85-22-02 BOEING: Amendment 39-5159. Applies to Model 737 series airplanes, certificated in any category, listed in Boeing Service Bulletin 737-57-1137, Revision 2, dated November 9, 1984. Unless previously accomplished, prior to the accumulation of 10,000 landings or within 180 days or 2,500 landings after the effective date of this AD, whichever occurs later, accomplish the following to detect cracking which may lead to failure of the body buttock line (BBL) 70.85 rib upper chord: \n\n\tA.\tVisually inspect the BBL 70.85 rib upper chord for cracks in accordance with Table I of the Flight Safety Addendum of Boeing Service Bulletin 737-57-1137, Revision 2, or later FAA-approved revisions. Repeat the inspections at intervals not to exceed 5,000 landings.\n \n\tB.\tIf cracks are detected, prior to further flight repair cracked parts in accordance with Table I of the Accomplishment Instructions or the Preventative Modification Part III or Special Preventative Modification Part IV of the"Accomplishment Instructions" in Boeing Service Bulletin 737-57-1137, Revision 2, or later FAA-approved revisions. \n\n\tC.\tParts repaired in accordance with the "stop drilling" interim action in Table I of the Accomplishment Instructions of Boeing Service Bulletin 737-57-1137, Revision 2, must be visually reinspected at intervals not to exceed 1,500 landings and must be repaired in accordance with the Preventative Modification Part III or Special Preventative Modification Part IV of Boeing Service Bulletin 737-57-1137, Revision 2, or later FAA-approved revisions, within two years after the effective date of this AD or within two years after the accomplishment of the interim repair, whichever occurs later. \n\n\tD.\tThe repetitive inspection requirements of this AD may be terminated if the Preventative Modification Part III or the Special Preventative Modification Part IV of the Accomplishment Instructions in Boeing Service Bulletin 737-57-1137, Revision 2, or later FAA- approved revisions, is incorporated.\n \n\tE.\tAirplanes may be ferried to a maintenance base for repairs or replacement of parts in accordance with FAR 21.197 and 21.199. \n\n\tF.\tFor the purpose of this AD, and when approved by an FAA Maintenance Inspector, the number of landings may be computed by dividing each airplane's time in service by the operator's fleet average time from takeoff to landing for the aircraft type. \n\n\tG.\tAlternate means of compliance which provide an acceptable level of safety may be used when approved by the Manager, Seattle Aircraft Certification Office, FAA, Northwest Mountain Region.\n \n\tH.\tUpon the request of an operator, an FAA Maintenance Inspector, subject to prior approval of the Manager, Seattle Aircraft Certification Office, FAA, Northwest Mountain Region, may adjust the repetitive inspection intervals specified in this AD to permit compliance at an established inspection period of that operator if the request contains substantiating data to justify the change for that operator. \n\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 FAA, Seattle Aircraft Certification Office, 9010 East Marginal Way South, Seattle, Washington. \n\n\tThis amendment becomes effective November 25, 1985.