An innovative thermal management system (TMS) that provides both effective active heat transfer and high passive thermal energy storage capacity has been developed and successfully demonstrated. The TMS integrates the high latent heat advantages of a phase change material with an actively cooled cold plate design. The resulting TMS concept has direct use on many transient system applications, where the amount of heat dissipated varies over time. The example discussed in this paper is the transient operation of electric flight control actuator hardware that is proposed for the More Electric Aircraft (MEA) Initiative. The development of the TMS concept, the successful fabrication and validation testing on actual flight control electronic hardware is provided. The advantages of the Thermal Management System include: significant weight savings, high thermal performance, high thermal energy storage capability, high reliability and reduced maintenance.