The first studies on helicopters were well in advance of the first airplanes. Leonardo da Vinci is credited with having first thought of a machine for vertical flight, the "airscrew," the design for which, dated 1493, was only discovered in the 19th century. It consisted of a platform surmounted by a helical screw driven by a somewhat rudimentary system, not unlike that of rubber-powered model aircraft. The great Tuscan genius wrote that if this instrument in the form of a screw were well made of linen, the pores of which had been stopped with starch, it should, upon being turned sharply, rise into the air in a spiral. However his design was never put to any practical use.

G.Apostolo "The Illustrated Encyclopedia of Helicopters", 1984

Just how Leonardo came to think of the helicopter flying principle is not quite clear. In view of his enormous mental powers, it is conceivable that this could have welled up from his own creative pools of genius. Of course the possibility of his having come in contact with the Chinese top either through his widespread reading or contact with travelers must also be considered. However this may have been, the fact remains that this great Italian designed and built models of the first helicopters intended for human flight.

One of the first of Leonardo's helicopter designs called for a shallow saucer-like gondola on which two upright posts were attached. Each of the posts carried a double set of wings. By means of a rather complicated system of cords, cylinders, and foot pedals, the pilot set the wings in motion with movements of his feet, hands, and head! Alas, the poor flyer, if he suddenly developed a cramp in his leg!

The wings of this craft were not of the flapping variety, but rather they moved in a horizontal plane, criss-crossing one another. This motion compressed the air between the wings and gave the craft lift. Leonardo provided his helicopter with a landing gear in the form of a pair of ladders about twenty-four feet long. These were intended not only to help the take-offs but also to cushion the craft when it landed. During flight they were supposed to be hauled into the gondola or fuselage.

Unlike many inventors, Leonardo was not above feeling that perhaps, should his helicopter ever reach the flying stage, an accident might occur. Therefore, along with a description of his craft, he also included the very wise suggestion that during the helicopter's test flight, the pilot fly it over water. In the event of an accident, he would thus be tumbled onto this yielding surface and unharmed.

While speaking of Leonardo's caution about flying, it is interesting to note that in connection with his helicopter studies he also devised what was perhaps the world's first parachute. The Italian genius was quite optimistic about his life-saving device; he showed this when he said, "If a man have a tent roof of caulked linen 24 feet broad and 24 feet high, he will be able to let himself fall from any great height without danger to himself."

The helicopter experiments also led Leonardo to design what many believe to be the first airplane instrument. This was a pendulum device that hung within a glass ring. "This ball within the ring will enable you to guide the apparatus straight ahead or aslant as you wish."

Craving perfection in all that he did, Leonardo soon began to feel unhappy with his first helicopter models. One of the major causes of his dissatisfaction was the manner of powering his flying machine. He came to the conclusion—one that was to profoundly affect aircraft experiments in the years ahead — that mechanical rather than human power must be used before a successful flying machine could be built.

With this thought in mind, he undertook some new experiments before designing a different model helicopter. Standing in the center of his studio one day, he took a large, thin ruler and swung it in rapid circles above his head. He felt a distinctive upward pull on his arm. From this he reasoned that it he could build a flying machine having a rapidly rotating wing above it— powered by mechanical means—he would achieve a successful aircraft. Leonardo proceeded to build a model of his new helicopter design, powering it with a spring motor.

Many of the helicopter models which he built are said to have taken to the air successfully. It is quite likely they were fashioned along the lines of those using a coiled spring for a motor. These craft had a wing-like rotor for rising into the air.

Among the last of the helicopter models designed by Leonardo was one which had the appearance of an artificial Christmas tree. More important to the great Italian, it is the design which historians say made him the partial originator of the word "helicopter." He described the craft with a good deal of confidence in its flying ability. "I say that this instrument made with a helix and is well made, that is to say, of flaxed linen of which one has closed the pores with starch and is turned with a great speed, the said helix is able to make a screw in the air and to climb high."

The helix he mentions is a Greek word meaning "spiral" or "twist." This was combined later with another Greek word, pteron, meaning "wing." In still later years through much usage, the words were fused in such a manner that the term "helicopter" came to be born.

As in his many other fields of endeavor, Leonardo da Vinci left his imprint on the very infant subject of aeronautics. By his work with ornithopters and helicopter models he is said to have begun the first sound experiments in search of a practical heavier-than-air flying machine. Leonardo was strongly convinced that if man were to accomplish his long desired goal of traveling in the sky above him, it would be by a flying machine based on the principle of the helicopter. A little more than two hundred years were to pass before Leonardo's ideas on flying machines were to be picked up and carried forward by a whole host of helicopter experimenters. Alas for this band of aeronautical pioneers, man's first ascent into the sky was made by an entirely different type of aircraft, the hot-air balloon.

Frank Ross Jr. "Flying Windmills", 1953