74-15-03 BOEING: Amendment 39-1897 as amended by Amendment 39-2550. Applies to all Boeing 707-300, -300B/C, -400 series airplanes listed in Boeing Service Bulletin 3168 with more than 5000 flights which have not accomplished Boeing Service Bulletin 2607 or 2427 part X(a). \n\tFor purposes of this AD, one flight is defined as one takeoff and landing. Compliance required as indicated. \n\tTo detect cracking in the upper wing skin under the external rib chord at WBL 59.24, on airplanes with more than 5000 flights, or more than 5000 flights since incorporation of Service Bulletin 2626, accomplish the inspections of (1) at the times specified in (2). Repetitive inspections are noted in paragraph (3) and terminating action is noted in paragraph (4). \n\t(1)\tInspect the wing skins for cracks around the 4 critical fasteners as defined in Boeing Service Bulletin 3168 by use of the procedures specified in (a) or (b) below. Wing skins found cracked are to be repaired prior to further flight inaccordance with Boeing Service Bulletin 3168 or 2607 or in a manner approved by the Chief, Engineering and Manufacturing Branch, FAA Northwest Region. \n\t\t(a)\tEddy current procedures as specified in Boeing Service Bulletin 3168. \n\t\t(b)\tUltrasonic inspection procedures as specified in Boeing Service Bulletin 3168. Reinspection of the wing skin is required at intervals not to exceed 200 flights until an eddy current inspection of (a) above has been accomplished, or the wing skin has been modified in accordance with Boeing Service Bulletin 2607 or a method approved by the Chief, Engineering and Manufacturing Branch, FAA Northwest Region. \n\t(2)\tAfter the effective date of this AD, aircraft with more than 10,000 flights, are to be inspected within the next 100 flights; airplanes with more than 7500 flights, within the next 200 flights; airplanes with more than 5000 flights, within the next 300 flights. \n\t(3)\tRepetitive inspections are to be accomplished at the times specified in (a) or(b) below, in accordance with the eddy current inspection procedures of Boeing Service Bulletin No. 3168, or in a manner approved by the Chief, Engineering and Manufacturing Branch, FAA Northwest Region. Wing skins found cracked are to be repaired prior to further flight in accordance with Boeing Service Bulletin No. 3168 or in a manner approved by the Chief, Engineering and Manufacturing Branch, FAA Northwest Region. Thereafter reinspect at intervals not to exceed those specified in (a) below. \n\t\t(a)\tFor airplanes which have been modified in accordance with Boeing Service Bulletin No. 2626, following the inspection required by paragraph (1)(a), reinspect at intervals not to exceed 2,000 flights. \n\t\t(b)\tFor airplanes which have not been modified in accordance with Boeing Service Bulletin No. 2626, inspect within 5,000 flights after accomplishment of the hole oversizing and eddy current inspections required by paragraph (1)(a) and at intervals thereafter not to exceed 2,000 flights.(4)\tReplacement of the upper wing skin in accordance with Boeing Service Bulletin No. 2607, or incorporation of Boeing Service Bulletin No. 2427 Part Xa, or modifications approved by the Chief, Engineering and Manufacturing Branch, FAA Northwest Region constitutes terminating action for this AD. \n\tThe manufacturer's specifications and procedures identified and described in this directive are incorporated herein and made a part hereof pursuant to 5 U.S.C. 552(a)(1). \n\tAll persons affected by this directive who have not already received these documents from the manufacturer may obtain copies upon request to Boeing Commercial Airplane Company, P. O. Box 3707, Seattle, Washington 98124. The documents may be examined at FAA Northwest Region, 9010 East Marginal Way South, Seattle, Washington. \n\n\tAmendment 39-1897 became effective on July 16, 1974. \n\tThis amendment 39-2550 becomes effective April 21, 1976.