Leonardo da Vinci's aerial screw used a large helical blade to suggest a way of rising into the air.
Drawn around 1489, the aerial screw resembles a giant screw or a modern helicopter rotor viewed as a spiral. Leonardo proposed that a linen-covered spiral structure, supported by a reed framework, could force air downward and lift itself upward when rotated.
The idea was inspired partly by the action of an Archimedes screw, a device used to move water. Leonardo transferred the screw principle from water to air, although the materials and power available in Renaissance Italy were not sufficient to make the machine fly.
The aerial screw is frequently described as a precursor to the helicopter, but it was not a functioning helicopter. Modern helicopter flight depends on powered rotor blades, engines, and careful aerodynamic control. Leonardo's sketch is important because it identifies vertical lift as a separate engineering problem from ordinary winged flight.