STAL Dovern

[LostCosmonaut]

Numerous countries attempted to develop turbojet engines in the post-WW2 period. There were many failures: the J40, TR-1, and others. One of these unsuccessful engines was the Swedish STAL Dovern.

 

 

 

Attempts to develop an indigenous jet engine began at STAL (Svenska Turbinfabriks AB) in the late 1940s. The first engine developed by STAL was the Skuten, in 1948. This was a small, axial flow turbojet with 6 combustion chambers producing roughly 6.2 kN of thrust. The Skuten was intended primarily as a ground-run technology demonstrator, I am not aware of any attempts or plans to fit it to an aircraft. In the meantime, the Swedes used British engine designs for their aircraft, such as the De Havilland Ghost on the J29.

 

Work on the STAL Dovern began in the late 1940s, and from the start, the engine was intended for operational use. The intended recipient was the SAAB 32 (Lansen) attack aircraft, then under development. This would require a much more powerful engine than the Skuten, and so the Dovern was itself much larger. Like the smaller engine, the Dovern was built as an axial flow turbojet. However, additional combustion chambers were added, bringing the total to nine. This, along with a large increase in the dimensions of the engine, resulted in the Dovern having a design output of over 32 kN. This was significantly more than the De Havilland Ghost powering the J29 at the time.

 

The STAL Dovern was first ground tested in February 1950, roughly two years after development began. By this time, the engine had matured into an axial flow design with a nine-stage compressor section, and nine combustion chambers arranged in a circular manner. Pressure ratio was about 5.2, superior to the Ghost, but inferior to the British Avon also under development in the same time period.

 

(a picture from 1954 Flight Global magazine comparing the Dovern and Ghost)

 

After about 3,000 hours of run time, a Dovern prototype was fitted to a Swedish Avro Lancaster (Tp 80) for further testing.

 

 

Testing of the engine in this manner began in June 1951, and revealed some issues. At certain power settings, the engine would suffer compressor surging, causing a loss of power and potential damage to the engine. Numerous redesigns of the compressor section somewhat alleviated the problem, though did not manage to cure it entirely.

 

By 1954, the Dovern had accumulated over 4,000 hours of runtime, including about 300 on the Lancaster testbed. An afterburning variant had also been developed, producing  45 kN. However, the engine was still not fully ready, and by this point the Lansen had already flown with an Avon engine fitted. As a result, it was decided to cancel the Dovern program, and instead use the Avon engine in both the Lansen and upcoming Draken (J35). (Some sources say that the Dovern was cancelled when it caught fire and destroyed the Lancaster test aircraft. However, this actually happened in 1956 while testing the RM-6/Avon, at which point the Dovern was already cancelled.) 16 units had been produced. An advanced version, called the Glan, had been under development for use in the Draken. It was also cancelled.

 

From this point, Swedish aircraft designs would use foreign engines. Though the Dovern was not fully developed, it cannot be said to be a failure for the Swedish aerospace industry. Producing world-class jet engines is highly difficult, requiring large amounts of experience and supporting industry. Only a few nations are truly capable of doing so even now (US, UK, France, Russia, and arguably China). For a country as small as Sweden, having an indigenous jet engine industry would be a truly Herculean feat.

 

Sources:

 

https://www.flightglobal.com/pdfarchive/view/1954/1954%20-%201015.html

http://www.x-plane.org/home/urf/aviation/text/reamotorer.html

http://en.valka.cz/topic/view/184837/SWE-STAL-Dovern