Heinkel HeS 011

The Heinkel HeS 011 was an advanced World War II jet engine built by Heinkel-Hirth. It featured a unique compressor arrangement, combining a three-stage axial compressor with a "diagonal" stage similar to a centrifugal compressor, along with a low-compression impeller in the intake to smooth out airflow. Practically every late-war German aircraft design was based on the HeS 011, but the engine was not ready by the time the war ended (May 8, 1945).

Starting in 1936, Junkers started a jet engine development project under the direction of Wagner and Müller, who worked on axial compressor designs. By 1940 they had progressed to the point of having a semi-working prototype, although it could not run under its own power and required a supply of externally compressed air. Hans Mauch, in charge of engine development at the RLM, decided that all engine development should take place at the existing engine companies, so Junkers purchased the Jumo engine company, planning to move the teams there.

Müller and half of the existing Junkers team decamped and were happily accepted by Ernst Heinkel, who had started German jet development when he set up a lab for Hans von Ohain in 1937. The two teams worked on their designs in parallel for some time, von Ohain's as the HeS 8 (or 109-001), and the Junkers team as the HeS 30 (109-006). However Helmut Schelp, who had taken over from Mauch, felt that the BMW 003 and Junkers Jumo 004 would reach production at about the same power levels long before either would be ready, and cancelled both of the Heinkel projects.

Schelp was nevertheless extremely interested in seeing one of his own pet projects, the diagonal compressor, adopted. Schelp had earlier convinced Heinkel to put some effort into another pet project of his, a twin-compressor single-turbine turboprop, but had given up on this and instead offered Heinkel his new design as a consolation prize. Like Junkers, Heinkel had recently purchased Hirth Motoren to avoid complaints from the RLM, so the von Ohain and Junkers teams were moved to Hirth to start work on the new design.

In some ways the HeS 011 can be considered a combination of the two teams' designs, a three-stage axial compressor from Müller's team, combined with a single-stage centrifugal compressor from von Ohain's, driven by a two-stage turbine. The engine operated at somewhat higher thrust levels, about 2,700 lbf (12 kN), as opposed to about 1,700 lbf (7.6 kN) thrust for the 003 and 004. Plans were also made for a turboprop version, the HeS 021, but the workload at Heinkel was so high that this project was later given to Daimler-Benz to complete.

Prototypes were available in 1944, and tested using a Heinkel He 111 bomber, mounting the engine on the external hardpoints under the fuselage. Over the next year practically all German aircraft designers based their projects on the 011, but the engine never entered production. In the end only 19 were built in total. One of these was mounted in the Messerschmitt Me P.1101 that was taken to the United States and some components integrated into the Bell X-5.