Junkers (OKB-1) Jumo 012

Eleven stage compressor, double stage aircooled turbine with axial flow
designed by Siegfried Decher until 1945 and Alfred Scheibe (1945-1947) and Brandner (since 1947)

Junkers Jumo 012A, Summer 1946

The Jumo 012 was a special designed engine for the Junkers Ju 287 and for the Heinkel He343. The engine was designed for thrust of 6000 to 6400 lbs with a weight of 4000 lbs. The RLM placed an order for ten prototype engines of the 109-012. Several engine parts were already finished, when the RLM advised Junkers to Transfer the further development work on the Jumo 012 to other companies, i.e. the Motorenwerke at Oberursel. Just a mockup of the engine was finished by the end of the war and one prototype engine was under assembly, when the end of the war stopped further activities.

When the Russians occupied Dessau, they decided to continue the Jumo 012 developement at the newly formed OKB-2 under the Management of Alfred Scheibe. A total of 15 engines were ordered for the end of 1946 and the engine was now intended for the EF132. As most of the design work documentation had been transfered to other companies in December 1944 or was lost in Dessau during the U.S. occupation period, the OKB-2 design Team had to redesign the Jumo 012 from existing parts in Dessau and from their mind. The first redesigned Jumo 012 was ready for static Tests at the end of June 1946, two more followed in July.

First testruns with the prototype engine Jumo 012 started in July 1946, but on 9th August 1946 this engine was destroyed during a test run due to high EGT at the max turnrate. Reason for that was the "Storchenschnabel"-Enlargement, which was taken over from the Jumo 004B and Jumo 012-V02 and -V03 showed the same effects as the crashed prototype engine.

In October 1946 the OKB-2 was transfered from Dessau to Kuibyschew in Russia. This caused further delays of the required modification of the Jumo 012. In Spring 1947 Ferdinand Brandner took over the Management of the OKB-2 from Alfred Scheibe and continued the Jumo 012 modification. The eight burner Chambers were exchanged against twelve ring burner Chambers. The front housing of the new Jumo 012 was exchanged against light metals reducing the Overall weight of the Jumo 012. Turbine and Compressor housings were made from steel. While the first Jumo 012 had a movable exhaust cone, the new Jumo 012 got a fixed cone.

The new engine was designated Jumo 012B. In Summer 1948 the first five Jumo 012Bs were built, but the following Tests did not Show sufficient reliability of the prototype engines. In June No. 5 underwent an endurance test. A compressor rear bearing broke down in the 28th hour. After repair the engine ran another 25 hours in July. During this test, cracks were found in turbine blades and compressor stator blades. In the end of July the endurance test on Jumo 012-V05 was aborted due to further findings on the engine and the engine was removed from the test Programme. On 22 October 1948 another endurance test was scheduled. During this endurance test run the prototype failed after 94 operating hours due to a cracked turbine blade.

Due to the failure and due to the fact that other jet engines offer more power at a more compact design, i.e. the British Nene based Klimov RD-45 of 1948, which was much more compact and less heavy than the Jumo 012B at the same thrust, the Jumo 012 developement was stopped in 1948 finally.

Already in March 1947 the conversion as a turboprop engine was requested by the Russian commission and the Jumo 012 was continued as PTL 022. This new engine used the technology ideas of the Jumo 022 and combined practical research results from the Jumo 012, i.e. a lot of components were taken over from the Jumo 012 for the PTL-022.

Technical Data:

Weblinks:

• Wikipedia.org - Jumo 012 Story and Data
• CIA.org - Jumo 012 Development at Kuybyshev (Report 21 Oct 1953)

introduced Nov 1996, transfered Aug 2017
http://hugojunkers.bplaced.net/
contents last updated 30 Aug 2017