AD 98-20-25 SUPERSEDED

This amendment adopts a new airworthiness directive (AD) that is applicable to certain Boeing Model 747-100 series airplanes. This action requires repetitive inspections to detect cracking of the outer chord of the Body Station (BS) 1480 upper and lower bulkhead and longeron splice fitting, and repair, if necessary. Alternatively, this action requires other repetitive inspections to detect cracking of the BS 1480 upper and lower bulkhead, bulkhead outer chord, web, skin, splice components, and lower bulkhead/stringer interface; and modification of the skin splice plate, the outer chord splice fitting, and the stringer interface of the lower bulkhead, if necessary. This amendment is prompted by a report indicating that fatigue cracking was found in the outer chord of the BS 1480 bulkhead at the overwing longeron splice, and that the longeron splice fitting was completely severed. The actions specified in this AD are intended to detect and correct fatigue cracking of theBS 1480 bulkhead outer chord and longeron splice fitting, which could result in reduced structural integrity of the fuselage and the inability to carry limit load.

Final rule; request for comments

98-20-25 BOEING: Amendment 39-10791. Docket 98-NM-256-AD. \n\n\tApplicability: Model 747-100 series airplanes, line positions 1 through 87 inclusive; 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 (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.To detect and correct fatigue cracking of the Body Station (BS) 1480 bulkhead outer chord and longeron splice fitting, which could result in reduced structural integrity of the fuselage and the inability to carry limit load, accomplish the following: \n\n\t(a)\tPrior to the accumulation of 10,000 total flight cycles, or within 45 days after the effective date of this AD, whichever occurs later, accomplish either paragraph (a)(1) or (a)(2) of this AD. \n\n\t\t(1)\tPerform a detailed visual inspection to detect cracking of the longeron splice fitting at BS 1480, the forward side of the outer chord of the BS 1480 bulkhead at the longeron splice fitting attachment bolts, and the aft side of the outer chord of the BS 1480 bulkhead within two inches above the outer chord splice fitting, on both the left and right sides of the airplane. \n\n\tNOTE 2: Figure 5 of Boeing Alert Service Bulletin 747-53A2390, dated July 31, 1997, provides an exploded view of the structural components of the splice area for the purpose of parts identification. (However, paragraph (a)(1) of this AD does not require the inspection described in Figure 5.) \n\n\t\t\t(i)\tIf any cracking is detected, prior to further flight, repair 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 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. \n\n\t\t\t(ii)\tRepeat the detailed visual inspection thereafter at intervals not to exceed 250 flight cycles, until the initial inspection required by paragraph (a)(2) of this AD is accomplished. \n\n\t\t(2)\tPerform detailed visual and eddy current inspections to detect cracking of the upper and lower bulkhead, bulkhead outer chord, web, skin, splice components, and lower bulkhead/stringer interface, in accordance with Figures 5 and8 of Boeing Alert Service Bulletin 747-53A2390, dated July 31, 1997. Additionally, for airplanes on which the inspection in "Plan B" of the service bulletin is accomplished, modify the skin splice plate, the outer chord splice fitting, and the stringer interface of the lower bulkhead, in accordance with the Accomplishment Instructions of the alert service bulletin. Accomplishment of these actions constitutes terminating action for the repetitive inspection requirements of paragraph (a)(1) of this AD. \n\n\t\t\t(i)\tIf any cracking is detected, prior to further flight, repair in accordance with the alert service bulletin, except as provided by paragraph (b) of this AD. \n\n\t\t\t(ii)\tRepeat the inspections thereafter in accordance with the flight safety inspection program specified in Figures 1 and 3 of the alert service bulletin. \n\n\t(b)\tWhere the alert service bulletin specifies that the manufacturer may be contacted for disposition of certain repair conditions, repair in accordance witha method approved by the Manager, Seattle ACO; 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. \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\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 ADcan be accomplished. \n\n\t(e)\tExcept as provided by paragraphs (a)(1)(i) and (b) of this AD, the actions shall be done in accordance with Boeing Alert Service Bulletin 747-53A2390, dated July 31, 1997. 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\n\t(f)\tThis amendment becomes effective on October 7, 1998.

