46-24-01: Wing Drain Holes

46-24-01 BOEING: (Was Mandatory Note 4 of AD-743-3.) Applies to A75L3, 75, A75, B75, E75, A75J1, A75N1, B75N1, D75N1 Series Aircraft. Compliance required at next periodic inspection. The lower wings lack adequate drainage just forward of the ailerons with the result that water is entrapped by the dural angle forming the lower rear edge of the wing at the aileron gap. Since this will cause eventual deterioration of the rib ends a No. 30 hole should be drilled through the fabric and the dural angle just outboard of the rib at the inboard end of the aileron cutout and each of the 12 ribs outboard of this station. The holes should be drilled aft of the rear spar and just forward of the 120 degrees bend in the dural angle. Care should be exercised to avoid damage to the rear spar while effecting this work. As a safety measure, a stop should be used on the drill to prevent penetration in excess of 1/2 inch.