a 9-BIT, Pipelined Gallium Arsenide Analog-Digital Converter

Excellent Short Take-Off and Landing (STOL) performance is achieved by Upper Surface Blowing (USB) aircraft as a result of mounting high by-pass turbofan engines over the forward part of the wing. High lift levels are generated by directing the engine exhaust over the wing upper surface to entrain additional airflow and by using the Coanda effect to turn the exhaust flow downward over a large radius "Coanda" flap. Commercial application of USB technology could reduce airport congestion and community noise if future configurations can be designed with economically acceptable cruise drag levels. An experimental investigation of the high speed aerodynamics of USB aircraft configurations has been conducted to accurately define the magnitude and causes of the powered configuration cruise drag. A highly instrumented wind tunnel model of a realistic USB configuration has been used which permitted parametric variations in the number and spanwise location of the nacelles and accurately modeled the engine power effects with turbofan propulsion simulators. The measured force data provides an accurate definition of the cruise drag penalty associated with each configuration and the constructed pressure contour plots provide detailed insight into their causes. It was found that the high speed aerodynamics of USB configurations is a complex interaction of jet induced and wing transonic flowfields. The presence of the nacelles on the wing upper surface created a severe drag penalty which increased with freestream Mach number, power setting and angle of attack. The more widely spaced two nacelle configurations exhibited improved flowfields at moderate Mach numbers but suffered from drag levels comparable to the baseline configuration for high speed cruise conditions. At high Mach numbers and power settings, all of the tested configurations displayed strong shocks and separated zones in the wing/nacelle junction regions. Detailed discussions of the causes of the cruise drag penalty and recommended future design improvements are presented.