3. Preliminary design (definition phase milestone "1" to milestone "2")

The preliminary design process brings together all the tasks involved in optimizing the expression of the functional requirement and moving from the requirement (CDCF) to the specified requirement (STB). It enables us to further refine the initial CDCF by using functional analysis methods, and to draw up the STB which, at the end of this process, will be fixed in a configuration applicable in the detailed design process. It therefore consists in refining the customer's needs from their perception to their most complete expression.

The final objective of the preliminary design (PD) (or "definition") phase is to create a circuit that meets performance, cost and schedule requirements. Design choices in the preliminary design phase mainly concern the architecture and functional sizing of components. Fluid system studies evolve with an increasingly precise level of detail...