“Through the ages there have been so many unusual inventions we deem them as weird and whacky flying machines. Some went on to become successful and others never made it from being just a proto-type. However, everything we publish here, infact did fly even though only one or two were ever produced.”
For Example this Ukrainian: Калинин К-7
Kalinin K-7 (Ukrainian: Калинин К-7) was a heavy bomber/Civillian transport 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 far below.
Designed by World War I Aviator Konstantin Kalinin with a wingspan close to that of a B-52 and a much greater wing area, the K-7 was one of the biggest aircraft built before the jet age. It had one engine fewer than of the B-52 as well, having an unusual arrangement of six pulling on the wing leading edge and one pushing at the rear.
The K-7 was built in two years at Kharkiv starting in 1931.
The K-7’s very brief first flight showed instability and serious vibration caused by the airframe resonating with the engine frequency. The solution to this was thought to be to shorten and strengthen the tail booms, little being known then about the natural frequencies of structures and their response to vibration.
K-7 first flew on 11 August 1933. The aircraft completed seven test flights before a crash due to structural failure of one of the tail booms on November 21, 1933. The accident killed 14 people aboard and one on the ground. Although two more prototypes were ordered in 1933, the project was cancelled in 1935 before they could be completed. In 1938 Kalinin was executed as an enemy of the state.
Crew: minimum 11
Capacity: 120 passengers in civilian configuration