Sir George Cayley (1773-1857), British engineer, aviation pioneer, and 6th Baronet of Brompton (from 1792). Cayley spent most of his life on the study of flight, carrying out his own experiments. In around 1808, he built and flew a large unmanned glider, thought to be the first heavier-than-air machine ever flown. He built and tested several designs, including a flapping-wing ornithopter, biplanes, and triplanes. He realised that stability and control were derived from the horizontal and vertical surfaces of an aircraft's tail, and that a lightweight propeller could be used to power an aircraft. In 1853, his coachman flew across a valley, in what was the first manned glider flight.