The U-2 is rightfully considered one of the most famous Russian aircraft. This multipurpose biplane, created in 1927, has become one of the most massive aircraft in the world. Serial production of the biplane continued until 1953, during this time more than 33 thousand aircraft of this type were produced. In peacetime, it was used as a training aircraft, becoming a real flying desk for thousands and thousands of Soviet pilots. Also, the aircraft was actively used in agriculture for the treatment of crops with fertilizers and pesticides and as a liaison aircraft. During the Great Patriotic War, the car was retrained into a light night bomber, successfully coping with this role.
In the mid-1920s, the young Soviet aviation faced a very urgent problem at that time - the creation of a modern, but easy-to-fly aircraft that could be used to refine the skills of numerous flight school students, which were opening in large numbers throughout the USSR. … In 1923, a young but already talented Soviet designer Nikolai Nikolaevich Polikarpov took up the design of the training machine. In October 1924, representatives of the Air Force finally formulated the general tactical and technical requirements for the aircraft for the initial training of pilots. They especially emphasized the desire to have a biplane with a low landing speed as such an aircraft. The requirements stipulated that the maximum flight speed should not exceed 120 km / h, and the landing speed - 60 km / h. The plane was supposed to be only a biplane scheme and built exclusively from materials available in the Soviet Union.
Under these requirements, Polikarpov created his plane. The delay was largely due to the waiting for the Soviet engine for the new car. By the middle of 1926, two low-power aircraft engines were designed in the USSR - M-11 (plant No. 4) and M-12 (NAMI). It was for them that the first model of the U-2 (the second training) was designed, the name Po-2 will receive the plane much later - only in 1944 after the death of the designer in tribute to his memory.
After testing new aircraft engines on snowmobiles, the designers opted for the M-11 engine, developed by A. D. Shvetsov. This air-cooled engine developed a maximum power of 125 hp. What makes it unique is the fact that the M-11 became the first aircraft engine of its own Soviet design, which went into mass production. For its time, it no longer possessed any outstanding characteristics, but it was technologically advanced in production, rather reliable, and also not very capricious to the oils and fuels used. A truly workers 'and peasants' engine for the workers 'and peasants' army. It was also important that the motor could be produced with minimal use of foreign materials and components. In the future, the engine was repeatedly modernized, boosted - up to 180 hp, and was also refined for production in wartime conditions.
It was with this engine that in mid-September 1927 Polikarpov presented a prototype of his aircraft to the Air Force Research Institute for comprehensive tests. The prototype with the M-11 engine was ready in June of the same year, but until September, the engine was being fine-tuned, in which Polikarpov himself took part. The tests of the aircraft showed that it possesses good flight characteristics, including spinning characteristics, and in general meets the previously voiced requirements of the Air Force, with the exception of the rate of climb. Having worked on improving the aerodynamics of the car and personally changing the design features of the wing, making it lighter and more streamlined, Polikarpov presented a second sample of the aircraft for testing.
The tests of the updated aircraft, which were conducted by test pilot Mikhail Gromov since January 1928, showed the excellent flight qualities of the aircraft. Already on March 29, 1928, a decree was issued on the construction of an experimental series of U-2 aircraft, which consisted of 6 aircraft. All of them were intended for trial operation in flight schools. And in May 1929, the serial production of aircraft began. Earlier in the fall of 1928, the international debut of the U-2 took place. This model was demonstrated at the 3rd International Aviation Exhibition in Berlin.
According to the scheme, the U-2 trainer was a single-engine two-seat biplane of a bracing structure, equipped with an M-11 air-cooled engine, developing a maximum power of 125 hp. The U-2 designed by Polikarpov, which entered service with the Red Army Air Force in 1930, was widely used as a liaison aircraft and reconnaissance aircraft. Back in 1932, a special combat training modification of the aircraft was developed, which received the designation U-2VS. This model was used to train pilots in the basics of bombing. The aircraft could carry 6 eight-kilogram bombs on bomb racks, it was difficult to call it a combat load, but it was this modification of the aircraft that proved to skeptics that a training aircraft could, if necessary, be suitable for war. A shooting point with a PV-1 machine gun was located in the rear cockpit of the U-2VS aircraft. It was this modification that for a long time remained the main communications aircraft of the Soviet Air Force and was widely used by the command staff. More than 9 thousand U-2 aircraft were produced in this modification.
But the main purpose of the aircraft has always been pilot training. For this, the U-2 had a number of undeniable advantages. Firstly, the aircraft was extremely simple and cheap to operate, it could be easily repaired, including in the field, which made its release very profitable for the Soviet Union, in which simplicity and low cost of technology were among the main criteria. Secondly, the biplane was very easy to fly, even an inexperienced pilot could fly freely on it, the plane forgave the pilot numerous mistakes (ideal for students and beginners) that would lead to an inevitable accident on another aircraft. For example, it was almost impossible for an airplane to go into a spin. In the event that the pilot let go of the rudders, the U-2 began to glide at a descent speed of 1 m / s and, if there was a flat surface under it, he could sit on it on his own. Thirdly, the U-2 could take off and land literally from any patch of flat surface, during the war years this made it indispensable for communication with numerous partisan detachments.
