How is aircraft electrical system sizing performed?

Electrical system sizing determines generator capacity and distribution architecture. Load analysis: Enumerate all electrical loads (continuous, intermittent), Define operational scenarios (ground, takeoff, cruise, emergency), Calculate demand in each scenario (diversity factors apply), and Size for worst-case continuous plus margins. Generator sizing: Meet maximum continuous demand with margin (typically 20%), Single generator inoperative capability, and Emergency loads covered by essential bus. Distribution: Bus architecture (split bus, single bus with ties), Voltage levels (115V AC, 270V DC for more electric), Load shedding hierarchy for degraded operations. Analysis scenarios: Normal operation (all generators), Degraded (one generator), and Emergency (battery/RAT only). Components: Generators (IDG or variable frequency), transformers, converters, batteries, and protection (circuit breakers, contactors). More Electric Aircraft: Significantly higher electrical demand (787: 1 MW), larger generators, active load management. Certification per FAR 25.1351-1363 electrical requirements.