The Alvis Leonides was a British air-cooled nine-cylinder

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, a directional coordinate in a polar coordinate system * Radial set * A bearing f ...

aero engine first developed by

Alvis Car and Engineering Company Alvis Car and Engineering Company Ltd was a British manufacturing company in Coventry from 1919 to 1967. In addition to automobiles designed for the civilian market, the company also produced racing cars, aircraft engines, armoured cars and oth ...

in 1936.

Design and development

Development of the nine-cylinder engine was led by Capt.

George Thomas Smith-Clarke George may refer to: People * George (given name) * George (surname) * George (singer), American-Canadian singer George Nozuka, known by the mononym George * George Washington, First President of the United States * George W. Bush, 43rd Presiden ...

. 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 The Bristol Bulldog is a British Royal Air Force single-seat biplane 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 of the most fam ...

(''K3183''), to carry out test flights. Development was continued at a reduced pace during the

Second World War World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposi ...

and following testing in an

Airspeed Oxford The Airspeed AS.10 Oxford is a twin-engine monoplane aircraft developed and manufactured by Airspeed. It saw widespread use for training British Commonwealth aircrews in navigation, radio-operating, bombing and gunnery roles throughout the Seco ...

and an

Airspeed Consul The Airspeed Consul is a twin-engined light transport aircraft and affordable airliner designed and produced by the British aircraft manufacturer Airspeed Limited. Introduced during the immediate post-war period, it was a straightforward conver ...

(''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 The Percival Prince is a British light transport of the early postwar period. It was a twin-engine, high-wing, cantilever monoplane of all-metal stressed-skin construction; the undercarriage was of retractable, tricycle type. Development ...

, which flew in July 1948 and the Westland

Sikorsky S-51 The Sikorsky H-5 (initially designated R-5 and also known as S-48, S-51 and by company designation VS-327Fitzsimons, Bernard, (general editor). ''Illustrated Encyclopedia of 20th Century Weapons and Warfare'' (London: Phoebus, 1978), Volume 20, ...

and Westland WS-51 Dragonfly helicopters. From 1959 the stroke was increased to 4.8 inches for the Series 530 (mainly the Mk. 531 for Twin Pioneers) rated at 640 hp. It was Britain's last high-power production piston aero-engine when manufacture ceased in 1966.

Variants

''Notes:'' LE designations from Air Ministry system ( where known); 500 series designations from Alvis company designation system; Mark numbers for civil variants. ;Alvis 9ARS: pre-war precursor to the Leonides – / 0.5:1 ;LE.1M:(Leonides 501/1) – /3,000 rpm/+6.6 lb boost/ 0.5:1 ;LE.2M:(Leonides 501/2) – 0.625:1 reduction gearing, remote accessories ;LE.3M:(Leonides 501/3) – 0.5:1 reduction gearing, remote accessories ;LE.4M:(Leonides 501/4) – 0.625:1 reduction gearing ;LE.12HMH:(Leonides 522/2) Horizontal direct-drive for helicopters ;LE.21HMV:(Leonides 522/1) Vertical direct-drive for helicopters ;LE.23HM:(Leonides 524/1) Vertical direct-drive for helicopters ;LE.24HMV:(Leonides 524/1) Vertical opposite rotation reduction-geared drive for helicopters ;LE.25HMV:(Leonides 523/1) ;Leonides 501:/3,000 rpm/+6.6 lb boost/ 0.5:1 ;Leonides 502: ;Leonides 503: ;Leonides 504: ;Leonides 514: ;Leonides 521: ;Leonides 522: ;Leonides 523: Helicopter vertical drive ;Leonides 524: Helicopter vertical drive ;Leonides 525: ;Leonides 530: Long stroke ;Leonides 531: Long stroke (+ 10mm), supercharger ratio 6.5:1 ;Leonides 532: Long stroke (+ 10mm), supercharger ratio 7.91:1 ;Leonides Mark 22:(Leonides 503/2) ;Leonides Mark 24:(Leonides 503/4) ;Leonides Mark 50:(Leonides 521/2) ;Leonides Mark 70:(Leonides 523/1) ;Leonides Mark 125:(Leonides 504/5) ;Leonides Mark 125 01/2:(Leonides 503/5) ;Leonides Mark 126:(Leonides 503/6A) ;Leonides Mark 127 01/2:(Leonides 503/7A) ;Leonides Mark 128:(Leonides 504/8B) ;Leonides Mark 130:(Leonides 503/7) ;Leonides Mark 138:(Leonides 531/8B) Long stroke (+ 10mm) ;Leonides Mark 173:(Leonides 524/1 & 525/1) Alvis Leonides Mk 173-02

Applications

* Agusta AZ.8L 4x 503/2 *

Bristol Sycamore The Bristol Type 171 Sycamore was an early helicopter developed and built by the helicopter division of the Bristol Aeroplane Company. The name refers to the seeds of the sycamore tree, ''Acer pseudoplatanus'', which fall with a rotating motio ...

— 1x Mk. 173, 550 hp (410 kW) * Cunliffe-Owen Concordia — 2x LE.4M, 550 hp *

de Havilland Canada DHC-2 Beaver The de Havilland Canada DHC-2 Beaver is a single-engined high-wing propeller-driven short takeoff and landing (STOL) aircraft developed and manufactured by de Havilland Canada. It has been primarily operated as a bush plane and has been use ...

Mk.2 — 1x 502/4, 520 hp, 520shp (388 kW) * Fairchild F-11-2 Husky — 1x 550 hp * Fairey Gyrodyne — one 525 hp to drive rotor and propeller *

Fairey Jet Gyrodyne The Fairey Jet Gyrodyne is a British experimental compound gyroplane built by the Fairey Aviation Company that incorporated helicopter, gyrodyne and autogyro characteristics. The Jet Gyrodyne was the subject of a Ministry of Supply (MoS) resear ...

