79-19-01 R2 BOEING: Amendment 39-3556 as amended by Amendment 39-4087 is further amended by Amendment 39-4486. Applies to all Boeing 720/720B, 707-300, 707-400, 707- 300B, and 707-300C series airplanes. \n\tA.\tAfter the effective date of this amendment, perform a low frequency eddy current inspection for cracks in the wing lower surface splice stringers in accordance with Boeing Service Bulletin 3226, Rev. 5, dated November 15, 1981, or later FAA approved revisions, or in a manner approved by the Manager, Seattle Aircraft Certification Office, FAA, Northwest Mountain Region. Inspections are to be made at the threshold times, within the prescribed initial interval and at repetitive intervals shown below: \n\tAt the inboard nacelle strut drag brace, the affected lower skin area covered by the fairing may be visually inspected for cracks and evidence of fuel leakage. If crack indications are noted in stringers, or skin cracks or fuel leakage are found at the diagonal brace fairing area, tank entry and inspection by high frequency eddy current of the wing splice stringers is required. \n\n\nAirplane\nThreshold\nInitial Inspection within\n\nRepetitive Interval \n\n\n\nunless accomplished \nwithin the last \n\n720/720B\n14,000 ldgs\n715 ldgs\n715 ldgs\n1,430 ldgs\n707-300/400\n21,000 ldgs\n1,675 ldgs\n1,675 ldgs\n3,350 ldgs\n707-300B\n19,000 ldgs\n1,425 ldgs\n1,425 ldgs\n2,850 ldgs\n707-300C\n17,000 ldgs\n725 ldgs\t\n725 ldgs\n1,450 ldgs \n707-300C\n\n17,000 ldgs\n1,425 ldgs\n1,425 ldgs\n2,850 ldgs \n\n(passenger only) \n\n\n\n\n\t\t\t\t\t\t\t\t\t\t \n\tB.\tIf cracks are found, repair prior to further revenue flight in accordance with a method approved by the Manager, Seattle Aircraft Certification Office, FAA, Northwest Mountain Region. \n\tC.\tFor the purpose of complying with this AD and subject to acceptance by the assigned FAA Maintenance Inspector, the number of landings may be determined by dividing each airplane's time-in-service by the operator's fleet average from takeoffto landing for the airplane type. \n\tD.\tUpon request of the operator, an FAA Maintenance Inspector, subject to prior approval of the Manager, Seattle Aircraft Certification Office, FAA, Northwest Mountain Region may adjust the inspection interval if the request contains substantiating data to justify the increase for that operator. \n\tE.\tAirplanes with cracked splice stringers may be flown in accordance with FAR 21.197 to a base where repairs can be performed. \n\tAll persons affected by this directive who have not already received these documents from the manufacturer may obtain copies upon request to the Boeing Commercial Airplane Company, P.O. Box 3707, Seattle, Washington 98124. These documents may also be examined at the FAA, Northwest Mountain Region, 9010 East Marginal Way South, Seattle, Washington. \n\n\tAmendment 39-3556 became effective September 18, 1979. \n\tAmendment 39-4087 became effective May 17, 1981. \n\tThis Amendment 39-4486 becomes effective November 15, 1982.