Junkers Jumo 211

The Jumo 211 was an inverted V-12 aircraft engine, Junkers Motoren's primary aircraft engine of World War II. It was the direct competitor to the famous Daimler-Benz DB 601 and closely paralleled its development. While the Daimler-Benz engine was mostly used in single-engined and twin-engined fighters, the Jumo engine was primarily used in bombers such as Junkers' own Ju 87 and Ju 88, and Heinkel's H-series examples of the Heinkel He 111 medium bomber.

Design and development
The Jumo 211 was developed by Dr. Franz Josef Neugebauer as scaled-up successor to the earlier Jumo 210. In 1934, even before the new Jumo 210 had completed its acceptance tests, the RLM sent out a request for a new 1,000 PS-class engine of about 500 kg weight. Both Jumo and Daimler-Benz responded, and in order to reach service before the new Daimler-Benz DB 600, the Jumo team decided to make their new design as similar as possible to their 210H model, currently in testing.

The resulting Jumo 211 was first prototyped at Jumo's Dessau plant in 1935 and started testing in April 1936. Like the 210H, it featured a mechanical direct fuel injection system using small pistons driven off the crankshaft, three valves per cylinder, and an inverted V layout. Limited production of the 1,000 PS Jumo 211A started in April 1937 at Dessau, with just over 1,000 completed before full production was started at Magdeburg in July. Three models were provided with varied settings for its two-speed supercharger, tuned for different low- versus high-altitude performance. The first prototype aircraft powered by the 211A appeared in late 1937.

Development of the 211 continued with the 211B being released in 1938, with a slightly increased maximum RPM of 2,400 which boosted power to 1,200 PS. The later 211C and 211D differed primarily in the propeller gear ratios and other features.

A major upgrade was started in 1940 in order to better compete with the 601, following in its footsteps with a pressurized cooling system. The resulting 211E proved to be able to run at much higher power settings without overheating, so it was quickly followed by the 211F which included a strengthened crankshaft and a more efficient supercharger. Running at 2,600 RPM the 211F delivered 1,340 PS and the 211J (a 211F with intercooler) delivered 1,420 PS. Further improvements to this basic line led to the 1,450 PS 211N and 1,500 PS 211P in 1943, they were equivalent to the 211F/J but with slight boost increases and running at up to 2,700 rpm. Continued development of the 211 line evolved into the 213.

The Jumo 211 became the major bomber engine of the war, in no small part due to Junkers also building a majority of the bombers then in use. Of course, since it was the Luftwaffe that selected the final engine to be used after competitive testing on prototypes (such as the Dornier Do 217), there is certainly more to it. Limited production capacity for each type, and the fact that the Jumo was perfectly capable (if not superior) in a bomber installation meant that it made sense to use both major types to the fullest; since the Daimler had a slight edge in a lightweight, single-engine application, that left the Jumo to fill in the remaining roles as a bomber engine. Even this wasn't enough in the end, and radial engines like the BMW 801 were increasingly put into service alongside the Jumo and DB series, most often in multi-engine installations like the Jumo. Total production of the 211 series amounted to 68,248 engines, including 1,046 prototypes and development engines, with a production peak of 1700 engines per month in the autumn of 1942. From 1937 to mid-1944, production was spread between factories in Magdeburg, Köthen, Leipzig, Stettin and Strasburg. With an output of nearly 69,000 examples, it was the most-produced German aviation engine of the World War II years.

Variants
Powers and rotational speeds are for take-off at sealevel.

Applications

 * Avia S-199
 * Dornier Do 217 - single engine test aircraft
 * Focke-Wulf Ta 154
 * Heinkel He 111E, H and Z
 * IAR 79
 * Junkers F 24kai Jumo 211 test bed
 * Junkers Ju 87
 * Junkers Ju 88
 * Junkers Ju 90
 * Junkers Ju 252
 * Messerschmitt Me 264
 * Messerschmitt Me 323
 * Savoia-Marchetti SM.79 (Romanian variants)