Figure 3.1 shows a sketch of a hand-launched glider, approximately 1 m in length, designed by Sir George Cayley in 1804 (a full-scale model is on view at the British Science Museum in South Kensington, London). Today, such a glider may seem trivial, almost a child's toy, but in 1804 that glider represented a major technological breakthrough. It was the first modern-configuration airplane. Here we see a heavier-than-air machine with a fixed wing, a fuselage, and horizontal and vertical tail structures. That was totally at variance with contemporary thought, which focused on omithopter concepts. Although da Vinci had come to the conclusion late in life that a flying machine could be designed with fixed (rather than flapping) wings, that idea had not been made available to the general public. Therefore, in terms of the practical advancement of aeronautics, George Cayley, two centuries later, was responsible for the concept of the modern-configuration aircraft. He proposed a fixed wing to generate lift, a separate mode of propulsion to overcome the “resistance” (drag) to the machine's motion through the air, and both vertical and horizontal tail surfaces for directional and longitudinal static stability.

That concept was first illustrated by Cayley in a very unconventional manner. In 1799 he engraved on a silver disk an outline of a fixed-wing aircraft (Figure 3.2). On one side is a sketch of the aircraft, a machine with a fixed wing, a fuselage (occupied by a person), horizontal and vertical tail structures at the rear end of the fuselage, and a pair of “flappers” for propulsion. The means to achieve lift (the fixed wing) and propulsion (the flappers) were clearly separate, in contrast to the actions of omithopter wings, which were intended to provide lift and propulsion all in the same motions.