During the Great Patriotic War, the combat potential of the “flying desk” was also revealed. At the very beginning of the war, due to the refinement of aircraft by aircraft mechanics, their bomb load increased to 100-150 kg, later, when aircraft factories were concerned with the combat qualities of the aircraft, the bomb load was increased to 250 kg. The fact that small low-speed biplanes, which, according to one of the designers "consisted of sticks and holes, the former for strength, the latter for lightness," suffered heavy losses, was true only for the first months of the war, when the Soviet command threw everything into battle. that was at hand, regardless of the loss of equipment. For this aircraft, daytime sorties to the front line were often fatal, since it could even be shot down by small arms fire from the ground.
But when the strengths and weaknesses of the U-2 were thoroughly studied, the situation changed. As a combat aircraft, it was used only as a light night bomber, which radically changed the position. It became almost impossible to shoot him down at night. The instrument panel was specially changed for the night use of the aircraft, and most importantly, flame arresters were installed. At night, the plane was not visible, and at an altitude of more than 700 meters it was still not heard from the ground. At the same time, with intense shooting and noise of equipment, even an altitude of 400 meters was considered safe in terms of detection. From such low altitudes, the accuracy of bombing in case of target visibility could be exceptional. During the Battle of Stalingrad, in some cases, U-2 night bombers were targeted up to a detached building.
Since 1942, the U-2 aircraft, which was renamed Po-2 in 1944 after the death of Polikarpov, was constantly modernized. Soviet design bureaus made various changes to the design, the sample was brought to mind, including during tests at the LII. After that, the approved copy became the standard for further serial production at aircraft factories. Armament also appeared on it - a YES machine gun on a pivot mount near the rear cockpit, there were variants of ShKAS on the wings or with PV-1 on the fuselage, which were considered as light attack aircraft. Devices were improved, new containers and locks were developed for transporting various ammunition and cargo, a radio station was added. The attitude towards work on a light night bomber was serious. Both the military and industry representatives approached the modernization work with the utmost responsibility. As a result, during the war years, the Soviet Air Force received an aircraft that could be called a stealth aircraft, this stealth machine fully corresponded to the American concept, which appeared only in the late 1970s. Paradoxically, stealth became the main weapon of this light bomber. At night it was not heard and was not visible, not only with the naked eye. The German radars that appeared during the war years also did not see the U-2. A small engine, as well as a fuselage made of plywood and percale (cotton fabric of increased strength), made it difficult for German wartime radars to detect the aircraft, for example, quite numerous Freya U-2 radars did not really notice.
Oddly enough, an additional and also very important protection of the fighter was its slow speed. The U-2 had a low flight speed (150 km / h - maximum, 130 km / h - cruising speed) and could fly at low altitudes, while faster aircraft risked crashing into trees, hills or terrain folds in such a situation. Luftwaffe pilots very quickly figured out that it was very difficult to shoot down a flying bookcase precisely because of two factors: 1) U-2 pilots could fly at the level of the treetops, where the plane was difficult to distinguish and difficult to attack; 2) the stall speed of the main German fighters Messerschmitt Bf 109 and Focke-Wulf Fw 190 was equal to the maximum flight speed of the U-2, which made it extremely difficult to keep the biplane in the fighter's sight for enough time for a successful attack. There is a known case when, already during the Korean War in 1953, while hunting for a Po-2 liaison aircraft, the American Lockheed F-94 Starfire jet crashed, trying to equalize the speed with the slow-moving one. Thanks to these qualities, during the war years, the aircraft was actively used by the Soviet Air Force as a liaison and reconnaissance vehicle.
At the same time, talking about the U-2 / Po-2 aircraft, many overlook a very important detail - it was the most flying Soviet aircraft of the Great Patriotic War. The pilots who crossed the line of 1000 sorties flew only on these machines; on other combat aircraft, rarely could anyone exceed the figure of 500 sorties. One of the reasons is that this aircraft forgave many piloting mistakes of young pilots, those very "take-off and landing" of wartime. On full-fledged combat aircraft, yesterday's graduates of flight schools were shot down often before they had time to turn into real pilots.
The sluggish biplane was also appreciated by the Germans themselves, who often referred to the plane in their memoirs, calling it a "sewing machine" or "coffee grinder" for the characteristic sound of the engine. They recalled him with an extremely unkind word, since the disturbing night raids greatly exhausted those who found themselves under the bombs of the Soviet U-2. Due to the low altitude and low speed, bombs could literally be dropped on the light of a flashlight, the headlights of a car, a fire or sparks flying out of a chimney. And the fear of making a fire in the harsh Russian winter is a weighty argument not to like this small aircraft of an archaic design.
The Soviet aircraft U-2 / Po-2 has become an excellent example of how you can effectively use all the available capabilities of technology, squeezing the maximum out of them. Soviet designers and pilots managed to turn into advantages even the obvious weaknesses of the aircraft, which makes this "flying desk", which during the war years was able to become a light bomber, a truly respectable aircraft, one of the symbols of the Great Patriotic War.
Flight performance of the U-2 (1933):
Overall characteristics: length - 8, 17 m, height - 3, 1 m, wingspan - 11, 4 m, wing area - 33, 15 m2.
The empty weight of the aircraft is 635 kg.
Takeoff weight - 890 kg.
The power plant is a five-cylinder air-cooled M-11D engine with a capacity of 125 hp (near the ground).
The maximum flight speed is up to 150 km / h.
Landing speed - 65 km / h.
Flight range - 400 km.
Service ceiling - 3820 m.
Crew - 2 people.
