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A combination of factors including market growth and engineering technology advancements in the next few years have raised the possibility of an economically and environmentally viable high-speed commercial transport (HSCT). McDonnell Douglas studies have found that the primary candidate for this application is a vehicle cruising at Mach 2.4. An engineering and environmentally conservative configuration cruising at Mach 1.6 is also being studied. The vehicle incorporates numerous advanced features including an airframe consisting of advanced composites and metals. Takeoff gross weights are on the order of 700,000 to 800,000 pounds for a design range of 5,500 nautical miles. Studies are focused on entry into service in the year 2005, with the authority to proceed with preliminary and full-scale development in 1998.

This paper identifies relevant high-payoff technologies and their performance goals required to enhance economic viability of the high-speed civil transport (HSCT). The emphasis is on the aerodynamic technologies, but improvements in several other technology areas are also addressed. Primary design constraints are presented to bound the problem and establish a baseline for comparison. The economics of planar and nonplanar configurations and their projected advances are discussed. Different approaches for improvements in skin friction, wave drag, and induced drag are presented. In addition to aerodynamics, integration of advancements in other areas also needs attention. Barrier problems are identified. It is concluded that performance enhancements achieved by developing and applying advanced aerodynamic technology will contribute significantly toward enhancing HSCT economic viability. However, improvements in other technology areas and manufacturing cost reductions are also needed.

Joint sponsored NASA and McDonnell Douglas studies applied to high-speed civil transports have identified that aerodynamic technology advancements are required to satisfy both mission performance and environmental compatibility. To meet these requirements, reductions must be made relative to current technology in takeoff gross weight, sonic boom, and jet (community) noise. The application of advanced computational fluid dynamic (CFD) methods to vehicle shaping and concepts that increase laminar boundary layer flow will improve aerodynamic drag. This will, in turn, reduce fuel burn, leading to a takeoff gross weight reduction. Computerized wing aerodynamic control surface deflections have been identified as opportunities to reduce wing aerodynamic loads and structural weight and at the same time correct undesirable aerodynamic pitching characteristics.

The paper provides an overview of the renewed interest in turboprop propulsion systems for future commercial transport designs. The potential operating cost advantage of advanced turboprop designs is shown relative to advanced turbofan designs. Critical technology items for the aerodynamic installation of turboprop propulsion systems are presented, along with experimental results addressing the main technology issue for wing-mounted turboprop installations. Nacelle installation effects are presented for overwing and underwing nacelles. The drag reduction for nacelle contouring is also shown. Wing/nacelle/power data are presented for the baseline wing geometry and for a wing modified to reduce the propeller power effects.

An initial wind-tunnel test was conducted to investigate the aerodynamic interactions between a propeller slipstream and a supercritical wing at transonic Mach numbers. The primary independent variables examined included Mach number, wing lift coefficient, and slipstream Mach number and swirl. The interference effects were found to be weak functions of free-stream Mach number, wing lift coefficient, and slipstream Mach number; swirl was found to have a significant effect. At a free-stream Mach number of 0.8 and a lift coefficient of 0.5, incremental drag results for 7° of swirl (upwash inboard) and a slipstream Mach number of 0.87 indicate a penalty equivalent to a 0.024 loss in propeller efficiency. However, at 11° the drag increment was favorable and was equivalent to a 0.032 increase in propeller efficiency. Wing pressure data indicated the effects of the slipstream were essentially restricted to that section washed by the slipstream.