"The main objective of this research was to investigate the lift and drag characteristics of a stepped airfoil with backward facing steps; apply active flow control technique to enhance the aerodynamic performance of stepped airfoils and examine the possibility of using such airfoils on Unmanned Aerial Vehicles (UAV's). A step was introduced at mid-chord, with a depth of 50% of the airfoil thickness at mid-chord position extending till the trailing edge of a NACA 4415 airfoil. Computational studies were conducted with the use of passive flow control constituting the activation of step and active flow control with the use of air injecting jets placed in the step cavity of the NACA 4415 airfoil with a goal of enhancing the aerodynamic performance. The jet angle and jet momentum coefficient were varied independently to identify the best setting for optimizing the aerodynamic performance of the stepped airfoil. Experimental studies of a scaled wing model with the same airfoil were conducted in a wind tunnel for a range of Reynolds numbers to validate some of the numerical results obtained for the cases of base and stepped airfoils. The results produced show that as much as 37% increase in C1 and as much as 12% increase in L/D ratios over conventional airfoil values could be obtained using stepped airfoils and further enhancement could be made with the employment of jets placed in the step cavities. The case study conducted as a part of this research focuses on the UAV RQ-2 Pioneer employing a stepped airfoil configuration by comparing its aerodynamic characteristics with the conventional NACA 4415 airfoil originally used on this aircraft. The primary objective of the case study was to identify and outline a step schedule for the flight envelope of the UAV Pioneer using a stepped airfoil configuration while applying active flow control to obtain enhanced aerodynamic performance over conventional NACA 4415 airfoil originally used and hence improve the flight performance characteristics like Range and Endurance of the aircraft"--Abstract, p. iii