84-23-05 BOEING: Amendment 39-4949. Applies to Boeing Model 737 series airplanes, certificated in all categories, listed in Boeing Service Bulletin 737-55A1029, Revision 3. To ensure continued structural integrity of the horizontal stabilizer, accomplish the following, unless previously accomplished: \n\n\tA.\tInspect the rear spar horizontal stabilizer attach lugs for cracks in accordance with instructions in Boeing Service Bulletin 737-55A1029, Revision 3, or later FAA approved revision, upon the accumulation of the threshold number of landings specified in Table I of the service bulletin or within 200 landings after the effective date of this AD, whichever occurs later. Repeat these inspections at intervals not exceeding those specified in Table I of the service bulletin. \n\n\tB.\tCracked parts must be replaced or repaired in a manner approved by the Manager, Seattle Aircraft Certification Office, FAA, Northwest Mountain Region before further flight. \n\n\tC.\tAirplanes may be flown to a maintenance base for repairs or replacement in accordance with FAR 21.197 and 21.199 with prior approval of the Manager, Seattle Aircraft Certification Office, FAA, Northwest Mountain Region. \n\n\tD.\tFor purposes of complying with the AD, subject to the acceptance by the assigned FAA Maintenance Inspector, the number of landings may be determined by dividing each airplane's hours time in service by the operator's fleet average time from takeoff to landing for the airplane type. \n\n\tE.\tAlternate means of compliance which provide an equivalent level of safety may be used when approved by the Manager, Seattle Aircraft Certification Office, FAA, Northwest Mountain Region. \n\n\tF.\tUpon request by the operator, an FAA Principal Maintenance Inspector, subject to prior approval by the Manager, Seattle Aircraft Certification Office, FAA, Northwest Mountain Region, may adjust the repetitive inspection interval in this AD, if the request contains substantiating data to justify the increase for the 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 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\tThis supersedes Amendment 39-4122 (46 FR 28147; May 26, 1981), AD 81-11-07. \n\tThis Amendment 39-4949 becomes effective December 15, 1984.