Aircraft wing designers have drawn their inspiration from birds since the dawn of aviation. But engineers are still finding ways of improving design based on examples found in the ornithological world.
Airbus senior manager of flight physics research David Hills says the European manufacturer has used nature "as a mentor" in the design of the A350 XWB's wings. "Conditions change - aircraft take off with full tanks of fuel so the amount of lift needed decreases. So what you'd like to do is have a series of wings, each optimised for different conditions. This is what we're trying to do with the variable camber and differential flaps," he says. "If you look to birds you see them do this all the time, especially in long-duration flights. They are twisting and bringing their wings in to adapt to conditions. This is what we're doing with the A350 XWB."
Since the development of the A320, Airbus has designed the flight-control system to automatically alleviate the effect of sudden gusts of wind, taking its inspiration from the wing feathers of birds, which act in the same way. Airbus has been continually improving this design, and Hills says that "on the A350 XWB it is at a point of significant refinement".
One day, airliner wings could have the shape and morphing characteristics of a leaf
In the world of unmanned air vehicles, one team of engineers has designed a morphed wing prototype which uses in-built shape memory alloy actuators that deform the shape of the wing when heated (Flight International, 20-26 July). Inspiration for this design was drawn from birds, as the University of Toronto's Professor Shaker Meguid, who is heading the morphed wing research programme, explains. He says: "To achieve flight mission adaptability, birds change the size and shapes of their wings.
"We are trying to use similar principles to morph aircraft wings to make them highly adaptable. A bird glides for maximum lift and folds its wings for reduced drag. This is the basic principle adopted from birds that prompted us to focus on wing planform."
Trees also played a part in inspiring the design because they have the ability to morph the shape of their leaves to decrease heat loss. "One could also mimic the shape and morphing characteristics of a leaf and apply them to an aircraft wing to optimise the aerodynamic characteristics of the wing," says Meguid.
He believes the technology behind the UAV morphed wing design could eventually be applied to civil aircraft, and claims that "some of the big airplane manufacturers are already interested in this technology and current research is being done to implement morphed wings". He adds: "The fact that morphing wings will be used in commercial aircraft is certain; the only unknown is when this will happen. Most likely it will be in the near future."
Hills disagrees, pointing out that unlike military aircraft, commercial airliners "do not need to drop like a stone, so we don't have the need" for morphed wings. However, while wing morphing on civil aircraft is out, wing twisting is something that is under consideration.
"We are looking at wing twisting," says Hills. "This is keeping the planform similar and using smart materials to change the shape of the wing. We are looking at whether there are enough benefits to progress with it."