79-17-02 R2 BOEING: Amendment 39-3526 as amended by Amendment 39-3563 is further amended by Amendment 39-3867. Applies to all Model 747 series airplanes certificated in all categories listed in Boeing Service Bulletin 747-53-2200. Compliance required within 300 hours time-in-service after the effective date of this AD unless already accomplished. \n\n\tTo prevent failure of the 7079-T6 truss and related 7079-T6 latch support fittings on the lower sill of the forward and aft lower cargo doorway, accomplish the following: \n\tA.\tWithin 300 hours time-in-service after the effective date of this AD unless already accomplished, visually inspect the 7079-T6 truss and related 7079-T6 latch support fittings on the lower sill of forward and aft lower cargo doorways for corrosion, cracking and blocked drainage paths in accordance with Boeing Service Bulletin 747-53-2200 dated May 8, 1979, or methods approved by the Chief, Engineering and Manufacturing Branch, Northwest Region. \n\tB.\tClear all blocked drainage paths, replace cracked latch support fittings, replace or repair corroded or cracked truss fittings in accordance with Boeing Service Bulletin 747-53-2200 Revision 1, before further flight. Cracked truss fittings may continue in service provided: cracks do not exceed limits in Service Bulletin 747-53-2200 Revision 1, no adjacent fittings are cracked, and provided the cracked fittings are visually inspected at intervals not to exceed 300 hours time- in-service. \n\tC.\tRepeat the inspection in accordance with paragraph A at intervals not to exceed 1,200 flight hours, until all affected fittings are replaced with 7075-T73 fittings. Apply BMS-3- 23 or equivalent to the internal lower sill areas after each inspection. Operators may make one more inspection at an interval not exceeding 2,000 flight hours (as required by AD 79-17-02, Amendment 39-3526, 44FR46782), measured from the last inspection conducted prior to the effective date of this amendment, before complyingwith the 1200 hour repetitive inspection. \n\tD.\tUpon request of an operator, an FAA Maintenance Inspector, subject to the prior approval by the Chief, Engineering and Manufacturing Branch, FAA Northwest Region, may adjust the repetitive inspection intervals specified in this AD if the request contains substantiating data to justify such adjustment. \n\tThe manufacturer's specifications and procedures identified and described in this directive are incorporated herein and made a part hereof pursuant to 5 U.S.C. 552(a)(1). \n\tAll persons affected by this directive who have not already received these documents from the manufacturer, may obtain copies upon request to Boeing Commercial Airplane Company, P.O. Box 3707, Seattle, Washington 98124. These documents may also be examined at FAA Northwest Region, 9010 East Marginal Way South, Seattle, Washington 98108. \n\n\tAmendment 39-3526 became effective August 15, 1979. \n\tAmendment 39-3563 became effective October 1, 1979. \n\tThis Amendment 39-3867 becomes effective September 13, 1980.