Roland Piquepaille

Airplanes, whether manned or unmanned, need to travel at various speeds. For example, a surveillance plane needs to fly fast to reach its destination point. Then, it needs to reduce its speed to achieve its surveillance mission. But with its fixed wings, it doesn’t offer the same level of efficiency during these two phases. That’s why Penn State engineers have devised airplane wings that change shape like a bird and have scales like a fish. Right now, the team has only built a tabletop model. So it will be a long time before you catch a plane and watch the wings disappear by looking through the window.

Dr. George Lesieutre, professor of aerospace engineering who leads the project, says, “Airplanes today are a design compromise. They have a fixed-wing structure that is not ideal for every part of a typical flight. Being able to change the shape of the wings to reduce drag and power, which vary with flight speed, could optimize fuel consumption so that commercial planes could fly more efficiently.”

Morphing wings can also be useful for military defense and homeland security when applied to unmanned surveillance planes that need to fly quickly to a distant point, loiter at slow speed for a period of time and then return, Lesieutre explains. Flying efficiently at high speed requires small, perhaps, swept wings. Flying at slow speed for long periods requires long narrow wings. The morphing wings designed by the Penn State team can change both wing area and cross section shape to accommodate both slow and fast flight requirements.

So how did these engineers design these morphing wings?

The essential features of the Penn State concept are a small-scale, efficient compliant cellular truss structure, highly distributed tendon actuation and a segmented skin. The cellular truss structure is the skeleton of the wing.

Since the underlying structure can undergo radical shape change, the overlaying skin of the wing must be able to change with it. Lesieutre says a concept that he thinks holds great promise is a segmented skin composed of overlapping plates, like the scales of a fish.

New Scientist

Some of the morphing work has been inspired by the study of birds, bringing the story full circle back to 1903. The all-important control demonstrated by the Wright brothers’ Flyer came not just from the first wind tunnel-tested aerofoils and rudder, but also from wing warping – a technology inspired by the Wrights’ observations of the way turkey vultures soared over the Miami river, near their Ohio home.