Sir George inherited Brompton Hall and its estates on the death of his father, together with the title of Baronet. Though born into a life of privilege and immense wealth, he could not be characterised as an idle aristocrat. Free from any concern about money, and in the optimistic spirit of the times, he launched himself into a bewildering variety of projects, mostly aimed at improving the world through science and technology.
He was a keen observer and chronicler of the natural world throughout his life. He was a Member of Parliament (for the Whig party). He was a founder member of the Polytechnic Institution (a national organisation set up in 1838 to educate the public on artistic and scientific matters), and for many years he served as its chairman. He was also a highly prolific inventor, although his ideas often made little impact because they were so far ahead of their time.
A number of his inventions were forgotten and then "re-invented" by others, many years later. Among the many things that he invented are self-righting life-boats, tension-spoke wheels, caterpillar tractors (which he called the Universal Railway), cow-catchers for railway locomotives, automatic signals for railway crossings, seat-belts, experimental designs for helicopters, and a kind of prototypical internal combustion engine fuelled by gun-powder. He also made contributions in the fields of prosthetics, heat engines, electricity, theatre architecture, ballistics, optics and land reclamation.
He is mainly remembered, however, for his flying machines. He is the first person known to have made a systematic study of the way air flows over wings. He built an alarming-sounding "whirling-arm apparatus" so that he could measure the force of the air on variously shaped specimens at various air-speeds and angles of attack. He also experimented with free-flying model gliders of various wing sections, in the stairwells at Brompton Hall. (Apparently he was forbidden from doing this while his wife was in the house.) These meticulously documented scientific experiments led him to develop an efficient cambered aerofoil and to identify the four vector forces that influence an aircraft: thrust, lift, drag, and weight. He discovered the importance of dihedral for lateral stability in flight, and he deliberately set the centre-of-gravity of many of his models well below the wings, for this reason. He also identified and investigated many other theoretical aspects of flight, and he is now widely acknowledged as the inventor of the science of aerodynamics.
By 1804 he was producing model gliders of a pattern that is startlingly similar to that of modern aircraft; a pair of large monoplane wings towards the front, with a smaller tailplane at the back comprising horizontal stabilisers and a vertical fin.
His experimental models became larger and larger until eventually he built a machine that could carry a person. After demonstrating that animals could fly in it safely, in late June or early July 1853 he persuaded his coachman to have a go. The glider was launched from a hill on the Brompton Estate by several teams of estate workers pulling on ropes and running downhill, and Sir George Cayley's coachman (his name is lost to history) flew the machine for a distance of between 100 and 200 metres across Brompton Dale into a meadow on the other side. This was the earliest recorded manned flight in a heavier-than-air machine. He landed safely, with no injury. It is often reported that as he stepped out of the machine he shouted at Sir George "I was hired to drive, not to fly!", and quit his job. Sir George was 79 years old at the time and not in the best of health, which perhaps to some extent excuses him for not risking his own neck in the glider.
Sir George is believed to have worked entirely alone on his development of a theory of flight. Although today we recognise his enormous achievements in this field, most of his contemporaries considered it to be no more than a whimsical hobby. Ultimately it can be argued that all his work on aerodynamics went to waste. Like his ideas for a caterpillar tractor or an internal combustion engine, his theories of aerodynamics sank into obscurity and had to be re-invented by others. Many of the advances made in the 1890s and 1900s by aviation pioneers such as Otto Lilienthal, Percy Pilcher and the Wright brothers were in fact rediscoveries of innovations that had been understood and described a half-century earlier by this extraordinary Yorkshireman.