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Unconventional configurations will almost certainly be needed to meet the “Earth friendly” emissions standards required to support sustainable growth in commercial aviation beyond the 2030s, but there is less certainty as to what shapes those unusual future airliners will take.
One potential design that recently successfully traversed another round of wind-tunnel tests is the transonic truss-braced wing (TTBW) concept under study by Boeing and NASA. Although in some respects it is a traditional “tube-and-wing” design, the concept of using a long-span, low-drag, truss-supported wing on a jet airliner makes it anything but conventional.
TTBW was developed under Boeing Research & Technologies’ (BR&T) NASA-funded Subsonic Ultra Green Aircraft Research (Sugar) program to identify and investigate configurations and technologies for N+3-generation (2030-time frame) fuel-efficient airliners. The concept, which is in the running to be tested as a piloted X-plane in the early 2020s, derives its high lift/drag efficiency from its slender, glider-like wing. In the version most recently tested, the TTBW has an aspect ratio (wingspan squared divided by area) of 19.55. This compares to 11 for the composite-wing Boeing 787 and 8 for the conventional-wing 747-400.