We tend to think of aeronautical engineering as having left the birds standing still sometime around the First World War, but since jet fighters can’t perch and quadcopters can’t snag salmon out of a stream, we still have a few things to learn. Taking a couple of pages from the avian playbook, 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.
Billions of people take to the air every year with even greater numbers projected for the foreseeable future. Not only is this part of one of the greatest on-going transportation revolutions in human history, but also poses grave problems in terms of energy and pollution. One major goal of modern aeronautical engineering is to find ways to make jet aircraft more efficient in terms of the amount burned because, on a global scale, even the smallest reduction can have very large economic and environmental benefits.
The Fraunhofer consortium’s project is part of Europe’s Smart Intelligent Aircraft Structures (SARISTU) program, which aims at a reduction of jet fuel by six percent. In this case, the strategy is to redesign the jet aircraft’s wing so it’s more like that of a bird. That doesn't mean we’ll be seeing 747s with feathers, but rather with wing sections that can alter their shape and so the flow of air over them, much in the same way as birds can spread or twist their feathers to give them the most lift in a desired situation.
In particular, the consortium is looking at a morphing flap. Modern wings have a very limited ability to change their shape, usually restricted to extending large, rigid landing flaps. “Landing flaps should one day be able to adjust to the air flow and so enhance the aerodynamics of the aircraft,” says Martin Schüller, researcher at the Fraunhofer Institute for ENAS.
Essentially, what the Fraunhofer engineers (and others working on shape-shifting wing systems like Flexsys) are doing is going back to Day One of the age of flight. When the Wright brothers took off from Kitty Hawk in 1903, their flyer didn't have flaps and ailerons, Instead, they used what was called “wing warping,” where lines and pulleys twisted the wing, so the air flowed in the desired manner. The morphing flap takes a high-tech approach to this.
It works by means of a mechanism that alters the shape of the flap under the control of a computer algorithm. The skin of which is made up of alternating hard a soft areas consists of a silicon skin with the flexible parts made of a elastomeric foam that stays pliable even down to minus 80⁰ C (minus 112⁰ F). Since this is still very much in the experimental stage, Fraunhofer isn’t keen to divulge too many technical details
Fraunhofer and its partners have built four prototypes that are 90 cm (35.4 in) long. Two of these are covered in skin. These will be used for engineering and wind tunnel testing, and will be on display at the ILA Berlin Air Show until May 25.