1940's German Jet Technology 3
Junkers Jumo-004 Turbojet Engine
Junkers had been developing turbo jets since 1936 and had built a working bench prototype by 1938 based on the axial flow design. The Luftwaffe and the German Air Ministry asked Junkers under Franz Anselm to build a pre-production test engine and by November 1940 the Jumo-004 would be ready for testing.
The engine had an eight stage compressor, behind which lay a simple arrangement of using six separate combustion chambers or ‘flame cans’ instead of the annular type, with a single stage turbine developed in conjunction with ‘Allgemeine Elektricitäts-Gesellschaft’-AEG in Berlin. Giving the engine a thrust output that reached 1,900 pounds on the production version. Junkers developed there turbo jet engine at a far greater pace than that of their rivals at BMW and both the Luftwaffe and Messerschmitt were quick to realise the more favourable of the two engine types being developed to meet the new jet fighter requirements set out.
On 18th July 1942, a pre-production model Me262 was fitted and flown with a pair of Jumo-004 turbo jet engines with great success. With continued successful trials and development, Junkers began full production deliveries from mid 1944, producing by the end of the war around 5,000 units and giving Messerschmitt 262 a flight speed of over 500mph. The Jumo-004 engine would also be fitted to various other last ditched Luftwaffe aircraft in an attempt to change the course of the now already lost war.
The Germans also devolved a unique way to start there turbo jet engines, hidden within the nose cone would be a small two stroke petrol engine. This donkey engine would be started with either an electric starter motor or a manual pull cord and used to drive the compressor and turbine up to the required rpm before engine ignition could take place. This system could be found on most axial flow engines by different manufactures including the Jumo-004 and BMW-003, indicating a general acceptance for this method of engine start.
Interestingly worth mentioning is that during the 1950’s and 60’s ‘centrifugal flow’ turbo jets engines would be developed to their maximum potential and would soon become a second choice power plant, but due to there serviceability and reliability they still enjoy limited use even today. On the other hand ‘axial flow’ turbo jets have changed the world around us because of there break from military applications to the civil airline industry. Where they have now evolved into what is known as ‘turbofan’ jet engines with multi stage compressors, wide cord bypass fans and multi stage turbines mounted on a twin axial arrangements, referred to as being ‘twin spool’. Amounting in the end to proving the German foresight correct!