Among a few 1930s flying wing designs this one stands out - an experimental aircraft designed as a bomber from the start, when relatively little was known about tailless planes' behavior.
A WWI bomber pilot, Kalinin served with the Ukrainian army during the Civil War, joined the Bolsheviks in 1919, studied in Moscow and Kiev, and graduated from the Politechnical Institute as an aeronautical engineer. He built his first plane, the K-1, at the Kiev Aircraft Repair Plant. It was the first Soviet plane with welded steel frame. Another important feature was elliptical wing, future Kalinin hallmark. From Kiev, he moved to Kharkiv where he established and managed a new design bureau and was among the founders of KhAI (Kharkiv Aviation Institute).
The designer tried to develop a lightweight multipurpose plane, suitable for different specialized modifications. Next steps in this direction were the K-2 and K-3, an airliner and a recovery aircraft. They were followed by the K-4 and K-5 – first Soviet serial-built airliners. The K-4, initially designed as a flying ambulance, entered passenger service in 1928 and set a speed/distance record next year, covering 10,400 km in 73 hours. It was quickly withdrawn from the civil airlines but its ambulance and photo-recce versions soldiered on well into 1930s. The K-5, introduced in 1930, remained the main Soviet airliner until 1940, 260 units built. Less successful was the K-6, a lightweight mailplane which didn't live up to the expectations. But the most famous (or rather, notorious) Kalinin design was a seven-engine twin-boom monster called K-7. The prototype, built in 1933, crashed on its 11th flight, killing 15. Further development of this ambitious design was canceled. OK, the K-7 is an undisputed Dieselpunk icon (or a cliche), over-hyped during the last decade. No need to bring it here. We'd better talk about the tailless K-12.
Kalinin started to develop his 12th design in 1933. The concept, too revolutionary for its time, met a lukewarm welcome. It was decided to test it thoroughly, and before the first (and only) "real" aircraft was built there was a wooden 1:2 scale model (non-powered but piloted), tested both in laboratory and in flight, as a towed glider. This model caused a lot of confusion: some sources call the actual K-12 "a scaled-down prototype". Another possible reason for this confusion is a color drawing from a Russian magazine featuring the Kalinin aircraft in military and "fancy" colors:
I owe you an explanation of the unusual livery, but first let me tell you that in early 1936, the K-12 was assembled in Voronezh (where Kalinin worked since 1934) and in July made its maiden flight. It was of modest dimensions (wingspan - 20.95m, length - 10.3m) but its wing area was 72 sq.m. We can compare it to a conventional Vickers Wellesley light bomber which was longer (11.96m), had a wider wingspan (22.73m) and wing area of only 58.5sq.m.
During test flights the K-12 showed good take-off capabilities, but was unstable in flight and demanded more powerful engines and more effective rudders. Initially it was supposed to be powered by 310hp M-49 engines (see a drawing below). In fact, a pair of 480hp M-22 was not enough.
The performance, as I've already stated, was far from perfect but not hopeless, and in summer 1937, the K-12 was introduced to the public during air parade at Tushino airfield near Moscow. For this occasion, it was dressed up like a firebird from Russian fairy tales, the Zhar-Ptitsa. Painted red and gold, with wooden mock-up turrets, the aircraft left the spectators impressed - to say the least, - and returned to Voronezh for further test and improvements.
Finally, the People's Commissariat for Defense Industry ordered a batch of 10 K-12 bombers*. Production was planned for 1938 - but in the spring this year Konstantin Kalinin was arrested, charged with espionage and anti-Soviet activities, and in October, after a short trial, executed in the Voronezh prison. The order was canceled and the only K-12 was dismantled. That's how the story ends.
Special thanks to Yelena Astakhova of the Aircraft of the World magazine (her article is available online, in Russian) and Alexey Kutovenko who provided some guidelines for this entry. Besides, Alexey built a gorgeous model of K-12, pictured above.
* Probably it's worth mention that by 1938, Kalinin developed a somewhat more conventional bomber, the K-13. It was his last design.