— one 525 hp to drive air compressor and propellers * Fiat G.49-1 — 1x 502/4 Mk 24, 550 hp * Handley Page H.P.R.2 Basic Trainer (''WE505'' only) — 1 x 502/4, 550 hp *

Harker Leo-cat Harker may refer to: People *Harker (surname) Municipalities *Harker, Cumbria, north of Carlisle, England *Harker, Florida, census-designated place located in Collier County, Florida *Harkers Island, North Carolina, census-designated place in Cart ...

— 1x 560 hp (418 kW) * Percival P.50 Prince — 2 x 501/4, 502/4, 503 or 504, 520 hp * Percival P.57 Sea Prince — 2 x Mk. 125, 550 hp * Percival P.66 President — 2 x 503/7A, Mk 128 01/2, 540/560 hp (400–420 kW) * Percival P.66 Pembroke — 2 x Mk. 127, 540 hp *

Percival Provost The Percival P.56 Provost is a basic trainer aircraft that was designed and manufactured by British aviation company Percival. During the 1950s, the Provost was developed for the Royal Air Force (RAF) as a replacement for the Percival Prentic ...

— 1x Mk. 126, 550 hp * Server-Aero Leo-cat — 1x 560 hp (418 kW) *

Scottish Aviation Pioneer The Scottish Aviation Pioneer was an STOL aircraft manufactured by Scottish Aviation in Scotland. It was used for casualty evacuation and communications and could accommodate a pilot and up to four passengers. Design and development The Pion ...

2 — 1 x 503/7A, Mk 128 01/2, 520 hp * Scottish Aviation Twin Pioneer CC.1 — 2 x 514/8, 550 hp * Scottish Aviation Twin Pioneer CC.2 — 2 x 531/8,Mk138, 640 hp (564 kW) * SR.N1 Hovercraft — the first hovercraft * Westland Dragonfly — 1x 521/1, 520shp * Westland Widgeon — 1x 521/1, 520shp

Survivors

*A Leonides 126-powered Hunting

(G-KAPW) with CAA permission to fly as XF603, owned by the Shuttleworth Trust and based at

Old Warden Old Warden is a village and civil parish in the Central Bedfordshire district of the county of Bedfordshire, England, about south-east of the county town of Bedford. The 2011 census shows its population as 328. The Shuttleworth Collection of ...

Bedfordshire Bedfordshire (; abbreviated Beds) is a ceremonial county in the East of England. The county has been administered by three unitary authorities, Borough of Bedford, Central Bedfordshire and Borough of Luton, since Bedfordshire County Council ...

is airworthy as of 2017, and is displayed to the public at home airshows during the airshow season. *The world's only surviving

Gloster Gauntlet The Gloster Gauntlet was a single-seat biplane fighter designed and produced by the British aeroplane manufacturer Gloster Aircraft in the 1930s. It was the last fighter to be operated by the Royal Air Force (RAF) to have an open cockpit, and ...

, formerly powered by a Bristol Mercury VI engine, is now powered by a Leonides 503. *A privately owned, Leonides-powered Percival Pembroke remains airworthy in March 2010. *Two privately owned Scottish Aviation Twin Pioneers are flying in Australia

Engines on display

Preserved Alvis Leonides engines are on public display at the following museums: * Fleet Air Arm Museum *

Gatwick Aviation Museum The Gatwick Aviation Museum is located in the village of Charlwood, in Surrey, United Kingdom on the boundary of Gatwick Airport. History Originally started in 1987 as a private collection by local businessman Peter Vallance, the museum becam ...

Midland Air Museum The Midland Air Museum (MAM) is situated just outside the village of Baginton in Warwickshire, England, and is adjacent to Coventry Airport. The museum includes the ''Sir Frank Whittle Jet Heritage Centre'' (named after the local aviation pionee ...

* Museum of Science and Industry (Manchester) *

Royal Air Force Museum Cosford The Royal Air Force Museum Cosford, located in Cosford in Shropshire, is a free (currently, 2022) museum dedicated to the history of aviation and the Royal Air Force in particular. The museum is part of the Royal Air Force Museum, a non-departme ...

* Shuttleworth Collection *

The Helicopter Museum (Weston) The Helicopter Museum in Weston-super-Mare, North Somerset, England, is a museum featuring a collection of more than 80 helicopters and autogyros from around the world, both civilian and military. It is based at the southeastern corner of the fo ...

*Cornwall Aviation Heritage Centre *

Solent Sky Solent Sky is an aviation museum in Southampton, Hampshire, previously known as Southampton Hall of Aviation. It depicts the history of aviation in Southampton, the Solent area and Hampshire. There is special focus on the Supermarine aircraft c ...

East Midlands Aeropark East Midlands Airport is an international airport in the East Midlands of England, close to Castle Donington in northwestern Leicestershire, between Loughborough (), Derby () and Nottingham (); Leicester is () to the south and Lincoln () north ...

Specifications (Leonides)

References

;Notes ;Bibliography * Gunston, Bill. ''World Encyclopedia of Aero Engines''. Cambridge, England. Patrick Stephens Limited, 1989. * Lumsden, Alec. ''British Piston Engines and their Aircraft''. Marlborough, Wiltshire: Airlife Publishing, 2003. .

External links

Scottish Aviation Twin Pioneer

whl.co.uk
(pages 6, 10 & 11)

virtualpilots.fi

{{Alvis aeroengines Aircraft air-cooled radial piston engines Leonides 1930s aircraft piston engines