Even before the Wright brothers flew at Kitty Hawk, North Carolina, aviators at the end of the 1800s knew that motorized flight was the wave of the future. They mounted motors to frame-strengthened balloons, called “dirigibles”, but the giant craft were slow and ungainly. Still, those brave innovators succeeded at making the sky a familiar, if not a comfortable, place to be. The stage was set for the next stage in human flight—gliding.
By the Book
Aerodynamics is part of an arcane branch of physics called "fluid mechanics." In the case of aerodynamics, scientists and engineers study the mob*on of air, including the forces it exerts on objects that move through it. Acrodynamicists study wing shapes, jet propulsion, and the extreme conditions of highspeed flight, among other things.
Although centuries had passed since the days of Leonardo, the master engineer was viewed as prophetic in the late nineteenth century when gliders began to replace balloons as the next major advance in aviation. Designs for the early gliders bore a striking resemblance to the articulated wings that Leonardo had sketched in his notebooks. But now science was coming to the aid of fancy, and engineers were puttering around with wing designs that took advantage of some of the new discoveries about the physical properties of air and the effect it can have on objects like wings. The newly fashionable science was called aerodynamics.
Sir George Cayley
The theoretical capabilities of gliders became apparent as early as 1804, when Englishman Sir George Cayley foreshadowed many of the later
discoveries of glider and airplane builders, earning himself the honored title of “father of aerial navigation.” Cayley’s greatest contribution to human flight was his understanding that, in order to sustain an aircraft in heavier-than-air flight—meaning without hot air or other gases to keep it buoyant—a designer had to create a structure so large that the force of air resistance on its wings was greater than the craft’s weight.
But Cayley’s insights went much further than describing the fundamentals of flight; he put into writing many of the very principles that we continue to practice today when we design safe, stable aircraft. The remarkable thing is that Cayley did it a full century before the Wright brothers were able to fly the first powered plane!
What’s more, based on the same naked-eye observations that Leonardo had made when trying to divine the secret of how birds fly, Cayley hypothesized correctly that birds produce lift in part thanks to the natural “camber”, or curve, of their wings. He also declared correctly that a bird’s outermost feathers provided a sort of propeller action that pushed it forward and gave it the necessary speed to provide adequate lift. (The mechanics of flight are something we’ll discuss later in Chapters 7, “How Airplanes Fly, Part 1: The Parts of a Plane,” and 8, “How Airplanes Fly, Part 2: The Aerodynamics of Flight.”)
Sir George Cayley war an impressively accurate prophet. In 1809, he wrote, "This noble art will soon be brought home to man’s convenience and… we shall be able to transport ourselves and families, goods and chattels more securely by air than by water, and with a velocity of 20 to 100 miles per hour."
Cayley even mapped out, in 1804, an airplane design that is basically indistinguishable from the design of those we fly today, with wings in front and tail surfaces in back. As we’ll see, even the brilliant Wright brothers didn’t put those structures into their configuration until long after their first powered flight.
For all his theoretical genius, Cayley never flew. But he inspired the very first glider daredevils, including Jean Marie Le Bris, who used a horse to tow a glider a few hundred feet in the air. Le Bris didn’t follow up on his experiments, however, and history mostly forgot him.