Air screw

the museum model
"I believe that if this mechanism is well made with starched linen cloth and if it is spun rapidly, the screw will ......... and it will rise up high into the air."

In studying the air screw, Leonardo anticipates by centuries the formulation of the tractive power of the helix. The screw has a 5 metre diameter and is made of reed, linen cloth and wire. The shaft is spun by four men who stand on the central platform and push the bars in front of them with their hands.
Manuscript B, sheet 83 v. , 1483-1486