93-17-06 BOEING: Amendment 39-8677. Docket 93-NM-24-AD. Supersedes AD 92-16-09, Amendment 39-8318. \n\n\tApplicability: Model 747 series airplanes; line positions 202 through 886 inclusive, equipped with General Electric CF6-45/50 series engines; certificated in any category. \n\n\tCompliance: Required as indicated, unless accomplished previously. \n\n\tTo prevent the loss of engine thrust control, accomplish the following: \n\n\t(a)\tFor those airplanes on which the new bracket assembly has not previously been installed in accordance with Boeing Alert Service Bulletin 747-76A2083, dated December 18, 1991, or Revision 1, dated May 28, 1992, accomplish the following: \n\n\t\t(1)\tPrior to or upon the accumulation of 9,000 total flight hours on the airplane, or within 600 flight hours after September 28, 1992 (the effective date of AD 92-16-09, Amendment 39-8318), whichever occurs later, perform a visual inspection of the number 1 strut idler pulley support bracket assembly to detect cracks; and inspect all associated fasteners for proper tightness; in accordance with Boeing Alert Service Bulletin 747-76A2083, dated December 18, 1991; Revision 1, dated May 28, 1992; or Boeing Service Bulletin 747-76A2083, Revision 2, dated February 25, 1993. \n\n\t\t\t(i)\tIf no crack is found in the bracket assembly, return the airplane to service and repeat the inspections required by paragraph (a) of this AD at intervals not to exceed 600 flight hours. \n\n\t\t\t(ii)\tIf only one crack is found in the bracket assembly and its length is two inches or less, prior to further flight, accomplish the procedures specified in either paragraph (a)(1)(ii)(A) or (a)(1)(ii)(B) of this AD: \n\n\t\t\t\t(A)\tAccomplish the interim repair described in Paragraph E. of the Accomplishment Instructions of Boeing Alert Service Bulletin 747-76A2083, Revision 1, dated May 28, 1992. Thereafter, repeat the inspections described in paragraph (a) of this AD at intervals not to exceed 100 flight hours. Within 750 flighthours after installation of the interim repair, replace the bracket assembly in accordance with Boeing Service Bulletin 747-76A2083, Revision 2, dated February 25, 1993. Replacement of the bracket assembly constitutes terminating action for the repetitive inspections required by this paragraph. \n\n\t\t\t\t(B)\tReplace the bracket assembly in accordance with Boeing Service Bulletin 747-76A2083, Revision 2, dated February 25, 1993. \n\n\t\t\t(iii)\tIf cracks are found in the bracket assembly, or if only one crack is found and its length exceeds two inches, prior to further flight, replace the bracket assembly in accordance with Boeing Service Bulletin 747-76A2083, Revision 2, dated February 25, 1993. \n\n\t\t\t(iv)\tIf any fastener is found to be loose, prior to further flight, tighten fastener to within specified torque limits, in accordance with Boeing Alert Service Bulletin 747-76A2083, dated December 18, 1991; Revision 1, dated May 28, 1992; or Boeing Service Bulletin 747-76A2083, Revision 2,dated February 25, 1993. \n\n\t\t(2)\tExcept as provided by paragraph (a)(1)(ii)(A) of this AD, within 12 months after the effective date of this AD, replace the bracket assembly, in accordance with Boeing Service Bulletin 747-76A2083, Revision 2, dated February 25, 1993. Replacement of the bracket assembly constitutes terminating action for the inspection requirements of this AD.\n \n\t(b)\tFor those airplanes on which the new bracket assembly has previously been installed in accordance with Boeing Alert Service Bulletin 747-76A2083, dated December 18, 1991, or Revision 1, dated May 28, 1992, accomplish the following: \n\n\t\t(1)\tWithin 30 days after the effective date of this AD, conduct a visual inspection of the strut web to detect cracking in the area of the pulley bracket, in accordance with Boeing Service Bulletin 747-76A2083, Revision 2, dated February 25, 1993. Conduct repetitive visual inspections in accordance with either paragraph (b)(1)(i), (b)(1)(ii), or (b)(1)(iii), as applicable. \n\n\t\t\t(i)\tIf the bracket assembly had been installed within the last 90 days prior to the effective date of this AD, repeat the visual inspection at the times specified in paragraphs (b)(1)(i)(A), (b)(1)(i)(B), and (b)(1)(i)(C). \n\n\t\t\t\t(A)\tWithin 90 days after accomplishing the initial visual inspection required by paragraph (b) of this AD; and \n\n\t\t\t\t(B)\tWithin 180 days after accomplishing the initial visual inspection required by paragraph (b) of this AD; and \n\n\t\t\t\t(C)\tWithin 360 days after accomplishing the initial visual inspection required by paragraph (b) of this AD. \n\n\t\t\t(ii)\tIf the bracket assembly had been installed within the last 91 through 180 days prior to the effective date of this AD, repeat the visual inspection at the times specified in paragraphs (b)(1)(ii)(A) and (b)(1)(ii)(B). \n\n\t\t\t\t(A)\tWithin 90 days after accomplishing the initial visual inspection required by paragraph (b) of this AD; and \n\n\t\t\t\t(B)\tWithin 270 days after accomplishing the initialvisual inspection required by paragraph (b) of this AD. \n\n\t\t\t(iii)\tIf the bracket assembly had been installed within the last 181 through 360 days prior to the effective date of this AD, repeat the visual inspection within 180 days after accomplishing the initial visual inspection.\n \n\t\t(2)\tIf no crack is detected within 360 days after accomplishing the initial visual inspection required by paragraph (b)(1) of this AD, no further action is required. \n\n\t\t(3)\tIf any crack is detected during any of the visual inspections required by paragraph (b) of this AD, prior to further flight, stop drill the crack and install a doubler over the affected area, in accordance with the Boeing 747 Structural Repair Manual, Section 51-40-02. \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 Aircraft Certification Office (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: 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 FAR 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)\tThe replacement shall be done in accordance with Boeing Service Bulletin 747-76A2083, Revision 2, dated February 25, 1993. 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. The inspections and tightening shall be done in accordance with Boeing Alert Service Bulletin 747-76A2083, dated December 18, 1991; and Boeing Alert Service Bulletin 747- 76A2083, Revision 1, dated May 28, 1992. The repair shall be done inaccordance with Boeing Alert Service Bulletin 747-76A2083, Revision 1, dated May 28, 1992. The incorporation by reference of these documents was approved previously by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR Part 51 as of September 28, 1992 (57 FR 38251, August 24, 1992). 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 September 30, 1993.