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Augmented Propeller Design with the use of a Passive Circulation Control Pressurization System Jonathan Kweder Circulation control is a high-lift device used on the main wing of an aircraft. This technology has been in the research and development phase for over sixty years primarily for fixed-wing aircraft when the early models were referred to as “blown flaps.” Circulation control works by increasing the near surface velocity of the airflow over the leading edge and/or trailing edge of a specially designed aircraft wing using a series of blowing slots that eject high velocity jets of air. The wing has a rounded trailing edge, and ejects the air tangentially, through these slots inducing the Coandă Effect. This phenomenon keeps the boundary layer jet attached to the wing surface longer than a conventional wing and thus increases the lift generated on the wing surface due to the relaxation of the Kutta Condition for the rounded trailing edge. The circulation control airflow adds to the lift force through conventional airfoil lift production, by altering the circulation of stream lines around the airfoil. The main purpose of the circulation control for fixed wing aircraft is to increase the lifting force when large lifting forces and/or slow speeds are required, such as at take-off and landing. Wing flaps and slats are currently used during landing on almost all fixed wing aircraft and on take-off by larger jets. While flaps and slats are effective in increasing lift, they do so with a penalty of increased drag. The benefit of the circulation control wing is that no extra drag is created from the movement of surfaces into the airflow around the wing and the lift coefficient is greatly increased. Taking advantage of circulation control generally includes the addition of extra weight to an aircraft or siphoning some of the power off the engine to run the circulation control hardware. It was the goal of this research to find an alternative way of pumping circulation control pressurization air to the trailing edge slot located on an unmanned aerial vehicle propeller. The design called for the rerouting of stagnation pressure on the frontal propeller area, through the inside of the propeller blades, to an ejection slot on the training edge of the propeller blade. This allowed for the forward velocity of the aircraft to drive the pressurization of the circulation control plenum passively, or without additional hardware. For this study, a Clark-Y airfoil section propeller with an overall diameter of 24 inches was designed and tested in both a West Virginia University wind tunnel and the vertical wind tunnel at Wright-Patterson Air Force Base as well as computationally through the use of Fluent software and Blade Element Analysis methods. The comparison of both the augmented propeller and the unaugmented (baseline) propeller showed a 5.74 percent increase in efficiency by using the circulation control augmentation. This increase in efficiency is shown to act over the entire range of flight envelopes of the aircraft. It is shown to be particularly beneficial at advance ratios above 0.30, normal operating conditions of propeller driven UAV’s.