The first reference to a Polikarpov twin-engine model capable of executing bomber actions comes from the first half of 1936. This sketch would originally receive the name VT or Vozduzhni Tank (Flying Tank), which would later become MPI (Mnogomiestni Puchechni Isterbitiel or Multiseat Gunship Fighter) and SVB (Samoliot Vozduzhnovo Buoy or Air Combat Plane).
At the beginning of February, at one of the government meetings, Polikarpov learned that the OKB-2 collective, under the direction of Shpitalni, had developed a powerful 37 mm automatic cannon with a high muzzle velocity. Unfortunately, this weapon had not been tested due to the absence of an aircraft capable of using it.
In turn, Polikarpov reported that his group had developed a development of the TsKB-44 model with excellent technical specifications that could be ideally used as an aerial gunship intended to combat armored formations.
In this way, the idea of creating the new model according to Shpitalni himself constituted “…the synthesis of the achievements of the OKB-2 in automatic weapons, Polikarpov ‘s research in aviation aerodynamics and Polikarpov’s group of colleagues in the direction of automatic weapons”.
Shortly after this meeting, at Factory No.39 Polikarpov would develop three versions of the new aircraft that Polikarpov began to call VIT (Vozduzhni Isterbitiel Tankov or Aerial Tank Fighter (Russian: Поликарпов ВИТ-1)). Unfortunately, Factory No.39 soon began producing the DB-3 bomber and Polikarpov with his group was transferred to Factory No.21. This fact, together with the non-inclusion of these works in the experimental construction plan, led to the closure of work on the VIT as of July 5, 1936.
Faced with this situation, Shpitalni, at the beginning of 1936, sent a document to the secretary of the STO before the SNK USSR, GD Basilievich, in which he requested authorization to build the new VIT model in Factory No.22. This document was accompanied by M-100- powered and M-34FRN- powered VIT variants. The conceptual ideas were signed by Locev (drawings), Sigayev (brigade head) and Polikarpov (constructor). The designs were also signed by Shpitalni.
This model was presented as an all-metal monoplane with a low wing and a twin-engine power plant, with excellent aerodynamic shapes. On both sides of the fuselage were located the two 37 mm cannons with a total reserve of 100 projectiles. The magazines with 5 projectiles each were located in an elevator powered by an electrical system.
In the bow area, in front of the pilot, there was a fixed 20 mm ShVAK cannon with 100 – 200 projectiles and a belt feed. A ShKAS machine gun with 540 rounds was located in the gunner’s cabin to defend the rear hemisphere. This machine gun was installed on a mobile mount that guaranteed firing to the right or left.
The gunner’s cockpit had a glass cover that could be raised above the fuselage, which guaranteed a shooting angle of 65º upwards, 15º downwards and 45º horizontally to the sides.
The model was capable of carrying 200 kg (2 FAB-100 or 20 AO-10 bombs). In case of elimination of the 37 mm guns, the bomb load reached 1000 kg (2 FAB-500 or 4 FAB-250).
In the descriptive memory it was explained:
“ – To judge the power of this aircraft it is enough to say, for example, that only the power of the weapons installed in the nose exceeds by more than 10 times the firepower of the most powerful fighter in service with our VVS.
… To date, neither in the USSR nor in foreign armies there is a combat vehicle designed for active action against large groups of tanks. “This task is solved by our aerial tank fighter (VIT).”
The reaction to this Shpitalni document was instantaneous. State funding was provided and a resolution was prepared to include the model in the experimental construction plan.
On the other hand, the basis for production in Factory No.22 was not delivered. In its place for the development of the VIT at the end of August 1936 Factory No.84 in Khimki was made available. This factory, formerly part of the civil aviation scheme, had outdated equipment and lacked qualified personnel. Under these conditions, construction work on Polikarpov ‘s two-seat anti-tank aircraft began.
Unfortunately, the idea of this type of aircraft did not find the necessary support within military circles at that time.
It is noteworthy that from its conception the VIT was conceived as a technological demonstrator designed to study construction and technological methods. On its basis, a family of seven aircraft models with different tasks would be developed, capable of sharing a large percentage of common elements. This family included:
- – Fast medium bomber with capacity for 800 kg of bombs inside the fuselage;
- – Dive bomber with 900 kg of bombs on external supports;
- – Long-range reconnaissance aircraft with a powerful armament of 4 20 mm cannons;
- – Ground attack aircraft armed with six cannons, two machine guns and 300 kg of bombs;
- – Fighter for large ground targets with two K-37 guns and two ShVAK;
- – Escort aircraft for heavy bombers;
- – Naval aircraft with floats with torpedo boat capacity.
By the end of 1936, the plans for the SVB version (Skorostnoi Visotni Bombardirovchik or High Altitude Fast Bomber) were practically finished. The word “visotni” represented a trend of the time, but in reality the model lacked a sealed cabin and turbochargers for high-altitude operations. In practice it was simply a high-speed medium bomber.
Based on this model, the plans for the model armed with VIT-1 2M-103 cannons would be developed. It is noteworthy that the “VIT” stamp appears on most of the SVB plans, but in that same period new plans were designed for the new model.
As weapons for destroying tanks, the use of two 37 mm ShFK-37 cannons of the OKB-15 NKV (as the Shpitalni construction bureau was now called) located in the wing roots was maintained. The name of these guns comes from the acronym Shpitalnovo Fyuselyazhno-krylevaya Pushka or Shpitalni Wing and Fuselage Gun.
