One of Leonardo’s most iconic images, the Aerial Screw (also known as the Helicopter) illustrates the ingenuity of da Vinci, and indicates (along with many other drawings!) his obsession with flying.
While this 15th Century (!) idea may never have got off the ground, for some basic technical reasons, it gave us an insight into the different ways in which Leonardo considered the challenge of human powered flying, and defines him as an inventor well ahead of his time.