90-06-18 R1 BOEING: Amendment 39-6541 as corrected by Amendment 39-6706. Docket No. 89-NM-105-AD. \n\n\tApplicability: Model 747 series airplanes, Groups 1, 2, and 3 as listed in Boeing Service Bulletin 747-32-2190, Revision 4, dated October 26, 1989, certificated in any category. \n\n\tCompliance: Required as indicated, unless previously accomplished. \n\n\tTo prevent landing gear collapse during landing due to corrosion and fatigue cracks, accomplish the following: \n\n\tA.\tInspect as follows: \n\n\t\t1.\tWithin the next 120 days after the effective date of this AD, perform a visual inspection, or a visual plus eddy current inspection, of the wing landing gear at the trunnion, for cracks and corrosion, in accordance with Boeing Service Bulletin 747-32-2190, Revision 4, dated October 26, 1989. \n\n\t\t2.\tIf no cracks or corrosion are found, repeat inspection described in paragraph A.1. of this AD at intervals not to exceed 6 months if the visual inspection option was selected for the previous inspection, or at intervals not to exceed 18 months if visual and eddy current inspection option was selected for the previous inspection. \n\n\t\t3.\tExcept as provided by paragraph A.4. below, if cracks or corrosion are found, prior to further flight, remove and rework or replace cracked/corroded parts in accordance with Boeing Service Bulletin 747-32-2190, Revision 4, dated October 26, 1989. \n\n\t\t4.\tIf only corrosion is found, as an alternative to paragraph A.3. of this AD, accomplish the terminating action described in Boeing Service Bulletin 747-32-2190, Revision 4, dated October 26, 1989, within 12 months after detection of corrosion, but no later than 36 months after the effective date of this AD; and high frequency eddy current inspect the wing landing gear trunnion at intervals not to exceed 6 months, until the terminating action is accomplished. \n\n\tB.\tModification in accordance with Boeing Service Bulletin 747-32-2190, Revision 4, dated October 26, 1989, constitutes terminating action for the reinspection requirements of paragraph A. above. \n\n\tC.\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 will either concur or comment, and then send it to the Manager, Seattle Aircraft Certification Office. \n\n\tD.\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. This information may be examined at the FAA, Northwest Mountain Region, Transport Airplane Directorate, 1601 Lind Avenue S.W., 5th Floor, Renton, Washington, or the Seattle Aircraft Certification Office, 1601 Lind Avenue S.W., 2nd Floor, Renton, Washington.\n \n\tAirworthiness Directive 90-06-18 R1 revises AD 90-06-18, Amendment 39-6541. \n\tThe effective date for the requirements of this AD remains April 23, 1990, as specified in Amendment AD 90-06-18, Amendment 39-6541. \n\n\tThis Amendment (39-6706, AD 90-06-18 R1) is effective on August 17, 1990.