, or AD 95-13-07, amendment 39-9287, has not been accomplished: Within 10 days after the effective date of this AD, accomplish the detailed visual inspection. \n\n\t\t\t(i)\tFor airplanes equipped with General Electric Model CF6-45 or -50 series engines and/or Pratt & Whitney JT9D-3 or -7 series engines, repeat the inspection thereafter at intervals not to exceed 180 flight cycles. \n\n\t\t\t(ii)\tFor airplanes equipped with Pratt & Whitney JT9D-70 series engines, repeat the inspection thereafter at intervals not to exceed 250 flight cycles. \n\n\t\t(2)\tFor airplanes on which the strut and wing modification required by AD 95-10-16, amendment 39-9233, or AD 95-13-07, amendment 39-9287, has been accomplished: Within 30 days after the effective date of this AD or within 150 flight cycles after accomplishment of the modification, whichever occurs later, accomplish the detailed visual inspection. \n\n\t\t\t(i)\tFor airplanes equipped with General Electric Model CF6-45 or -50 series engines or Pratt & Whitney JT9D-70 series engines, repeat the inspection thereafter at intervals not to exceed 600 flight cycles. \n\n\t\t\t(ii)\tFor airplanes equipped with Pratt & Whitney JT9D-3 or-7 series engines, repeat the inspection thereafter at intervals not to exceed 350 flight cycles. \n\nCorrective Actions \n\n\t(b)\tIf any cracking or fracture of any attachment fitting is detected during any inspection required by paragraph (a) of this AD, prior to further flight, replace the fitting with a new steel fitting in accordance with a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate; or in accordance with data meeting the type certification 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 Manager's approval letter must specifically reference this AD. \n\nAlternative Methods of Compliance \n\n\t(c)\tAn 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 3: 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\n\t(d)\tSpecial 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\n\t(e)\tThis amendment becomes effective on May 10, 1999.

On May 10, 1995, the FAA issued AD 95-10-16, amendment 39-9233 (60 FR 27008, May 22, 1995), applicable to certain Boeing Model 747 series airplanes equipped with Pratt & Whitney Model JT9D series engines (excluding Model JT9D-70 series engines); and on June 16, 1995, the FAA issued AD 95-13-07, amendment 39-9287 (60 FR 33336, June 28, 1995), applicable to certain Boeing Model 747 series airplanes equipped with General Electric Model CF6-45 or -50 series engines, or Pratt & Whitney Model JT9D-70 series engines. Both of those AD's require modification of the nacelle strut and wing structure, inspections and checks to detect discrepancies, and correction of discrepancies. The requirements of those AD's are intended to prevent failure of the nacelle strut and subsequent separation of the nacelle from the wing. \n\n\tSince issuance of those two AD's, the FAA has received a report indicating that a fractured steel attachment fitting of a diagonal brace to the number 2 nacelle strut was found during a routine service inspection of a Boeing Model 747 series airplane equipped with General Electric Model CF6-50 series engines. This is the first report of a fractured steel attachment fitting on a Model 747 series airplane that was found after the strut and wing were modified in accordance with AD 95-13-07 or AD 95-10-16. However, the report clarifies that the steel fitting had been installed during production rather than during the modification required by AD 95-13-07. The FAA points out that the replacement of the fitting with a new steel fitting is only part of the modification required by the previously referenced AD's. The manufacturer reported that the crack initiation, which began at the far aft fastener hole on the inboard side of the lower flange of the attachment fitting, was attributed to fretting and galling and is indicative of fatigue. The airplane had accumulated 54,852 flight hours and 11,124 flight cycles, and the strut and wing modification had been accomplished in accordance with AD 95-13-07 at 50,357 flight hours and 10,085 flight cycles. \n\n\tWhile this is the first report of a fitting failure after modification in accordance with AD 95-13-07, cracking or fracture of a steel attachment fitting of the diagonal brace to the nacelle strut, if not corrected, could result in failure of a nacelle strut diagonal brace load path and possible separation of the nacelle from the wing. \n\n\tThe attachment fittings on the Pratt & Whitney series engines are similar to the attachment fittings on the General Electric series engines that are addressed in this AD. Therefore, all of the attachment fittings on either of these engines may be subject to the same unsafe condition. However, the configurations of these engines are different in that some have enhanced structural capability; therefore, the FAA has determined that a somewhat longer repetitive inspection interval for those configurations is appropriate. \n\nExplanation of the Requirements of the Rule \n\n\tSince an unsafe condition has been identified that is likely to exist or develop on other Boeing Model 747 series airplanes of the same type design, this AD is being issued to detect and correct fatigue cracking or fracture of the steel attachment fittings of the diagonal brace to the nacelle struts, which could result in failure of the nacelle strut diagonal brace load path and possible separation of the nacelle from the wing. This AD requires repetitive detailed visual inspections to detect such cracking or fracture. This AD also requires replacement of the attachment fittings with new steel fittings, if necessary, 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\nInterim Action \n\n\tThis is considered to be interim action until final action is identified, at which time the FAA may consider further rulemaking. \n\nDetermination of Rule's Effective Date \n\n\tSince 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 \n\n\tAlthough 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\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 99-NM-49-AD." The postcard will be date stamped and returnedto the commenter. \n\nRegulatory Impact \n\n\tThe regulations adopted herein will not have substantial direct effects 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, in accordance with Executive Order 12612, it is determined that this final rule does not have sufficient federalism implications to warrant the preparation of a Federalism Assessment. \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 andProcedures, 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\n\tAir transportation, Aircraft, Aviation safety, Safety. \n\nAdoption of the Amendment \n\n\tAccordingly, 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 \n\n\t1. The authority citation for part 39 continues to read as follows: Authority: 49 U.S.C. 106(g), 40113, 44701. § 39.13 (Amended) \n\t2. Section 39.13 is amended by adding the following new airworthiness directive:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 99-NM-49-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.\n\n\tInformation pertaining to this amendment may be obtained from or examined at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington.

Tamara L. Anderson, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 227-2771; fax (425) 227-1181.