Kalinin K-7 Aircraft

Kalinin K-7 (Russian: Калинин К-7) was a heavy experimental aircraft designed and tested in the Soviet Union in the early 1930s. K-7 was of unusual configuration with twin booms and large underwing pods housing fixed landing gear and machine gun turrets. In the passenger version, seats were arranged inside the 2.3 meter (7 ft 7 in) thick wings. The airframe was welded from KhMA chrome-molybdenum steel.

The original design called for six engines in the wing leading edge but when the projected loaded weight was exceeded, two more engines were added to the trailing edges of each wing, one right and one left of the central passenger pod. However V.Nemecek states in his book "The History of Soviet Aircraft from 1918" that there was only one further pusher engine added—this agrees with the specification supplied below. K-7 first flew on 11 August 1933.