Explore the variable speed operation and shift response of a prototype of a continuously variable rotorcraft propulsion system and development of a Comprehensive Variable Speed Rotorcraft Propulsion system Modeling (CVSRPM) tool.Simulate the drive system dynamics in steady forward speed condition in an attempt to build upon previous variable speed rotorcraft propulsion studies by including, fully nonlinear first principles based transient gas-turbine engine model with shaft flexibility and incorporating a basic flight dynamics model to account for interactions with the flight control system. Explore the interactions between the various subsystems and obtain insight into the continuing development of variable speed rotorcraft propulsion systems and a study of various variable ratio transmissions that have already been explored.