The FAA has received a report indicating that a six-inch fatigue crack was found in the outer chord of the Body Station (BS) 1480 bulkhead at the overwing longeron splice on a Boeing Model 747-100 series airplane. The report also indicated that the longeron splice fitting was completely severed. The effects of such fatigue cracking could severely reduce the capability of the overwing longeron to carry lateral load. Such fatigue cracking, if not corrected, could result in reduced structural integrity of the fuselage and the inability to carry limit load. \n\nExplanation of Relevant Service Information \n\n\tThe FAA has reviewed and approved Boeing Alert Service Bulletin 747-53A2390, dated July 31, 1997, which describes procedures for repetitive inspections to detect cracking of the BS 1480 upper and lower bulkhead, bulkhead outer chord, web, skin, splice components, and lower bulkhead/stringer interface; and repair, if necessary. The alert service bulletin also describes, as part of a certain inspection plan, procedures for modification of the skin splice plate, outer chord splice fitting, and the stringer interface of the lower bulkhead. Accomplishment of the actions specified in the alert service bulletin is intended to adequately address the identified unsafe condition. \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 airplanes of the same type design, this AD is being issued to detect and correct fatigue cracking of the BS 1480 bulkhead outer chord and longeron splice fitting, which could result in reduced structural integrity of the fuselage and the inability to carry limit load. This AD requires either repetitive detailed visual inspections to detect cracking of the outer chord of the BS 1480 upper and lower bulkhead and longeron splice fitting, and repair, if necessary; or accomplishment of certain actions specified in the alert service bulletin described previously, except as discussed below. \n\nDifferences Between Proposed Rule and Alert Service Bulletin \n\n\tOperators should note that the alert service bulletin applies to all Boeing Model 747-100, -200, and -300 series airplanes. This AD only applies to Model 747-100 series airplanes, line positions 1 through 87 inclusive, which have a different configuration of the longeron splice fitting than later Model 747 series airplanes. The severe fatigue damage that prompted the FAA to mandate the actions required by this AD has only been observed on the longeron splice fitting and outer chord of the BS 1480 bulkhead of Model 747-100 series airplanes having line positions 1 through 87 inclusive. As discussed below, the FAA is currently considering requiring repetitive inspections and modification of the upper and lower bulkhead and overwing longeron at BS 1480 for all Boeing Model 747-100, -200, and -300 series airplanes. \n\n\tIn addition, although the alert service bulletin recommends accomplishing the inspection prior to the accumulation of 10,000 total flight cycles or within 1,000 flight cycles after the release of the alert service bulletin, whichever occurs later, the FAA has determined that such a compliance time would not address the identified unsafe condition in a timely manner. In developing an appropriate compliance time for this AD, the FAA considered not only the manufacturer's recommendation, but the degree of urgency associated with addressing the subject unsafe condition, the average utilization of the affected fleet, and the time necessary to perform the inspection. In light of all of these factors, the FAA finds a compliance time of 10,000 total flight cycles or 45 days after the effective date of this AD, whichever occurs later, for initiating the required actions to be warranted, in that it represents an appropriate interval of time allowable for affected airplanes to continue to operate without compromising safety. \n\n\tOperators also should note that, although the alert 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. \n\nInterim Action \n\n\tThis is considered to be interim action. The FAA is currently considering further rulemaking action to supersede this AD to require inspections and modification of the upper and lower bulkhead and overwing longeron at BS 1480 for all Boeing Model 747-100, -200, and -300 series airplanes. However, the planned compliance time for the initial inspection and installation of the modification is sufficiently long so that notice and opportunity for prior public comment will be practicable. \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 98-NM-256-AD." The postcard will be date stamped and returned to 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 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\n\tAir transportation, Aircraft,Aviation safety, Incorporation by reference, 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. 98-NM-256-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.\n\n\tThe service information referenced in this AD may be obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124-2207. This information may be examined 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.

Bob Breneman, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 227-2776; fax (425) 227-1181.