World War I
Siemens-Schuckert designed a number of heavy bombers early in World War I, building a run of seven Riesenflugzeug. Intended to be used in the strategic role in long duration flights, the SSW R-series had three 150 h.p Benz Bz.III engines in the cabin driving two propellers connected to a common gear-box through a combination leather-cone and centrifugal-key clutch in SSW R.I to the SSW R.VII models (the SSW R.VIII utilized four engines). In the case of engine failure, which was extremely common at the time, the bomber could continue flying on two engines while the third was repaired by the in-flight mechanic. Two transmission shafts transferred the power from the gear-box to propeller gear-boxes mounted on the wing struts. Although there were some problems with the clutch system, the gear-box proved to be reliable when properly maintained. The SSW R.1 through the SSW R.VII designs were noted for their distinctive forked fuselage. Several of these aircraft (SSW R.V through the SSW R.VII) fought on the Eastern Front. Although interesting in concept, the cost of these and the R-types from other companies was so great that the air force eventually abandoned the concept until more practical designs arrived later in the war.
The first fighter designed at the works was the Siemens-Schuckert E.I which appeared in mid 1915, and which was the first aircraft to be powered by the Siemens-Halske Sh.I, a new rotary, developed by Siemens-Schuckert, in which the cylinders and the crankshaft rotated in opposite directions. A small number of production machines were supplied to various Feldflieger Abteilung to supplement supplies of the Fokker and Pfalz monoplane fighters used at the time mainly for escort work. The prototype SSW E.II, powered by the inline Argus AsII, crashed in June 1916, killing Franz Steffen, one of the designers of the SSW R types. By early 1916 the first generation of German monoplane fighters were outclassed by the Nieuport 11 and the Nieuport 17 which very quickly followed it; and Siemens-Schuckert were supplied with a captured Nieuport 17 to "study". The resulting SSW D.I was powered by the Siemens-Halske Sh.I, but was otherwise a fairly literal copy of the Nieuport 17. This aircraft was the first Siemens-Schuckert fighter to be ordered in quantity, but by the time it became available in numbers (well into 1917) it was outclassed by contemporary Albatros fighters.
Development of the Sh.I engine resulted in the eleven-cylinder, 160 hp Sh.III, perhaps one of the most advanced rotary engine designs of the war. The D.I fighter also formed the basis for a series of original designs, which by the end of 1917 had reached a peak in the Siemens-Schuckert D.III, which went into limited production in early 1918, and found use in home defense units as an interceptor, due to its outstanding rate of climb. Further modifications improved its handling and performance to produce the Siemens-Schuckert D.IV. Several offshoots of the design included triplanes and a parasol monoplane, but none saw production.
Interwar production
With the end of the war production of the D.IV continued, mainly for sales to Switzerland who flew them into the late 1920s. With the signing of the Treaty of Versailles the next year all aircraft production in Germany was shut down. Siemens-Schuckert immediately disappeared, but Siemens-Halske continued sales of the Sh.III and started development of smaller engines for the civilian market. By the mid-1920s their rotary engines were no longer in vogue, but "non-turning" versions of the same basic mechanicals led to a series of 7-cylinder radial engines, the Sh.10 through Sh.14A, delivering up to 150 hp in the 14A. The Sh.14A became a best-seller in the trainer market, and over 15,000 of all the versions were eventually built.
Siemens-Halske no longer had any competitive engines for the larger end of the market, and to address this they negotiated a license in 1929 to produce the 9-cylinder Bristol Jupiter IV. Minor changes for the German market led to the Sh.20 and Sh.21. Following the evolution of their smaller Sh.14's, the engine was then bored out to produce the 900 hp design, the Sh.22. In 1933 new engine naming was introduced by the RLM, and this design became the Sh.322, when Siemens was given the 300-block of numbers. The Sh.322 design had reliability problems and never became popular.
