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Jet Engine Development in Germany

Revolutionary technology takes time to mature. Sometimes there are breakthroughs that enable accelerated maturing processes, but maturing still needs time. Pumping unrestricted investments into immature technological R&D can certainly improve the pace of progress, but cannot guarantee the solution of all problems inherent in new technology. The story of jet engine development in Germany during WWII is a classical example of premature introduction of immature technology into operational use.

Read the first column in the series: “Genesis of the Jet Age“

Jet engine development started in Germany in the mid 30s and enjoyed generous corporate support. As a result, Germany was the first country to fly a jet-propelled aircraft. However, jet engines were a technological novelty and their technology required many refinements in order to make them ready for field deployment. One of the main problems affecting jet engine development was the exposure of large parts of the engine to high temperatures and great rotational speeds. The compressor and turbine of jet engines were particularly complicated and delicate components operating under high physical forces. German developers faced more difficulties then their colleagues abroad, because the Reich’s Air Ministry decided in 1940 to concentrate R&D on a more advance form of engine – the axial-flow engine. On paper its design was quite straightforward, but in practice its developers were sailing largely through uncharted waters.

The Jumo 004 (front) and Japanese version of the BMW 003 engines. Their slender shape is obvious in this view (author’s collection)
The Jumo 004 (front) and Japanese
version of the BMW 003 engines. Their
slender shape is obvious in this
view (author’s collection)

Two big firms lead the way in German jet engine development: Jumo and BMW. In the meantime the Reich’s Air Ministry contracted Messerschmitt to develop the Luftwaffe’s next generation jet fighter – the Me 262. BMW made faster progress and on March 25, 1942, a prototype Me 262 took off for the first time powered by two BMW P3302 development engines. The aircraft was also equipped with a single piston engine as a safety measure. It was a wise move because soon after take-off both jets failed. Major flows were found in the failed engines and BMW’s engineers were forced to redesign most of the engine. The next jet powered test flight took place on July 17 of the same year with two Jumo 004 engines. This flight was successful, but it was clear that much development work was still necessary.

 

There were multiple problems with the new engines. Fuel flow control was difficult and the engines responded haphazardly and slowly to throttle movements. The engine frequently caught fire or flamed out. Fuel pipe seals tended to burst as result of high ambient temperatures and there were many cases of leaks. Leaking fuel caused frequent engine fires. Turbines and compressors throwing blades caused catastrophic failures. The rotating parts also caused excessive vibrations, which had to be dealt with.
A large portion of these difficulties was caused by the fact that some part manufacture required the use of expensive metals, like chrome, nickel, cobalt and molybdenum. These metals were scarce in wartime Germany so simple metals were used instead in series production engines. Especially problematic was the manufacture of turbine blades from simple sheet steel with aluminum coating. Since the heat resistance factor of these alloys was below the requirement, a special cooling mechanism had to be devised. It was not enough and the average life span of production engines was only 25 hours – mainly because of damage hot exhaust gas caused to the turbine blades.
An Me 262 during operational evaluation, Spring 1944 (Credit: NARA – public domain)
An Me 262 during operational
evaluation, Spring 1944
(Credit: NARA – public domain)

The test flights conducted in 1942 demonstrated not only the potential of axial-flow engine, but also the immaturity of its technology. The Germans found out the hard way over the next couple of years that revolutionary technology cannot mature overnight, even with large investments and with the availability of highly developed testing facilities. Only in mid summer 1944 the Jumo 004B engine was finally ready for series production, and even then it was imperfect. BMW’s design, the 003 engine, took even longer to develop. Besides suffering from the same problems plaguing the Jumo engine, its fuel flow control was hopelessly ineffective. It was finally ready for production in late summer 1944, and only after its designers adopted the more successful Jumo throttle mechanism.

By the time jet aircraft appeared on the front, Germany’s situation was already desperate. Former German generals and historians argued after WWII that faulty decision-making and lack of commitment bore the main blame for the late appearance of German jets. These notions overlooked the nature of jet engine as a completely new and very complicated technology. Furthermore, detailed historical studies prove that developers of jet technology enjoyed generous official support at least from late 1939 and by 1941 the Luftwaffe decided that its new generation fighter is going to be a jet fighter. Well publicized are orders Hitler gave in November 1943 and May 1944 to produce the Me 262 solely as a fighter-bomber. These decisions created only insignificant delay, because the design changes they required were not so difficult to implement. Anyway, at that time the engines were still not ready for series production. As aviation historian Alfred Price wrote: “…at this time (May 1944) the poor reliability of the 004 engines precluded the operational use of the Me 262 in any rule.”
Hitler reversed his decision after the Normandy landings, but even when they entered service, German jets continued to suffer from the temperamental nature of their engines.
BMW 003 engine installed on this grounded He 162 last resort fighter (Credit: NARA – public domain)
BMW 003 engine installed on this
grounded He 162 last resort fighter
(Credit: NARA – public domain)

One interesting and often overlooked advantage jet engines offered Germany was simpler fuel logistics. German jets required no special fuel like piston engines, which required high-octane fuels. The Me 262 was even flown experimentally on crude Romanian oil, experiencing no meaningful problems.

Unfortunately for the Germans, by the time jets started entering mass production, Germany suffered from general oil shortage. As a result, most of the jet planes produced in Germany spent most of their short time-span grounded.

 

To sum things up, German jet engine development suffered from two fundamental flows:
  1. The Germans tried to rush jet technology into service, but by concentrating their efforts from an early stage on the axial-flow design they skipped an important evolutionary stage. Huge investments in axial-flow engine R&D could not overcome all the technical difficulties involved in its development. Money could not buy, for example, the special metals required for the heat-resistant parts. The British started investing large amounts of money in Whittle’s project only in 1940. It helped them close the gap with the Germans only because their engine was less complicated. As a result, at the end of WWII British jet engines were less modern, but more reliable, while German engines were more advanced, but less reliable.
  2. Over-optimism regarding the quick maturing of advance technologies is a striking feature of German WWII leadership. It is especially evident in the jet story. For instance, in 1940 the Air Ministry planned to introduce a jet fighter into operational service by the end of 1942. It was a ridiculous notion as any aeronautical engineer at the time knew well it will take between two and three years to complete the development of a conventional fighter not to mention a revolutionary new type of aircraft.
It can be said that in contrast to what many Luftwaffe generals and scholars argued after WWII, from the technological perspective, German jets came too early. Due to the technological immaturity of their engines they were far from being the technological marvels they appear to be.
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About the author: Dr. Daniel Uziel researches different aspects of modern German history, military history, and war and media. In recent years he is researching the history of the German aviation industry. He conducted part of this research as a fellow at the US National Air & Space Museum.

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About

Dr. Daniel Uziel studied history and international relations in the Hebrew University and in the Freiburg University. He researches different aspects of modern German history, military history, and war and media. In recent years he is researching the history of the German aviation industry. He conducted part of this research as a fellow at the US National Air & Space Museum.

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