Boeing’s Transonic Truss-Braced Wing (TTBW) airliner is a radical rethinking of aircraft design that could redefine standards of efficiency and sustainability. The concept, first developed in 2010, is now being built as a full-scale demonstrator with ambitious goals for fuel efficiency. If the project proceeds as planned, Boeing expects that planes of this design could be operational between 2030 and 2035.

The Transonic Truss-Braced Wing (TTBW) Unveiling

In January 2019, Boeing revealed its innovative concept – the Transonic Truss-Braced Wing (TTBW) airliner. A result of a collaborative project with NASA that began in 2010, this concept aircraft incorporates a lightweight, ultra-thin, and highly aerodynamic wing design, supported by diagonal trusses. The design aims to provide optimal fuel efficiency. The TTBW is intended to fly up to Mach 0.80, similar to current jetliners’ speed but faster than any preceding truss-braced wing concept.

With a wingspan of 170 feet (51m), the TTBW concept plane is smaller than the A350 and the 787 Dreamliner, but still larger than the 737 MAX 8, which it surpasses by 53 ft (16m). A crucial factor in the TTBW design is its modified wing sweep and ultra-thin design, which minimize the induced cruise drag of the high aspect ratio wing. Wind tunnel tests have so far shown a remarkable 9-10% reduction in fuel burn for the wings alone. NASA and Boeing hope that when combined with other emerging technologies, the plane could achieve a 30% reduction in fuel burn compared to current next-generation narrowbody jets, like the A320neo or 737 MAX.

“Together with expected advancements in propulsion systems, materials, and systems architecture, a single-aisle airplane with a TTBW configuration could reduce fuel consumption and emissions by up to 30% relative to today’s most efficient single-aisle airplanes, depending on the mission,” stated Boeing.

To tackle the logistical issues associated with large wingspans, Boeing plans to use folding wingtips, a feature showcased on the 777X. The TTBW design proposes a significant adaptation where the wings would fold almost in half, with the truss providing support. This design could help circumvent difficulties related to fitting the aircraft into airport gates or hangars.

A New Era of Sustainable Aviation

Despite the fact that many concept aircraft proposed by Boeing and Airbus never materialize, researchers have confidence in the TTBW’s potential for mainstream use. Since 2010, Boeing has been developing the TTBW design through its partnership with NASA in the Subsonic Ultra Green Aircraft Research (SUGAR) program. They envision aircraft based on this design being operational by 2030-2035.

The current TTBW design, known as the X-66A, recently received its ‘X’ designation from the US Air Force. The ‘X’ refers to experimental aircraft designs that explore new technologies. The X-66A is the first X-plane designed specifically to usher in “a new era where aircraft are greener, cleaner, and quieter.”

The TTBW design does come with some challenges, such as fuel storage, due to the wings being much thinner than conventional airliners. The project is also banking on the integration of advanced propulsion systems, so its viability also depends on technological advancements in other areas.

Moving Forward with a Full-Scale Demonstrator

Boeing announced a full-scale demonstrator in January, which will use a shortened MD-90 airframe. The demonstrator is scheduled to undergo a year of flight testing at the NASA Armstrong Flight Research Center in 2028. Boeing has proposed two potential designs for TTBW narrowbodies – the VS-1 and VS-2 – that would accommodate between 130–160 and 180–210 passengers, respectively.

Pratt & Whitney will power the demonstrator with its PW1100G geared turbofan. With single-aisle aircraft accounting for nearly half of worldwide aviation emissions due to their extensive use, NASA aims to target this market segment for significant emission reductions.

$1 Billion in Funding

NASA has pledged to invest $425 million into the project over the next seven years, with Boeing and partners committing $725 million during the same period.

NASA Administrator Bill Nelson stated, “Our goal is that NASA’s partnership with Boeing to produce and test a full-scale demonstrator will lead to future commercial airliners that are more fuel efficient, with benefits to the environment, the commercial aviation industry, and passengers worldwide. If we are successful, we may see these technologies in planes that the public uses in the 2030s.”

As Boeing seeks a successor to the 737 family by the early 2030s, the TTBW concept could play a crucial role in shaping its future narrowbody designs. While this groundbreaking redesign of conventional aircraft will undoubtedly face certification challenges, the significant funding and progress made on the TTBW suggest that we may be hearing more about this concept in the years to come.

What potential impacts do you foresee the Boeing Transonic Truss-Braced Wing (TTBW) airliner having on the future of commercial aviation, particularly with regards to sustainability and fuel efficiency? Let us know in the comments below.