Hyper Engine - Hyper-engine Class Powerplants For The Luftwaffe

Hyper-engine Class Powerplants For The Luftwaffe

Nazi Germany's own attempts during the late 1930s to create aviation powerplants in the "hyper engine" power output class initially started with the foreknowledge that unlike the United States, the Third Reich did not have the large production capacity for aviation powerplants as the Americans did, and twin-engined aircraft powered with two "hyper-engine" class powerplants were more realistic for heavy bomber-sized airframes, given their own restricted production capacity in comparison with the American aviation industry. The first attempts by the Third Reich to get to "hyper engine" power output levels began, roughly simultaneous with both the RLM's original "Bomber A" heavy bomber specification of June 3, 1936, and in August of the same year with the private venture Heinkel He 119 high-speed reconnaissance aircraft projects' need for such powerplants. The need for such high-output powerplants was initially intended to be met by the Daimler-Benz firm in 1936-37, through mounting a pair of Daimler-Benz inverted V12 engines, in a "side-by-side" manner within a common mount, and mechanically coupling the two powerplants together at their forward ends into a single "power system", using a common gearbox at the front of the arrangement with a single propeller shaft. The first example of such a "coupled" powerplant was created by combining two Daimler-Benz DB 601 engines in the aforementioned manner to create the "DB 606" before World War II in February 1937, in time for both airframe designs to have their powerplants ready and in the initial stages of production. This line of thinking led to the continuation of the format in creating ever more powerful "power systems"; using the Daimler-Benz DB 605 design in a similarly-twinned format resulted in the "DB 610" in June 1940, and the Daimler-Benz DB 603 twinned-up in such a form to create the most powerful of the cumbersome "coupled" power systems, the "DB 613" in March 1940. None of these "power systems" really ever had all their design flaws worked out during the war years, some of which were also related to airframe design issues in how the "power systems" were mounted onto the airframe, and housed in their nacelles. Such issues in airframe powerplant installation design partially contributed to the endlessly troubled career of the Luftwaffe's only heavy bomber design to see production, the Heinkel He 177A. The operational front-line versions of the Greif only used the Daimler-Benz produced coupled engine systems for propulsion, resulting in Reichsmarschall Hermann Göring's complaints in August 1942 that derisively labeled the Daimler-Benz firm's "coupled" engine concept, as used in the He 177, as "welded-together engines".

Simultaneously with the early development of the "coupled" engines, was Daimer-Benz's attempt at creating a hyper-class aviation powerplant using only one common crankcase, the twenty-four cylinder Daimler-Benz DB 604, with four banks of six cylinders each, arranged in an upper and lower set with a 60º angle between each bank per set. Possessing essentially the same displacement of 46.5 litres (2830 in2) as the initial version of the Junkers Jumo 222, the DB 604 was intended to have A and B versions of opposite rotation, like the coupled engines did, but as its protracted development was diverting valuable German aviation powerplant research resources, and with more development of the DB 610 coupled engine giving improved results at the time, the Reich Air Ministry stopped all work on the DB 604 in September 1942.

The BMW company's work with radial engines resulted in the BMW 802 eighteen-cylinder air-cooled radial engine design, which was close to being a hyper engine, being in the same general class in size, number of cylinders, and output power as the famous American Double Wasp powerplant, with the incredibly complex Wasp Major-class BMW 803 28-cylinder liquid-cooled radial being a total failure in testing of its prototypes.

The Junkers company's 24-cylinder Junkers Jumo 222, liquid cooled six-bank inline engine, with four cylinders in each bank, came the closest to being Nazi Germany's only production "hyper engine" candidate during the war years, intended to power the Bomber B design competition's most likely success, the Junkers Ju 288 advanced medium bomber, as well as many other German multi-engined advanced combat aircraft projects. The 222 was a remarkably compact and efficient engine design, being almost identical in cylinder number, displacement and weight to the British Napier Sabre H-type four-bank inline engine, and the best attempt at creating a German "hyper engine", but as with the BMW designs, never came close to being a production-ready aircraft powerplant, with just under 300 examples produced in total between several different versions.