A method and apparatus, for manufacturing a duct for a fluid management system of an aircraft. A filament-fed additive manufacturing apparatus is used to perform the additive manufacturing process. The additive manufacturing apparatus comprises a nozzle, wherein the nozzle receives material in the form of a filament and adds said material to the duct in a location proximate to the nozzle location, and wherein the nozzle moves in a generally helical path relative to the duct.