Close Support Aircraft Polikarpovv

In 1936, the design bureau of N.N. Polikarpova began work on a multi-purpose aircraft, which became the ancestor of a small family of experimental machines. The first prototype, the air tank destroyer VIT-1, was built in the summer of 1937.

VIT-1 (SVB, MPI-1) is a three-seat multipurpose aircraft, air tank destroyer, air combat aircraft, dive bomber, reconnaissance aircraft, multi-seat cannon fighter, short-range high-speed bomber with 2M-103 engines. The aircraft is all-metal, designed according to the strength standards of fighters for a 13-fold overload. Scheme - low-wing with vertical tail, gently turning into an oval fuselage. The cockpit of the pilot and rear gunner is above the wing spars. The fuselage is semi-monocoque, its frame is formed by closed profiles and riveted frames. The spars of the wing are welded, trussed, tubular of KhMA steel, ribs are shaped of duralumin profiles and braces-pipes. The plumage is all-duralumin, rudders with aerodynamic axial compensation and trim tabs. The landing gear wheels retracted back into the engine nacelles, the tail wheel did not retract.

The layout of the water radiators - special retractable baskets in which they were placed - was unusual for a twin-engine aircraft. Baskets were hung under the wing, on the outside of the engines, controlled automatically by a thermostat. Depending on the temperature, the water radiators were extended into the air stream, or almost completely retracted into the wing.

On the VIT-2, the baskets retractable in flight were abandoned and the water radiators were transferred to the wing roots, thus solving the problem of reducing the cross-sectional area of ​​the radiator. The oil temperature was controlled by changing the opening angle of the oil cooler flap. Such a scheme made it easy to implement automatic oil temperature control (ARTM).

Armament - two Shpitalny cannons (37 mm) forward, in the center section near the fuselage, one ShVAK-20 cannon in the nose of the fuselage (movable + - 10 ° to the sides) and one ShKAS machine gun on the rear turret, bombs 2 × 500 kg on the external sling and up to 600 kg in the fuselage. Seven variants of weapons were developed. Here an attempt was made to implement the idea of ​​destroying tanks from the air with powerful cannon fire and bombs. The first flight was in the summer of 1937. Speeds of more than 450 km/h and a flight range of 1000 km were achieved. It was decided to put more powerful engines on the plane and make some changes to the design.

The main drawback was the relatively large weight of the gun and the lack of tape feed.

The range flight test program was not fully completed, due to the fact that the design of the VIT-1 aircraft was unfinished and, according to the test pilot of the range, flights on it were dangerous.

When firing in flight from both guns, such a feature as a "stopping sensation in forward motion" was revealed.

When firing from one cannon, the aircraft turned towards the firing cannon. Naturally, this should have affected the accuracy of shooting with a long burst. The fact is that the recoil of the guns was commensurate with the thrust of the VMG.

I must say that all the developers of anti-tank aircraft, which were created subsequently, had to face this problem to one degree or another.

The performance characteristics of Polikarpov's twin-engine aircraft are given according to factory test data:

Such positive qualities of the VIT-1 aircraft were noted as a stable dive at angles up to 35 ° from an altitude of 2500-3660 m. The climb was steady. The plane landed normally, but was strict in piloting. The run is small.

All flights on the VIT-1 were carried out with the landing gear extended due to the failure of the emergency winch for retracting the landing gear, and therefore the above-mentioned shortcomings of the machine manifested themselves to a greater extent

On takeoff, the aircraft was unstable, tended to turn to the right, but the latter was parried quite well by the engines

The takeoff was relatively long. The aircraft was somewhat rough in control. In addition, the aircraft was characterized by slight tail vibrations, as well as long-period oscillations of the entire aircraft, shocks at first every 40 seconds, and when firing from cannons even after 5-8 sec.

All these were "childhood illnesses" of almost any new aircraft of that time.

Bibliography

• "The history of designs of planes in USSR 1938-1950" /Vadim Shavrov/
• "Planes of Stalin falcons" /Konstantin Kosminkov and Dmitriy Grinyuk/
• "The Soviet planes" /Alexander Yakovlev/