This study focuses on the use of active flow control to reduce hover download on a 10.5% scale V- 22 powered model. In hover mode, approximately 10% of the total thrust is lost due to drag on the airframe. Two sources of download were investigated: impingement of downwash onto the wing and the fountain flow between the rotors. The download from the wing and fountain contribute 58% and 17.5% of the download respectively1. Encouraged by the results of two-dimensional active flow control testing2,3, which indicated significant download reductions on the V-22 airfoil, similar configurations were constructed for test and evaluation on a complete three-dimensional model of the V-22. Download measurement showed that a 15% reduction in download could be achieved with an oscillatory jet injected into the flow on the upper flap surface. A preliminary investigation using threedimensional PIV was performed in an effort to better understand the tiltrotor flow characteristics. The PIV data indicates that semi-span tiltrotor testing with an image plane has major effects on the global flow.