This collaborative academic exercise consisted in two stages of conceptual design.

The first stage was focused mainly in designing a CS-23 category commuter aircraft for regional commercial purpose (up to 19 passengers).

The aim was to cover a gap below small airliners. These are often difficult to fill in order to be profitable and, therefore, there are only connections between big cities. The use of these commuter aircraft could link those smaller airports and be faster than using existing railway or road connections.

We used Raymer and Sadraey books for a good application of the theory and OpenVSP and XFLR5 software to refine our design.

We focused on optimizing the plane for its mission operations: medium to short range and below 3000 m flight altitude. Lower fuel is going to be needed, the cabin is unpressurized, then a more practical rectangular cross-section fuselage is selected, and the plane is designed to be a bit more compact but respecting a good cabin space.

We had the Dornier Do228 as our reference point.

The second stage came with a surprise, the simulated development of the aircraft needed to adapt to next generation requirements. It must be electric from now on, let's forget the turboprop.

After several calculation iterations with the two possible propulsion technologies, batteries and hydrogen, we opted for the latter in its liquid state for volume advantages. With the weight of the batteries, range and passenger would need to be drastically reduced. However, selecting liquid hydrogen was not an easy solution, we need to store 5+ cubic meters of LH2 in the plane.

Filling the same plane with numerous tanks all over the plane is a ridiculous solution that violates system integration requirements, rises the costs, makes maintenance practically impossible and worsens the plane performance and cabin capacity.

A realistic design approach was key and defined a better overall airplane. After some research, custom cylindrical LH2 tanks seemed perfectly possible. Mounting them on top of the fuselage was a clever solution that just had a drawback, which is increasing the frontal area, with its corresponding drag gain.

This solution does not affect the CG balance, leaves the wing structure intact, inertia increase is kept minimum, eases maintenance through a top shell that covers the tanks, makes a wider cabin for all 19 passengers and would enable different propulsion configurations without any major redesign.