Boeing will study the certification challenges of its Transonic Truss-Braced Wing (TTBW) ultra-efficient airliner concept as part of a new phase of work following wind tunnel tests that prove the basic viability of the 737-class aircraft design for typical airliner cruise speeds of Mach 0.8.
Wing sweep was increased to enable cruise speed to rise from Mach 0.745 to Mach 0.8. To rebalance the resulting change in the aircraft’s center of gravity, the wing root was moved forward and the inboard strut was moved aft and no longer positioned directly beneath the wing.
“The big carrot here is a dramatic increase in vehicle wing aspect ratio which gives us a significant decrease in induced drag”, Boeing TTBW program manager Neal Harrison said. A lot of technology has to be demonstrated and matured, including the wing-strut join. The tests also showed that the design revisions improved high speed efficiency. “Total vehicle performance was improved by moving the jury strut outboard”, he adds. The low speed tests, which ran through November 2019, used a 14-ft. span 8% scale model and evaluated several high-lift designs. Boeing said that “there remains significant potential for high-lift system performance improvement with additional study”.
Key study areas will include investigations of high-speed buffet; alternate high-lift systems development; transonic wind tunnel tests at higher Reynolds numbers; detailed aeroelastic analysis and development of roadmaps for demonstrating structural concepts and key acoustic technologies.
Collected and summarized from the source below by Minh Pham https://aviationweek.com/aerospace/boeing-plans-next-steps-ultra-efficient-airliner-concept