Light Night Bomber Polikarpov

There is usually an idea that the U-2VS appeared during the Great Patriotic War. In fact, as early as December 7, 1931, Deputy Chairman of the Revolutionary Military Council, Deputy People's Commissar for Military and Naval Affairs Ya. B. Gamarnik reported that it was proposed that the U-2 M-11 aircraft be introduced into service with the Red Army as an escort aircraft. It was supposed to accompany the infantry, cavalry and motorized units on the march with the aim of reconnaissance of the terrain lying ahead. At the same time, it was calculated that the escort aircraft could be transported in combat formations of marching columns in tow or in the back of a lorry.

The Chief of the Red Army Air Force Ya. I. Alksnis agreed with this proposal, but noted that it was necessary to install weapons on the U-2. This version of the U-2 - U-2VS - was created at the Polikarpov Design Bureau in 1932, and in 1933 it successfully passed state tests and was put into service. In June-July 1933, the U-2VS underwent military trials at the Borisoglebsk school. Based on their results, it was concluded that it is advisable to use the aircraft as a combat training aircraft. The U-2VS was produced in a relatively large series in 1935-36. 468 were built. Aircraft acceptance was carried out in accordance with the requirements set forth in the aviation standard 93 STU, developed by the SUAI United Bureau of Standardization.

The standard determined the basic geometric dimensions of the U-2 M-11 - U-2VS aircraft.

Weight characteristics: flight weight - 1064.00 kg.

empty aircraft weight - 726.22 kg,

full load weight - 237.76 kg.

Small arms provided for the use of forward fire in the form of a synchronous wing-mounted PV-1 machine gun with a stock of 200 rounds (belt feed) and rear fire - a turret TUR-7 under the Degtyarev DT machine gun with a stock of 252 cartridges, located in four removable magazines.

The bomber armament provided for the suspension of six 8 kg bombs. The bomb release control is mechanical. Bombing sight - AP-2.

On the pilot's dashboard there were: a speed indicator, an altimeter, direction and slide indicators, navigation devices - a compass and a clock, engine control devices - a tachometer, an oil pressure gauge, an oil thermometer. To improve the view of the rear hemisphere, a mirror was installed, an intercom for communication between the crew members was provided.

Instrumentation of the observer's cabin included: speed indicator, altimeter, pressure gauge and oil thermometer, compass.

To ensure landing at night, two landing torches were installed under the lower wing.

If at first it was planned to use the U-2VS mainly as a light combat aircraft, then later it mainly began to be used as a training aircraft for teaching the use of small arms and bomber weapons. In particular, this was mentioned in the report on the special tests of the U-2VS at the beginning of 1938. An FT-1 photographic installation was additionally installed on the plane for training in conducting photographic reconnaissance.

With the beginning of the big war, the standard U-2 variants available at hand began to be converted into light night bombers. The revision was carried out both at the Polikarpov Design Bureau, and at serial plants and in the field army by the engineering and technical staff of combat units and aircraft repair shops. As a result, the design of the combat U-2 had a large number of different options. The formation of the established appearance of the U-2VS production aircraft during the war period proceeded gradually and ended approximately by the middle of 1944.

In the period from 4 to 8 September 1941, in stationary aircraft repair shops No. 163 of the Air Force of the Kalinin Front in Torzhok, 12 U-2 aircraft were equipped with special cassettes made of sheet iron for dumping incendiary ampoules AZ-2 (tin ball with a capacity of 1 liter ). The ampoules contained a "KS" mixture that was self-igniting in air.

Each cassette consisted of five pipes rigidly connected to each other. Each tube contained 10 ampoules. Two of these cassettes were attached under the lower wing consoles. Dump control - mechanical (cable from the simplest mechanical bomb release). When dropped, all ten pipes opened at the same time. In this case, the outermost ampoules fell out simultaneously, and the rest sequentially fell out in series.

September 10, 42nd U-2 equipped in a similar way began to be used against enemy manpower and combat equipment. The action was overwhelming. One hit of an ampoule in any German tank or vehicle was enough to destroy them.

Unfortunately, the effective ignition of the "KS" mixture was highly dependent on meteorological conditions (mainly on the ambient temperature) and on the presence of flammable materials in the target area. In conditions favorable for the use of the "KS" mixture, the results of the U-2 strikes against tanks and other targets were very high.

