<![CDATA[The transition toward more-electric aircraft (MEA) architecture has fundamentally transformed the onboard electromagnetic environment, creating challenges that extend beyond traditional equipment-level electromagnetic compatibility (EMC) qualification. Contemporary aircraft integrate high-power electronic converters, distributed power generation, advanced digital avionics, and densely packaged subsystems within severely weight- and space-constrained airframes. While these technologies provide operational benefits, they also generate complex Electromagnetic Interference (EMI) phenomena that conventional component-level testing cannot fully characterize. This paper presents a system-level framework for quantifying EMI exposure and evaluating mitigation strategies in MEA. The framework combines source characterization, installation-dependent coupling path analysis, and functional susceptibility assessment to enable structured, margin-based evaluation of system-level EMC. Four normalized metrics are introduced: the Source Severity Index (SSI), Coupling Strength Ranking (CSR), Functional Margin Ratio (FMR), and Mitigation Effectiveness Factor (MEF). Together, these metrics provide quantitative tools for identifying dominant EMI contributors, characterizing worst-case coupling configurations, assessing functional robustness margins, and objectively comparing alternatives to mitigation. The framework explicitly addresses installation-driven EMC degradation mechanisms, including cable routing geometry, parasitic inductance, bundled harness mutual coupling, and production discontinuities. Application examples demonstrate that mitigation of coupling paths can provide the highest improvement in functional margin, particularly in installation-dominated EMI scenarios. In the evaluated case, coupling path mitigation achieved an MEF of 2.67, corresponding to approximately 8.5 dB improvement. These findings demonstrate the value of system-level, quantitative EMC assessment for MEA architectures and provide a structured basis for prioritizing mitigation actions, improving electromagnetic robustness, and supporting more reliable integration of advanced electrical and electronic systems in aircraft]]>
