91-20-06 BOEING: Amendment 39-8040. Docket 91-NM-56-AD. Supersedes AD 89-22-03. \n\n\tApplicability: Model 747-100 and -200 series airplanes, manufactured prior to January 1, 1981; equipped with General Electric CF6-45/50 or Pratt and Whitney JT9D-70 engines; as listed in Boeing Service Bulletin 747-26-2162, dated September 20, 1990, certificated in any category. \n\n\tCompliance: Required as indicated, unless previously accomplished. \n\n\tTo preclude cross connection of the engine nacelle fire extinguishing plumbing during maintenance, accomplish the following: \n\n\tA.\tWithin 10 days after October 24, 1989 (the effective date of Amendment 39- 6353, AD 89-22-03), and thereafter, immediately following any maintenance action which could cause mis-plumbing, conduct an inspection of the engine fire extinguishing system plumbing in accordance with Boeing Service Bulletin 747-26A2094, Revision 1, dated March 25, 1983. \n\n\tB.\tBefore further flight, correct any discrepancy detected during the functional tests required by paragraph A. of this AD. \n\n\tC.\tWithin 18 months after the effective date of this amendment, modify the engine fire extinguisher system plumbing in accordance with Boeing Service Bulletin 747-26-2162, dated September 20, 1990. Accomplishment of this modification constitutes terminating action for the repetitive inspections required by paragraph A. of this AD. \n\n\tD.\tAn alternative method of compliance or adjustment of the compliance time, which provides an acceptable level of safety, may be used when approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate. \n\n\tNOTE: The request should be forwarded through an FAA Principal Maintenance Inspector, who may concur or comment and then send it to the Manager, Seattle ACO. \n\n\tE.\tSpecial flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate airplanes to a base in order to comply with the requirements of this AD. \n\n\tF.\tThe modification shall be done in accordance with Boeing Service Bulletin 747- 26-2162, dated September 20, 1990. 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. Copies may be inspected at the FAA, Northwest Mountain Region, Transport Airplane Directorate, 1601 Lind Avenue SW., Renton, Washington, or at the Office of the Federal Register, 1100 L Street NW., Room 8401, Washington, D.C. \n\n\tAirworthiness Directive 91-20-06 supersedes AD 89-22-03, Amendment 39-6353. \n\tThis amendment (39-8040, AD 91-20-06) becomes effective on November 7, 1991.