BMW X (engine)
The BMW X was a small five-cylinder radial engine for sport and training aircraft. Although this engine proved successful at several large-scale events in 1930, including that year's round-Europe flight, only a few were built. The successor model to the BMW X five-cylinder radial engine, the BMW Xa, was introduced in 1931, with the swept volume increased from to . Power output went up from . The Xa was also not built in any quantity and was mainly installed in training and sport aircraft.