AD 47-42-11

47-42-11 DOUGLAS: (Was mandatory Note 8 of AD-781-1.) Applies to the Following DC-6 Aircraft: Serial Numbers 42854 to 42894, Inclusive; 43000 to 43012, Inclusive; 43055, 43056, and 43062.

Rework to be accomplished not later than December 15, 1947. (See Note 47-42-19.)

Cracks have been found near the ends of the tail stub extension of the horizontal stabilizer front spar caps, top and bottom, just inboard of the stabilizer joint. In order to prevent cracks from traveling to a point which may impair the airworthiness of the aircraft, the rework described below shall be accomplished. Until such time as the rework is accomplished, inspect the area in question at every No. 2 inspection period according to instructions contained in Douglas Telegram A-214-529, 012/RLT, dated July 25, 1947.

A. Cut a 7/8-inch diameter hole through skin and doubler only, 1 5/16 inches inboard and 21/32 inch aft of inboard fitting attaching bolt. Use special tools furnished by Douglas Aircraft Co., being careful not to scratch the spar cap. Strip primer off 7/8-inch diameter area on spar cap and inspect for cracks with high-power lens (40 power). If cracks are found, make a record of the location and extent of crack.

B. Drill 0.250-inch diameter stop hole through spar cap, 1 5/16 inches inboard and 21/32 inch aft of inboard fitting attaching bolt and burr, regardless of whether cracks are found. If cracks are found that will extend inboard beyond the location of the stop hole, do not operate airplane until further salvage rework instructions have been obtained. Cover holes in skin and doubler with sheet metal plug and fabric patch cemented in place. (Douglas E.O. No. 5339013 (Salvage E.O. Serial No. 375) describes the rework of installing the stop hole.)