RUAV (Rotorcraft based Unmanned Aerial Vehicle) have been exploited in various fields such as surveillance, reconnaissance and search. Most of the study in this area is focused on single RUAV; however using multiple unmanned vehicles is big advantage to accomplish the mission in a short time and effective way. Moreover little amount of research has been undertaken in the development of multiple RUAV control systems. This paper proposes a behavior-based decentralized approach that allows an RUAV to carry out its own mission of flying to a specified region while the distances between RUAVs are maintained constantly to avoid collision. The main goal of the proposed controller is to make the RUAV cooperate among each other to achieve the defined task. In this research Reynold's flocking model based behavior approach has been utilized. Along with this the testing environment for multiple RUAV is developed to validate proposed control algorithm. Complete setup is implemented and run under QNX RTOS, based on PC104 embedded board. The multiple RUAV is tested and evaluated using HILS (Hardware-In-the-Loop Simulation). To validate the proposed approach, simulation is performed to achieve the waypoint with multiple RUAVs.