Last but not least is the detail design phase. During this phase, engineers must use the existing designs to fabricate the actual aircraft. It specifically determines the design, location and quantity of elements such as rubs, spars, sections and more. Furthermore, all aerodynamic, structural, control and performance aspects are achieved and tested in full in the previous preliminary design stage. The detail design stage, rather, is used to turn these designs into a working aircraft. It may also include flight simulations to test the design and ensure it functions as intended.