By the end of the 1920s of the last century, transport and passenger aviation began to develop in the Soviet Union. There was a need to design and manufacture aircraft capable of transporting cargo and passengers over long distances. The design bureau under the leadership of K.A. Kalinin received a government order for the production of a transcontinental passenger aircraft, work on which began in 1928.
Would you like to see this plane fly?
NOT REALLY
The new aircraft, designed in two versions, was a fundamentally new development and embodied all the advanced technologies of its time. Experienced aircraft designer K.A. Kalinin was appointed chief designer. By 1932, the technical design was ready, and the design bureau team began producing an experimental model. Construction of the giant aircraft began in November 1932; after 9 months it was ready.
Transport and passenger at the same time
The new aircraft had its own functional features: it was conceived as a transport and passenger vehicle at the same time, i.e. had to be multi-purpose. The wing design of the K-7 was especially different: it was truly gigantic in size, elliptical in shape, made of a thick metal profile. Initially they planned to make it from wood, but its strength turned out to be insufficient, so the wood was replaced with metal.
Smaller model of K-7
The wing was long - 53 meters. In its middle there was a center section 6 meters wide, 10.6 meters long and 2.33 meters high. Rooms for passengers and cargo were equipped here. The plane had a good supply of fuel - 14 tanks. The cabin, located in front, served for the crew: there were two pilots, a mechanic, a navigator and a radio operator. The remaining seven crew members were located in other areas of the aircraft. There were a total of 12 team members for service. There was a telephone connection between them.
S-7 - Sikorsky reconnaissance aircraft
In the late spring of 1912 I.I. Sikorsky and his closest friends arrived in St. Petersburg and immediately began work. Several aircraft were under construction at the same time. The S-6B and S-7 aircraft were specially prepared to participate in the military airplane competition. The S-6B had a design that was basically the same as the S-6A, but in a two-seat version.
Unlike the heavy S-6B, the S-7 reflected the concept of a high-speed aircraft, and therefore a monoplane design was chosen. The aircraft was developed by a group consisting of G.P. Adler, B.V. Volyansky and others. The plane used some parts from the S-6A. The aircraft was built in July 1912. It was a two-seat monoplane with a landing gear similar to the S-6A. The fuselage was covered with plywood, the wings did not warp, but had ailerons, which was new. The empennage without a keel with a frame steering column. The car was equipped with a 70 hp Gnome engine. In the competition, the S-7 aircraft was piloted by factory pilot G.V. Yankovsky. However, due to a chassis failure, the competition program could not be completed. Soon the plane was sold to Bulgaria, where it took part in hostilities.
Unique device parameters
The technical characteristics of the K-7 are unique. The length of the aircraft was 28 meters with a wingspan of 53 meters; its mass was 21,000 kg, and it could lift up to 19,000 kg of cargo into the air. It could reach a maximum speed of 234 km/h. and rise to a height of 5,500 meters. Its flight range could be no more than 1,000 km. An aircraft of such enormous mass was powered by 6 AM-34 engines of 750 hp each. each, but this was not enough due to their relatively low power. We had to change the design by adding the missing seventh engine (it was located on the trailing edge of the wing).
For the first time, an aircraft of this model used a new chassis design with balloon-type wheels; Our industry has not produced such wheels.
Fixed idea
Aircraft designer Konstantin Kalinin has been designing relatively small aircraft for a long time. But apparently this was not enough for him, because in 1930 he came up with the project of a grandiose heavyweight. Embodied in metal, it became one of the largest aircraft built in the world in the 1930s.
Kalinin was haunted by the idea of an airplane—a flying wing.” The engineer sincerely believed that this progressive scheme would sooner or later determine the future of aviation. And I tried my best to contribute to this. The giant K-7 project was not tailless, but the wing space in it was used to the fullest.
It was truly huge. Not only was the span a respectable 53 meters, but the area also reached half a thousand square meters. m. The ceiling height inside the wing reached two meters.
The aircraft designer’s plan was simple - to create a good multi-purpose super-heavy aircraft, prove the objective benefits of the concept, and then promote the tailless design, a full-fledged flying wing.”
Launch of production
It was necessary to establish their production. Another innovation that was used in the production of the K-7 was revolutionary for the Soviet economy: for the first time, chrome-molybdenum pipes were used in structures that combine increased strength and low weight. Previously, such pipes were purchased abroad in Sweden, but in the process of working on a new model, the country began producing such pipes at a metallurgical plant in Dnepropetrovsk.
