Unmanned Aerial Vehicles (UAV) have been attractive for years for many researchers and companies worldwide due to their commercial and military applications. The main problem of UAV is the absence of certification and the poor reliability that prevent their integration in the civil airspace. The problem can be overcome by improving the UAV nominal control and by designing a Fault-Tolerant Control System (FTCS). This paper deals with the design of a nominal control law of a UAV. Actually, planes are naturally unstable, that is why a particular attention must be paid in the design of a control law able to stabilize the system and let it track a predefined path. The design of a control law using eigenstructure assignment technique is developed in this paper and validated in simulation to a model of a small UAV.