Elastic Wings Promise Greater Aircraft Fuel Efficiency

Ever since Leonardo Da Vinci, mechanized aviation has been all about imitating the streamlined flight of the bird. And, more recently, it’s been all about energy efficiency. Now a German company is developing aircraft wing flaps that change their shape to accomplish both.

More than 2.2 billion tickets are bought each year for plane travel – a form of transportation powered by jet fuel, which creates a huge carbon footprint on the Earth’s atmosphere.

It’s not surprising, then, that aircraft manufacturers are looking for ways to reduce fuel consumption.

Like Leonardo, aviation researchers are studying birds. It’s long been known that birds can situate their feathers to optimize airflow around their wings for more efficient flight and landing, something current aircraft have been able to do in only a limited way because of their rigid construction. This is one problem being studied by the EU’s Smart Intelligent Aircraft Structures project, or SARISTU.

Current aircraft include landing flaps at the trailing edge of their wings that are extended to manipulate airflow for safe and efficient landing. But this flap also is rigid, limiting its effectiveness. As part of the SARISTU project, the Fraunhofer Institute for Electronic Nano Systems (ENAS) and its partners are developing wing flaps for airplanes that change shape like a bird’s wing for greater efficiency.

“Landing flaps should one day be able to adjust to the air flow and so enhance the aerodynamics of the aircraft,” says Martin Schüller, an ENAS researcher in Chemnitz, Germany.

ENAS and its partners have already developed a mechanism that changes the shape of the landing flap to accommodate airflow. And ENAS, along with the Italian Aerospace Research Center and the University of Naples, has developed the software to control the flaps’ shape shifting.

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This may be cutting-edge 21st-century technology, but it actually harkens back to the Wright brothers’ historic flight at Kitty Hawk in 1903. Their craft lacked the ailerons and landing flaps of modern aircraft, but had flexible wings whose shape could be warped by lines and pulleys to control air flow.

So how do you make landing flaps elastic in modern planes? “We’ve come up with a silicon skin with alternate rigid and soft zones,” says Andreas Luehring of Fraunhofer Manufacturing Engineering and Applied Materials Research, or IFAM. “There are five hard and three soft zones, enclosed within a silicon skin cover extending over the top.”

Besides the design, Fraunhofer said in a statement, is the elastic material itself, which remains flexible from 55 degrees below zero to 80 degrees above zero Celsius (67 degrees below zero to 176 above zero Fahrenheit).

The upshot is that if the flexible landing flaps become a viable solution, the airline industry can reduce fuel consumption by 6 percent. This may sound small, but multiply that by millions of flights, and that’s a lot of jet fuel that hasn’t burned.

Fraunhofer and its partners have built four prototypes, two of them covered with the elastic skin. Each prototype is 90 cm (35.4 inches) long. These will be used for engineering and wind tunnel testing, and were displayed at the ILA Berlin Air Show from May 20-25.

By Andy Tully of Oilprice.com