85-20-03 BOEING: Amendment 39-5142. Applies to Model 727-100, -100C, and -200 series airplanes listed in Boeing Service Bulletin Number 727-53A0173, dated July 12, 1985, certificated in any category. To detect cracks in the Body Station 1183 pressure bulkhead web and vertical beams, accomplish the following: \n\n\tA.\tOn airplanes with less than 40,000 flight cycles on the effective date of this AD, visually inspect within the next 400 flight cycles after the effective date of this AD, or prior to the accumulation of 25,000 flight cycles, whichever occurs later after the effective date of this AD, the aft pressure bulkhead web for cracks in accordance with Figure 1 of Boeing Service Bulletin 727-53A0173, dated July 12, 1985, or later FAA-approved revision: \n\n\t\t1.\tIf no cracks are detected, repeat the inspection in paragraph A., above, at intervals not to exceed 400 flight cycles until inspected in accordance with paragraph C., below. \n\n\t\t2.\tIf cracks are detected, inspect the vertical beams in accordance with Figures 2 and 3 of Boeing Service Bulletin 727-53A0173, dated July 12, 1985, or later FAA-approved revisions. Repair all cracks prior to further flight in accordance with the applicable provisions of paragraphs III.C., III.D., III.E, and III.F. of Boeing Service Bulletin 727-53A0173, dated July 12, 1985, or later FAA-approved revision, and Boeing Drawing Number 65C31492, Revision N/C, or later FAA-approved revision; or in a manner approved by the Manager, Seattle Aircraft Certification Office. Repeat the visual inspection required by paragraph A., above, at intervals not to exceed 400 flight cycles until inspected in accordance with paragraph C., below. \n\n\tB.\tOn airplanes with 40,000 or more flight cycles, visually inspect within the next 200 flight cycles after the effective date of this AD, the Body Station 1183 pressure bulkhead web for cracks in accordance with Figure 1 of Boeing Service Bulletin 727-53A0173, dated July 12, 1985, or later FAA-approved revision. \n\n\t\t1.\tIf no cracks are detected, repeat the inspection in paragraph A., above, at intervals not to exceed 200 flight cycles until inspected in accordance with paragraph C., below. \n\n\t\t2.\tIf cracks are detected, inspect in accordance with Figures 2 and 3 of Boeing Service Bulletin 727-53A0173, dated July 12, 1985, or later FAA-approved revision. Repair all cracks prior to further flight in accordance with the applicable provisions of paragraphs III.C., III.D., III.E., and III.F. of Boeing Service Bulletin 727-53A0173, dated July 12, 1985, or later FAA-approved revision; and Boeing Drawing Number 65C31492, Revision N/C, or later FAA-approved revision; or in a manner approved by the Manager, Seattle Aircraft Certification Office, FAA, Northwest Mountain Region. Repeat the visual inspection required by paragraph A., above, at intervals not to exceed 200 flight cycles until inspected in accordance with paragraph C., below. \n\n\tC.\tWithin 3800 flight cycles after the effective date of this AD or upon the accumulation of 25,000 flight cycles, whichever occurs later, visually inspect the Body Station 1183 pressure bulkhead vertical beams for cracks in accordance with Figure 2 of Boeing Service Bulletin 727-53A0173, dated July 12, 1985, or later FAA- approved revision. If cracks longer than 2 inches are detected, inspect the vertical beams and web in accordance with Figures 1 and 3 of Boeing Service Bulletin 727-53A0173, dated July 12, 1985, or later FAA-approved revision. Repair all cracks prior to further flight in accordance with the applicable provisions of paragraphs III.C., III.D., III.E., and III.F. of Boeing Service Bulletin 727-53A0173, dated July 12, 1985, or later FAA-approved revision; and Boeing Drawing Number 65C31492, Revision N/C, or later FAA-approved revision; or in a manner approved by the Manager, Seattle Aircraft Certification Office, FAA, Northwest Mountain Region. Repeat the visual inspection of this paragraph at intervals notto exceed 3800 flight cycles. \n\n\tD.\tTo terminate the repetitive inspection requirements of this AD, incorporate the reinforcement of the Body Station 1183 bulkhead vertical beams in accordance with Paragraph II.D. of Boeing Service Bulletin 727- 53-55, Revisions N/C through 2; or Paragraph III.D. of Boeing Service Bulletin 727-53-55, Revision 3, or later FAA-approved revision; or in a manner approved by the Manager, Seattle Aircraft Certification Office, FAA, Northwest Mountain Region. \n\n\tE.\tSpecial flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate airplanes to a base for the accomplishment of inspections and/or modifications required by this AD. \n\n\tAll persons affected by this proposal who have not already received copies of the service bulletins may obtain copies upon request from the Boeing Commercial Airplane Company, P.O. Box 3707, Seattle, Washington 98124. These documents may be examined at the FAA, Northwest Mountain Region, 17900 PacificHighway South, Seattle, Washington, or the Seattle Aircraft Certification Office, 9010 East Marginal Way South, Seattle, Washington. \n\n\tThis amendment becomes effective October 15, 1985.