"Being in want of a simple & light first mover on a small scale for the purpose of some preparatory experiments on aerial navigation, I constructed one in which the force of gunpowder & the heat evolved by its explosion, acting upon a quantity of common air, was employed."

Like many before him, Sir George Cayley imagined that man would fly with the aid of flapping wings and in 1805 made a sketch of a Winged Flying Machine (an ornithopter) in his notebook. Later in 1807 he built a gunpowder engine that could have powered it. Cayley is likely to have been influenced in the design of his gunpowder engines by the work of the renowned Dutch scientist Christian Huygens which was published in 1666.

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After many years working on hot-air engines, Cayley built a second gunpowder engine to drive 'flappers' on the 1850 flat-winged monoplane. These hinged fans were designed to provided forward propulsion rather than direct lift. However given the construction materials available to Cayley, it is unlikely that his explosive (internal combustion) engines would have worked for very long.