66-18-02 DOUGLAS: Amdt. 39-264 as amended by Amendment 39-972. Applies to All DC-3 series aircraft including Military Type C-41, C-41A, C-47, C-47A, C-47B, C-48, C-48A, C-49, C-49A, C-49B, C-49C, C-49D, C-49J, C-49K, C-50, C-50A, C-50B, C-50C, C-50D, C-51, C-52, C-52A, C-52B, C-52C, C-53, C-53B, C-53C, C-53D, C-68, C-117A and R4D series except R4D-8 aircraft, certificated in all categories. \n\n\tCompliance required as indicated. \n\n\t(a) Unless already accomplished within the last 400 hours' time in service, within 50 hours' time in service after March 15, 1963, inspect the wing lower attach angles of both the outer wing and center section between the front and rear spars for cracks between the attach bolt holes. Use at least a 4-power magnifying glass. Reinspect at intervals not to exceed 450 hours' time in service from the last inspection. \n\n\t(b) Unless already accomplished in accordance with AD 39-24-01 and AD 52-22-03, or AD 63-04-01, (or AD 63-04-01 as amended by AD Card No. 63-20), the following modifications must be accomplished within 500 hours time in service after March 15, 1963, except that airplanes being presented for an initial airworthiness certificate must be so modified before that certificate will be issued: \n\n\t\t(1) All outer wing lower surface doublers, P/N's 570602-206 and -207 or P/N's 5115200-206 and -207 shall be replaced with new doublers fabricated from 0.072 material in the manner described in Douglas Service Bulletin DC-3 No. 262, reissued June 14, 1963. \n\n\t\t(2) All outer wing lower surface doublers, P/N's 570602-208 and -209 or P/N's 5115200-208 and -209 shall be replaced with new doublers fabricated from 0.064 material in the manner described in Douglas Service Bulletin DC-3 No. 262, reissued June 14, 1963. \n\n\t\t(3) All outer wing lower surface attach angles shall be replaced with new angles fabricated for proper installation with the new heavier doublers in the manner described in Douglas Service Bulletin DC-3 No. 262, reissued June 14, 1963, except that aircraft modified to incorporate doublers and attach angles described in Douglas Service Bulletins No. 220 and No. 146, respectively, are satisfactory until parts must again be replaced per (d). \n\n\t\t(4) The wing center section lower surface shall be modified by incorporating witness holes, installing new wrap around doublers attached to the wing skin and new attach angles as described in Douglas Service Bulletin DC-3 No. 262, reissued June 14, 1963, except that modifications made prior to the effective date of this amendment in accordance with Douglas Drawing 5406787 "D", "E" or "F" are satisfactory until parts must again be replaced. \n\n\t\t(5) Certain airplanes have been reworked in accordance with Service Sketch 624, which incorporates a lower center wing attach angle doubler, between front and center spars, which is 3/8 inch wider than standard in order to accomplish Service Bulletin No. 262. This rework is satisfactory. In such cases, rework in accordance with Service Sketch 624 must be accomplished at each subsequent replacement of the wing attach angles and doublers. \n\n\t\t(6) The proper installation alignment of the attach angles and doublers described in (b)(1), (2), (3), and (4) shall be maintained. This shall be accomplished by the use of satisfactory jigs or by FAA-approved equivalent means. Douglas jig fixtures P/N's A652-5110506-1-1F2 and A652-5110506-1F2 or P/N's C652-5110500-101-1-1F1 and C652-5110500-101-1F1 or those that meet the criteria of Advisory Circular AC 39-1, are considered to be satisfactory for alignment purposes. \n\n\t(c) After the accumulation of 7,500 hours' but before 8,000 hours' time in service and after the accumulation of 11,500 but before 12,000 hours' time in service following any modification prescribed by (b) the outer wings shall be removed, affected areas must be thoroughly cleaned and inspections must be conducted as follows: \n\n\t\t(1) Inspect the center wing skin and outer wing attach angle doublers for cracks along the radius of the bent-up flange at the attachment joint. Conduct the inspections with at least a 6-power magnifying glass or by dye penetrant; \n\n\t\t(2) Inspect the center and the outer wing attach angles including the areas between the attaching bolt holes for evidence of cracks. Remove all paint to permit inspection with at least a 6-power magnifying glass or by dye penetrant; and \n\n\t\t(3) Make visual inspections through the witness holes in the center section at the front and center spars for evidence of cracks. \n\n\t(d) The modifications specified in (b) shall be reaccomplished within each 16,000 hours' of service after the original modification unless an inspection per (c) reveals no cracks and the reinspections are conducted at intervals not to exceed 2,000 hours' of service. \n\n\t(e) If the maintenance records cannot verify the time in service since the modifications prescribed in (b), one of the following must be accomplished:(1) Accomplish the modifications at the time and in the manner prescribed in (b); or \n\n\t\t(2) Conduct the inspections prescribed in (c) within 500 hours' time in service after March 15, 1963, and thereafter reinspect per (c) at each 2,000 hours' time in service until the modifications per (b) are again accomplished. \n\n\t(f) Any cracked parts found during the inspections required by (a), (c) and (d) shall be replaced with new parts before further flight. These new parts shall then be inspected within the inspection periods specified in (a) and (c). All uncracked parts that are not replaced will continue to be inspected at the periods previously established in accordance with (a) and (c). Uncracked parts that are not replaced after 16,000 hours' time in service shall be reinspected at intervals not to exceed 2,000 hours' time in service. \n\n\t(g) Whenever wings are being replaced after modification per (b); whenever spar butt plates on the center and outer wing, the compression angles on the center wing or the waffle plates on the outer wing are reworked or replaced; or whenever one outer wing is substituted for another, the following tolerances shall be maintained: \n\n\t\t(1) Compression angles attached to corrugation and stringers and the spar cap butt plates of the center wing must be held in plane with the wrap around doubler on the attach angle to a plus 0.004 inch/minus 0.000 inch. \n\n\t\t(2) The waffle plates attached to the stringers and the spar cap butt plates of the outer wing must be held in plane with the wrap around doubler on the attach angle to a plus 0.006 inch/minus 0.000 inch. \n\n\t\t(3) Tolerances of a maximum of 0.010 inch interference to a maximum of 0.010 inch clearance between the compression angles and waffle plates and between the spar cap butt plates, are acceptable if previously accomplished per AD 58-12-01. The tolerances set forth in (g)(1) and (2) shall be used for all attach angle installations subsequent to the effective date of this AD. \n\n\tNOTE: These new tolerances will allow a flush to a 0.010 inch interference between the compression angles and plates when the wing is installed. This interference fit assures the most effective distribution of loads across the joint and the maximum service life. \n\n\t(h) Upon request of the operator, an FAA maintenance inspector, subject to the prior approval of the Chief, Aircraft Engineering Division, FAA Western Region, may adjust the repetitive inspection intervals specified in this AD to permit compliance at an established inspection period of the operator if the request contains substantiating data to justify the increase for such operator. \n\n\t(i) FAA-approved revisions to Douglas Service Bulletin DC-3 No. 262, reissued June 14, 1963, are also considered satisfactory in complying with this AD. \n\n\tThis supersedes AD 65-27-02. \n\n\tAmendment 39-264 effective July 26, 1966. \n\n\tThis amendment (39-972) becomes effective April 16, 1970.