Leonardo’s helicopter sketch illustrates a device that was designed to allow for human powered flight. The sketch is of a device that included a wooden base and frame that was connected to a screw-shaped canopy. This sketch was one of the first attempts at creating a rotary flight device, the same concept behind modern day Helicopters. While some scholars argue that this sketch was actually a device used for pageants, the physical principles behind it as a device for human flight were actual sound. The fundamental reason that this device could never function as a flying machine is that humans do not have enough strength to generate the power that would have been necessary to allow the machine to get airborne.
Isaacson, Walter. Leonardo Da Vinci: the Biography. Simon & Schuster, 2018.