K-7

The Kalinin K‑7 was a radical Soviet aircraft designed by Konstantin Kalinin in the early 1930s, intended as a heavy transport and passenger platform for the burgeoning Soviet air network. First flying in August 1933, the nine‑engine monoplane featured an immense 38‑metre (125‑ft) wingspan, a thick, low‑aspect‑ratio wing, and a distinctive multi‑tail arrangement of three vertical stabilizers. Its three front‑mounted Curtiss V‑12 engines and six additional engines mounted on the wing’s upper surface supplied the power required to lift a payload of up to 5 tonnes, while the spacious interior could accommodate 150 passengers or freight, a capacity unprecedented for its time.

The K‑7’s most striking characteristic was its structural daring: a lightweight steel‑tube framework combined with fabric covering, and a series of reinforced spars that allowed the aircraft to achieve a maximum speed of about 260 km/h (162 mph) and a service ceiling near 3 500 m. Although only two prototypes were built and the program was terminated after a catastrophic crash in November 1933, the K‑7 demonstrated how extreme wing loading and multi‑engine layouts could be managed, influencing later Soviet designs such as the Tupolev ANT‑25 and the massive transport concepts of the post‑war era. Its brief career remains a vivid illustration of experimental ambition in early aviation history.

Konstantin Kalinin

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Design & Classification