90-11-02 BOEING: Amendment 39-6601. Docket No. 89-NM-200-AD. \n\n\tApplicability: Model 747 series airplanes, listed in Boeing Alert Service Bulletin 747- 53A2317 dated December 21, 1989, certificated in any category. \n\n\tCompliance: Required within one year after the effective date of this AD, unless previously accomplished. \n\n\tTo prevent an APU fire from penetrating the APU firewall, accomplish the following: \n\n\tA.\tVisually inspect the APU firewall penetration located near Buttock Line Zero and Water Line 355 in accordance with Boeing Alert Service Bulletin 747-53A2317 dated December 21, 1989. If the firewall penetration is found to contain an aluminum plug assembly, prior to further flight, replace the aluminum plug assembly with a titanium or the equivalent stainless steel plug assembly, in accordance with the service bulletin listed above. \n\n\tB.\tAn alternate means of compliance or adjustment of the compliance time, which provides an acceptable level of safety, may beused when approved by the Manager, Seattle Aircraft Certification Office, FAA, Northwest Mountain Region. \n\n\tNOTE: The request should be forwarded through an FAA Principal Maintenance Inspector (PMI), who will either concur or comment, and then send it to the Manager, Seattle Aircraft Certification Office. \n\n\tC.\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 Airplanes, P.O. Box 3707, Seattle, Washington 98124. These documents may be examined at the FAA, Northwest Mountain Region, Transport Airplane Directorate, 17900 Pacific Highway South, Seattle, Washington, or Seattle Aircraft Certification Office, 9010 East Marginal Way South, Seattle, Washington. \n\n\tThis amendment (39-6601, AD 90-11-02) becomes effective on June 19, 1990.