Boeing and NASA Unveil Lightweight, Ultra-Thin, More Aerodynamic Transonic Truss-Braced Wing Concept

January 11, 2019

Courtney E. Howard

Engineers at Boeing and NASA are collaborating on a lightweight, ultra-thin Transonic Truss-Braced Wing (TTBW) concept, designed to be more aerodynamic and fuel-efficient than current designs, as part of the Subsonic Ultra Green Aircraft Research (SUGAR) program focusing on innovative aerospace concepts that reduce noise and emissions while enhancing performance.

Boeing engineers have revealed the newest TTBW design, which researchers say will fly higher and faster than the previous TTBW concepts and offer unprecedented aerodynamic efficiency while flying at Mach 0.80. Originally, the TTBW was designed to fly at speeds of Mach 0.70 – 0.75. To increase the aircraft’s cruise speed, the new concept now has an optimized truss and a modified wing sweep.

The truss is able to carry lift more efficiently, which engineers credit to adjustments made to the wing sweep angle following extensive wind tunnel testing at NASA Ames Research Center. The end result is a more integrated design that significantly improves vehicle performance, researchers say.

From end-to-end, the folding wings measure 170 feet – a high wingspan made possible by the presence of a truss, which supports the extended length of the ultra-thin wing.

Boeing and NASA have been studying the TTBW concept as part of the SUGAR program for nearly a decade. Work on the program has informed cutting-edge designs and contributed to promising developments for the future of aviation centered on potential climate-saving flight technologies, alternative fuels, electric aircraft, subsonic aviation concepts, and improved aerodynamics, propulsion, and sustainable materials.

SAE International is a tremendous resource for more information, both bleeding-edge and historical in nature, on these and other mobility engineering topics; visit https://www.sae.org/ for more on automated and connected, more-electric, connected, and sub/super/hypersonic vehicles and enabling technologies.

Concepts and technologies stemming from SUGAR include:

SUGAR High— a high-span, high-aspect-ratio, high-lift-to-drag truss-braced wind concept that has been tested in aeroelastic and high-speed wind tunnels and is preparing for a low-speed wind tunnel test. It is currently estimated to deliver an 8 percent reduction in fuel burn compared to a conventional cantilever (non-strut-braced) wing. Additionally, the high wing allows easier more efficient integration of large diameter fans and open rotor propulsion systems for additional fuel burn benefits.

SUGAR Volt— the first concept for a hybrid-electric commercial airliner, which played a major role in electrifying the current interest in small and large electric aircraft at companies, government labs, and universities around the world. Much like a hybrid car, the SUGAR Volt can decrease fuel use and substitute electrical energy, which, if from a renewable grid source (wind, solar, etc.), can significantly reduce the life cycle greenhouse gas emission of a conventional airliner. Boeing was awarded a new contract to continue studying the SUGAR Volt and a NASA hybrid electric concept called the STARC-ABL or single-aisle turbo-electric aircraft with an aft boundary layer propulsor.

SUGAR Freeze — uses liquefied natural gas, fuel cells, cryogenically cooled electric motors, advanced battery energy storage, and aft fuselage boundary layer ingestion propulsion for potential benefits.

Courtney E. Howard is editorial director and content strategist at SAE International. Contact her by e-mail at This email address is being protected from spambots. You need JavaScript enabled to view it..