The design of high lift device has great importance in development of transport aircraft, for both manufacturers and operators. With this motivation, a preliminary structural design of a 4-bar mechanism as an actuator of a single-slotted Fowler flap was developed. Fundamental concepts about the subject, such as overlap, gap and Fowler motion, was presented. Aiming the aerodynamic requirements, the mechanism was synthesized in order to reach three critical points: cruise, landing and take-off. For landing and take-off conditions, the loads were estimated and applied on the flaps to evaluate and to size the linkage system. The kinematics and kinetics of the movement was studied by two methods: analytical and numerical by multibody simulation. In order to refine the sizing, a finite element analysis was employed to determine the margins of safety and to drive optimization studies. Thus, with static and fatigue analysis performed and safety margins calculated, the topological optimization was performed in two components, achieving a reduction of 29.3% (1.9 kg) in the first and 38.3% (2.0 kg) in the second, representing 13.46% in the total mass of the system.