AD 99-10-09

This amendment adopts a new airworthiness directive (AD), applicable to certain Boeing Model 747-100, -200, and 747-SP series airplanes and military type E-4B airplanes, that requires repetitive inspections to detect cracking of the wing front spar web, and repair of cracked structure. This amendment also provides for optional terminating action for the repetitive inspection requirements. This amendment is prompted by reports indicating that fatigue cracks were found on the aft surface of the wing front spar web. The actions specified by this AD are intended to detect and correct such fatigue cracking, which could result in a fuel leak, and consequent increased risk of a fire.

Final rule

99-10-09 BOEING: Amendment 39-11162. Docket 97-NM-100-AD. \n\n\tApplicability: Model 747-100, 747-200, and 747-SP series airplanes and military type E-4B airplanes; as listed in Boeing Service Bulletin 747-57A2303, Revision 1, dated September 25, 1997; 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 (d) 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\tNOTE 2: Inspections and modifications accomplished prior to the effective date of this AD in accordance with Boeing Alert Service Bulletin 747-57A2303, dated December 19, 1996, are considered acceptable for compliance with the applicable action specified in this amendment. \n\n\tTo detect and correct fatigue cracking of the wing front spar web, which could result in a fuel leak, and consequent increased risk of a fire, accomplish the following: \n\nInitial and Repetitive Inspections \n\n\t(a)\tPerform an ultrasonic inspection to detect cracking of the wing front spar web at the fastener rows behind and between the upper link fittings for the number 2 and 3 engine struts, in accordance with the Accomplishment Instructions of Boeing Service Bulletin 747-57A2303, Revision 1, dated September 25, 1997, at the time specified in paragraph (a)(1) or (a)(2) of this AD, as applicable. \n\n\t\t(1)For airplanes identified as Group 1, 2, 3, or 5 in the alert service bulletin: Inspect prior to the accumulation of 12,500 total flight cycles, or within 15 months after the effective date of this AD, whichever occurs later. Repeat the inspection thereafter at intervals not to exceed 2,200 flight cycles. \n\n\t\t(2)\tFor airplanes identified as Group 4, 6, 7, 8, 9, or 10 in the alert service bulletin: Inspect prior to the accumulation of 18,000 total flight cycles, or within 15 months after the effective date of this AD, whichever occurs later. Repeat the inspection thereafter at intervals not to exceed 3,000 flight cycles. \n\nCorrective Actions \n\n\t(b)\tIf any crack is found during any inspection required by paragraph (a) of this AD, prior to further flight, accomplish either paragraph (b)(1) or (b)(2) of this AD. \n\n\t\t(1)\tAccomplish the terminating action in accordance with the Accomplishment Instructions of Boeing Service Bulletin 747-57A2303, Revision 1, dated September 25, 1997.Accomplishment of this action constitutes terminating action for the repetitive inspection requirements of this AD; or \n\n\t\t(2)\tRepair 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. 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\nOptional Terminating Action \n\n\t(c)\tReplacement of the affected wing front spar web with a new shot-peened wing front spar web in accordance with the Accomplishment Instructions of Boeing Service Bulletin 747-57A2303, Revision 1, dated September 25, 1997, constitutes terminating action for the repetitive inspection requirements of this AD, and, for the modified area only, for the repetitive inspection requirements of AD 98-15-21, amendment 39-10672. \n\n\tNOTE 3: The area subject to the optional terminating action specified in paragraph (c) of this AD overlaps with part of the wing front spar that is the subject of AD 98-15-21.\n\nAlternative Method of Compliance \n\n\t(d)\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 4: 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(e)\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\nIncorporation by Reference \n\n\t(f)\tThe inspections and replacement shall be done in accordance with Boeing Service Bulletin 747-57A2303, Revision 1, dated September 25, 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\nEffective Date \n\n\t(g)\tThis amendment becomes effective on June 15, 1999.

