Siddeley Puma

Siddeley Puma
Name	Siddeley Puma
Caption	Siddeley Puma inline engine (schematic)
Type	Aircraft inline engine
Manufacturer	Armstrong Siddeley Motors
Introduced	1918
Primary user	Royal Air Force
Produced	1917–1920s

Siddeley Puma is a British inline six-cylinder liquid-cooled aero engine developed during the late stages of the First World War for use in British military aircraft. The design emerged from the wartime consolidation of British aero-engine companies and was installed in several contemporary Royal Air Force types and prototypes. Its operational life extended into the immediate post-war era, influencing later Armstrong Siddeley Motors developments and light civil aviation conversions.

Development

The Puma traces its origins to licensed and indigenous projects pursued by Humber Limited, William Beardmore and Company, and Leyland Motors before consolidation under Siddeley-Deasy and later Airco corporate structures that merged into Armstrong Whitworth and Armstrong Siddeley Motors. Influenced by designs from France and contemporary work at Rolls-Royce, the Puma was produced to meet specifications drawn up by the Air Ministry Technical Department and tested at Royal Aircraft Establishment facilities at Farnborough. During its development, the Puma was evaluated alongside contemporaries such as the Sunbeam Cossack, Bristol Jupiter, Napier Lion, and Rolls-Royce Eagle, and it underwent bench and flight trials at RAF Hendon and No. 1 Aeroplane Supply Depot maintenance units. Industrial resources were coordinated through wartime committees including the Ministry of Munitions and the War Office, with production contracts dispersed to firms like Leyland Motors, Humber Limited, Armstrong Whitworth, and Austro-Daimler licensed partners.

Design

The engine was a straight-six, liquid-cooled design featuring a single overhead camshaft and cast-iron cylinders with a forged crankcase produced under Ministry of Munitions wartime standardization. Cooling was by a radiator system compatible with contemporary installations on aircraft such as the Airco DH.4, Bristol F.2 Fighter, Handley Page O/400, and Royal Aircraft Factory B.E.2c. The Puma’s bore and stroke parameters placed it in the medium-power category between smaller inline units like the Green D.4 and larger powerplants such as the Napier Lion. Carburation and ignition systems were influenced by suppliers including Bosch, Lucas Industries, and Kingston, and lubrication practices mirrored standards promulgated at Royal Aircraft Factory engineering sessions. Manufacturing techniques borrowed from Automobile Club contractors and lessons from Vickers Limited and Sopwith Aviation Company production lines aided interchangeability and maintenance in frontline squadrons.

Variants

Several factory and contractor variants emerged, including high-compression and lower-geared versions intended for bomber, reconnaissance, and light transport roles. Contractors such as Leyland Motors, Humber Limited, Armstrong Whitworth, Sunbeam Motor Car Company, and Beardmore introduced minor dimensional and component changes for compatibility with airframes by Airco, Bristol Aeroplane Company, Handley Page, and Vickers. Experimental installations tested different reduction gear ratios and supercharging concepts evaluated at the Royal Aircraft Establishment and by No. 3 Squadron flight trials. Post-war adaptations by Armstrong Siddeley Motors engineers considered derailleur-like accessory drives, improved carburettors from Clerkson suppliers, and revised cooling jackets trialed on prototypes by de Havilland and Westland Aircraft.

Operational history

The Puma entered squadron service with Royal Air Force squadrons in 1918 and was fitted to types operated by units such as No. 3 Squadron RAF, No. 6 Squadron RAF, and No. 10 Squadron RAF. It served in bomber reconnaissance roles from bases at Saint-Omer and Hawkinge during the last months of the Western Front campaign. Maintenance records from RAF Depot workshops and accounts by personnel seconded from Royal Army Service Corps units indicate mixed reliability under combat conditions, with overheating and crankcase wear recorded in reports submitted to the Air Ministry Directorate of Technical Services. After the armistice, surplus Puma-engined aircraft were allocated to training schools at Central Flying School and to colonial postings in Iraq and Egypt under the Mesopotamian campaign administrative arrangements. Comparative assessments in post-war trials placed the Puma between contemporaries like the Sunbeam Arab and Rolls-Royce Eagle in terms of power-to-weight and fuel consumption.

Applications

The engine was installed in a range of types including the Airco DH.9, Airco DH.4A, Bristol M.1C conversions, Handley Page O/400 remanufactures, and various prototypes by Vickers, Avro, De Havilland, and Westland Aircraft. It was also used in civil conversions of wartime transports operated by companies such as Handley Page Transport, Imperial Airways precursor firms, and private operators emerging during the 1920s. Experimental maritime and airship installations were trialed by Royal Naval Air Service successor units in coordination with Admiralty engineering sections, and several builders fitted the Puma to ambulances and mailplanes employed on routes connecting London with Paris and Brussels in the immediate post-war market.

Survivors and legacy

Few intact Puma engines survive; preserved examples are held by collections at the Science Museum, London, Royal Air Force Museum, Brooklands Museum, and specialist archives at Farnborough Air Sciences Trust and private collections associated with Shuttleworth Collection. The engine’s design and production experience informed later developments at Armstrong Siddeley Motors culminating in radial and inline types that influenced 1930s British civil and military aviation. The Puma appears in contemporary technical journals alongside analyses by engineers from Royal Aircraft Establishment and is cited in manufacturer records held at the National Archives (United Kingdom) and papers of firms such as Rolls-Royce Limited and Leyland Motors as a case study in wartime production and post-war civil adaptation.

Category:Aircraft engines Category:1910s aircraft engines