Percy Sinclair Pilcher (16 January 1867 – 2 October 1899) was a British inventor and pioneer aviator who was his country's foremost experimenter in unpowered flight near the end of the nineteenth century.

He built a hang glider called The Bat which he flew for the first time in 1895;[1] Later that year Pilcher met Otto Lilienthal, who was the leading expert in gliding in Germany.

[3] Based on the work of his mentor Otto Lilienthal, in 1895–1896 Pilcher built a glider called Hawk with which he broke the world distance record when he flew 250 m (820 ft) in 1897 on the grounds of Stanford Hall, Leicestershire.

[2][7] On 30 September 1899, having completed his triplane, he had intended to demonstrate it to a group of onlookers and potential sponsors, including the eminent Member of Parliament John Henniker Heaton, in a field near Stanford Hall.

It was on temporary loan to the 1911 Scottish Exhibition of National History, Art and Industry, when a November storm caused damage to the building, and to the glider which was repaired before being put on display again in the museum.

Further major conservation work was completed in the summer of 2016, and it is back again on display in its usual place, suspended above the atrium of the Science and Technology galleries of the National Museum of Scotland.

When the centenary of the Wright brothers' flight approached, a new effort was made to find the lost work, and some correspondence was found in a private American collection.

Based on Lilienthal's work, Pilcher understood how to produce lift using winglike structures, but at this time a full mathematical description was years away, so many elements were still missing.

Pilcher's breakthrough, thanks to correspondence with another pioneer, Octave Chanute, was to stack smaller, lighter wings one atop the other in an arrangement we know today as the biplane or triplane.

In 2003, a research effort carried out at the School of Aeronautics at Cranfield University, commissioned by the BBC2 television series Horizon, has shown that Pilcher's design was more or less workable, and had he been able to develop his engine, it is possible he would have succeeded in being the first to fly a heavier-than-air powered aircraft with some degree of control.