Cassettes could also be loaded with small fragmentation bombs.

The engineering staff of the 31st garden (commander - S.A. Rudenko) adapted the cluster of small bombs KM B from the Il-2 aircraft for suspension on the U-2, which made it possible to raise the total load (with fragmentation bombs weighing from 1 to 25 kg, as well as incendiary ampoules АЖ-2) up to 300 kg. This significantly increased the combat effectiveness of the U-2 when operating against enemy manpower, and when using incendiary ampoules AZH-2 - and against tanks of all types. In addition, the navigator's cockpit was equipped with places for placing small aerial bombs and grenades for dropping them manually.

Since the beginning of 1942, the combat versions of the U-2 began to be produced at serial aircraft factories. At first, the U-2VS aircraft had only 4 nodes for the suspension of bombs weighing up to 32 kg (Der-5 bomb racks), which was clearly not enough for the effective combat use of the aircraft. Therefore, improvements were made in the combat units. Combat U-2VS by the forces of the technical staff of the aviation workshop and aviation units began to be equipped with six beam holders of the Der-6 type, which made it possible to suspend high-explosive bombs of the FAB-50 and FAB-100 types. On some U-2, bomb racks were installed under the Der-21 lock, which extended the suspension, except for bombs of caliber up to 100 kg inclusive, KD-1-6 cassettes. Each cassette could hang six bombs with a caliber of 8 to 25 kg. Some U-2s were equipped with eight RO-82 or RO-132 rocket guns - 4 guns for each plane of the lower wing. When it became necessary to destroy the long-term defensive fortifications of the Germans (bunkers, bunkers, armored caps, etc.), the craftsmen of the front-line aviation workshops, having strengthened the lower part of the aircraft fuselage, carried one high-explosive bombs of 250 kg caliber on it. Unique was the suspension under the fuselage of a U-2 bomb of 500 kg and the installation of two machine guns on the lower wing produced by engineer K. A. Moskatov.

Air bombs were dropped and PCs were launched by pressing the button of the simplest electric bomb release device.

In order to standardize and unify the U-2 weapons, the Chief Engineer of the Red Army Air Force A. I. Repin in the spring of 1942 legalized the bomb armament of the U-2 aircraft in the form of six Der-7 bomb racks with a maximum bomb load of up to 300 kg. However, the combat units continued to encounter a wide variety of U-2 weapons, made both by local craftsmen and at factories.

In June 1942, in the NIP AV of the Red Army Air Force, field tests were carried out for the U-2VS manufactured by plant number 387 (the report was approved on June 30, 42), which, in addition to the standard six external bomb racks, was equipped with two internal cylindrical cassettes of small bombs ... The cassettes were installed inside the fuselage behind the navigator's cabin and allowed loading with small bombs of 2.5 to 15 kg caliber. Both cassettes contained: either 68 fragmentation bombs of the AO-2.5sch or AO-2.5-2 type, or 48 incendiary bombs of the ZAB-2.5 type, or 16 AO-8 fragmentation bombs, or 10 AO-10, or 8 bombs of the AO-15 type.

The small arms of the U-2VS plant of the 387th plant consisted of a ShKAS course machine gun (300 rounds) mounted on the right plane of the lower wing, and one YES machine gun of 7.62 mm caliber (ammunition 4 stores 64 rounds each) on a pivot mount near navigator.

In the conclusions of the report, it was noted that the cassettes of plant # 387 expand the range and effectiveness of the combat use of the U-2VS. It was recommended to install 2 wing-mounted ShKAS machine guns, and replace the YES machine gun at the navigator with ShKAS.

In the period from May 25 to May 28, 1943, the anti-tank U-2VS, armed with underwing clusters of small bombs of two types: ABK-P-100, which contained 33 PTAB-2.5-1.5 bombs, was tested at the NIP AV Air Force , and BAS-1, designed for 20 such bombs. The U-2VS was tested with the following types of bomb armament: 4xABK-P-100 and 6xBAS-1.

Tests have shown that when the PTAB was dropped from a height of 200 m from level flight at a flight speed of 110-120 km / h using ABK-P-100 cassettes, the total area of ​​ruptures occupied a 12x124 m band, and when using BAS-1 cassettes - 13x192 m.

