89-12-10 BOEING: Amendment 39-6230. \n\tApplicability: Model 747-100, 747-200, 747-300, and 747-SP series airplanes, certificated in any category. \n\tCompliance: Required as indicated, unless previously accomplished. \n\n\tTo minimize the fire hazard as a result of lower wing surface fuel tank access door penetration due to impact from low energy engine and tire debris, accomplish the following: \n\n\tA.\tWithin the next 8 months after the effective date of this AD, replace the two inboard fuel tank access doors on each lower wing skin (Nos. 544AB and 545AB) on the left wing and (Nos. 644AB and 645AB) on the right wing, with doors having impact resistance equivalent to that of 2024-T3 aluminum 0.140-inch thick, as approved by the Manager, Seattle Aircraft Certification Office, FAA, Northwest Mountain Region in accordance with the procedures described in Section 28-11-02 of the Boeing Model 747 Maintenance Manual. The replacement doors must also be fire resistant, as defined in theFederal Aviation Regulations, Part 1. \n\n\tB.\tWithin the next 30 months after the effective date of this AD, replace the following 14 lower wing surface fuel tank access doors, seven on the left wing (Nos. 546AB, 546BB, 552AB, 552BB, 552CB, 552DB, and 552EB), and seven on the right wing (Nos. 646AB, 646BB, 652AB, 652BB, 652CB, 652DB, and 652EB), with doors having impact resistance equivalent to that of 2024-T3 aluminum 0.140-inch thick, as approved by the Manager, Seattle Aircraft Certification Office, FAA, Northwest Mountain Region, in accordance with the procedures described in Section 28-11-02 of the Boeing Model 747 Maintenance Manual. The replacement doors must also be fire resistant, as defined in the Federal Aviation Regulations, Part 1. \n\n\tC.\tAn alternate means 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, FAA, Northwest Mountain Region.NOTE: 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\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 Airplanes, P.O. Box 3707, Seattle, Washington 98124. These documents may be examined at FAA, Northwest Mountain Region, Transport Airplane Directorate, 17900 Pacific Highway South, Seattle, Washington, or at the Seattle Aircraft Certification Office, 9010 East Marginal Way South, Seattle, Washington. \n\n\tThis amendment (39-6230, AD 89-12-10) becomes effective on July 8, 1989.