AD 95-12-26

This amendment supersedes an existing airworthiness directive (AD), applicable to certain Boeing Model 747SP series airplanes, that currently requires repetitive inspections for cracks in the web of the wing front spar over engine numbers 2 and 3, and repair, if necessary. This amendment requires additional inspections in an area beyond that specified in the existing AD. This action also would provide for a new, optional modification, which, if accomplished, would constitute terminating action for the repetitive inspections. This amendment is prompted by a report of cracking in the web in an area outside the inspection zone specified in the existing AD. A crack in the web that is not detected before it extends outside the chord footprints can allow fuel leakage. The actions specified by this AD are intended to prevent fuel leakage onto an engine and a resultant fire due to cracking in the web of the wing front spar.

Final rule

95-12-26 BOEING: Amendment 39-9279. Docket 94-NM-120-AD. Supersedes AD 90-17-18, Amendment 39-6702. \n\n\tApplicability: Model 747SP series airplanes; variable numbers RG001 through RG142 inclusive, and RG171 through RG222 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 use the authority provided in paragraph (f) of this AD to request approval from the FAA. This approval may address either no action, if the current configuration eliminates the unsafe condition; or different actions necessary to address the unsafe condition described in this AD. Such a request should include an assessment of the effect of the changed configuration on the unsafe condition addressed by this AD. In no case does the presence of any modification, alteration, or repair remove any airplane from the applicability of this AD. \n\n\tCompliance: Required as indicated, unless accomplished previously. \n\n\tTo prevent fuel leakage onto an engine and a resultant fire, accomplish the following: \n\n\t(a)\tFor airplanes on which the "terminating modification" (between front spar station (FSS) 640 and FSS 670) specified in Boeing Alert Service Bulletin 747-57A2259, dated February 15, 1990; or Revision 1, dated September 6, 1990; has not been accomplished: Within the next 6 months after September 21, 1990 (the effective date of AD 90-17-18, amendment 39-6702), perform a visual and an ultrasonic inspection of the front spar web between FSS 636 and FSS 675, in accordance with Boeing Alert Service Bulletin 747-57A2259, dated February 15, 1990; or Revision 1, dated September 6, 1990. If no crack is found, repeat these inspections at intervalsnot to exceed 1,000 landings until the inspections required by paragraph (b) of this AD are accomplished. \n\n\t(b)\tFor airplanes on which the "terminating modification" (between FSS 640 and FSS 670) specified in Boeing Alert Service Bulletin 747-57A2259, dated February 15, 1990; or Revision 1, dated September 6, 1990; has not been accomplished: Prior to the accumulation of 4,000 total landings on the airplane, or within 6 months after the effective date of this AD, whichever occurs later, perform the inspections specified in paragraphs (b)(1), (b)(2), and (b)(3) of this AD to detect cracks in the web between FSS 628 and FSS 675, in accordance with Boeing Alert Service Bulletin 747-57A2259, Revision 2, dated June 9, 1994. Accomplishment of these inspections terminates the repetitive inspection requirement of paragraph (a) of this AD. If no crack is found, repeat these inspections thereafter at intervals not to exceed 1,000 landings. \n\n\t\t(1)\tPerform an ultrasonic inspection in theweb under the upper and lower chord footprints; and \n\n\t\t(2)\tPerform a high frequency eddy current inspection in the web in an area one inch below the upper chord and one inch above the lower chord footprints; and \n\n\t\t(3)\tPerform a detailed visual inspection in the forward face of the web of the wing front spar at fastener locations in the web-to-stiffeners and web-to-rib posts. \n\n\t(c)\tFor airplanes on which the "terminating modification" specified in Boeing Alert Service Bulletin 747-57A2259, dated February 15, 1990; or Revision 1, dated September 6, 1990; has been accomplished: Prior to the accumulation of 4,000 total landings on the airplane, or within 6 months after the effective date of this AD, whichever occurs later, perform the inspections specified in paragraphs (c)(1), (c)(2), and (c)(3) of this AD to detect cracks in the web between FSS 628 and FSS 636, in accordance with Boeing Alert Service Bulletin 747-57A2259, Revision 2, dated June 9, 1994. If no crack is found,repeat these inspections thereafter at intervals not to exceed 1,000 landings. \n\n\t\t(1)\tPerform an ultrasonic inspection of the web under the upper and lower chord footprints; and \n\n\t\t(2)\tPerform a high frequency eddy current inspection of the web in an area one inch below the upper chord and one inch above the lower chord footprints; and \n\n\t\t(3)\tPerform a detailed visual inspection of the forward face of the web of the wing front spar at fastener locations in the web-to-stiffeners and web-to-rib posts. \n\n\t(d)\tIf any crack is found during any inspection required by this AD, prior to further flight, accomplish a terminating modification (between FSS 623 and FSS 670) in accordance with Boeing Alert Service Bulletin 747-57A2259, Revision 2, dated June 9, 1994; or in accordance with a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate. \n\n\t(e)\tModification of the wing front spar web between FSS 623 and FSS 670 in accordance with Boeing Alert Service Bulletin 747-57A2259, Revision 2, dated June 9, 1994; or in accordance with a method approved by the Manager, Seattle ACO; or in accordance with AD 95-10-16, amendment 39-9233; constitutes terminating action for the requirements of this AD. \n\n\t(f)\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, FAA, Transport Airplane Directorate. 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(g)\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(h)\tThe inspections and modification shall be done in accordance with Boeing Alert Service Bulletin 747-57A2259, dated February 15, 1990; or Boeing Alert Service Bulletin 747-57A2259, Revision 1, dated September 6, 1990; or Boeing Alert Service Bulletin 747-57A2259, Revision 2, dated June 9, 1994; as applicable. 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(i)\tThis amendment becomes effective on July 31, 1995.