Calculations show that a pilot with good flight and shooting training in daytime conditions could well provide in one run the probability of hitting a single tank using ABK-P-100 cassettes about 0.5 and no more than 0.4 in the case of using BAS cassettes -one.

Such high results are explained, first of all, by the fact that the area occupied by one tank was about 20-22 m & # 178; and the hit of at least one PTAB into the tank was quite enough to disable it, in most cases irrevocably.

Based on the results of field tests of the anti-tank U-2VS, military pilots concluded that it was possible to use such an aircraft at the front for its intended purpose (that is, against tanks) only on a moonlit night or when the target was illuminated with luminous bombs. Daytime use of the U-2 against tanks was ruled out due to the strong saturation of the front edge with enemy air defense weapons and fighters.

From the very beginning of the conversion of the U-2 into combat vehicles, the flight and technical personnel of the Air Force faced the problem of ensuring effective aiming when bombing from the U-2. Bomb sights for the U-2, providing the required bombing accuracy during the day and, most importantly, at night, were not in service with the Red Army Air Force. Therefore, as a bomb sight on the U-2, various devices were used, mostly of a homemade nature. On some aircraft on the starboard side, mechanical sighting devices NV-5 were installed. However, due to the low flight speeds of the U-2, the aiming angles were small and were just in the "blind zone" of the view of the lower front hemisphere (because of the lower wing). So aiming bombardment was very difficult. Only after a slot was made in the lower wing of the aircraft, the aiming conditions during bombing returned to normal.

Despite the solution found, the need for a special bomb sight for the U-2 aircraft has not disappeared. Already by May 1942, at plant No. 387 of the NKAP, the simplest airborne sight was developed and tested, which was installed on all U-2 aircraft produced by this aircraft plant.

However, this sight also did not fully meet the requirements of the U-2 combat use, since it was designed for bombing only from horizontal flight in the wind plane at a flight altitude of no more than 1000 m. Therefore, in June 1942, the Main Directorate of the Air Force gave assignment to plant No. 217 to develop an improved sight for the U-2 and R-5 aircraft. The new sight was supposed to provide aiming during bombing, both from horizontal flight and from planning (up to 30) during the day and, mainly, at night and had the simplest builder of aiming angles and a scale of sighting and drift angles. The sight created in accordance with this task in the period from September 28 to October 2, 1942 passed military tests in the 989th Nbap and showed good results. However, the airborne sighting device of plant No. 387 was still adopted for service as it showed the best results in comparative field tests. The sight of plant No. 217 after tests carried out at the Research Institute of AV of the Red Army Air Force in May 1943 was approved by the Chief Engineer of the Red Army Air Force, General A.I. Repin, for installation on the U-2 only a year later, in June 1944, after the completion of the finalization works, with the assignment of the code NP-U-2 (NKPB-8).

NKPB-8 provided bombardment from level flight at speeds of 30-200 km / h in the range of aiming angles from + 85 ° to 0 °. In this case, the aiming angle was determined for heights from 50 to 500 m.

The small arms of the combat U-2 usually consisted of an upper defensive pivot installation VU-U-2 for a 7.62 mm ShKAS rapid-fire machine gun, equipped with the simplest KPT-5 mechanical sight with an MF-5 weather vane. The aforementioned versions of the U-2VS with a YES defensive machine gun were produced. Starting from the middle of 1944, due to the fact that the pivot defensive installation on the U-2 under the ShKAS machine gun had small firing angles, it was replaced by the DT machine gun. The standard ammunition for the ShKAS consisted of a cartridge belt with a capacity of 500 rounds, and for the DT machine gun - from 5 stores of 63 rounds in each.

In addition to the defensive machine gun, on the part of the U-2 combat units, a fixed ShKAS or PV-1 machine gun was also installed on the lower left or right wing for forward firing (ammunition from 500 to 800 rounds, depending on the height of the cartridge box). The installation of the machine gun on the right or left plane of the aircraft depended on what kind of receiver was on the machine gun. At the same time, the right and left installations were exactly the same, with the exception of the upper part of the rear mount of the carriage. The reload handle was mounted on the corresponding board.