Polikarpov presented the design of the aircraft in two variants: multiseat gunfighter or MPI and anti-tank aircraft or VIT. On January 31, 1937 the evaluation commission reviewed the model of the MPI-1 version with two M-103 engines and on July 25, by government decision, the experimental construction plan was approved for the current year in which it was considered. the construction of two examples of the multiseat gunfighter with two M-103 960 hp engines with a maximum flight speed of 500 – 550 km at an altitude of 5000 meters.
The VIT-1 was designed as a low-wing two-seat monoplane with beautiful aerodynamic shapes and smooth skin on a thin fuselage. The landing gear was of a retractable type and a monoplane tail with a single empennage.
The fuselage, built entirely of metal, had an oval cross section. The construction was semi-monocoque.
The central section constituted a combination of closed duralumin profiles and skeletal structures of welded steel tubes.
The wing, with a double spar, had a trapezoidal shape in the plane with rounded ends and ended at the junction with the fuselage, presenting the characteristic extensions of many Polikarpov models. The wing profile used was the Clark Y with a relative thickness of 14% at the root and 6.35% at the ends.
The wing spars were constructed of welded chrome-molybdenum steel tubes. The ribs were built with duralumin profiles, except for the engine area, where they were replaced by welded steel tubes. The ailerons featured aerodynamic and weight compensation.
The tail section was all metal. The stabilizer was fixed to the fuselage structure. The empennage was constructed of duralumin.
The entire cell was calculated according to resistance standards for fighters, supporting overloads of up to 13g.
The landing gear was of the conventional tailwheel type. The landers with the wheels were retracted backwards, inserting into the lower area of the power nacelles. The retraction system was pneumatic. The main wheels had brakes. The tail wheel was not retractable.
The 860 hp M-103 engines were selected as the power plant. The composition of the cooling radiators was somewhat unusual for a twin-engine aircraft. The radiators were located in retractable structures equipped with tunnels for the entry of air. These structures were located on the wing extrados on the outer sides of the power nacelles and depending on the flight regime, they extended or were practically hidden in the wing. Control was carried out with the help of a thermostat.
The VIT-1’s armament was the most powerful installed on any Soviet fighter up to that time and consisted of two 37 mm ShFK-37 cannons located in the wing roots.
The defensive armament consisted of a TUR-10 turret with a ShKAS machine gun on the rear fuselage, which would later be replaced by one of the SUDB-3 type, similar to that used in the Ilyushin DB-3 bomber, which was produced in the Factory No. 32.
The normal bomb capacity reached 600 kg on internal supports and up to 1000 kg of bombs (two FAB-500) could be installed outside.
The crew was made up of two people: pilot and gunner. Both crew members were located in a cabin on the wing spars. No shielding was provided.
On October 14, 1937, the assembly of the first flying example of the MPI-1 gunfighter was completed. The prototype was built in the Moscow factory No.84, where Polikarpov had been transferred with his team in the second half of 1936. Some time later this would begin to be called VIT-1 (Vozduzhni Isterbitiel Tankov or Aerial Tank Fighter No.1). This would be the definitive name used from now on to refer to the plane.
The first flight with Valeri Pavlovich Chkalov at the controls took place on October 31. On November 16, during the third test flight, the navigator’s cockpit would be occupied by designer Nikolai Polikarpov.
The VIT managed to reach a fairly high maximum speed for its time, of 494 km/h at 3000 meters altitude. The range recorded at 90% of maximum speed was about 1000 km.
The factory tests, carried out until February 1938, would never be completed due to the impossibility of achieving the specified performance. The plane did not manage to exceed 500 km/h and some problems related to longitudinal and transverse stability were evident.
Despite this, the model proved to have development prospects and only the lack of support from the GUAP prevented its presentation to the state acceptance tests. The VIT-1 incorporated powerful weapons for the time: two 37 mm ShFK-37 (K-37) cannons in the wings, so the VVS decided to receive the model to develop range tests, basically aimed at fine-tuning the cannons.
In these exercises, held at the weapons range near Noginski between July 13, 1938 and July 31, 1939, the guns received an excellent rating and the pilots appreciated the excellent diving qualities of the model. GF Baidukov and MM Gromov participated as pilots for the NII VVS in these tests. Unfortunately, the plane was not yet “polished” and had problems characteristic of any plane under development. On the other hand, firing both cannons in unison practically stopped the plane in flight, while firing just one of them forced the plane to turn to that side, slightly diverting the shot from the desired trajectory.
Testing was stopped after NIP AV VVS test pilot Major Anshitkov refused to continue flying the VIT-1 prototype. This was mainly due to the fact that he was a weapons test pilot and not an airplane test pilot, so flights in an unfinished airplane became especially difficult for him.
In the summer of 1937, in parallel with the military version VIT-1, the project of a civil model was developed, designed to participate in a Paris – New York competition, flying over the Atlantic. This race was scheduled for 1938, but finally it did not take place and the project was abandoned.
- A total of five VIT-2 were built.
VIT-1
Powerplant: 2 x 960 hp М-103
Wingspan: 16.50 m
Wing area: 40.40 m²
Length: 12.70 m
Height: 3.40 m
Empty weight: 4013 kg
Normal takeoff weight: 6453 kg
Wing loading: 159 kg/m²
Power load: 3.3 kg/hp
Maximum speed at sea level: 450 km/h
Cruising speed: 417 km/h
Practical range: 1000 km
Maximum climbing speed: 595 m/min
Practical ceiling: 8000 m
Time to 5000 m: 8.4 min
Takeoff run: 390 m
Landing run: 460 m
Accommodation: 2
Armament: A ShVAK cannon in nose / two 37 mm cannons in wings / 1 x ShKAS machine gun in turret.
Bombload: 600 kg internal / 1000 kg external.
All Aero 