Electromobility and especially airmobility is increasing its share among all transportation sectors. Along the process, hydrogen-electric propulsion relying on polymer electrolyte membrane (PEM) fuel cells as a most promising and key disruptive solution, is gradually stretching its popularity among aircraft belonged to more segments. However, in the trend, aviation still put stringent requirements on the 1) efficiency, 2) specific power, 3) specific energy, and 4) reliability, of these fuel cell systems. Effective cooling could be a main contributor to all the aforementioned requirements. Based on our previous simulation work proposing a novel cooling solution, namely PCHP cooling, in our current project EFACA (Environmentally Friendly Aviation for all Classes of Aircraft), we are building a test rig demonstrating the cooling concept. Currently, we are in the stage of detailing the design of the test rig including the selection of the major component, especially the phase-change refrigerant and deciding their optimal operating settings. For these purposes, we are taking two paths, 1) thermodynamic modeling approach, and 2) industrial practices, i.e., engineering know-hows and market availability. In this presentation, we are going to show our findings and decisions so far along the progress of building such test rig.