New aeroplane wing tests a flying success
Rigorous wind tunnel tests have shown that a new flexible deformable aircraft wing concept developed by EU-funded researchers can increase lift during take-off, achieve greater efficiencies in flight and reduce noise.
Aeroplane wings capable of ‘intelligently’ changing shape in response to flying conditions could reduce drag and lead to significant reductions in fuel consumption and emissionsconsumption and emissions. A key challenge to date, however, has been reconciling sufficient wing adaptability with the need for structural strength and stiffness.
To address this, the EU-funded SADE project has developed and tested deformable wing parts made of a glass fibre-reinforced polymer under varying wind speeds and angles, representing take-off, cruising and landing.
Flexible flying materials
The team focused on the leading edges of wings, where mechanical flaps are used during take-off and landing. Researchers replaced conventional flaps and slots with a ‘smart’ flexible, deformable leading edge. “The absence of slots reduces noise while shape adaptation of the wing tips increases aerodynamic efficiency,” explains project coordinator Hans Peter Monner from the German Aerospace Centre (DLR). “The skin we developed has a highly even surface quality, enough bending stiffness to carry loads, but is deformable.”
Strain gauges, pressure tubes and optical measurements were employed to evaluate performance, and results were compared with predictions using an innovative computational fluid dynamics model. “No structural damage to the stressed skins was detected after rigorous testing, demonstrating the potential for developing smart morphing airframe technologies for commercial aircraft,” says Monner. “This could lead to greener and cheaper air transport.”
Following completion of the project, Monner says the next step is to operate a flight test of the new wing material. In addition, of the team is looking into transferring the project’s results to other high-tech sectors in search of fuel efficiencies, such as the automotive industry.
Scaling up the concept
The project began by developing models of possible low-weight structures – flexible in one direction, stiff in the other – that could lead to more efficient flight. “Few solutions survived the model stage,” says Monner. “Models are easily made but they do not necessarily give an answer on aerodynamic and structural behaviour in flight.”
The project team next assembled a one-to-one scale wing section for rigorous tested in a wind tunnel. The wing design was constructed to replicate that of a medium range single-aisle aircraft like the A320. Testing was carried out in a tunnel owned by the project’s Russian partner, the Central Aerodynamic Institute (TsAGI). The facility comprises a very large continuous tunnel with an open test section designed for low-speed, full-scale investigations.
Every configuration was applied, and the model taken down for inspection each time. Various wind speeds of between 30 and 50 m/sec were used, and the wind direction was also changed. The seamless, adaptable leading-edge device developed by the project demonstrated significant acoustic benefits in flight, while offering increased lift for take-off.
“The wind tunnel experiment represents a milestone for morphing technologies like this,” says Monner. “It demonstrated that large deformations are possible even for load-carrying structures at full scale. We have taken adaptive wing technology further towards more efficient, quieter wings thanks to this collaborative research.”
Investment in research remains vital to the competitiveness of Europe’s aeronautics industry, and represents 10 % of industry turnover. The European Commission is continuing to support European R&D efforts in this field through the Horizon 2020 funding programme under the “Smart, Green and Integrated Transport challenge” and two Joint Technology Initiatives, Clean Sky and the SESAR Joint Undertaking.