89-04-05 BOEING: Amendment 39-6132. Applicability: Model 747 series airplanes, Groups 1, 2, and 3 as listed in Boeing Service Bulletin 747-53- 2112, Revision 4, dated February 25, 1988, certificated in any category. \n\n\tCompliance: Required as indicated, unless previously accomplished. \n\n\tTo prevent failure of the body skin and the canted pressure bulkhead structure, accomplish the following: \n\n\tA.\tFor Group 1 airplanes on which the initial inspection requirements of Airworthiness Directive (AD) 84-18-02 have not been conducted as of the effective date of this AD, and which have not been modified by incorporation of a doubler in accordance with Boeing Service Bulletin 747-53-2112. \n\n\t\t1.\tPrior to the accumulation of 4,000 landings or within the next 100 landings after the effective date of this AD, whichever occurs later, and thereafter at intervals not to exceed 1,000 landings, perform a detailed visual inspection of the nose gear wheel well forward lower corners, exterior and interior area, for cracks, in accordance with Boeing Service Bulletin 747-53-2112, Revisions 3 or 4. Additionally, perform a high frequency eddy current (HFEC) inspection of the chord and doubler for cracks at the two forward hinge fairing attach bolt locations, in accordance with Boeing Service Bulletin 747-53-2112, Revisions 3 or 4. \n\n\t\t2.\tCracks found while conducting the inspections required by paragraph A.1., above, must be repaired as follows: \n\n\t\t\ta.\tIf the crack is visible on an interior surface, or exceeds any of the limits defined in paragraph A.2.b., below, repair in accordance with a method approved by the Manager, Seattle Aircraft Certification Office, FAA, Northwest Mountain Region, prior to further flight. \n\n\t\t\tb.\tIf the crack is visible from an exterior surface only and has not progressed into the vertical leg of the nose wheel well forward bulkhead lower chord and does not extend forward of the first row of skin fasteners, repair in accordance with a method approved by the Manager, Seattle Aircraft Certification Office, FAA, Northwest Mountain Region, prior to the accumulation of 500 additional landings, provided that a detailed visual inspection is performed at intervals not to exceed 100 landings. \n\n\t\t3.\tInspections are to continue after repair. If additional cracks are found, repair in accordance with a method approved by the Manager, Seattle Aircraft Certification Office, FAA, Northwest Mountain Region, prior to further flight. \n\n\tB.\tFor Group 1 airplanes on which the initial inspection requirements of AD 84-18-02 have been conducted as of the effective date of this AD, and which have not been modified by incorporation of a doubler in accordance with Boeing Service Bulletin 747-53-2112: Continue to perform the repetitive inspections, and to make repairs, if necessary, in accordance with the requirements of paragraph A., above. \n\n\tC.\tFor Group 1 airplanes on which the initial inspection requirements of AD 84-18-02 have notbeen conducted as of the effective date of this AD, and which have been modified by incorporation of a doubler, in accordance with Boeing Service Bulletin 747-53-2112: \n\n\t\t1.\tInspect the nose gear wheel well forward lower corners at the times and using the methods specified in either paragraph C.1.a. or C.1.b., below. \n\n\t\t\ta.\tOption I: External inspection. \n\n\t\t\t\tWithin 1,500 landings after modification or within the next 100 landings after the effective date of this AD, whichever occurs later, perform an external detailed visual inspection of the nose gear wheel well forward lower corner structure for cracks in accordance with Boeing Service Bulletin 747-53-2112, Revision 4, dated February 25, 1988. After the initial inspection, continue to inspect as follows: perform external general visual inspections at intervals not to exceed 100 landings, and external detailed visual inspections at intervals not to exceed 1,000 landings, in accordance with Boeing Service Bulletin 747-53-2112, Revision 4, dated February 25, 1988. \n\n\t\t\tb.\tOption II: External and internal inspection. \n\t\t\t\tWithin 1,500 landings after modification or within the next 100 landings after the effective date of this AD, whichever occurs later, perform an external and internal detailed visual inspection of the nose gear wheel well forward lower corner structure for cracks, in accordance with Boeing Service Bulletin 747- 53-2112, Revision 4, dated February 25, 1988. Repeat external and internal detailed visual inspections at intervals not to exceed 1,500 landings. \n\n\t\t2.\tIf cracks are found, repair in accordance with a method approved by the Manager, Seattle Aircraft Certification Office, FAA, Northwest Mountain Region, prior to further flight. \n\n\t\t3.\tInspections are to continue after repair. If cracks are found, repair in accordance with a method approved by the Manager, Seattle Aircraft Certification Office, FAA, Northwest Mountain Region, prior to further flight. \n\n\tD.