The K-7 aircraft was planned to be produced in two versions: passenger and military. The passenger glider could carry 128 passengers and transport them by air over a distance of up to 5,000 km.
Since long flights were expected, in the future it was planned to produce a luxury aircraft with 64 sleeping places in bunk cabins for 8 people. For the convenience of the crew, a wardroom and a radio room were equipped; For the first time, it became possible for mechanics to approach running engines during flight. For passengers there is a kitchen, a buffet and windows through which you can watch the flight.
The military version involved the production of a landing type aircraft capable of lifting 112 paratroopers and a tank or other equipment into the air. It is armed with 8 20 mm cannons and 8 7.62 mm machine guns. This equipment was installed in the wings so well that fire could be fired from almost any point. The aircraft could take on board a colossal amount of ammunition - up to 16,500 kg.
Gigantomania
It was not only the wing and dimensions that were unusual about the K-7.
Attention was immediately attracted by the grandiose chassis bogies - three wheels on each. Entrance to the plane was actually through one of the trolleys - there was a door on its casing
Having passed it, it was necessary to climb the stairs and get into the huge wing - and then into the cockpit.
There were seven engines. At first they wanted to get by with six, but then, to improve the performance, they added one more. The seventh engine was placed at the rear and equipped with a pusher propeller - this decision later became fatal for the car.
In the bomber version, it was planned to liberally scatter defensive weapons throughout the aircraft - as many as four autocannons and eight machine guns. Moreover, two electric trolleys driven by winches and a cable were supposed to deliver additional ammunition to the two rear firing points of the shooters.
On the same topic: How domes did not obscure the sky: pre-war dreams of Soviet paratroopers and reality
The crew was suitably sized - 12 people. There were two pilots, as well as navigators. There was even a boatswain who also served as a paramedic.
The K-7, as befits a giant car, was frighteningly expensive. Kalinin decided to assemble the frame from chrome-molybdenum pipes - the material was purchased for foreign currency and was worth its weight in gold. This did not speak in favor of the car, but the designer, apparently, hoped to amaze the selection committees with other characteristics.
The K-7 never flew with bombs, but the most optimistic calculations suggested that it would be able to lift 16,600 kg. Having calculated more precisely, the sturgeon was cut several times. So, in February 1933, the ceiling was determined to be 12.3 tons. The bombs were supposed to be hidden inside the same huge wing.
An external sling was also planned, which would make it possible to carry heavier ammunition - then they only thought about a ton. However, options were developed for paratroopers in which a wide variety of cargo was placed between the chassis bogies, up to an eight-ton light tank.
Designer Kalinin (in the center) with the K-7 crew
The paratroopers themselves, in full gear, could carry 112 people. Or 128 passengers - Kalinin also pinned his hopes on using his car in the national economy.
First flight and tragedy
The first flight of the K-7 took place on August 21, 1933. The first pilot was test pilot M.A. Snegirev, the second was the designer Kalinin himself. The first tests showed good flight and technical characteristics of such a huge mechanism. A total of ten flights took place. On November 21, 1933, the plane did not return from the flight: an accident occurred, as a result of which 15 crew members died. Experts were unable to determine the cause of the plane crash. In the future, it was planned to produce two passenger and one military K-7 before 1935, but they were never manufactured.
Despite the tragic ending to the history of the creation of the K-7, it left a bright mark on the history of the world aircraft industry: at that time this aircraft was the only one - there were no others like it in the world.
It flies!
The K-7 made its first attempt to take off on August 19, 1931. It was unsuccessful - the tail of the car was not rigid enough. Then they began to urgently strengthen the wing. Two days later, everything was ready, the plane was allowed to fly. The place of the co-pilot was occupied by the designer himself.
Very soon he had to take part in the control - the cables on two rudders broke at once. The car began to shake. In order to somehow turn it around and send it back, Kalinin had to help the first pilot - the strength of one person at the helm of the faulty aircraft was not enough. Somehow they turned around and sat down. On the ground, the designer received a stick from his superiors.
The problem was fixed only in September, but new ones followed, one after another. Apparently, Kalinin’s sharp transition from small aircraft to giants was not in vain. But it was too late to replay the game - the engineer was trying to hastily bring the car to perfection, fixing one fault after another.
