91-05-17 BOEING: Amendment 39-6917. Docket No. 90-NM-209-AD. \n\n\tApplicability: Model 747 series airplanes, line numbers 002 through 226, certificated in any category. \n\n\tCompliance: Required as indicated, unless previously accomplished. \n\n\tTo prevent loss of the horizontal stabilizer, accomplish the following: \n\n\tA.\tWithin the next 30 days after April 13, 1990 (the effective date of Amendment 39-6556), perform either a close detailed visual inspection or a high frequency eddy current (HFEC) inspection of the fuselage station 2598 bulkhead upper web in the corners of the access cut-out, in accordance with Boeing Alert Service Bulletin 747-53A2332, dated March 8, 1990. Repeat these inspections as follows: \n\n\t\t1.\tIf the immediately preceding inspection was accomplished visually, the next inspection must be conducted within 250 landings. \n\n\t\t2.\tIf the immediately preceding inspection was accomplished using HFEC, the next inspection must be conducted within 1,000 landings. \n\n\tB.\tIf cracks less than 1.5 inches are found, repair prior to further flight, in accordance with repair procedures defined in Boeing Alert Service Bulletin 747-53A2332, dated March 8, 1990, or accomplish the terminating modification specified in paragraph E. of this AD. Inspect repairs for cracks in accordance with paragraph A. of this AD, until the terminating modification specified in paragraph E. of this AD, is accomplished. \n\n\tC.\tIf cracks are found that are 1.5 inches or longer, modify prior to further flight by installing the terminating modification specified in paragraph E. of this AD. \n\n\tD.\tWithin the next 30 days after April 13, 1990 (the effective date of Amendment 39-6556), remove the fastener common to the web and the tab on the vertical stiffener, at each corner of the upper bulkhead cut-out, and perform a high frequency eddy current inspection of the open hole in accordance with Boeing Alert Service Bulletin 747-53A2332, dated March 8, 1990. If no cracks are found, replace the fastener with a 1/16-inch oversized equivalent fastener. If any cracks are found, prior to further flight, accomplish the repair and inspections required by paragraph B. of this AD, or modify prior to further flight in accordance with the terminating modification specified in paragraph E. of this AD. \n\n\tE.\tWithin the next 2 years after the effective date of this AD, accomplish the terminating modification specified in Boeing Alert Service Bulletin 747-53A2332, dated March 8, 1990. Installation of the modification constitutes terminating action for the inspections required by this AD. \n\n\tF.\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 (ACO), FAA, Transport Airplane Directorate. \n\n\tNOTE: The request should be submitted directly to the Manager, Seattle ACO, and a copy sent to the cognizant FAA Principal Inspector(PI). The PI will then forward comments or concurrence to the Seattle ACO. \n\n\tNOTE: Any alternate means of compliance previously approved for paragraph G. of AD 90-07-11, Amendment 39-6556, constitutes an alternate means of compliance with paragraph F. of this AD. \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 information from the manufacturer may obtain copies upon request to Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124. This information may be examined at the FAA, Northwest Mountain Region, Transport Airplane Directorate, 1601 Lind Avenue SW., Renton, Washington. \n\n\tAirworthiness Directive 91-05-17 supersedes AD 90-07-11, Amendment 39-6556. \n\n\tThis amendment (39-6917, AD 91-05-17) becomes effective on April 5, 1991.