The Bristol Perseus was a British nine-cylinder, single-row, air-cooled

radial Radial is a geometric term of location which may refer to: Mathematics and Direction * Vector (geometric), a line * Radius, adjective form of * Radial distance (geometry), a directional coordinate in a polar coordinate system * Radial set * A ...

aircraft engine An aircraft engine, often referred to as an aero engine, is the power component of an aircraft propulsion system. Aircraft using power components are referred to as powered flight. Most aircraft engines are either piston engines or gas turbin ...

produced by the Bristol Engine Company starting in 1932. It was the first production

sleeve valve The sleeve valve is a type of valve mechanism for piston engines, distinct from the usual poppet valve. Sleeve valve engines saw use in a number of pre–World War II luxury cars and in the United States in the Willys-Knight car and light tru ...

aero engine.

Design and development

In late 1925 and early 1926, the

Royal Aircraft Establishment The Royal Aircraft Establishment (RAE) was a British research establishment, known by several different names during its history, that eventually came under the aegis of the Ministry of Defence (United Kingdom), UK Ministry of Defence (MoD), bef ...

(RAE) published a series of papers by

Harry Ricardo Sir Harry Ralph Ricardo (26 January 1885 – 18 May 1974) was an English engineer who was one of the foremost engine designers and researchers in the early years of the development of the internal combustion engine. Among his many other works, ...

on the

principle. The main advantages over the traditional

poppet valve A poppet valve (also sometimes called mushroom valve) is a valve typically used to control the timing and quantity of petrol (gas) or vapour flow into or out of an engine, but with many other applications. It consists of a hole or open-ended ch ...

s was better

volumetric efficiency Volumetric efficiency (VE) in internal combustion engine engineering is defined as the ratio of the equivalent volume of the fresh air drawn into the cylinder during the intake stroke (if the gases were at the reference condition for density) to th ...

and the ability to operate at higher rotational speeds. This allowed a smaller engine to produce the same power as a larger one, leading to better fuel efficiency and compact design, particularly in multi-row radial engines.

Roy Fedden Sir Alfred Hubert Roy Fedden MBE, FRAeS (6 June 1885 – 21 November 1973) was an engineer who designed most of Bristol Engine Company's successful piston aircraft engine designs. Early life Fedden was born in the Bristol area to fairly weal ...

, Bristol's primary engine designer, became interested in the concept and by 1927 he had constructed a working two-cylinder V as a test bed, with the idea of developing it into a V-12. Problems cropped up on the design, notably the sleeves bursting during the power stroke and stripping their driving gears. A long series of tests and materials changes and improvements required six years and an estimated £2 million to cure. By 1933, the problems had been worked out and the Perseus went on to become the first sleeve valve aero-engine in the world, to be put into large quantity production. The result was a

Bristol Mercury The Bristol Mercury is a British nine-cylinder, air-cooled, single-row, piston radial engine. Designed by Roy Fedden of the Bristol Aeroplane Company it was used to power both civil and military aircraft of the 1930s and 1940s. Developed from ...

-sized engine adapted to the sleeve valve system, the Perseus, and its smaller cousin, the Bristol Aquila. The first production versions of the Perseus were rated at 580

horsepower Horsepower (hp) is a unit of measurement of power, or the rate at which work is done, usually in reference to the output of engines or motors. There are many different standards and types of horsepower. Two common definitions used today are t ...

(433 kW), the same as the Mercury model for that year, which shows that the sleeve system was being underexploited. The engine was quickly uprated as improvements were introduced and by 1936 the Perseus was delivering 810 hp (604 kW), eventually topping out at 930 hp (690 kW) in 1939, while the Perseus 100 with an increased capacity of 1,635 cu in (26.8 L), produced at 2,700 rpm at 4,250 ft (1,296 m). This far outperformed even the most developed versions of the Mercury. The Perseus saw limited use in the civilian field, notably on the Short Empire flying-boats but was more common in the expanding military field, where it was found on the

Westland Lysander The Westland Lysander is a British Army cooperation aircraft, army co-operation and liaison aircraft produced by Westland Aircraft that was used immediately before and during the Second World War. After becoming obsolete in the army co-operat ...

reconnaissance aircraft and the Vickers Vildebeest,

Blackburn Botha The Blackburn B.26 Botha was a four-seat reconnaissance and torpedo bomber. It was produced by the British aviation company Blackburn Aircraft at its factories at Brough and Dumbarton. The Botha was developed during the mid 1930s in response ...

Skua The skuas are a group of predatory seabirds with seven species forming the genus ''Stercorarius'', the only genus in the family Stercorariidae. The three smaller skuas, the Arctic skua, the long-tailed skua, and the pomarine skua, are called ...

and Roc

bomber A bomber is a military combat aircraft that utilizes air-to-ground weaponry to drop bombs, launch aerial torpedo, torpedoes, or deploy air-launched cruise missiles. There are two major classifications of bomber: strategic and tactical. Strateg ...

s. The main contribution of the Perseus is that its design was used as the basic piston and cylinder for two "twinned" (double-row) types: the tremendously successful Bristol Hercules and

Bristol Centaurus The Centaurus was the final development of the Bristol Engine Company's series of sleeve valve radial aircraft engines. The Centaurus is an 18-cylinder, two-row design that eventually delivered over . The engine was introduced into service ...

engines. It was in these designs that the advantages of the sleeve valve were finally put to good use and by war's end, the Centaurus was one of the most powerful engines in the world.

Applications

''Note:''List from Lumsden, the Perseus may not be the main powerplant for some of these types *

* Blackburn Roc * Blackburn Skua *

Bristol Bulldog The Bristol Bulldog is a British Royal Air Force single-seat biplane Fighter aircraft, fighter designed during the 1920s by the Bristol Aeroplane Company. More than 400 Bulldogs were produced for the RAF and overseas customers, and it was one ...

* Bristol Type 148 * Cunliffe-Owen Flying Wing * de Havilland Flamingo * de Havilland Hertfordshire * Gloster Goring *

Hawker Hart The Hawker Hart is a British two-seater biplane light bomber aircraft that saw service with the Royal Air Force (RAF). It was designed during the 1920s by Sydney Camm and manufactured by Hawker Aircraft. The Hart was a prominent British aircraf ...

* Saro A.33 * Short Empire * Short Scylla * Vickers Vellox * Vickers Vildebeest Mk.IV * Westland Lysander Mk.II

Specifications (Perseus XII)

Bristol Perseus sleeve valve radial engine

References

Notes

Bibliography

* Bridgman, L, (ed.) (1998) ''Jane's Fighting Aircraft of World War II.'' Crescent . * Gunston, Bill. ''World Encyclopedia of Aero Engines''. Cambridge, England. Patrick Stephens Limited, 1989. * Gunston, Bill. ''Development of Piston Aero Engines''. Cambridge, England. Patrick Stephens Limited, 2006. * Lumsden, Alec. ''British Piston Engines and their Aircraft''. Marlborough, Wiltshire: Airlife Publishing, 2003. . {{Bristol aeroengines Aircraft air-cooled radial piston engines

Perseus In Greek mythology, Perseus (, ; Greek language, Greek: Περσεύς, Romanization of Greek, translit. Perseús) is the legendary founder of the Perseid dynasty. He was, alongside Cadmus and Bellerophon, the greatest Greek hero and slayer of ...