Air Screw

This is certainly one of Leonardo's most famous designs since it one recognizes an ancestor of the helicopter.

This craft made of reeds, linen, and iron thread would have been operated by four men who, by rotating a shaft, could lift themselves off the ground.

It is clear that the mechanism so conceived could never have taken off, but the idea remains that with the force of an adequate motor, the machine would actually have spun itself into the air and off the earth.

Credit : HK Sciences Museum.