Most electrified aircraft propulsion (EAP) studies define a concept architecture and compute its potential benefits and key dependencies while attempting to answer the question: Can this architecture “buy its way” onto an aircraft? An important follow-on question is when will the architecture become physically and economically viable? Answering these two questions is the goal of the performance assessment process, a systematic method of analyzing the trade-offs when choosing an EAP system over a traditional one. Its methodologies and assumptions must be reasonable, and detailed comparisons to an appropriate baseline architecture must be included. This chapter outlines a systematic performance assessment process for EAP concept architectures, providing a means of deriving system-level figures of merit. Key steps in the process are identified and details are given for how they might reasonably be performed. Concepts and conclusions from earlier chapters are incorporated as needed. This serves as a guide to aircraft designers – new and old – who are beginning to delve into this exciting field and starting to explore the large design space enabled by EAP configurations.

This paper advocates the theory of 'Complex Dynamic Systems', developed in the sciences as a suitable framework for the understanding of the evolution of varieties and uses of English through time and space. After looking into earlier applications of this theory in linguistics, it surveys core properties of such systems and illustrates their relevance by applications to specific processes of change in the history of English. It then investigates processes of lexicosemantic diffusion and syntactic restructuring in World Englishes within this framework, trying to document its applicability.