Animals Plants Other things

Everything began with the bird's flight!

For centuries humans tried in vain to produce propulsion and lift by the beating of wings in order to fly like birds. But the accurate imitation of the bird's flight with muscle power wasn't and isn't possible. This led to an evolutionary dead end and is a very good example that nature can't directly be copied. Also Otto Lilienthal, who studied the birds very exactly and is the founder of the modern bionics, experimented first in vain with striking wings. But after his very long and global study of the birds he detected the meaning of the curved wings, which are very important for the lift. Being used to working out problems systematically, he concentrated himself on gliding first by using rigid wings to produce the necessary lift and the propulsion energy was won by the loss of height.- 1891 he succedded in gliding 15m with wings made of willow twigs and 10 m² of cotton material, as in the right picture is shown. In 1896 when Otto Lilienthal died in a plane crash, his flight tests were world famous and numerous flight techincians continued his work. Thus 1909 Igo Etrich, Lilienthal's pupil presented the first motorized flightmodel.

But what is so special about bird's wings?

That is the most important characteristic of flight. But nature has still further inventions which reduce the energy expenditure of the bird's flight: The difference of pressure cannot be preserved at the tip of the wings.
This produce a whirlwind like at the tip of plane's wings (see picture at the left). Sea-birds, like the Albatros reduce this so-called induced resistance through very long "fingers" at the tip of their wings (picture on the right). This invention was also used for high speed gliding airplanes. Therefore about 30 - 50% more propulsion energy can be used.


For land birds the associated large span wouldn't be useful. Therefore these birds have developed fringed wings which produce lots of small whirlwinds. Depending on the flight attribute (slow, fast), the position of the "fingers" has to be so that the many small whirlwinds don't become a large one again. (Pictures) This attribute has not been technically used so far but such constructions are being worked on. Here a so-called Mono-Winglet is used, but it isn't so efficient.