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Jaguar
	Armstrong Siddeley Jaguar IV
Type	Radial engine
National origin	United Kingdom
Manufacturer	Armstrong Siddeley
First run	21 June 1922

The Armstrong Siddeley Jaguar is an aircraft engine developed by Armstrong Siddeley. The Jaguar was a petrol-fuelled air-cooled 14-cylinder two-row radial engine design. The Jaguar III was first used in 1923, followed in 1925 by the Jaguar IV and in 1927 by the Jaguar VI. In 1925 the Jaguar became the first production aero engine incorporating a geared supercharger.^[1]

Design and development

The Jaguar was developed from the Royal Aircraft Factory RAF.8 design proposal of 1916. The RAF.8 was the work of a design team led by F.M. Green, and incorporated the findings of research into aluminium air-cooled cylinders by Samuel D. Heron and Professor A. H. Gibson.^[2] Disillusioned by political and press criticism of the Royal Air Factory, Green and his design team, including Heron, left the Factory in January 1917 and took up positions with the Siddeley-Deasy company. There they were required by official policy to suspend work on the RAF.8 and focus efforts to get the unreliable Siddeley Puma into effective service, an engine that had been ordered in large numbers despite a lack of testing.^[3] As a result, the RAF.8 design, then known as the Jaguar, was not run until 21 June 1922.

Initial performance was not as expected; as a result the stroke was increased to 5.5 in (139.7 mm) on all variants after the Jaguar I. By that time, the engine had been fitted with a gear-driven supercharger. Throughout its career the Jaguar suffered from vibration due to the lack of a crankshaft centre bearing.^[4] The most powerful version of the engine, the Jaguar VIC, produced a maximum of 490 hp (365 kW) on takeoff at 1,950 rpm and weighed 910 lb (413 kg).^[5] The later Lynx was designed using one row of Jaguar cylinders.^[6]

Variants

Jaguar I: 1922, 300 hp.
Jaguar II: 1923, 385 hp, increased stroke, capacity 1,512 cu in (24.8 L).
Jaguar III: 1923, 385 hp.
Jaguar IIIA: 1923, 380 hp.
Jaguar IV: 1925, 385 hp, twin carburettors
Jaguar IVA: 420 hp, Geared propeller drive.
Jaguar IVC: 1928, 400 hp, revised connecting rod design, enclosed valve gear.
Jaguar IV(S): 1925, 365 hp, fully supercharged.^{[nb 1]}
Jaguar V: 1928.
Jaguar VI: 1927.
Jaguar VI(S): 1928, supercharged version of Jaguar VI.
Jaguar VIC: 1927, 470 hp, geared propeller drive version of Jaguar VI.
Jaguar VID: 1928.
Jaguar VIIA: 1929, 400 hp, fully supercharged.
Jaguar VIII: 1928, 405 hp, fully supercharged, geared propeller drive

Applications

Engines on display

A preserved Armstrong Siddeley Jaguar is on public display at the Science Museum (London).

Specifications (Jaguar I)

Sectioned Armstrong Siddeley Jaguar on display at the Science Museum (London)

Data from Lumsden^[8]

General characteristics

Type: 14-cylinder 2-row radial engine
Bore: 5 in (127 mm)
Stroke: 5 in (127 mm)
Displacement: 1,375 cu in (22.5 L)
Length: 41 in (1,041 mm)
Diameter: 43 in (1,092 mm)
Dry weight: 710 lb (322 kg)

Components

Supercharger: Gear driven
Fuel system: Carburettor
Cooling system: Air-cooled

Performance

Power output: 300 hp (224 kW)
Compression ratio: 5:1
Fuel consumption: 19 gal/hr (71 L/hr) at cruise
Power-to-weight ratio: 0.42 hp/lb (0.7 kW/kg)

References

Notes

^ MS and FS refer to the supercharger blower speeds: Moderate/Fully Supercharged. Moderate Supercharging referred to low- to medium-altitudes operation, Full Supercharging to medium- to high-altitude operation^[7]

Citations

^ "World Encyclopedia of Aero Engines – 5th edition" by Bill Gunston, Sutton Publishing, 2006. p.13
^ Gunston (1993), p. 123.
^ Ewer (2023), p. 8.
^ Lumsden (2003), p. 63.
^ Lumsden (2003), Part 4 - Engine Performance Figures.
^ Gunston (1989), p. 18.
^ "Development of the Aircraft Supercharger". Flightglobal Archive.
^ Lumsden (2003), pp. 63–66.

Bibliography

Ewer, Peter (2023). "William Weir: architect of air power? The First World War chapter". The International Journal for the History of Engineering & Technology: 1–19. doi:10.1080/17581206.2023.2237080.
Gunston, Bill (1989). World Encyclopedia of Aero Engines. Cambridge, England: Patrick Stephens Limited. ISBN 1-85260-163-9.
Gunston, Bill (1993). The development of piston aero engines. Sparkford: Stephens. ISBN 978-1-85260-385-4.
Lumsden, Alec (2003). British Piston Engines and their Aircraft. Marlborough, Wiltshire: Airlife Publishing. ISBN 1-85310-294-6.