Armstrong Siddeley Heritage Trust
Armstrong Siddeley Jaguar Aero-Engines
The Armstrong Siddeley Jaguar was descended from an engine designed by a team of engineers at the Royal Aircraft Factory (RAF) in 1916, known as the R.A.F.8. In 1917, the RAF Factory was reorganised to concentrate on research and development, leaving manufacturing to commercial companies. The development team was transferred to work on the engine at the Siddeley-Deasy company; however, this work was deferred due to issues with the Siddeley Puma engine. In 1919, Siddeley-Deasy was acquired by Armstrong Whitworth, with the company name changing to Armstrong Siddeley.
Jaguar Front view Rear View Side View
A Government contract to develop the R.A.F.8 was awarded to Armstrong Siddeley in June 1919, who named it the Jaguar.
The Jaguar was a fourteen-cylinder, air-cooled, radial aero-engine. The cylinders are arranged in two staggered rows of seven, mounted on a barrel shaped crankcase. The cylinders are made of aluminium, with hemispherical combustion chambers, each with one inlet and one exhaust valve. The valves are operated through push rods and rocker arms. The valves are actuated by a cam ring at the front of the crankcase.
Ignition is by two B.T.H. magnetos, with one operating the inlet-side plugs and the other operating the port-side plugs. Between 1923 and 1929, there were many variants of the Jaguar, including direct-drive, geared, and supercharged models. The Jaguar was the first production aero-engine in the world to be supercharged, which gave increased performance up to 11,500 feet. Engine power varied from 385hp to 470hp.
The Mk I Jaguar's first test run took place in June 1920, when it produced a disappointing 300 hp. The second engine in the Jaguar series had the stroke increased from 5" to 5.5"; this change gave a satisfactory output of 365hp. This version was ordered into production by the Air Ministry.
Several hundred Jaguar engines were produced and fitted to over forty different types of aircraft. By 1929, the engine's power was inadequate compared to competitors and it was therefore superseded by the more powerful Armstrong Siddeley Panther.
Jaguar III Credit: London Science Museum
Jaguar Mk IV
Gloster Grebe Jaguar IV
Some examples of Jaguar powered aircraft are shown below.
Hawker Danecock (Dankok) Jaguar IV
Hawker Hoopoe Jaguar V Credit AirHistoryNet
Gloster Grebe Jaguar IV
Heinkel HE VIII Geared Jaguar
Fairy Flycatcher Jaguar IVC
A.W. Argosy Jaguar IIIA
Avro 642 Jaguar VID
Farman Goliath Jaguar IIIA
Siskins Jaguar III or IV
The reliability of the Jaguar engine is demonstrated in the following article.
Alan Cobham became the first person to fly from England to South Africa and back in his Jaguar Mk IV-powered de Havilland D.H. 50J biplane.
He began his epic flight from London on 16 November 1925. The outward journey lasted 94 days and covered 8,125 miles, reaching Cape Town, South Africa, on 17 February 1926.
The return flight commenced on 26 February 1926 and reached London only 16 days later. The same engine was used throughout the flight and received only routine maintenance.
Immediately after landing, King George V invited him to Buckingham Palace. For this impressive pioneering flight, Cobham was awarded the Air Force Cross.
These images are best viewed when enlarged. The left-hand image shows Sir Alan Cobham with photographer B. W. G. Emmott, who took cinematograph equipment to make a film of the flight, and his flight engineer, Elliot.
Leading Particulars of Jaguar Engines
Engine Type 14-cylinder, two-row air-cooled, radial aero-engine
Mk I. Bore/Stroke 5 x5 inch. (127x127 mm). Volume 1375 cu. in. (22.5 litre)
All other Mks Bore/Stoke 5.5 x5 inch (127x139.7 mm) Volume 1512.5 cu. in. (24.8 litre)
Variants
MK I
1922 300hp (220kW) Direct Drive
Mk II
1923 385hp (278kW) Direct Drive, Plan Fan.
Mk III
1923 385hp (287kW) Direct or Geared Drive, Engine Speed Fan.
Mk IIIA
1923 380hp (280kW) Direct Drive, Engine Speed Fan. The compression ratio increased to 5.1:1.
Mk IV
1925 385hp (287kW) Direct Drive, Engine Speed Fan, Dual Carburettor.
Mk IVA
420hp (310kW) Gear Epicyclic Drive, Engine Speed Fan.
Mk IV*
The MK IV, reconditioned to almost Mk IVC standard. 400hp (300kW).
Mk IVC
400hp (300kW) Direct Drive, Engine Speed Fan. New one-piecemaster rod and enclosed valve gear.
Mk IV(S)
1928 The world's first production engine to have a supercharger fitted. 365hp (272kW), Direct Drive.
Mk V
1928 Direct Drive, Engine Speed Fan.
Mk VI
1927 Direct Drive, no other details known.
Mk VI(S)
1928 Supercharged version of the Mk VI.
Mk VIC
1927 Epicyclic version of the Mk VI(S).
Mk VID
1928 No details known.
Mk VIIA
1929 400hp (300kW) Direct Drive, Fully Supercharged.
Mk VIII
1928 405hp (302kW) Epycyclic Drive, Supercharged.
For the interest of the technically minded, here is an Air Ministry test sheet for a Jaguar Mk IV from 1929. Apologies for the cropping and poor quality of this almost 100-year-old document. Click on the document to enlarge.
