AFRL Demonstrates Upper Surface Blowing Concept

Applications

• Military and Commercial Significance:
• In this version of USB, airflow generated by a ducted fan channels into a plenum inside the wing instead of exhausting through a conventional nozzle. The flow then exits the plenum through a narrow, aft-facing blowing slot that runs along the wingspan on the upper side of the wing just aft of the leading edge. The resulting jet entrains air over the wing’s upper surface, similar to the “ejector” concept. It also acts like a “jet flap,” thus increasing both thrust and lift. This increase should enable very low-speed flight as well as short takeoff and landing operations.
• Engineers have examined powered lift since the 1950s; however, they have had little success putting the theory into practice. One obstacle to successful implementation has been weight and efficiency penalties due to the plumbing. Another obstacle, low-speed performance, often comes with a severe cruise drag penalty. The current effort targets risk reduction by demonstrating the concept in a small UAV, where design changes can be made inexpensively and rapidly.
• Powered lift technology may one day increase the speed range at which large air vehicles, such as tanker or transport aircraft, can fly. Powered lift could enable these air vehicles to fly at speeds just above a hover, without interfering with maximum speed. In addition, it may decrease the ground footprint required for takeoff and landing.