AD 98-08-15

This amendment adopts a new airworthiness directive (AD) that is applicable to certain Boeing Model 747-100, -200, and -300 series airplanes. This action requires repetitive detailed visual and/or borescope inspections to detect discrepancies of certain areas of the wing strut. This amendment also provides for an optional terminating action for the repetitive inspections. This amendment is prompted by reports that fatigue cracking was found in the vertical chords, midspar webs, and canted closure webs. The actions specified in this AD are intended to detect and correct fatigue cracking and stress corrosion of the wing strut, which could result in failure of the strut-to-wing interface, and consequent separation of the engine and strut from the airplane.

Final rule; request for comments

98-08-15 BOEING: Amendment 39-10464. Docket 98-NM-83-AD. \n\n\tApplicability: Model 747-100, -200, and -300 series airplanes having line positions 1 through 886 inclusive, certificated in any category; excluding airplanes on which the strut/wing modification has been accomplished in accordance with AD 95-13-07, amendment 39-9287; or AD 95-10-16, amendment 39-9233; and excluding airplanes designated as Group 5 in Boeing Service Bulletin 747-54A2179, Revision 2, dated December 4, 1997.\n \n\tNOTE 1: This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been otherwise 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 fatigue cracking or stress corrosion of certain areas of the wing strut (the midspar fitting vertical leg, aft bulkhead vertical chords, the midspar webs, and the canted closure webs), which could cause failure of the strut-to-wing interface, and consequent separation of the engine and strut from the airplane; accomplish the following: \n\n\t(a)\tPerform detailed visual and/or borescope inspections to detect fatigue cracking, stress corrosion, or fracture of the midspar fitting vertical legs, the aft torque bulkhead vertical chords, the midspar webs and the midspar canted closure webs at the time specified in paragraph (a)(1), (a)(2), or (a)(3) of this AD, as applicable; in accordance with Part III of Section III of the Accomplishment Instructions of Boeing Alert Service Bulletin 747-54A2179, Revision 2, dated December 4, 1997. Thereafter, repeat the inspections in accordance with and at the times specified in the alert service bulletin. \n\n\t\t(1)\tFor airplanes identified as Group 1 in the alert service bulletin: Perform the inspections on the inboard struts and the outboard struts, prior to the accumulation of 5,000 total landings, or within 90 days after the effective date of this AD, whichever occurs later. \n\n\t\t(2)\tFor airplanes identified as Group 6 in the alert service bulletin: Perform the inspections on the inboard struts, prior to the accumulation of 5,000 total landings or within 90 days after the effective date of this AD, whichever occurs later. \n\n\t\t(3)\tFor airplanes identified as Groups 2, 3, and 4 in the alert service bulletin: Perform the inspections on the inboard struts, prior to the accumulation of 12,000 total landings, or within 90 days after the effective date of this AD, whichever occurs later. \n\n\t(b)\tIf any fatigue cracking, stress corrosion, or fracturing is detected during any inspection required by paragraph (a) of this AD that is within the limits specified in Boeing Alert Service Bulletin 747-54A2179, Revision 2, dated December 4, 1997, prior to further flight, repair in accordance with the alert service bulletin. \n\n\t(c)\tIf any fatigue cracking, stress corrosion, or fracturing is detected during any inspection required by paragraph (a) of this AD that is beyond the limits specified in Boeing Alert Service Bulletin 747-54A2179, Revision 2, dated December 4, 1997, prior to further flight, accomplish corrective actions in accordance with a method approved by the Manager, FAA, Transport Airplane Directorate, Seattle Aircraft Certification Office (ACO), Seattle, Washington. \n\n\t(d)\tAccomplishment of the strut/wing modification specified in paragraph (d)(1) or (d)(2) of this AD,as applicable, constitutes terminating action for the requirements of this AD. \n\n\t\t(1)\tFor airplanes equipped with General Electric Model CF6-45 or -50 series engines, or Pratt & Whitney Model JT9D-70 series engines: Accomplish the strut/wing modification in accordance with Boeing Alert Service Bulletin 747-54A2158, Revision 2, dated August 15, 1996. \n\n\t\t(2)\tFor airplanes equipped with Pratt & Whitney Model JT9D series engines (excluding Model JT9D-70 engines): Accomplish the strut/wing modification in accordance with Boeing Alert Service Bulletin 747-54A2159, Revision 2, dated March 14, 1996. \n\t(e)\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\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\n\t(f)\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(g)\tExcept as provided by the requirements of paragraph (c) of this AD, the actions and the terminating modifications shall be done in accordance with Boeing Alert Service Bulletin 747- 54A2179, Revision 2, dated December 4, 1997; Boeing Service Bulletin 747-54A2158, Revision 2, dated August 15, 1996; and Boeing Service Bulletin 747-54A2159, Revision 2, dated March 14, 1996. \n\n\t\t(1)\tThe detailed visual and borescope inspections shall be done in accordance with Boeing Alert Service Bulletin 747-54A2179, Revision 2, dated December 4, 1997. The incorporation by reference of that service bulletin was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. \n\n\t\t(2)\tThe strut/wing modification, if accomplished, shall be done in accordance with the Boeing Alert Service Bulletins listed in the following table. The incorporation by reference of those documents was approved previously by the Director of the Federal Register on January 22, 1997 (61 FR 66201, December 17, 1996): \n\n\nReferenced Service Bulletin\nRevision Level\nDate \n747-54A2158\n2\nAugust 15, 1996 \n747-54A2159\n2\nMarch 14, 1996\n\n\t\t(3)\tCopies 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(h)\tThis amendment becomes effective on April 28, 1998.

