In Aeronautics, the Structural sub-system is responsible to devise how the UAV will be built, select the materials it will be built of, perform FEM (Finite Element Method) analysis on its structures and later on to fabricate it.
In order to do so successfully, cooperation with the rest of the sub-systems is crucial.

Design Process:

 Structural engineers need to calculate an initial estimation on the UAV’s empty weight and find ways to minimize it as much as possible, minimizing the empty weight maximizes the payload that the UAV can carry. Furthermore, they are required to bring the center of gravity to a desired location.
The main objective of the structural sub-system is to ensure that the fabrication of the UAV happens in the most optimal way. For this to happen the subsystem initially works in parallel with the aerodynamics design sub-system during the design phases, in order to determine some first estimations about the aircraft.

In the conceptual design phase, a MatLab based tool has been created, that is capable to predict with a certain level of accuracy, the weight and centre of gravity of the UAV. The tool uses as inputs initial dimensions that are given by the aerodynamics design sub-system and returns a weight estimation, alongside a centre of gravity estimation. This is later confirmed with an initial 3D CAD of the aircraft.

During the initial designing phase, the sub-system needs to decide on what materials the UAV will be constructed from. The mission of the aircraft, alongside its weight estimation need to be taken into consideration, so that the chosen material can handle all the stresses that will be applied to it.
The sub-system needs to research what materials can be used and chose the most suitable one.
Composite materials, such as Carbon Fiber or Fiberglass, are mostly used, since they provide the required strength while keeping the weight of the aircraft to a minimum.

After the designing phase, the structural sub-system creates a more detailed 3D CAD of the UAV. During this process the team configures how the aircraft assembly will take place and how the parts will be connected to each other. After everything is put together, a more accurate presentation of how the UAV will look like is presented to the team. Alongside that, the final weight and centre of gravity is also provided by the program.

The final phase is where every piece comes together and the construction of the UAV is under way. The sub-system uses well known methods for the creation of the parts (such as resin infusion), and in some certain scenarios they might need to configure ways by themselves on how the built process will take place. After every part is constructed, the vehicle is put together and its ready for its first flight.