Alvis Leonides

The Alvis Leonides and Leonides Major were British air-cooled radial piston aero-engines.

Design and development

Leonides

Development of the 9-cylinder engine was led by Capt. George Thomas Smith-Clarke. The prototype engine, the 9ARS weighing 693lb and developing 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 Dragonfly helicopters. From 1959 the stroke was increased to 4.8 inch 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.

Leonides Major

In 1951 Alvis started development of a 14 cylinder, two row radial developed from the Leonides. Certification covered the Mk. 702/1 at for aeroplanes at 875 hp and the 751/1 for helicopters at 850 hp. The only numerous model of the Major was the Mk. 755/1.This was a medium supercharged, de-rated, obliquely mounted direct-drive and fan cooled engine fitted to the Westland Whirlwind Mks. 5, 6, 7 and 8.

Installations

Production

* Bristol Sycamore – 1x Mk. 173, 550hp (410kW)
* Percival P.66 President/Prince - 2 x 503/7A, Mk 128 01/2, 540/560hp (RAF: Pembroke, RN; Sea Prince)
* Percival Provost – 1x 126, 550-hp (410kW)
* Scottish Aviation Pioneer – 1 x 503/7A, Mk 128 01/2, 540/560hp
* Scottish Aviation Twin PioneerCC1 – 2 x 514/8, 550hp
* Scottish Aviation Twin PioneerCC2 – 2 x 531/8,Mk138, 640hp
* Westland Dragonfly – 1x 521/1, 520shp (388kW)
* Westland Widgeon – 1x 521/1, 520shp (388kW)
* Westland Whirlwind 1 x 755/1 Mk 155, 780hp (Major)

Conversions

* Harker Leo-cat – 1x 560 hp (418 kW)
* Server-Aero Leo-cat – 1x 560 hp (418 kW)

Prototypes

* Agusta AZ8-L 4x 503/2
* Bristol Type 173 Mk1 & 2 – 2x 550 hp; Mk3 – 2x 850 hp Major
* de Havilland Canada DHC-2 Beaver Mk.2 – 1x 502/4, 520 hp
* Fairey Gyrodyne – one 525 hp to power compressor
* Handley Page Herald – four 870 hp Leonides Major
* Handley Page H.P.R.1 Marathon – two Major
* Handley Page H.P.R.2 ("WE505" only) – 1 x 502/4 550 hp
* SR-N1 Hovercraft - the first hovercraft

pecifications (Leonides)

pistonspecs

type= 9-cylinder supercharged air-cooled radial piston engine.
bore= 4.8 inch (122 mm)
stroke= 4.41 inch (112 mm)
displacement= 718.6 in3 (11.8 L)
length=
diameter= 41 inch (1.04 m)
width=
height=
weight= 815 lb (370 kg)
valvetrain= Two pushrod-actuated poppet valves per cylinder with sodium-cooled exhaust valve.
supercharger= Single speed, single stage, boost pressure automatically linked to the throttle.
turbocharger=
fuelsystem= Hobson single-point fuel injection unit.
fueltype= Petrol, 115 Octane
oilsystem= Dry sump
coolingsystem= Air-cooled.
power= 550 hp (410 kW)
specpower=
compression=
fuelcon=
specfuelcon=
oilcon=
power/weight=

Trivia

The world’s only surviving Gloster Gauntlet, formerly powered by a Bristol Mercury VI engine, is now powered by a Leonides 503.

References

* "World Encyclopedia of Aero-Engines" – Bill Gunston – ISBN 1 85260 597 9

External links

* http://www.airliners.net/info/stats.main?id=351 (Scottish Aviation Twin Pioneer)
*http://www.whl.co.uk/pdfs/history_rotor_t_z.pdf (Pages 6, 10 & 11)
* http://www.warbirdalley.com/provost.htm
* http://www.helicoptermuseum.co.uk/westland.htm
* http://www.virtualpilots.fi/feature/photoreports/gauntletflies/
* http://www.nzwarbirds.org.nz/bvr.html (Beaver)
* http://www.hovercraft-museum.org/srn1.html
* http://avia.russian.ee/helicopters_eng/west_dragon.php (Dragonfly)