Dr Naomi Allen • 25.01.23 •  2 mins

New programmes by both Airbus and Boeing, which will culminate in the flight testing of high aspect ratio wings, are a great boost on the journey to Net Zero 2050. ATI Senior Technologist, Naomi Allen, explores why.

There has been a real buzz this week in the aerospace R&T community, following the announcement that NASA and Boeing have signed an agreement to carry out a Sustainable Flight Demonstrator programme which will aim to validate the Transonic Truss-Braced Wing (TTBW) concept. This is a project more than a decade in the making, with this wing configuration being one of the concepts created by the NASA-Boeing SUGAR program (Subsonic Ultra-Green Aircraft Research) which started in 2008.

But why are high aspect ratio wings so important? When aircraft wings generate lift, vortices are created at the wing tips, causing drag that the propulsion systems have to work to overcome. Making the wing longer and more slender (achieving a higher aspect ratio) weakens the tip vortices, creating less drag and reducing aircraft fuel consumption. Both Boeing and Airbus suggest that the fuel used by the aircraft could be reduced by up to 10% through adopting higher aspect ratio wings. Reducing the fuel consumption always benefits both climate impact and the cost of flying, regardless of whether the aircraft uses kerosene, SAF or hydrogen.

High aspect ratio wings are clearly worth adopting, but they don’t come without challenges. Making the wings longer moves the loads they support outward from the fuselage, increasing the stresses at the wing roots.

Finding a means of managing wing loads has been a critical barrier to overcome before we can see these wings on production aircraft. The Boeing approach is to use a truss-braced configuration, but Airbus have also been in the news in recent weeks talking about the technologies they plan to use to achieve this.

Airbus’s Extra Performance Wing project (part-funded by the ATI), is looking at technologies which, when combined, could be used to reduce the wing load caused by turbulence. Extreme turbulence causes the highest loads seen by the wing, and therefore drives the design of the wing structure.  Extra Performance Wing is using a Cessna Citation VII to flight test technologies including a flapping wing tip and a multi-functional trailing edge which can be used to modify the wing shape, mimicking a bird’s ability to adapt to flight conditions. This could reduce the maximum loads on the wing, enabling the use of higher aspect ratios and unlocking their potential fuel burn benefits.

With such a big opportunity for reduced fuel consumption on the table, it’s no surprise that both Airbus and Boeing are working to develop technologies required to enable high aspect ratio wings. These projects represent the culmination of years of simulation and wind tunnel testing, with the planned flight tests set to provide validation of these concepts at an aircraft-level. Those of us who keep a close eye on the development of technologies for sustainable aircraft will be waiting eagerly for the outcomes, hopefully taking us one step closer to Net Zero 2050.

Cover image: Artist concept of commercial aircraft families with a Transonic Truss-Braced Wing configuration from the Sustainable Flight Demonstrator project. © Copyright: Boeing

Further reading:

NASA Picks Boeing’s Transonic Truss-Based Wing For Sustainable X-Plane | Aviation Week Network

Airbus Progresses With Folding-Wing Project | Aviation Week Network