AD 52-18-02

52-18-02 DOUGLAS: Applies to All Models DC-6, DC-6A and DC-6B Series Aircraft.

To be accomplished as indicated.

I. Inspection.

A. At intervals not to exceed 250 hours for airplanes having in excess of 4,000 flight hours, periodically inspect the forward flange of the lower front spar cap at Station 120 1/2 at left and right hand using dye check inspection method or equivalent. This is the location of the bolt that attaches the inboard nacelle inboard attach angle to the spar cap flange. This bolt must be removed for this inspection. Any crack found must be properly repaired prior to further flight. This inspection shall be continued until the area is reinforced as outlined in item II.

B. At intervals not to exceed 35 flight hours for airplanes having in excess of 4,000 flight hours, perform a visual inspection of the forward flange of the lower front spar cap left hand and right hand at the bolt attachment of the lower inboard nacelle inboard attach anglepaying particular attention to the upper and forward exposed area of the flange adjacent to the bolt. The spar area shall be thoroughly cleaned before inspection. Any suspicion of cracking shall be checked using dye check method or equivalent with the bolt removed. Airplanes that have been repaired wherein the cracks have been ground out of the flange and the flange area reinforced in accordance with Douglas Drawing 5482662-A shall also be visually inspected.

C. No special inspection is required on airplanes having a total service time under 4,000 hours.

II. Reinforcement.

Aircraft not incorporating the reinforcement during production shall have the spar cap and other reinforcements added in the inboard nacelle area according to Douglas Drawings 5482863 and 5482950. Reinforcement should be accomplished by September 1, 1953, on airplanes having over 4,000 hours flying time by that date. Airplanes with less than 4,000 hours time as of September 1, 1953, should be reinforced prior to accumulation of 4,000 hours flying time.

Any airplane incorporating the temporary repair per Douglas Drawing 5482662-A shall have the permanent reinforcement incorporated at the next engine change not to exceed 1,500 hours. High time airplanes and those with repaired flanges should be given priority in accomplishing these reinforcements.