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an airworthiness directive (AD) that is applicable to certain Boeing Model 747-100, -200, and 747-SP series airplanes and military type E-4B airplanes was published in the Federal Register on May 28, 1998 (63 FR 29151). That action proposed to require repetitive inspections to detect cracking of the wing front spar web, and repair of cracked structure. That proposal also provided for optional terminating action for the repetitive inspection requirements. \n\nComments \n\n\tInterested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received. \n\n\tOne commenter supports the proposed rule, and one commenter has no objection to the proposed rule. \n\nRequest to Allow Use of Additional Service Information \n\n\tTwo commenters request that the proposed rule be revised to allow inspection and modification of the wing front spar web to be accomplished in accordance with the original issue of Boeing Alert Service Bulletin 747-57A2303, dated December 19, 1996. The notice of proposed rulemaking (NPRM) proposed to require inspection and modification of the wing front spar web in accordance with only Boeing Service Bulletin 747-57A2303, Revision 1, dated September 25, 1997. The commenters point out that Boeing Service Bulletin 747-57A2303, Revision 1, states that no more work is necessary for airplanes inspected or modified in accordance with the original issue of the service bulletin. One of the commenters states that revising the final rule to allow inspection and modification of the wing front spar web in accordance with the original issue of the service bulletin would preclude the need for affected operators to obtain approval for an alternative method of compliance \n\n\tThe FAA concurs with the commenters' request to allow inspection and modification of the wingfront spar web in accordance with the original issue of Boeing Alert Service Bulletin 747-57A2303. The FAA has reviewed the original issue of the service bulletin and determined that the procedures in the original issue are substantially similar to those described in Revision 1. Therefore, "NOTE 2" has been added to this final rule to specify that inspections and modifications accomplished prior to the effective date of this AD in accordance with the original issue of Boeing Alert Service Bulletin 747-57A2303 are considered acceptable for compliance with this AD. \n\nRequest to Terminate Repetitive Inspections Required by AD 95-02-15 \n\n\tOne commenter requests that the proposal (Docket number 97-NM-100-AD) be revised to state that, if the terminating action proposed in the NPRM (replacement of the wing front spar web with a new shot-peened wing front spar web) is accomplished, certain inspections outboard of front spar station inboard (FSSI) 669 that are currently required by AD 95-02-15, amendment 39-9134 (60 FR 9613, March 21, 1995), are no longer necessary. The commenter points out that the subject area in the proposal overlaps considerably with the subject area of AD 95-02-15. The commenter also states that a similar revision should be made to the NPRM for docket number 97-NM-82-AD, which proposed the supersedure of AD 95-02-15, to state that certain inspections outboard of FSSI 669 are no longer necessary if the replacement of the wing front spar web with a new shot-peened wing front spar web is accomplished in accordance with this AD. The commenter states that addressing the area of overlap in the final rule would preclude the need for affected operators to obtain FAA approval for an alternative method of compliance for the inspections of the subject area of AD 95-02-15. \n\n\tThe FAA partially concurs with the commenter's request to revise the NPRM's for docket numbers 97-NM-82-AD and 97-NM-100-AD. On July 15, 1998, the FAA issued AD 98-15-21, amendment 39-10672 (63 FR 39487, dated July 23, 1998), which supersedes AD 95-02-15. Because that AD has already been issued, no revision to that final rule will be made at this time. However, the FAA concurs that accomplishment of the optional terminating action specified in this final rule would eliminate the need for inspections in accordance with AD 98-15-21 for the modified area only (i.e., FSSI 669 to FSSI 697 inclusive). Therefore, paragraph (c) of this final rule has been revised to state that replacement of the affected wing front spar web with a new shot-peened wing front spar web in accordance with Boeing Service Bulletin 747-57A2303, Revision 1, constitutes terminating action for repetitive inspections in accordance with AD 98-15-21 for the modified area only. In addition, "NOTE 3" has been added to this final rule to clarify that the area subject to the optional terminating action specified in paragraph (c) of this final rule overlaps with part of the wing front spar that is the subject of AD 98-15-21. \n\nRequest to Approve Alternative Method of Compliance for Terminating Action \n\n\tOne commenter requests that the proposed rule be revised to allow modifications of the wing front spar web accomplished previously in accordance with Boeing Service Letter 747-SL-57-084-C, dated October 12, 1996, and Boeing Repair Drawing 112U8040, to be considered terminating action for the requirements of this AD. The commenter states that such a modification was coordinated through the manufacturer, and the commenter has accomplished the modification on several of its airplanes. \n\n\tThe FAA does not concur with the commenter's request to approve an alternative method of compliance for the terminating action. The service letter and repair drawing referenced by the commenter are not approved by the FAA. Therefore, the FAA finds that modifications accomplished in accordance with these data may not be adequate to ensure that the unsafe condition is adequately addressed. Inaddition, the FAA finds that adding such an alternative method of compliance for the terminating action to the final rule would unduly complicate this AD action and may be confusing to some operators. However, the operator may request approval of an alternative method of compliance in accordance with paragraph (d) of the final rule. No change to the final rule is necessary in this regard. \n\nExplanation of Changes Made to the Proposal \n\n\tThe FAA has revised paragraph (b)(2) of the final rule to add a provision that allows repair of any crack in the subject area to be accomplished 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\nConclusion \n\n\tAfter careful review of the available data, including the comments noted above, the FAA has determined that air safety and the public interest require the adoption of the rule with the changes described previously. The FAA has determined that these changes will neither increase the economic burden on any operator nor increase the scope of the AD. \n\nCost Impact \n\n\tThere are approximately 190 airplanes of the affected design in the worldwide fleet. The FAA estimates that 95 airplanes of U.S. registry will be affected by this AD, that it will take approximately 64 work hours per airplane to accomplish the required inspection, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the inspection required by this AD on U.S. operators is estimated to be $364,800, or $3,840 per airplane, per inspection cycle. \n\n\tThe cost impact figure discussed above is based on assumptions that no operator has yet accomplished any of the requirements of this AD action, and that no operator would accomplish those actions in the future if this AD were not adopted. \n\n\tShould an operator elect to accomplish the optional terminating modification, itwould take approximately 518 work hours per airplane to accomplish the modification, at an average labor rate of $60 per work hour. Required parts would cost approximately $17,000 per airplane. Based on these figures, the cost impact of the optional terminating modification is estimated to be $48,080 per airplane. \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\tFor the reasons discussed above, I certify that this action (1) is not a "significant regulatory action" under Executive Order 12866; (2) is not a "significant rule" under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and (3) 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. A final evaluation has been prepared for this action and it is contained in the Rules Docket. A copy of it 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\n PART 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: