Few people today have heard of Sir George Cayley but indeed much of the intellectual edifice, upon which the principles of modern aerodynamics rest, can be attributed to the genius of this great thinker. Born in December 1773, this Yorkshire baronet was the first to imagine the airplane. A hundred years before the Wright Brothers, he had established the science of aviation and set forth powerful ideas that gave us wings.
As a child, George Cayley grew up with the ballooning craze that swept across Europe at the time. In November of 1783, Frenchmen Jean-François Pilâtre de Rozier and the Marquis d’Arlandes were the first to ascend into the skies in a hot-air balloon. They forayed into the heavens over the city of Paris for 25 minutes, covering 9 kilometers before landing safely. This “lighter-than-air” vehicle was a great contrivance, courtesy of the Montgolfier brothers of France. Even though their reasoning was incorrect (as the lifting occurred due to expansion of heated air and not a certain lighter-than-air gas given off by the fire, as the Montgolfier brothers had thought) this invention would later inspire much of the ballooning technological prowess that would later ensue and ushered in a new frontier of flying grace that fed a rising European obsession with lighter-than-air flight.
Ballooning however did not capture the young George Cayley’s fascination for quite long and he started to think of heavier-than-air flight. He quickly came to believe that winged vehicles were flying’s future. He was more interested in practical vehicles that can be controlled and steered instead of vehicles that have a chance dependence on the whim of the wind and that are subject to air currents. As such, in his early twenties, he experimented on the Chinese flying top and by 1796 had built a bow-powered helicopter model driven by elastic bands. He continued to build airplane models at his estate in Scarborough, North Yorkshire.
By 1799, Cayley would define the principles of modern-day aviation and establish the concept of the modern airplane by conceiving a full aircraft design that exhibited a remarkable breakaway from previous ideas of powered aviation. In his elegant design, he replaced the flapping-wing principle of the ornithopter model with wings that were fixed. Etching his ideas on both sides of a silver medallion (shown below), his sketch depicted the aerodynamic forces of lift (perpendicular to flow) and drag (parallel to flow) on a wing, a concept that inspired the Wright Brothers, a century later. Besides the fixed wing, the design showed a cruciform stabilizing tail that had vertical and horizontal surfaces (rudder and elevator to steer the vehicle like a boat) and a boat-like fuselage to carry the operator. The design also shows flapping blades (primitive aerial oars) to generate forward thrust. They were to be pulled by the pilot in rowing fashion. However, Cayley knew that power produced by human muscle alone would be insufficient to sustain flight and as such, he tried to build a first mover, a mechanical engine to sustain powered flight. But unfortunately for him, the mechanical power plants of the time did not have suitable output for such technology and steam engines were simply too heavy for flight. The development of gas-fuelled internal combustion engines in the 19th Century would later give the Wright Brothers this last missing piece of technology a century later.
Cayley’s idea of separating lift and thrust was quite significant indeed. The wings were fixed so as to produce lift and only lift. The thrust would be provided by a separate propulsion system and not the wings. This is the concept of the modern airplane, laid down centuries ago by Sir George Cayley. The Wright Brothers would refine his model to invent the real thing.
One remarkable thing to me is that Cayley’s idea of fixed rigid wings was inspired by observing nature. He was quite fascinated to note that birds can stay airborne and sail for extended periods of time without flapping their wings. He carefully studied bird flight and gained insights from their wing shapes and movements (including the idea that curved wings generated more lift than flat ones). To me, this demonstrates the interconnectedness of different areas of science and further reinforces the notion that all knowledge is useful.
Cayley’s 1799 design was far from the beginning. In 1804, he constructed a whirling arm apparatus (with a wing portion at the end) to carry out experiments to study aerodynamic lift and drag. The same year, he built a model monoplane glider that incorporated his novel ideas. It contained an adjustable cruciform tail at the rear that could change position relative to the fuselage, a kite-looking wing at the front, and quite wonderfully, a movable weight to adjust the centre of gravity and observe the resulting effects. In 1809, he published a landmark monumental publication titled “On Aerial Navigation”. It was the first treatise on theoretical and applied aerodynamics and indeed one of the most important. In it, Cayley showed, for the first time, that: 1) Lift is generated by a region of low pressure on the upper surface of the wing and that 2) Cambered wings generate lift more efficiently than a flat surface. “I feel pretty confident,” wrote Cayley “that this noble art will soon be brought home to man’s general convenience, and that we shall be able to transport ourselves and families, and their goods and chattels, more securely by air than by water.”
A polymath, Cayley was active in many other fields and pursued broad scientific activities, from Newtonian physics to optics, electricity, combustion engines, ballistics, and various other disciplines. Cayley would resume airplane design activities in 1849, when he constructed a full-scale triplane glider which he tested with a 10 year old boy aboard. Amazingly enough, it carried the young boy several yards on a short flight in the world’s first unpowered manned free flight.
And, in 1853, he constructed a large fixed-wing glider which he tested with his very nervous coachman aboard. It lifted into the air and later touched down rather roughly 900 metres from the liftoff point. “Please, Sir George!” exclaimed the coachmen, “I wish to give notice — I was hired to drive, not fly!” It is said that he immediately quit his job afterwards 😀
Sir George Cayley died at the age of 83 in 1857, leaving behind leaving behind him a legacy of a life devoted to reaching the skies, laying down the foundations of modern flight, and inspiring the next wave of innovators.
Featured image courtesy of: Yorkshire Philosophical Society