Thierry M. FAURE
Centre
de Recherche de l’Armée de l’air (CReA), École de l’Air, 13 661, Salon
Air, France
The dream of flight, first developed by the observation of nature, was
inspired from birds and insects. However, the whirling fall and glide of seeds
from trees like the sycamore, allowing a wide dissemination of the specie, is
an alternative way of flight. That is probably the origin of conception of the Chinese
top (reported by Ge Hong circa 400 BC), which is a small toy consisting in two blades
attached to a stick, which rotation between the hands of an operator, generates
lift and its vertical flight [1]. The idea of using blade rotation, to fly a machine
carrying a man, was developed by Leonardo da Vinci at the end of the XVth
Century. His thinking was to adapt the Archimedes’ screw, which is a device for
raising water from the ground level, to the vertical translation of a machine
in the air (Figure 1). If no light and high-strength material existed at
that time and no engine was available to provide enough power to fly that
machine, its design was wrong in its mechanical concept. Contrary to the seeds
falling from a tree, or the Chinese top, the shaft-driven rotor generates a
torque which is transmitted to the nacelle making it swirl and leads to a loss
of control. Thus, the lack of a proper counter-reacting torque system is the main
drawback of that design. In addition, the rotor shape is far from an optimum
use in the air.






