Liquid Hydrogen (LH2) appears as one of the leading solutions for sustainable aviation, with rear-fuselage tanks being one of the preferred options for fuel integration in conventional tube & wing designs. Studies have already identified some limitations of these concepts concerning the larger horizontal tailplane required. However, no studies so far considered the industry approach of sharing a single tailplane in an aircraft family for this type of aircraft.

The thesis draws some first guidelines for the design of LH2 aircraft families with rear tanks, with a special focus on the performance penalties due to tailplane commonality and its comparison to conventional designs. For this purpose, a methodology has been developed that systematically sizes the tailplane of an aircraft considering potential family members already in the preliminary design stage. The results revealed that lower performance penalty due to tailplane commonality can be expected for an LH2 family compared to kerosene powered designs.

The demand for environmentally friendly aviation has increased the interest in alternative concepts, such as hybrid-electric propulsion systems. A novel conceptual hybrid-electric sizing methodology was devised, which provides a detailed engine performance prediction and an accurate sizing of the powertrain components. The performance prediction methodology individually scales user-provided origin fan and engine core performance maps to generate a coherent engine performance map according to prescribed point performance requirements, while the component sizing methodology estimates individual component masses and determines their positions based on defined knowledge-rules. For each methodology, a dedicated design tool was created for easy integration into conceptual design workflows. A verification of the methodology via case studies assessing generated example aircraft concepts confirmed not only the validity of the obtained results, but also demonstrated a high accuracy at low computational costs. The exhibited robustness and sensitivity encourage the use of the methodology for future studies on hybrid-electric propulsion.