AD 63-23-01

63-23-01 DOUGLAS: Amdt. 638 as amended by Amendment 39-973. 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.

Compliance required as indicated.

(a) Unless already accomplished within the last 400 hours' time in service after the next 50 hours' time in service after the effective date of this AD, inspect the wing upper attach angles on both the outer wing and center section between the front and rear spars for cracks. Use at least a 4-power magnifying glass. Reinspect at periods not to exceed 450 hours' time in service from the last inspection. Replace cracked attach angles before further flight.

(b) At the next wing removal, inspect all wings in the manner specified in (c), and reinspectat intervals not to exceed 8,000 hours thereafter.

(c) At the time specified in (b), the removed wings shall be thoroughly cleaned and inspected as follows:

(1) Inspect the center and outer wing upper attach angle doubler for cracks along the radius of the bent-up flange at the wing attachment point. Conduct the inspection with a 6-power magnifying glass or dye penetrant.

(2) Inspect the center and outer wing upper attach angles including the areas between the attaching bolt holes for evidence of cracks. Remove all paint to permit inspection with a 6-power magnifying glass or by dye penetrant.

(d) Replace, before further flight, any cracked parts found during the inspection set forth in paragraph (c) with new parts per Douglas Service Bulletin DC-3 No. 262, Reissue No. 1 June 14, 1963, or later FAA-approved revisions.

(e) The proper installation alignment of the attach angles and doublers described in (d) 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.

(f) The parts replaced in accordance with paragraph (d) shall be inspected in accordance with the requirements of paragraphs (b) and (c). All uncracked parts which are not replaced shall continue to be inspected per the inspection procedure of (c) with adherence to the previously established inspection schedules for these parts.

(g) Whenever wings are being replaced after modification per (d); 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 being reworked or replaced; or whenever one outer wing is substituted for another, the following tolerances shall be maintained:(1) Compression angles attached to the corrugations and stringers and the spar cap butt plates of the center wing must be held in plane with the wrap around doublers on the attach angle to within plus 0.004 inch/minus 0.000 inch.

(2) 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 doublers on the attach angle to within plus 0.006 inch/minus 0.000 inch.

NOTE-The tolerances ranges set forth in (g)(1) and (g)(2) will allow a flush to 0.010 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.

(Douglas Service Bulletin No. 262, Reissue No. 1, June 14, 1963, or later FAA-approved revisions, covers this same subject.)

Amendment 638 effective December 6, 1963.

This Amendment (39-973) becomes effective April 16, 1970.