91-22-08 BOEING: Amendment 39-8068. Docket No. 91-NM-113-AD. Supersedes AD 74-21-01, Amendment 39-1982. \n\n\tApplicability: Model 727 series airplanes, certificated in any category. \n\n\tCompliance: Required as indicated, unless previously accomplished. \n\n\tTo detect cracking in the main landing gear (MLG) wheel well pressure floor, accomplish the following: \n\n\t(a)\tFor airplanes with line numbers 001 through 1102, except those modified in accordance with Boeing Alert Service Bulletin 727-53A0124, original release, dated May 3, 1974; Revision 1, dated September 27, 1974; or Revision 2, dated May 2, 1975: Prior to the compliance time specified in paragraph (a)(1) or (a)(2) of this AD, whichever occurs earlier, perform a detailed visual, high frequency eddy current (HFEC), or dye penetrant inspection for cracks in the pressure floor at body station (BS) 910, in accordance with Boeing Alert Service Bulletin 727-53A0124, Revision 3, dated November 30, 1989, or earlier FAA-approved revisions. \n\n\t\t(1)\tPrior to the accumulation of 15,000 landings or within 800 landings after November 2, 1974 (the effective date of AD 74-21-01, Amendment 39-1982), whichever occurs later; or \n\n\t\t(2)\tPrior to the accumulation of 12,000 landings or within 2,000 landings after the effective date of this AD, whichever occurs later. \n\n\t(b)\tFor airplanes with line numbers 001 through 1102, except those modified in accordance with Boeing Alert Service Bulletin 727-53A0124, original release, dated May 3, 1974; Revision 1, dated September 27, 1974; or Revision 2, dated May 2, 1975: Prior to the accumulation of 12,000 landings or within 2,000 landings after the effective date of this AD, whichever occurs later, perform a detailed visual, HFEC, or dye penetrant inspection for cracks in the pressure floor at BS 900 and BS 920, in accordance with Boeing Alert Service Bulletin 727-53A0124, Revision 3, dated November 30, 1989, or earlier FAA-approved revisions. \n\n\t(c)\tFor airplanes withline number 1103 and subsequent, and earlier airplanes that have been modified in accordance with Boeing Alert Service Bulletin 727-53A0124, original release, dated May 3, 1974; Revision 1, dated September 27, 1974; or Revision 2, dated May 2, 1975: Prior to the accumulation of 12,000 landings since manufacture or within the next 3,000 landings after the effective date of this AD, whichever occurs later, perform a detailed visual, HFEC, or dye penetrant inspection to detect cracks in the pressure floor at BS 910, and BS 920 between buttock line (BL) 00 and right BL 10, in accordance with Boeing Alert Service Bulletin 727-53A0124, Revision 3, dated November 30, 1989. \n\n\t(d)\tThe inspections required by paragraphs (a), (b), and (c) of this AD must be repeated in accordance with the following schedule: \n\n\t\t(1)\tRepeat the inspections required by paragraphs (a) or (b) of this AD at intervals not to exceed 2,000 landings. \n\n\t\t(2)\tRepeat the inspections required by paragraph (c) of this AD at intervals as follows: \n\n\t\t\t(i)\tIf the immediately preceding inspection was performed using a visual or dye penetrant inspection technique, the next inspection must be performed within 4,000 landings. \n\n\t\t\t(ii)\tIf the immediately preceding inspection was performed using an HFEC inspection technique, the next inspection must be performed within 5,000 landings. \n\n\t(e)\tIf cracks are detected that do not exceed the interim repair limits listed in Table V of the Accomplishment Instructions of Boeing Alert Service Bulletin 727-53A0124, Revision 3, dated November 30, 1989, prior to further flight, repair in accordance with the interim repair described in Part I of the Accomplishment Instructions, or the permanent repair described in Part II of the Accomplishment Instructions of that service bulletin, or repair in accordance with Boeing Drawing 65C36247, Revision New. The interim repair must be replaced, within 600 landings after accomplishment, with the permanent repair. \n\n\t(f)\tIf cracks are found that exceed the interim repair limits listed in Table V of the Accomplishments Instructions of Boeing Alert Service Bulletin 727-53A0124, Revision 3, dated November 30, 1989, prior to further flight, accomplish the permanent repair described in Part II of the Accomplishment Instructions of that service bulletin, or repair in accordance with Boeing Drawing 65C36247, Revision New. \n\n\t(g)\tBlind fasteners installed in accordance with Part II of Boeing Alert Service Bulletin 727- 53A0124, Revision 3, dated November 30, 1989, may be used as an interim repair only. The blind fasteners have a life limit of 10,000 landings before they must be replaced with solid fasteners in accordance with Part II of that service bulletin. The blind fasteners must be inspected for loose or missing fasteners after accumulating 3,000 landings since installation or within 1,000 landings after the effective date of this AD, whichever occurs later, and thereafter must be inspected at intervals not to exceed 2,500 landings until replaced. Blind fasteners installed prior to the effective date of this AD must be replaced prior to the accumulation of 10,000 landings since installation or within 3,000 landings after the effective date of this AD, whichever occurs later. \n\n\t(h)\tTerminating action for the repetitive inspection requirements of this AD is as follows: \n\n\t\t(1)\tIncorporation of the preventative modification described in Part III or Part IV, as applicable, of the Accomplishment Instructions of Boeing Alert Service Bulletin 727-53A0124, Revision 3, dated November 30, 1989, constitutes terminating action for the repetitive inspection requirement of paragraph (d) of this AD. \n\n\t\t(2)\tRepair or modification in accordance with Boeing Drawing 65C36247, Revision New, constitutes terminating action for the repetitive inspection requirement of paragraph (d) of this AD. \n\n\t\t(3)\tIncorporation of the permanent repairs in accordance with paragraph (e) or (f) of this ADconstitutes terminating action for the repetitive inspection requirement of paragraph (d) of this AD for the repaired area only. \n\n\t(i)\tAn alternative method of compliance or adjustment of the compliance time, which provides an acceptable level of safety, may be used when approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate. \n\n\tNOTE: The request should be forwarded through an FAA Principal Maintenance Inspector, who may concur or comment and then send it to the Manager, Seattle ACO. \n\n\t(j)\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\t(k)\tThe inspection requirements shall be done in accordance with Boeing Service Bulletin 727-53A0124, Revision 3, dated November 30, 1989. The repair requirements shall be done in accordance with Boeing Service Bulletin 727-53A0124, Revision 3, dated November 30, 1989; or in accordance with Boeing Drawing 65C36247, Revision New. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR Part 51. Copies may be obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124. Copies may be inspected at the FAA, Northwest Mountain Region, Transport Airplane Directorate, 1601 Lind Avenue S.W., Renton, Washington, or at the Office of the Federal Register, 1100 L Street N.W., Room 8401, Washington, D.C. \n\n\tAirworthiness Directive 91-22-08 supersedes AD 74-21-01, Amendment 39-1982. \n\n\tThis amendment (39-8068, AD 91-22-08) becomes effective on December 13, 1991.