IMHO it was used because of its feature like the toughness, durability and being not ferromagnetic. It is malleable, easy to form. It has good casting properties. By varying the proportions of copper and zinc, the properties of the brass can be changed nicely, allowing hard and soft brasses. But mostly because of the tolerance to the corrosion causing by many fluids e.g. moisture, oil, also gases and the self-lubricating feature improving sliding that are much greater than of the cupper. For the reasons the brass is used for making of many aircraft parts ( but not only ). So you may find the matal alloy as the pumps or their parts, pipes, valves, bushings etc.