\tFor Group 1airplanes on which the initial inspection requirements of AD 84-18-02 have been conducted as of the effective date of this AD, and which have been modified by incorporation of a doubler, in accordance with Boeing Service Bulletin 747-53-2112: Continue to perform the repetitive inspections, and to make repairs, if necessary, in accordance with the requirements of paragraph C. of this AD. \n\n\tE.\tFor Group 2 airplanes on which the initial inspection requirements of AD 84-18-02 have not been conducted as of the effective date of this AD, and which have not been modified by incorporation of the hinge fairing rework or modification doublers in accordance with Boeing Service Bulletin 747-53-2112: Perform the inspections and repairs, if necessary, in accordance with the requirements of paragraph A. of this AD, except that repetitive inspection intervals shall not exceed 2,000 landings. Inspections are to continue after repair. If cracks are found, repair in accordance with a method approved by the Manager, Seattle Aircraft Certification Office, FAA, Northwest Mountain Region, prior to further flight. \n\n\tF.\tFor Group 2 airplanes on which the initial inspection requirements of AD 84-18-02 have been conducted as of the effective date of this AD, and which have not been modified by incorporation of the hinge fairing rework or modification doublers in accordance with Boeing Service Bulletin 747-53-2112: Continue to perform the repetitive inspections, and to make repairs, if necessary, as described in paragraph A. of this AD, except that repetitive inspection intervals shall not exceed 2,000 landings. \n\n\t\tInspections are to continue after repair. If cracks are found, repair in accordance with a method approved by the Manager, Seattle Aircraft Certification Office, FAA, Northwest Mountain Region, prior to further flight. \n\n\tG.\tFor Group 2 airplanes on which the initial inspection requirements of AD 84-18-02 have not been conducted as of the effective date of this AD,and which have been modified by incorporation of the hinge fairing rework in accordance with Boeing Service Bulletin 747-53-2112: \n\n\t\t1.\tPrior to the accumulation of 6,000 landings after modification or within the next 100 landings after the effective date of this AD, whichever occurs later, perform a low frequency eddy current (LFEC) inspection for cracks in the underskin doubler at the nose gear wheel well forward lower corners, in accordance with Boeing Service Bulletin 747-53-2112, Revision 4, dated February 25, 1988. Repeat low frequency eddy current inspections in the underskin doubler at intervals not to exceed 2,000 landings. \n\n\t\t2.\tIf a crack is found that is visible on an interior surface or exceeds any of the limits in paragraph G.3., below, repair in accordance with a method approved by the Manager, Seattle Aircraft Certification Office, FAA, Northwest Mountain Region, prior to further flight. \n\n\t\t3.\tIf an underskin doubler crack is found that is not visible from the interior and has not progressed into the vertical leg of the nose wheel well forward bulkhead lower chord and does not extend forward of the first row of fasteners, repair in accordance with a method approved by the Manager, Seattle Aircraft Certification Office, FAA, Northwest Mountain Region, prior to the accumulation of 500 additional landings, provided that a detailed visual inspection of the nose gear wheel well forward corner structure is performed at intervals not to exceed 100 landings. \n\n\t\t4.\tInspections are to continue after repair. If cracks are found, repair in accordance with a method approved by the Manager, Seattle Aircraft Certification Office, FAA, Northwest Mountain Region, prior to further flight. \n\n\tH.\tFor Group 2 airplanes on which the initial inspection requirements of AD 84-18-02 have been conducted as of the effective date of this AD, and which have been modified by incorporation of hinge fairing rework only in accordance with Boeing Service Bulletin 747-53-2112: Continue to perform the repetitive inspections, and to make repairs, if necessary, in accordance with the requirements of paragraph G. of this AD. \n\n\tI.\tFor Group 2 airplanes on which the initial inspection requirements of AD 84-18-02 have been conducted as of the effective date of this AD, and which have been modified by incorporation of the hinge fairing rework and modification doublers in accordance with Boeing Service Bulletin 747-53-2112: \n\n\t\t1.\tIf the underskin doubler was not cracked at the time of modification, within 10,000 landings after the modification or within 1,000 landings after the effective date of this AD, whichever occurs later, perform an internal and external detailed visual inspection for cracks, in accordance with Boeing Service Bulletin 747-53-2112, Revision 4, dated February 25, 1988. Repeat internal and external detailed visual inspections at intervals not to exceed 2,000 landings. \n\n\t\t2.