Drawings by Leonardo Da Vinci showing a life preserver, the aerodynamics of vertical flight, and a wooden wing operated by a hand crank. Da Vinci's life preserver was a leather bag that was filled with air. The air in the bag would cause the bag to be buoyant. This would allow humans to grab on and float. It was designed to keep people's heads above the water to allow them to breath. It is like a modern day lifeguard life jacket or even a beach doughnut tube. Da Vinci's helicopter is a world renowned example of his ability to think centuries ahead of his time. The design was drawn in 1493, 450 years earlier than an actual helicopter would take to the air. The helicopter was designed as a human powered machine. It was designed to work by having two men standing in the central circular platform. Each man would take hold of a wooden shaft and walk around the central shaft. This would rotate the blades of the helicopter and supposedly produce flight.