Aerial Screw

The Aerial Screw is believed to be the predecessor of the helicopter. This invention wasn't made by Da Vinci. The invention's schematics were left in his journal along with all of his notes. The invention was made to compress air to obtain flight. Basically to build up enough momentum to hover above ground. Based on Leonardo's notes the Aerial Screw was supposedly made up of reed, linen, and wire. Unlike the helicopter, the Aerial Screw was to be powered by four men instead of two. There wasn't any weapons placed on the machine while the helicopter usually has gun attachments. 

Universal Leonardo: Leonardo Da Vinci Online. (2011). Retrieved December 9, 2011. From http://www.universalleonardo.org/

The Flying Machine (Ornihopter)

The Hang Glider is a modified version of Leonardo Da Vinci's invention: The Flying Machine.To accomplish the success of this prototype, Leonardo studied how bats flew. He carefully examined the exoskeleton of its wings. This would be the base of invention. Leonardo calls it "The Great Bird". The Flying Machine was designed as a bat. So the wings had to move. Going up and down and then stop to glide. This design was to sustain flight rather than to push forward based on human power and wind.  Unlike Da Vinci's invention the hang glider is a equilateral triangle that is used for the sole purpose of gliding. Da Vinci's invention was actually imitating a bat. There are many models made from his notes, But none will be as good as the original.

Carroll Gray. FLYING MACHINES (2003). Retrieved December 2,2011.
 From http://www.flyingmachines.org/davi.html