The machine gun stack was controlled by means of a special thrust and trigger mounted on the aircraft control handle. Moreover, all the devices for the descent that were available on the machine guns were removed.

A cartridge box (usually made of plywood) was installed in the cockpit behind his seat. On the U-2 with double control, a cutout was made in the middle of the box for the passage of manual control rods into the navigator's cockpit; on other modifications, the cutout was not made. In the upper corner of the box there was a roller (wooden, metal or plastic), which facilitated the movement of the cartridge strip. The cartridge box was attached to the cockpit floor in special slots with belts.

From the cartridge box, the tape entered the receiver of the cartridge duct installed in the fuselage side, then, leaving the fuselage, it passed through a special chute made of plywood, pasted over with canvas. Through the chute, the tape fell into the cartridge receiver of the machine gun.

The entire ammunition supply system - the cartridge box, the cartridge channel and the receiver on the machine gun - was located in one line, which ensured a reliable supply of cartridges.

The installation of only one course machine gun on the combat U-2 was mainly due to weight considerations. In some cases, stationary machine guns for forward firing were installed on each plane of the U-2. The equipment of the U-2 with one course machine gun practically did not change its flight data, except that it reduced the flight speed by 4-5 km / h.

For aiming when firing from a course machine gun or rocket projectiles, both the simplest ring and optical (type OP-1) sights were used. The ring sight was installed on the platform in front of the visor of the first cockpit on the right, the column with the front sight - in front of the visor on a wooden boss, and the column with rings - on the platform of the front tape of the gas tank.

The installation of the optical sight was practically no different from the installation of the mechanical one.

Zeroing of machine guns was carried out at a distance of 200 m.

I must say that in the process of forming its standard appearance, the U-2VS was periodically tested at the Air Force Research Institute and, taking into account their results, was refined. For example. U-2VS with M-11D standard of the 1st half of 1944, produced by plant '# 387 in 1943 (# 4504), in December of the same year did not pass state tests. After that, it was taken to plant number 51 for revision. The vehicle was equipped with a new rifle mount for a DT machine gun with extended firing angles, which made it possible to fire not only at air, but also at ground targets, and a GS-350 generator was installed (as on the U-2NAK). noise suppressor ShPG-2, a new sight for bombing at night NP-U-2 (NKPB-8), modified the power supply system of gyro devices, etc. After that, the aircraft was re-subjected to state tests, which it successfully passed. The U-2VS modified in this way was adopted as a standard for the 1944 series.

The changes in the serial version of the U-2VS relative to the base aircraft, established by mid-1944, were mainly reduced to the following:

- under the lower wing were installed b bomb racks of the Der-7 type with cable-controlled dropping, providing a suspension of up to 300 kg of bombs:

- a bomber sight (night) NKPB-8 was installed in the front cockpit:

- to improve downward visibility and aiming, a cutout was made in the right wing next to the fuselage:

- a pivot machine gun mount was installed behind the rear cockpit for a 7.62-mm ShKAS machine gun with belt (250-400 rounds of ammunition) or magazine feed, or under a 7.62-mm DT machine gun with five discs (63 rounds each);

- in addition to the compass, variometer, altimeter and direction indicator that were on the U-2, an artificial horizon was installed powered by an additional large Venturi tube located on the left side of the aircraft in front of the front cockpit;

- ANOs were installed and a landing light under the left wing (on the base U-2 it was optional);

- the ShPG-2 noise suppressor was installed;

- the GS-350 generator was installed;

- on the 1944 standard, an easily removable control handle was installed in the second cockpit and an elevator trimmer.

The flight weight of the serial U-2VS compared to the base U-2 was 388 kg more, which naturally led to a decrease in flight data. With a full bomb load, the U-2VS with the M-11D engine had maximum speeds: near the ground - 134 km / h, at an altitude of 1000 m - 100 km / h, the practical ceiling under the same conditions dropped to 1550 m.Without bombs, flight data is not were very different from those of the base aircraft.

Photo	Description
	Drawing U-2VS (LNB)
	U-2VS I-11D with a ShKAS machine gun on a pivot mount.

Bibliography

• The history of designs of planes in USSR 1938-1950 /Vadim Shavrov/
• World of Aviation №1 2000. / Vladimir Ivanov, Andrey Korshunov, Vladimir Perov, Oleg Rastrenin /