From the cost-effective viewpoint of low cost Bank-to-Turn (BTT) Unmanned Air Vehicles (UAV) and target drone, a low cost flight control system, with the fewest number of sensors, is studied in this paper for the fixed-wing UAV. The structure of the control system is described which is able to estimate necessary information to provide stabilization and guidance for a small fixed wing BTT UAV. The practical flight control system structure and control law for roll hold loop, altitude hold loop, trajectory tracking loop are designed based on the sensor configuration with only a MEMS rate gyro, a MEMS pressure sensor and global positioning system (GPS) receiver only. A prototype low cost autopilot is trial-produced to control a typical UAV. The Experimental results show the effectiveness of navigation and control methods of f the proposed methodology.