The aim of this study was to estimate aerodynamic characteristics of Unmanned Aerial Vehicle (UAV) in flight mode at a flight altitude of 100m using Computational Fluid Dynamics (CFD) in ANSYS software. Firstly, aerodynamic characteristics of UAV was estimated for steady case and then for unsteady case to investigate effect of time in comparison the different of air flow for these cases. Secondly, effect of initial velocity and frequency of fluctuation were performed using User Define Function (UDF) in ANSYS software. The motion speed was changed in a sinusoidal form with amplitudes of 10, 15, 20 and 25 m/s and two oscillation frequencies of 0.1 and 0.2 Hz. Research results showed that speed amplitude did not affect the aerodynamic quality of the aircraft in the selected speed range. Meanwhile, the frequency of oscillation affected quite a lot on the aerodynamics of the aircraft. Finally, at velocity 20m/s, the side slip angle was varied from 0 to 12 degree to carry out effect of slide slip angle. The UAV tended to lose lift, increase drag, leading to a strong reduction of aerodynamic quality when increasing side slip angle. This indicates an unfavourable influence of side slip angle on the aerodynamic characteristics of the UAV.