\tIf the underskin doubler was cracked at time ofmodification, within 2,000 landings after modification or within 1,000 landings after the effective date of this AD, whichever occurs later, perform an internal and external detailed visual inspection for cracks, in accordance with Boeing Service Bulletin 747-53-2112, Revision 4, dated February 25, 1988. Repeat internal and external detailed visual inspection at intervals not to \nexceed 2,000 landings. \n\n\t\t3.\tIf cracks are found, repair in accordance with a method approved by the Manager, Seattle Aircraft Certification Office, FAA, Northwest Mountain Region, prior to further flight. \n\n\t\t4.\tInspections are to continue after repair. If cracks are found, repair in accordance with a method approved by the Manager, Seattle Aircraft Certification Office, FAA, Northwest Mountain Region, prior to further flight.\n \n\tJ.\tFor Group 3 airplanes which have not been modified by incorporation of the external doubler in accordance with Boeing Service Bulletin 747-53-2112: \n\n\t\t1.\tPrior to theaccumulation of 6,000 landings after hinge fairing modification or within 1,000 landings after the effective date of this AD, whichever occurs later, perform a low frequency eddy current inspection for cracks in the underskin doubler at the nose gear wheel well forward lower corners, in accordance with Boeing Service Bulletin 747-53-2112, Revision 4, dated February 25, 1988. Repeat low frequency eddy current inspections in the underskin doubler at intervals not to exceed 2,000 landings. \n\n\t\t2.\tIf a crack is found that is visible on an interior surface or exceeds the limits defined in paragraph J.3., below, repair in accordance with a method approved by the Manager, Seattle Aircraft Certification Office, Northwest Mountain Region, prior to further flight. \n\n\t\t3.\tIf an underskin doubler crack is found that is not visible from the interior and has not progressed into the vertical leg of the nose wheel well forward bulkhead lower chord and does not extend forward of the first row offasteners, repair in accordance with a method approved by the Manager, Seattle Aircraft Certification Office, FAA, Northwest Mountain Region, prior to the accumulation of 500 additional landings, provided that a detailed visual inspection of the nose gear wheel well forward corner structure is performed at intervals not to exceed 100 landings. \n\n\t\t4.\tInspections are to continue after repair. If additional cracks are found, repair in accordance with a method approved by the Manager, Seattle Aircraft Certification Office, FAA, Northwest Mountain Region, prior to further flight. \n\n\tK.\tFor Group 3 airplanes which have been modified by incorporation of the external doubler in accordance with Boeing Service Bulletin 747-53-2112: \n\n\t\t1.\tIf the underskin doubler was not cracked at time of modification, within 10,000 landings after modification or within 1,000 landings after the effective date of this AD, whichever occurs later, perform an internal and external detailed visual inspection for cracks, in accordance with Boeing Service Bulletin 747-53- 2112, Revision 4, dated February 25, 1988. Repeat internal and external detailed visual inspections at intervals not to exceed 2,000 landings. \n\n\t\t2.\tIf the underskin doubler was cracked at the time of modification, within 2,000 landings after modification or within 1,000 landings after the effective date of this AD, whichever occurs later, perform an internal and external detailed visual inspection, in accordance with Boeing Service Bulletin 747-53-2112, Revision 4, dated February 25, 1988. Repeat internal and external detailed visual inspections at intervals not to exceed 2,000 landings. \n\n\t\t3.\tIf cracks are found, repair in accordance with a method approved by the Manager, Seattle Aircraft Certification Office, FAA, Northwest Mountain Region, prior to further flight. \n\n\t\t4.\tInspections are to continue after repair. If cracks are found, repair in accordance with a method approved by the Manager, Seattle Aircraft Certification Office, FAA, Northwest Mountain Region, prior to further flight. \n\n\tL.\tAn alternate means 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, FAA, Northwest Mountain Region. \n\n\tNOTE: The request should be forwarded through an FAA Principal Maintenance Inspector (PMI), who may add any comments and then send it to the Manager, Seattle Aircraft Certification Office. \n\n\tM.\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 Boeing Commercial Airplanes, P. O. Box 3707, Seattle, Washington 98124. These documents may be examined at the FAA, Northwest Mountain Region, 17900Pacific Highway South, Seattle, Washington, or Seattle Aircraft Certification Office, FAA, Northwest Mountain Region, 9010 East Marginal Way South, Seattle, Washington. \n\n\tThis amendment supersedes AD 84-18-02, Amendment 39-4906, which was effective October 8, 1984. \n\n\tThis amendment (39-6132, AD 89-04-05) becomes effective March 15, 1989.