Experiments were conducted on ducted lift fan models designed for new VSTOL vehicle applications. Such ducted fan models, designed and fabricated in-house, were investigated with wind tunnel and hover experiments. In each case, the primary flight environment was considered to be edgewise with the duct. The aerodynamic characteristics were determined for three single ducted lift fan models and a dual (tandem) ducted fan model using a six-component balance. Highlights from the hover tests include the effect of rotor tip clearance on thrust as well as duct thrust augmentation. The wind tunnel tests showed that the single ducted fans were limited in forward flight due to poor aerodynamic efficiency. While the dual fan model performed better in forward flight in terms of lift and drag, low L/D values are typically experienced in comparison with fixed wing aircraft. Thus a trade study was performed with one of the single ducted fan models which attempted to reduce the drag in forward flight by using inlet vents. A second trade study was performed which examined the effectiveness of exit vanes for control. Finally, flow characteristics were investigated for select cases with the use of a smoke wire.
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