*† ‡ § . This paper considers the feasibility of incorporating a switched reluctance starter generator within the high -pressure (HP) region of a large civil aero -engine, specifically in terms of achievable power densities, inverter rating, machine losses and the consequent cooling requirements. The high -pressure shaft of a typical large turbo -fan e ngine rotates at speeds of ~15000rpm on a typical flight duty cycle, and up to ~20000rpm in an over -speed condition, with ambient temperatures of the order of 300 to 400°C and the required powe r rating is in excess of 100kW. This harsh operating environmen t necessitates a multi -physics design approach, encompassing mechanical, thermal, electromagnetic and electrical disciplines, and serves to quantify the performance trade -offs that result from closely integrating an electrical machine into the harsh enviro nment of an aircraft engine. Nomenclature PFE = Iron loss density (W/kg) � = Electrical conductivity ( � -1 ) � = Mass density (kg/m 3 ) � = Period of flux waveform (s) d = Lamination thickness (m) B = Instantaneous flux density (T) ke = Excess loss coefficient kh,a,b = Hysteresis loss coefficients