Da Vinci’s Aerodynamics

by Dr. Richard Stimson

in History of Flight

Leonardo da Vinci, one of the most creative genius of the Renaissance, had an enduring infatuation with flying during the period between 1488 to 1514, a time when Columbus discovered America. His obsession drove him to write a collection of manuscripts with over 500 sketches on the topic. Many of his ideas were a precursor of the modern airplane.

His most famous flying machine designs were ornithopters, or machines that were to be powered by man by flapping bat-like wings like a bird.

In one of his best known designs, a man lies face down on the body of the machine and flaps the wings by pumping the stirrups with his legs much like modern pedal powered airplanes.

Just as the Wright Brothers, da Vinci based his ideas on the study of bird flight. He observed that: “A bird is an instrument working according to mathematical law, an instrument which is within the capacity of man to reproduce with all its movements.”

Implicit in his statement is that da Vinci was searching for the governing laws upon which bird flight is made possible. Knowing these laws, he could then use them to design a machine.

He was the first person to understand the mechanics of bird flight. From his observations he came to realize that the up-and-down flapping of the bird’s wings did not contribute much to lift. What the flapping did do was provide thrust for propulsion.

Da Vinci was the first to consider the scientific concept of lift, the force that enables a flying machine to fly.

His initial concept of lift was wrong. He thought that a high-pressure, high-density region of air was formed under a lifting surface that in turn exerted an upward force on that surface.

Later in life he changed his ideas on lift to the correct modern concept that lift is created primarily because the pressure over the top of a wing is less that the pressure on the bottom of the wing as air flows over it.

He invented the first barometer and anemometer to use in his studies.

Da Vinci also concluded correctly that a flying machine could have fixed wings and have a separate mechanism for propulsion, a thoroughly modern idea.

Additionally, He understood the phenomenon of drag, the resistance that a body incurs when moving through air. He postulated that both lift and drag were proportional to the surface area of the body and velocity of the wind over the body.

He was partially correct on the relationships. The velocity function is actually “velocity squared.”

He further understood that streamlining the shape of a body would reduce drag. In this regard he said that the streamlined shape of fish aids them in maneuvering in water.

His sketches of various flow patterns of airflow around a body represent the first qualitative understanding of experimental aerodynamics.

Da Vinci was the first to recognize that when studying the flow of air over a body, it didn’t make any difference whether the body was moving through still air or whether the air was moving over a stationary body as long as the relative velocity was the same in both cases. This insight provided the basis for the use of wind tunnels as a tool in the of study aerodynamics.

Safety of the pilot was a concern of da Vinci. He invented the first parachute using the model of a kite. The kite is an old technology, having been invented in China around 1000 BC.

It is obvious that da Vinci made significant contributions to the state of the art of aerodynamics. Unfortunately, after his death in 1519, his contributions were not available for use by others until the nineteenth and twentieth centuries. By that time it was too late to add to what others had discovered.

The problem was that he never published his work nor constructed or flew any of his machines. All of his ideas were in his notes and these were difficult to interpret because he wrote in a reverse mirror-like fashion. After his death the notes were dispersed and essentially became lost from view. Most people know of him for his famous paintings of the Last Supper and the Mona Lisa.

Sir George Cayley did not rediscover da Vinci’s ideas on lift and drag and the concept of a fixed-wing airplane until three centuries later in 1809. Cayley did not have the benefit of da Vinci’s notes.

By the time the Wright Brothers began construction of their 1900 glider, they had researched the available aerodynamic data of the day. It is not known whether they had in their extensive library any information on da Vinci.

The work of their predecessors did not furnish the Wrights with many answers but it did help them focus on the problems to be solved.

The Wrights, using a wind tunnel they constructed, contributed to the advancement of engineering knowledge on calculating lift and drag and design of airfoils.

Their most revolutionary contribution was the concept of wing warping for lateral control of a flying machine. Wilbur’s inspiration for this idea came from watching birds; much as da Vinci had done centuries before.

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