88-11-04 BOEING: Amendment 39-5909. Applies to Model 737 series airplanes, as listed in Boeing Alert Service Bulletin 737-57A1081, Revision 10, dated July 16, 1987, certificated in any category. Compliance required as indicated, unless previously accomplished. \n\n\tTo ensure structural integrity of the wing front spar upper chord structure, accomplish the following: \n\n\tA.\tWithin 100 flight hours after the effective date of this AD, unless previously accomplished within the last 900 flight hours, visually inspect for cracks the forward side of the wing front spar upper chord from front spar station (FSS) 90 to FSS 225, both left and right sides, in accordance with Boeing Alert Service Bulletin 737-57A1081, Revision 10, dated July 16, 1987. Repeat these inspections at intervals not to exceed 1,000 flight hours. \n\n\tB.\tAlternate means of compliance for paragraph A., above, only for airplanes which have been inspected in accordance with AD 74-01-01 and on which the spar chord segment, left FSS 108 to FSS 198 and/or right FSS 108 to FSS 198, was found to be free of cracks at the last inspection: Visually inspect that chord or chords for cracks in the forward side of the wing from FSS 90 to FSS 225, in accordance with Boeing Alert Service Bulletin 737-57A1081, Revision 10, dated July 16, 1987, within 900 flight hours from the last inspection, or within 100 flight hours after the effective date of this AD, whichever occurs later. Repeat these inspections at intervals not to exceed 1,000 flight hours. \n\n\tC.\tApply organic corrosion inhibitor after each inspection required by paragraph A. or B., above, in accordance with Boeing Alert Service Bulletin 737-57A1081, Revision 10, dated July 16, 1987. \n\n\tD.\tIf cracks are found as a result of the inspections required by paragraph A. or B., above, accomplish the following: \n\n\t\t1.\tIf cracks less than two inches in length are found, stop drill prior to further flight, in accordance with Boeing Alert Service Bulletin 737-57A1081, Revision 10, dated July 16, 1987. Thereafter, reinspect daily, using eddy current or dye penetrant inspection methods. If crack growth is observed, or prior to the accumulation of 400 hours time-in-service after stop drilling, whichever occurs first, repair in accordance with Boeing Alert Service Bulletin 737-57A1081, Revision 10, dated July 16, 1987. After repair, continue to inspect in accordance with paragraph A., above. \n\n\t\t2.\tIf cracks are equal to or greater than two inches in length, repair prior to further flight, in accordance with Boeing Service Bulletin 737-57A1081, Revision 10, dated July 16, 1987. After repair, continue to inspect in accordance with paragraph A., above. \n\n\tE.\tInstallation of new and improved upper chord segment in accordance with Boeing Service Bulletin 737-57-1081, Revision 7, dated March 21, 1980, is considered terminating action for the repetitive inspections required by this AD for the structure replaced. However the repetitive inspections required by paragraph A., B., or D., above, as applicable, must continue for the structure not replaced. \n\n\tF.\tAn alternate means of compliance or adjustment of the compliance time, which provide an acceptable level of safety and which has the concurrence of an FAA Principal Maintenance Inspector, 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 to a base in order to comply with the requirements of this AD. \n\n\tAll persons affected by this directive who have not already received the appropriate service 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 be examined at the FAA, Northwest Mountain Region, 17900 Pacific Highway South, Seattle, Washington, or Seattle Aircraft Certification Office, FAA, Northwest Mountain Region, 9010 East Marginal Way South, Seattle, Washington. \n\n\tThis amendment 39-5909 supersedes AD 74-01-01, Amendment 39-2799; and AD 87-05-52, Amendment 39-5627. \n\n\tThis amendment 39-5909 becomes effective June 13, 1988.