48-52-01 DOUGLAS: Applies to All DC-6 Aircraft. \n\n\tTo be accomplished not later than June 1, 1949. \n\n\t1.\tRevise method of connecting power leads to main bus through Burndy limiters. \n\n\t2.\tReroute generator and starter cables in No. 4 nacelle to eliminate possibility of abrasion of power cables. \n\n\t3.\tInstall stainless steel combustion air intake ducting on all heaters. \n\n\t4.\tRevise wing heater exhaust outlets to preclude nacelle fluids contacting exhaust piping. \n\n\t5.\tInstall expansion turbine oil drain and filling drain. \n\n\t6.\tInstall ducting from the wing and tail heater combustion air blowers to the outside skin of the nacelles and tail section. Ducting within the nacelles to be of stainless steel. \n\n\t7.\tDelete present wing heater 1.4 pounds CO2 bottles and eject the fuselage nose CO2 banks to either wing heater. CO2 to go into the heater deicing and combustion air and into the area surrounding the heaters. Controls for the new system to be grouped with and worked in the same sequence as the tail and cabin heater fire extinguisher system. \n\n\t(Douglas DC-6 Service Bulletins No. 220, revised February 18, 1948; 270, dated March 8, 1948; 231, revised January 19, 1948; 259, revised March 12, 1948; 255, revised February 26, 1948; 256, revised February 12, 1948; and 272, revised April 8, 1948; cover the above items consecutively.)