This book provides the latest achievements of numerical methods and experimental means developed and demonstrated by the DLR researchers for the CleanSky 2 LPA Cross Capability Demonstrator (XDC). These developments have been made in order to establish design processes and tools for the prediction, assessment, and measurement of the integration of future propulsion systems for large passenger aircrafts. The XDC thus provided high-fidelity CFD and CAA tools as well as further developed prediction tools for noise and aero-elastics and advanced testing means. For each of the methods a short introduction is given and their applicability is described using examples from the project helping to find the right method supporting future design and integration work.