53-08-02 DOUGLAS: Applies to All Model DC-6 Series Aircraft (Fuselage Numbers 1 to 213 Inclusive). \n\n\tCompliance required as indicated. \n\n\tThe following inspections and rework pertain to the center wing lower skin panel and stringers inboard of Station 60 at both sides of the two access doors (fore and aft). The accomplishment of this change is for repair of details which have failed due to fatigue and to make general reinforcement of the affected area. \n\n\t1.\tInspection. \n\n\t\t(a)\tConduct following inspection as soon as practical but not later than the next 50 hours of operation unless already accomplished and continuing thereafter at periodic intervals nearest to 500 flying hours from the time of initial inspection until permanent rework is accomplished as outlined in items (2) and (3). Using at least an 8-power magnifying glass and/or dye check method or equivalent, make inspection for cracks in the door doubler, bottom wing skin and stringers in the area of Station 52 between the front and center spars. If cracks are found in any of these details, make repairs as indicated in item 2 before next scheduled flight. \n\n\t\t(b)\tIf no cracks are found in any of the details mentioned in 1(a) install preventive reinforcements as outlined in item 3. \n\n\t2.\tRepair. \n\n\t\t(a)\tIf a crack is found in the lower skin panel at Station 52 greater than 2 1/2 inches long or if cracked stringers are found in the area of Station 52, make repair and modify the door doubler splice as per Douglas Drawing 5460214. (Refer to Kit A of Douglas Service Bulletin No. 521.) \n\n\tNOTE: This repair must be supplemented by reinforcing remaining areas of rework as outlined in part 3(c). \n\n\t\t(b)\tIf a crack is found in the skin less than 2 1/2 inches long (without stringers being cracked), in the area of Station 52, make repair as per Douglas Drawing 5460328-501. (Refer to Kit F of Douglas Service Bulletin No. 521.) \n\n\tNOTE: This repair must be supplemented by reinforcing remaining areas of rework as outlined in part 3(c). \n\n\t\t(c)\tIf a crack is found in the door doubler only in the area of Station 52, repair per Douglas Drawing 5460328-1. (Refer to Kit E of Douglas Service Bulletin No. 521.) \n\n\tNOTE: This repair must be supplemented by reinforcing remaining areas of rework as outlined in part 3(c). \n\n\t3.\tPreventive Reinforcement. \n\n\t\t(a)\tIf no cracks are found in the area of Station 52 on airplane fuselage Nos. 1-69 install reinforcements to the stringers and door doubler no later than May 1, 1953, as per Drawing 5460275-1 or Douglas Service Bulletin No. 440. (Refer to Kit B of Douglas Service Bulletin No. 521.) \n\n\t\t(b)\tIf no cracks are found in the area of Station 52 on airplane fuselage Nos. 70-213, install reinforcement to the door doubler as per Drawing 5460275-501 no later than September 1, 1953. (Refer to Kits C and D of Douglas Service Bulletin No. 521.) \n\n\t\t(c)\tIf cracks are found by inspection and repaired by reinforcements as outlinedin part 2(a), (b) or (c), these repairs must be supplemented by reinforcing the stringers and/or door doublers at all other areas outlined in 3(a) and (b). This should be accomplished no later than May 1, 1953, on airplanes having fuselage Numbers 1 through 69 and no later than September 1, 1953, or a period not to exceed 1,500 flying hours (whichever occurs first), on airplanes having fuselage numbers 70 to 213 inclusive. Airplanes incorporating local reinforcements shall be given an external inspection at periods not to exceed 35 flying hours in addition to the 500-hour inspection outlined in part 1 (a) until the complete rework has been accomplished. \n\n\t(See Douglas Service Bulletin No. 521 dated May 29, 1952, and Douglas Service Letter No. 128 dated June 27, 1952, for applicable models subject to the above-mentioned reworks.) \n\n\tThis supersedes AD 52-27-01.