The early Fokker Eindecker, designated E.I, mounted the seven-cylinder, 80-horsepower Oberursel U.0 rotary petrol engine, a license-built copy of the Frenchdesigned Gnome Lambda or Delta rotary engines that the fledgling German aircraft industry had been producing before the outbreak of World War I. The later E.II and E.III Eindeckers were powered by the Oberursel U.1 nine-cylinder, 100-horsepower rotary engine, while the E.IV was fitted with the 14-cylinder Oberursel U.III.
The engines were air-cooled and reliable. However, although the plane was light, it could achieve a maximum speed of only 140 kilometres per hour (87 miles per hour) with the larger powerplant.
This view reveals the configuration of the 100-horsepower Oberursel U.1 nine-cylinder radial engine. The radial engine was both praised and criticised in service for Germany