A gas turbine engine 10 comprises at least one rigid raft assembly that has a fluid passageway 210 at least partially embedded therein. The fluid passageway 210 is at least a part of a fluid system. In addition to the fluid passageway 210, the rigid raft assembly 200 also has at least a part of another system. For example, the rigid raft assembly may also include electrical conductors 252, which are part of an electrical system. The rigid raft assembly 200 may be lighter, easier to assemble, more robust and more compact than conventional solutions for providing systems to gas turbine engines.