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) by superseding AD 90-17-18, amendment 39-6702 (55 FR 33279, August 15, 1990), which is applicable to certain Boeing Model 747SP series airplanes, was published as a supplemental notice of proposed rulemaking (NPRM) in the Federal Register on February 21, 1995 (60 FR 9645). The action proposed to require repetitive inspections to detect cracks in the web of the wing front spar in an area beyond that specified in the existing AD, and modification, if cracking is found. The action also proposed to provide for a new, optional modification, which, if accomplished, would constitute terminating action for the repetitive inspections.\n \n\tInterested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the single comment received. \n\n\tThe commenter supports the proposed rule. \n\n\tSince the issuance of the supplemental NPRM, the manufacturer completed development of the modification program for the engine struts on the affected airplanes; subsequently, the FAA approved that program. On May 10, 1995, the FAA issued AD 95-10-16, amendment 39-9233 (60 FR 27008, May 22, 1995), which is applicable to Boeing Model 747 series airplanes equipped with JT9D-3 and -7 series engines, including those airplanes affected by this AD. That AD requires incorporation of the modification program discussed previously. Paragraph (e) of this final rule has been revised to indicate that installation of a terminating modification in accordance with AD 95- 10-16, amendment 39-9233, constitutes terminating action for the requirements of this AD. \n\n\tAfter careful review of the available data, including the comment noted above, the FAA has determined that air safety and the public interest require the adoption of the rule with the change previously described. The FAA has determined that this change will neither increase the economic burden on any operator nor increase the scope of the AD. \n\n\tThere are approximately 35 Model 747SP series airplanes of the affected design in the worldwide fleet. The FAA estimates that 11 airplanes of U.S. registry will be affected by this AD. The FAA estimates that it will take approximately 22 work hours per airplane to accomplish the required inspections (between front spar stations 628 and 675) specified in this AD, and that the average labor rate is $60 per work hour. Based on these figures, the total cost impact of the AD on U.S. operators is estimated to be $14,520, or $1,320 per airplane. \n\n\tThe total 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 terminating modification that is provided by this AD action, it will take approximately 644 work hours to accomplish it, at an average labor rate of $60 per work hour. The cost of required parts will be $21,800. Based on these figures, the total cost impact of the terminating modification will be $60,440 per airplane. \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.\tThe authority citation for part 39 continues to read as follows: Authority: 49 U.S.C. App. 1354(a), 1421 and 1423; 49 U.S.C. 106(g); and 14 CFR 11.89. § 39.13 - (Amended) \n\n\t2.\tSection 39.13 is amended by removing amendment 39-6702 (55 FR 33279, August 15, 1990), and by adding a new airworthiness directive (AD), amendment 39-9279, to read as follows: