Junkers Jumo 210

Junkers Motorenwerke

Industry	Aircraft engine manufacturing
Founded	1916
Headquarters	Dessau , Germany
Products	Aircraft engines, including the Jumo 210 series

Template:Infobox aero engine

The Jumo 210 represented Junkers' initial mass-produced inverted V12 gasoline-powered aircraft engine, introduced in the early 1930s. Output varied by model, ranging from 610 to 730 PS, and it can be viewed as a comparable counterpart to the Rolls-Royce Kestrel. Although it was originally designed for widespread use across nearly all pre-war aircraft designs, rapid advancements in aviation technology soon pushed it toward the lower end of the power spectrum by the late 1930s. With most designs adopting the significantly larger Daimler-Benz DB 600, production of the Jumo 210 was relatively brief before Junkers developed a more powerful successor, the Junkers Jumo 211.

Design and development

Junkers Motorenwerke’s earliest gasoline aviation engines were the L1 and L2 SOHC liquid-cooled inline-six units from the early to mid-1920s. This series evolved through to the L8 model and was based on the BMW IIIa inline-six SOHC engine from World War I, which BMW permitted as they had ceased further development of their wartime designs. The Junkers L55 marked the company’s first venture into V12 aviation engines, utilizing two straight-six L5 engines combined into an "upright" liquid-cooled V12 configuration similar to the contemporary BMW VI engine.

Work on what became the Jumo 210 began in 1931 under the designation L10. This was Germany’s first genuinely modern aero engine featuring an inverted-V arrangement, three valves per cylinder (two intake and one exhaust), a standard supercharger, and a cast cylinder block. Uniquely, its cylinders were integrated into a block along with one side of the crankcase; two such components were bolted together side-by-side to complete the engine assembly. This contrasted with typical construction methods that involved three separate parts: two cylinder blocks plus a separate crankcase.

Static testing of the L10 commenced on October 22, 1932. Following the establishment of the RLM in 1933, engine designations were standardized by manufacturer, assigning Junkers engines numbers in the "200" series; thus, the L10 was redesignated as the Jumo 210. Certification was obtained in March 1934, and its maiden flight occurred on July 5, 1934, installed in a Junkers W33. Although development targeted an output of approximately 700 PS, initial prototypes delivered closer to 600 PS, leading to some industry dissatisfaction. Nonetheless, nearly all German aircraft designs at that time were built around this engine, which contributed to their relatively modest size compared to foreign counterparts.

On July 5, 1934, a Junkers W33 equipped with a Jumo 210 variant producing 680 hp took flight.

Production began in late 1934 with the Jumo 210A model rated at 610 PS (602 hp, 449 kW). Subsequent upgrades in 1935 yielded the Jumo 210B and 210C variants delivering around 640 PS (631 hp, 471 kW). These versions incorporated an improved supercharger along with a dump valve to prevent overboost conditions. The B model featured propeller gearing at a ratio of 1:1.55 (propeller to engine rpm) optimized for higher speeds, while the C was geared at 1:1.63 for slower flight regimes. In 1936, further enhancements introduced the Jumo 210D and E models producing approximately 670 PS (661 hp, 493 kW). These retained similar gearing to earlier models but added a two-speed supercharger for enhanced takeoff power and altitude performance.

The Jumo 210G incorporated a direct fuel injection system engineered by August Lichte. This system employed a small pump piston adjacent to each cylinder driven by the crankshaft. Fuel delivery used a check valve preventing backflow into fuel lines and was timed precisely during intake strokes. Integrating this injection mechanism increased takeoff power by roughly 20 PS without raising boost pressure and improved fuel efficiency. Consequently, most newer German aero engines adopted fuel injection technology. The Jumo 210G produced roughly 730 PS (720 hp, 534 kW) and was reserved for high-speed aircraft such as the Bf 109 and Bf 110, but not for slower types like the Ju 87.

Although plans existed for further variants like the Jumo 210F and H, these never reached production. The Jumo 210H—with twin exhaust valves per cylinder—served as a developmental step toward the Jumo 211 starting in 1935. Additionally, a specialized version called Jumo 210-S was developed by DVL featuring rotary disc valves similar to those used in KM-8 torpedo engines. Production of Jumo 210 engines concluded around 1938.

Applications

• Arado Ar 68 - installed exclusively in the Ar 68E variant
• Focke-Wulf Fw 159
• Focke-Wulf Fw 187
• Heinkel He 112
• Junkers Ju 87 - fitted solely on the Ju 87A model
• Messerschmitt Bf 109 - utilized only in the Bf 109 A through D versions
• Messerschmitt Bf 110 - applied exclusively to the Bf 110 A and B variants
• Messerschmitt Me 262 V1 - used during the initial test flight; after failure of the prototype’s BMW 003 axial-flow jet engines shortly after liftoff, the aircraft was returned using only the nose-mounted Jumo 210 engine

Bibliography

• Bingham, Victor. Major Piston Aero Engines of World War II. Airlife Publishing, Shrewsbury, UK, 1998. ISBN 1-84037-012-2.
• Christopher, John. The Race for Hitler's X-Planes: Britain's 1945 Mission to Capture Secret Luftwaffe Technology. History Press, Stroud, UK, 2013. ISBN 978-0-7524-6457-2.
• Gunston, Bill. World Encyclopedia of Aero Engines: From the Pioneers to the Present Day. Sutton, Stroud, UK, Fifth Edition, 2006. ISBN 0-7509-4479-X.
• Kay, Antony. Junkers Aircraft & Engines 1913–1945. Putnam Aeronautical Books, London, 2004. ISBN 0-85177-985-9.

A History of Aircraft Piston Engines, Herschel Smith. The Hugo Junkers Homepage – engines section covering L-series powerplants

Further reading

• Walter Zuerl, Deutsche Flugzeug Konstrukteure, Curt Pechstein Verlag, München, Germany, 1941

External links

• http://hugojunkers.bplaced.net/index.html (previously junkers.de.vu, now inactive)
• https://web.archive.org/web/20091027094642/http://geocities.com/hjunkers/ju_jumo210_a1.htm