91-09-12 BOEING: Amendment 39-6976. Docket No. 90-NM-245-AD. \n\n\tApplicability: All Model 737-300, 737-400, and 737-500 series airplanes, certificated in any category. \n\n\tCompliance: Required within the next 36 months after the effective date of this AD, unless previously accomplished. \n\n\tTo preclude cross connection of the engine fire extinguishing wiring and plumbing during maintenance, accomplish the following: \n\n\tA.\tFor airplanes listed in Boeing Service Bulletin 737-26-1067, dated June 28, 1990: Modify the engine fire extinguishing system wiring and plumbing in accordance with the service bulletin. Accomplishment of this modification constitutes terminating action for the repetitive inspections and functional tests required by Airworthiness Directive 89-03-51, Amendment 39-6213, on Boeing Model 737-300, 737-400, and 737-500 airplanes following maintenance on the engine fire extinguishing wiring and plumbing. \n\n\tB.\tFor airplanes line position 1890 and subsequent on which PRR 34774 or an equivalent modification was incorporated during production: The repetitive inspections and functional tests required by Airworthiness Directive 89-03-51, Amendment 39-6213, are terminated. \n\n\tC.\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\tD.\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\tAll persons affected by this directive who have not already received the appropriate service documents from the manufacturer may obtain copies upon request to Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124. These documents may be examined at the FAA, Northwest Mountain Region, Transport Airplane Directorate, 1601 Lind Avenue SW., Renton, Washington. \n\n\tThis amendment (39-6976, AD 91-09-12) becomes effective on May 28, 1991.