A rotorcraft assessment platform (CREATION) is currently developed at Onera. The final objective is to quantify the impact of the introduction of new technologies on the rotorcraft performance. The paper presents the selection process and the predesign of the turboshaft engine with three levels of details. The statistical level (level 0) is a basic selection of an existing engine from a database. The second level (level 1) is a Brayton-Joules cycle tuned to reach the specification of a selected engine. Finally, the last level (level 2) is presented. This level performs a predesign and an optimization based on the engine weight + the block fuel minimization used for the mission. This last approach demonstrates that high pressure ratio are not always the solution to optimize the fuel consumption during a given mission.