K-7 in factory tests
Performance characteristics of VVA-14
— Chief designer: R.L. Bartini - First flight: September 4, 1972 - Units produced: 2
VVA-14 crew
— 3 pilots
Dimensions VVA-14
- Wing span, m: 28.50 - Length, m: 25.97 - Height, m: 6.79 - Wing area, m²: 217.72
Weight VVA-14
— Aircraft empty weight: 35,356 kg - Maximum weight: 52,000 kg
Engine VVA-14
- Number of engines: 12 lifting engines (only on VVA-14) and 2 propulsion engines (on the 14M1P ekranolet) - Lifting engine: turbofan RD-36-35PR - Lifting engine thrust: 43 kN (4400 kgf) - Maintaining engine: D-30M - Main engine thrust: 67 kN (6800 kgf)
Speed VVA-14
- Maximum speed, km/h: 760 - Cruising speed, km/h: 640 - Loitering speed, km/h: 360
Flight range of VVA-14
— 2450 km
Practical ceiling VVA-14
— 10,000 meters
Armament VVA-14
- 2 aircraft torpedoes, or 8 aircraft mines IGMD-500, or 16 aircraft bombs PLAB-250, with a maximum combat load of 4000 kg.
Performance characteristics of the S-10 aircraft
Crew, people………………………2Engine…………………PD x 1, “Gnome” 80Power, hp……………………….80Wingspan, m / wing area, m2 ……………………16.9/46.0 Aircraft length / aircraft height, m…………………8.0 / n/d Weight: maximum take-off / empty, kg……………… ……1011/567Full load, kg……………………434Maximum ground speed, km/h………………………99Practical ceiling, m………………………3420Maximum range, km…… ………………500
The collapse of last hopes
On November 21, 1933, another test flight took place - it was to be the last.
The pilot decided to give the engines a strong load - this caused vibration in the tail booms. On one of them, a spar burst, which jammed the elevator. Apparently, this coincided with an attempt to descend after the sound of a breaking beam, and the giant, deprived of altitude control, went down. The K-7 did not fly to the ground for long, the impact ignited the fuel, and the plane quickly caught fire. Of the 20 people, only five were saved.
This discouraged Kalinin, but did not stop him. He hastily rushed to improve the project - and they even began making a second plane in Kharkov. But the attitude towards K-7 was no longer the same - it was soon aggravated by the disaster of Maxim Gorky in May 1935.
Design
A gigantic elliptical wing with a thick profile with a span of 53 m and an area of 452 m², from which came two tail booms of a triangular cross-section, carrying the tail horizontal and vertical empennage with a mechanism for turning. The wing had a straightened center section 6 m wide, 10.6 m long and 2.33 m high, where rooms for people and cargo were located. Semi-elliptical consoles were attached to the center section, which housed 14 fuel tanks. The center section was sheathed with duralumin, the consoles with canvas. Three spars were installed in the wing. The flanges of the middle spar were made of two parallel pipes located and fastened with a welded gusset. The wing ribs are steel, made of pipes with struts and braces. From the rear wing spar to the tail there were triangular truss-type beams with ducts that protected the plane from accidentally touching the ground. For the frame, chrome-molybdenum pipes were used, which were used for the first time in the USSR.
The cabin protruded forward along the axis of the aircraft and housed two pilots, a navigator, a radio operator and a chief mechanic. The remaining seven crew members were in other compartments of the aircraft and were talking to each other on an internal telephone.
Seven AM-34 engines with 750 hp each. With. (one of them, with a pusher propeller, is located at the rear of the fuselage). In-flight mechanics had access to the engines directly from the wing.
The chassis consisted of two widely spaced bogies of a truss structure with oil-air shock absorption of the wheels, which was first used in Soviet practice for heavy vehicles. Also, for the first time, “Good-Year” balloon wheels were used on aircraft of this class. The chassis bogies had three wheels and were equipped with fairings - “pants” made of sheet metal, and the left one housed the entrance door and a staircase to the wing. This design of the landing gear allowed the aircraft to have a horizontal parking position.
The tail is biplane, the fins are connected by a zener diode. The K-7 rudders and ailerons are equipped with servo rudders mounted on light beams. Servo rudders on the horizontal tail are mounted close to the rudders. To save the pilot from the extreme loads at the helm of an aircraft weighing 40 tons, Kalinin came up with electric power steering, which did not yet exist at that time.
Strange numbering of Yak aircraft
Anyone who tries to study the history of Yak aircraft will immediately stumble upon an incomprehensible numbering of various models. They are not in order, but in the following sequence:
- Naturally, the Yak-1 comes first;
- Then comes the Yak-7 plane;
- Next comes the Yak-9;
- And the Yak-3 model line ends.
This numbering is explained quite simply, all these 4 aircraft are varieties of two aircraft - the Yak-1 and Yak-3. The Yak-7 and Yak-9 aircraft were created on the basis of the same model, only later their development went in different directions.
