BMW X

The BMW X was a small five-cylinder radial engine for sport and training aircraft. Although it proved successful at several large-scale events in 1930, including that year round-Europe flight, only a few were built. Its successor, the BMW Xa, was introduced in 1931 with the swept volume raised from 2.2 to 2.9 litres and the power output from 37 to 51 kilowatts, and it too was not built in any quantity and was mainly installed in training and sport aircraft. The X has an 83 millimetre bore and an 80 millimetre stroke, and the Xa a 90 millimetre bore and a 92.5 millimetre stroke, with a 2.93 litre displacement, air cooling, overhead valves worked by pushrods and rockers, and a dry weight of 73 kilograms. Applications included the BFW M.23 and M.31, the Gerner G.IIR and the Klemm L25.