Siemens-Schuckert Werke GmbH, subsidiary of electrical giant, began building large non-rigid airships 1907, followed by aeroplanes from 1909, but discontinued 1911 after nephew killed flying. Aeroplane department reopened September 1914, Franz and Bruno Steffen joining as designers and creating series of R-types (Riesenflugzeug = giant aircraft). R.I (May 1915) had 2 tractor propellers driven by 3 x 150-hp engines in nose. R.II-R.VII were broadly similar in layout but larger, all with tail carried by rear fuselage in form of triangular booms, one inverted over the other. R.VIII had 6 x 300-hp Basse und Selve engines in fuselage with shafting to tractor and pusher propellers, and was largest aircraft of 1918. SSW Kann, never completed, was to have had 4 x 750-hp steam turbines. Fighters began with E.I monoplane (October 1915), 20 being built, followed by E.II and III, and more important D-types based loosely on Nieuport fighters: D.I. (1916), 95 delivered, next to reach production being D.IV (1918) extremely fast-climbing interceptor with 160-hp Siemens-Halske, about 120 complete at Armistice plus prototypes of D.VI parasol monoplane.