Alvis Leonides
9-cylinder radial piston engine family by Alvis
The Alvis Leonides is a British air-cooled nine-cylinder radial aero engine first developed by Alvis Car and Engineering Company in 1936.
Design and development
Development of the nine-cylinder engine was led by Capt. George Thomas Smith-Clarke. The prototype engine, called 9ARS and which weighed 693 lb and developed 450 hp, was run in December 1936. In 1938 Airspeed (1934) Ltd lent their test pilot, George Errington, and their much rebuilt Bristol Bulldog (K3183), to carry out test flights. Development was continued at a reduced pace during the Second World War and following testing in an Airspeed Oxford and an Airspeed Consul (VX587). Alvis was ready to market the engine in 1947 as the Series 500 (502, 503 and sub-types) for aeroplanes and Series 520 for helicopters. (Most helicopter engines were direct drive — no reduction gearbox — with a centrifugal clutch and fan cooling). The first production use was the Percival Prince, which flew in July 1948 and the Westland Sikorsky S-51 and Westland WS-51 Dragonfly helicopters. From 1959 the stroke was increased to 4.8 inches for the Series 530 (mainly the Mk.
“Alvis Leonides” enters the record as 9-cylinder radial piston engine family by Alvis. Crown Archives preserves that source wording while asking what Alvis, Leonides and 9-cylinder can confirm, complicate or overturn.
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Vocabulary and entity names are the principal evidence signals here, because they determine the precision of every later search. The source revision retrieved here is dated Jul 11, 2026. The linked authority identifier is Q449389. None of the 0 selected statements returned an explicit reference. The first chronological checks are 1936, 1938, 1934 and 1947.
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This entry incorporates text from “Alvis Leonides” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.