AD 61-23-04

61-23-04 DOUGLAS: Amdt. 363 Part 507 Federal Register November 7, 1961. Applies to All Models DC-6, DC-6A, and DC-6B Aircraft Serial No. 42854 Up To and Including Serial No. 44429.

Compliance required as indicated.

Several Instances have been reported of spanwise cracks found in the center wing, front spar lower outboard cap. The cracks were approximately 3 inches in length and were located on the aft side of the spar cap body just outboard of the landing gear fitting (Station 163 approximately). Instances have also been reported where cracks have progressed forward into adjacent bolt holes. As a result of the foregoing, the following must be accomplished on the affected area of lower front spar caps having in excess of 15,000 hours' time in service unless the affected area has already been reworked, repaired or replaced as specified in paragraphs (b), (c), or (d).

(a) Within the next 3,000 hours' time in service, accomplish a dye penetrant inspection or equivalent for cracks in the aft tang of the outboard front spar lower cap for a spanwise distance of 5 inches from the inboard end (Station 163 approximately) and rework in accordance with (b), (c), or (d), as required.

(b) If no cracks are detected by the inspection prescribed in (a), the area must be reworked as necessary prior to further flight per Item 4(a) of Section I of Douglas Service Bulletin No. 802, reissued October 21, 1960.

(c) If, during the inspection prescribed in (a), cracks are detected which exceed 3 inches in length along the radius of the aft tang or extend forward beyond the end bolt holes, the spar cap must be replaced prior to further flight except ferry flight in accordance with the provisions of CAR 1.76. When installing a replacement spar cap, the rework specified in Item 4(a) of Section I of Douglas Service Bulletin No. 802 reissued October 21, 1960, or equivalent, must be incorporated.

(d) If, during the inspection prescribed in (a), cracks are detected which do not exceed the limits set forth in (c), replacement of the spar cap is optional. If replaced, the rework instructions specified in (c) must be incorporated. If not replaced, the spar cap must be repaired and inspected per Section II of Douglas Service Bulletin No. 802, reissued October 21, 1960, or equivalent, prior to further flight except ferry flight in accordance with the provisions of CAR 1.76.

(Douglas Service Bulletin No. 802, reissued October 21, 1960, covers the same subject.)

This directive effective December 7, 1961.