The FAA has received several reports of cracking of the vertical chords, midspar webs, and canted closure webs on the inboard and outboard struts of certain Boeing Model 747 series airplanes. Investigation has revealed that the cracking in the vertical chords was due to fatigue and stress corrosion. Additionally, the investigation revealed that the cracking in the midspar webs was due to fatigue. Such fatigue cracking and stress corrosion, if not corrected, could result in failure of the strut-to-wing interface, and consequent separation of the engine and strut from the airplane. \n\nOther Relevant Rulemaking \n\n\tAD 97-12-03, amendment 39-10045 (62 FR 31331, June 9, 1997) currently requires inspections for cracking, corrosion, and fracturing of the lower and upper horizontal clevis of the strut midspar fittings; and replacement of discrepant parts with new parts, or rework, if necessary. Boeing Alert Service Bulletin 747-54A2179, Revision 1, dated November 27, 1996, is cited in AD 97-12-03 as the appropriate service information. \n\nExplanation of Relevant Service Information \n\n\tThe FAA has reviewed and approved Boeing Alert Service Bulletin 747-54A2179, Revision 2, dated December 4, 1997, which describes, among other actions, procedures for performing repetitive detailed visual and/or borescope inspections to detect fatigue cracking, stress corrosion, and fracturing of certain parts of the wing spar (the midspar fitting vertical legs, aft torque bulkhead vertical chords, midspar webs, and midspar canted closure webs). The alert service bulletin also describes procedures for certain repair, rework, and replacement actions. The initial inspection and repetitive intervals recommended in the alert service bulletin will detect fatigue cracking, stress corrosion, and fracturing of the subject area in a timely manner.\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 747-100, -200, and -300 series airplanes of the same type design, this AD is being issued to detect and correct fatigue cracking, stress corrosion, or fracturing of certain areas of the wing spar (the midspar fitting vertical legs, aft torque bulkhead vertical chords, midspar webs, and midspar canted closure webs), which could cause failure of the strut-to-wing interface, and consequent separation of the engine and strut from the airplane. This AD requires repetitive inspections to detect fatigue cracking, stress corrosion, or fracturing of certain areas of the wing spar (the midspar fitting vertical legs, aft torque bulkhead vertical chords, midspar webs, and midspar canted closure webs) to be accomplished in accordance with the alert service bulletin described previously. Also, if any fatigue cracking, stress corrosion, or fracturing is detected that is within the limits specified by the alert service bulletin, certain corrective actions (repair) shall be accomplished in accordance with the alert service bulletin. Certain other corrective actions that are outside the limits specified by the alert service bulletin shall be accomplished in accordance with a method approved by the FAA. \nDifferences Between the Rule and the Relevant Service Information \n\n\tOperators should note the following differences between the rule and the relevant alert service bulletin: \n\n\t1. If any fatigue cracking, stress corrosion, or fracturing is detected during any inspections required by this AD that is outside the limits specified in the alert service bulletin, corrective actions must be accomplished in accordance with a method approved by the FAA. \n\n\t2. Additionally, operators should note that, while this AD cites Boeing Alert Service Bulletin 747-54A2179, Revision 2, dated December 4, 1997, as the appropriate service information for this AD, this AD does not supersede the requirements of AD 97-12-03, which cites Revision 1 of the same alert service bulletin as the appropriate service information. \n\n\t3. Although the alert service bulletin referenced in this AD provides procedures to detect and correct fatigue cracking, stress corrosion, or fracturing of the midspar fitting vertical legs, aft torque bulkhead vertical chords, midspar webs, and midspar canted closure webs for certain airplanes identified as Group 5 airplanes, this AD does not require any action for those airplanes. At this time, the FAA has not received any reports of cracked structure on the airplanes designated as Group 5 airplanes. However, the FAA may consider further rulemaking if additional information indicates that the identified unsafe condition is found on Group 5 airplanes.\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-83-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, itis 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: