Upgrading process of any aircraft or UAV system leads to a new design verification in almost every aeronautical field and at the end to an accepted compromise between all design points with the aim of reaching a light, reliable, durable and economical aircraft. A change in the center of aircraft mass position is in a direct correlation with aircraft performance and stability. Any additional change on the existing aircraft or UAV (implementation of a new system or a component) requests analysis of the aircraft mass, position of the center of mass and aircraft performances. This paper presents an analysis of the change in the center of mass position of the medium range UAV due to the integration of the aircraft rescue system at the wing hardpoint, and comparison of the aircraft performances before and after that integration.