86-09-07 R1 BOEING: Amendment 39-5306 as amended by Amendment 39-5580. Applies to Model 747 series airplanes listed in Boeing Alert Service Bulletin 747-53A2267, dated March 28, 1986, certificated in any category. \n\n\tTo prevent a condition that could lead to depressurization of the airplane accomplish the following, unless already accomplished: \n\n\tA.\tPerform an external visual inspection of lower longitudinal lap joint areas for corrosion in accordance with Boeing Alert Service Bulletin 747-53A2267, dated March 28, 1986, or later FAA- approved revision. \n\n\t\t1.\tInspect within the next 100 landings after the effective date of this amendment, or within 4,000 flight hours or 15 months from the last inspection of each lap joint area, provided no corrosion was found at that inspection, whichever is later. \n\n\t\t2.\tIf corrosion is found and is associated with cracks, skin penetration, or missing fasteners; or if it exceeds a total length of 20 inches along any 40-inch distance; repair before further flight in accordance with paragraph C., below. Reinspect airplanes with less severe corrosion at intervals not to exceed 1,000 flight hours or 6 months, whichever is sooner. \n\n\t\t3.\tIf no corrosion is found, reinspect at intervals not to exceed 4,000 flight hours or 15 months, whichever is sooner. \n\n\tB.\tIf corrosion is found in the longitudinal lap joint area, perform an internal inspection of the body frames for cracking in the vicinity of each corroded lap joint area before further flight in accordance with Boeing Alert Service Bulletin 747-53A2267, dated March 28, 1986, or later FAA- approved revision, unless already accomplished within the last 1,000 landings. Repeat the frame inspections thereafter at intervals not to exceed 1,000 landings until terminating action is performed on the lap joints in accordance with paragraph C., below. Repair cracks before further flight in accordance with an FAA-approved method. \n\n\tC.\tTerminating action for the repetitiveinspections of paragraphs A. and B., above, is repair of the lap joints in accordance with Boeing Service Bulletin 747-53A2267, dated March 28, 1986, or later FAA-approved revision. \n\n\tD.\tApply organic corrosion inhibiting compound in accordance with Boeing Service Bulletin 747-53A2267, Revision 1, dated September 25, 1986, or later FAA-approved revisions. \n\n\tE.\tFor the purposes of complying with this AD, the number of landings may be determined to equal the number of pressurization cycles where the cabin pressure differential was greater than 2.0 psi. \n\n\tF.\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. \n\n\tG.\tSpecial flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate airplanes unpressurized to a base for the accomplishment of inspections and/or modifications requiredby this AD. \n\n\tH.\tFor Boeing Model 747SR airplanes only, based on continued mixed operation of cabin pressure differentials, the reinspection intervals specified in paragraph B. of this AD may be multiplied by a 1.2 adjustment factor. \n\n\tAll persons affected by this proposal who have not already received the appropriate service information from the manufacturer may obtain copies upon request to the Boeing Commercial Airplane Company, P.O. Box 3707, Seattle, Washington 98124-2207. These documents may be examined at the FAA, Northwest Mountain Region, 17900 Pacific Highway South, Seattle, Washington, or the Seattle Aircraft Certification Office, 9010 East Marginal Way South, Seattle, Washington. \n\n\tAmendment 39-5306 superseded AD 76-05-05, Amendment 39-2538, as amended by Amendments 39-2698, 39-2961, and 39-3430. \n\n\tAmendment 39-5306 became effective May 27, 1986. \n\tThis amendment, 39-5580, becomes effective March 30, 1987.