Inspired by nature

Apr 30, 2007 07:34 GMT  ·  By

The history of aviation, though short (only a bit more than a century) has known the most advances in terms of design technology, building materials and performances of civilian and military aircrafts. The first planes were made of wood, cardboard and cloth, now they are built using the latest development in artificial fibers, polymers and nanotechnology.

However, during this time, almost no designers went beyond the fixed wing model, considered up to now, the most efficient.

And while we struggle to develop new artificial compounds, nature offers us a helping hand. Ten Dutch and Swedish scientists, based in Wageningen, Groningen, Delft, Leiden, and Lund, have shown how "wing morphing" makes swifts such versatile flyers. Their study proves that swifts can improve flight performance by up to three-fold numbers that make wing morphing the next big thing in aircraft engineering.

Swifts (Apus apus) are some of the most efficient birds when it comes to active flying (flapping the wings instead of just gliding). They spend nearly their entire lives in the air, eating, mating and even sleeping in flight. The common swift travels 4.5 million kilometers (2.8 million miles) in its lifetime, roughly the same as six round trips to the Moon or 100 times around the Earth.

Researchers have proved how these master aviators change the shape of their wings to improve performance, providing clues as to how aircraft engineers can improve their designs.

They looked at 15 pairs of real swift wings taken from dead birds from sanctuaries by placing them in a wind tunnel and varying their orientation to measure the effect of wing shape and position on flight efficiency.

Scientists learned that flying slowly with extended wings gives swifts maximum flight efficiency. But swept wings deliver a better aerodynamic performance for flying fast and straight. Swept wings are also better for fast and tight turns; but this time swept wings are better because they do not break as easily as extended wings.

They found that swifts could adjust the shape of their wings to increase the efficiency of their glide or to make faster turns.

Extended wings provided the best slow glide, whereas those swept back away from the head functioned better at high speeds. Extremely fast turns required swept-back wings, as extended wings had the tendency to break under the extreme force. Elsewhere, swept-back wings did not flutter; they protected against bone fractures under these conditions of high force.

Findings further revealed that a proper co-ordination of the wings in relation to each activity allowed the birds to fly 60 percent further in a single glide and improve their turning efficiency by three times.

Morphing wings are the latest trend in aviation. The best wing shape to save fuel costs depends on flight speed. These birds inspired NASA to design a revolutionary "morphing wing" aircraft. Also, the so-called micro-aircrafts, which are the size of a bird, begin to exploit the benefits of varying wing shapes. These tiny flyers, equipped with cameras and sensors to assist in surveillance and espionage, imitate faithfully the flight behavior and appearance of birds.

The next applications will hopefully be extended to larger unmanned aircrafts to make them benefit from nature's outstanding biological achievements.