Truss braced wing design and test 1.0 introduction/background:as part of the NASA fundamental aeronautics program, the fixed wing (FW) project is performing research into concepts, technologies, and…

Truss braced wing design and test 1.0 introduction/background:as part of the NASA fundamental aeronautics program, the fixed wing (FW) project is performing research into concepts, technologies, and tools that will enable dramatic reductions in noise and emissions, and increase the performance (fuel burn and reduced field length) characteristics of subsonic/transonic fixed wing aircraft. The FW project pursues a multi-generational approach addressing the needs of today but with an emphasis on establishing the technological foundations necessary to enable the capabilities needed in the decades ahead. NASA subsonic transport system level metrics/goals are shown below in table 1. Table 1: NASA's technology goals for future subsonic vehicles this effort is intended to identify high pay-off research that builds on the existing knowledge and results of the truss-braced wing (TBW) research to further refine and advance the TBW design configuration and validate the lift/drag (l/d) aerodynamic performance for on and off design conditions. The TBW is a technology concept that has the potential to change the design space by affecting the trades between wing sweep, thickness, speed, lift, and weight. These trades can enable very high aspect ratio, high span wings that may contribute significantly to an overall fuel burn reduction goal of -60% for transport aircraft entering into service in the 2030-35 timeframe, market permitting, relative to 2005 best-in-class aircraft. Current aerodynamic predictions for high-speed and low-speed aerodynamic performance for high span tbws are limited by a shortage of relevant empirical data. This uncertainty, when cycled through performance and sizing, results in significant variations in aircraft wing area and other parameters important to the wing design and optimization. Cruise drag uncertainty is primarily caused by unknown strut-wing interference. Empirical data for a transonic strut-wing fairing is not known to exist. Additionally, nacelles are quite different than struts and the attainable level of interference is currently unknown. Low-speed analyses and optimization of spanwise flap deflection is necessary for an accurate prediction of takeoff performance. This results in uncertainty in the low-speed performance of the aircraft as lift to drag ratio is equally important as maximum lift coefficient. Existing methods for determining the dynamic effects of large roll and pitch rates are insufficient for high aspect ratio wings. Roll damping estimates based on conventional wing aspect ratios may be insufficient to estimate roll control power required. Effects of aileron and/or spoiler deflection must be considered in the performance and in aeroelastic coupling to the spanload and thus to the roll damping. Due to the high wing span, allowable roll angle for takeoff and landing will be lower than a conventional aircraft, possibly affecting crosswind control. Another potential concern is the roll-YAW coupling. The high span wing, especially at high roll rates that can result in separated flow near the wing tips, can lead to unusually large yawing moment coefficient due to roll rate derivative (i.e., CNP values) values which may affect vertical tail sizing beyond the normal trim, engine-out, and directional stability criteria. For the pitch axis, understanding changes in basic wing+body stability levels in both the cruise and in the high-lift configurations is also essential. In order to mitigate these uncertainties, higher fidelity aerodynamic data at off-design conditions are needed to augment and improve the structures, loads, and stability and control analyses in addition to the primary on-design cruise drag (l/d) for the TBW configuration. 2.0 scope, objective(s), applicable documents, and acronyms: 2.1 scope: the scope of this task order is to refine the design of a transonic TBW aircraft with high-fidelity tools, and any r