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Leonard Frederick George Butler (1887-1943), aircraft engine designer
Educated in Somerset
Worked with the designers at Rolls-Royce for a short period.
Returned to Brazil Straker as chief draughtsman.
Designed the 2-row 350hp Mercury radial engine.
1918 Appointed chief designer of Cosmos Engineering, which had been formed to acquire the aircraft interests of Brazil Straker.
Butler was then, for a long time, associated with Roy Fedden, chief engineer at Bristol Engine Co, producing a series of successful engines including the Lucifer, Pegasus, Perseus, Taurus and Hercules.
1941 Retired from the position of chief designer of the Bristol Engine company. He was then appointed as special adviser to the aero-engine division
1943 Died at Paddington station.
1942/43 Obituary 
Leonard Frederick George Butler was born in 1887 and educated at Sexey's School, Somerset.
After a brief period as Draughtsman with Crossley Motors, Ltd., he returned to Brazil, Straker as Chief Draughtsman in 1912. He designed the Mercury 350 h.p. double-row engine and was appointed Chief Designer of the Cosmos Engineering Company, which was formed in 1918 to manufacture this engine.
Subsequently the Cosmos Engineering Company was taken over by the Bristol Aeroplane Company, and he became an Assistant Engineer in the Aero-Engine Department, later becoming Chief Designer. Working in association with Sir Roy Fedden, the "Jupiter," "Lucifer," "Pegasus," "Mercury," "Perseus," "Taurus," and "Hercules " engines were produced. He remained Chief Designer until 1941, when he was appointed Technical Adviser to the Aero-Engine Division of the Bristol Aeroplane Company.
He died suddenly on 3rd September, 1943, at the age of 56.
He was elected a Graduate in 1911 and transferred to Associate Member in 0925.
1943 Obituary