K-4

The Kalinin K-4 was an airliner built in the Soviet Union in the late 1920s which was also adapted for use as a photographic survey aircraft and as an air ambulance. A further development of the K-1, it was a conventional high-wing, strut-braced monoplane with separate enclosed cabin and cockpit. Kalinin undertook the design to offer a locally produced alternative to pioneering Ukrainian airline Ukrvozdukhput, which was at that time flying Dornier designs. The structure was of mixed wood and metal construction, but with major assemblies designed in both wood and metal versions, allowing them to be interchanged. The design also featured a variable-incidence horizontal stabiliser, and the engine mounting was intended to facilitate the ready interchange of different powerplants.