U-2ShS (headquarters and sanitary) - (presenter - V.G.Sigaev, elaboration for putting on the conveyor - Zhiklenkov).

The plane was designed and built in 1943. The limousine with the M-11F engine was actually a universal transport plane that met the needs of not only wartime, but also peacetime. As a limousine and an ambulance could transport five people - the pilot and one passenger were placed in the cockpit, three passengers in the rear cockpit. In the ambulance version, two wounded on a stretcher and a paramedic in the cockpit or one wounded on a stretcher, two in seats in the rear cockpit and a paramedic in the cockpit were accommodated in the rear cockpit. Another wounded man could have taken the place of a medical worker. A cargo version of the aircraft was also envisaged - 2 crew members were placed in the front cockpit, and the rear cockpit, by removing the seats, was converted into a cargo compartment, in which, in terms of dimensions, an M-11 engine, barrels of gasoline, compressed gas cylinders, pipes, profiles, etc. In addition, instead of cargo, the compartment could accommodate an aero pollinator. Conversion of the aircraft from a command plane to an ambulance or cargo plane took about 10 minutes.

The prototype aircraft was designed and built within one month. The U-2ShS passed state tests in the fall of 1943. With the M-11F, despite the increased flight weight, the speed at the ground increased to 163 km / h. The aircraft was accepted for serial construction at plant No. 494 in the summer of 1944. Preparation of serial drawings was carried out in the OKB from July 7 to July 14, 1944. The lead aircraft of military series No. 9440101 with an M-11D engine was produced in August 1944 (after death NN Polikarpova) and was called Po-2ShS. The presented aircraft did not pass government tests due to manufacturing defects - for example, a stretcher for the wounded did not fit in the cockpit. The aircraft was delivered to plant # 51, where it was being refined. It was built in a small series.

It should be noted that the failure of the serial Po-2 (AL and VS) state tests was associated, first of all, with manufacturing defects allowed by serial factories. In many ways, these defects were due to the insufficiently high qualifications of the working personnel of serial plants - the most experienced workers were at the enterprises of the NKAP, which produced the main combat aircraft. At the factories where the U-2 was made, for example, there were many teenagers. This does not in the least detract from the labor feat of the rear workers during the war years, but it shows the objective obstacles and difficulties in the production of high-quality aircraft, even such simple ones as the U-2.

Photo	Description
	U-2ShS drawing
	U-2ShS
	The location of the stretcher on the Po-2ShS
	Sanitary U-2ShS

Light transport and liaison aircraft First flight: 1930 Polikarpov

It was decided to develop the design of a light transport and liaison aircraft based on the agricultural U-2AP with good takeoff and landing properties, which allowed it to be operated from unprepared sites, and a relatively large payload.

The first plane was made for Sergei Mironovich Kirov. In place of the tank for pesticides, a comfortable (at that time) cabin for the passenger, increased in height, was installed, which was closed by a sliding lid. To reduce aerodynamic drag, an elliptical fairing was installed behind it. For the same reason, the cockpit canopy was expanded by changing the shape. A soft seat and a folding table were placed in the passenger cabin. Two rectangular light windows provided a good view from it. The wiring to the rudder was made mainly internal, cable. A lot of work was invested in the creation of the machine by N.G. Michelson, V.L. Korvin-Kerber, S.A. Moskalev. Modified in this way for the transportation of a particularly important person, the U-2 began to be called an aircraft "for special use" or abbreviated as SP (U-2SP).

In the summer of 1930, the carefully crafted aircraft was rolled out of the assembly shop. After the tests, which passed quite quickly and with little to no remarks, the aircraft was handed over to the customer - S.M. Kirov.

The joint venture aroused natural interest among other "especially important persons" from among the heads of regions, individual departments and services. The "Obkomovsky" aircraft was very much needed in the traditional Russian off-road conditions.

At the end of 1930, at a meeting of the board of Aviatrest, the question was raised about the organization of mass production and the construction of fifteen joint ventures in 1931. But soon this order was canceled by Aviatrust, due to the relatively small number of expected annual orders. However, the plant was allowed to produce a small number of machines, having converted "overplanned" APs for this purpose.

Part of the U-2SP aircraft was also built in a three-seater version. At the same time, the folding table was removed, and another folding seat was installed instead.

The setting for the use of "over-planned" AP for their conversion into U-2SP was reflected in the annual reports of the plant: in the documentation sent to the leadership of the aircraft industry, only the fulfillment of planned targets was recorded - i.e. manufactured machines of the AP type. Naturally, the joint ventures converted from them were not mentioned there.

Nevertheless, in 1931 - 1933, about 60 machines of this type were built. In 1934, their production was stopped, since A.S. Yakovlev’s “AIR” was officially accepted as the “obkom” machine.

The successful operation of the joint venture drew the attention of the leadership of the Main Directorate (GU) of the Civil Air Fleet to it. This took into account the relatively small volume of passenger traffic over short distances in our country in those years. In addition, the Civil Air Fleet needed a vehicle for transporting mail, cargo, emergency delivery of spare parts, for training, training and parachute training of flight personnel.

Based on the complex use of the aircraft, after negotiations with the design bureau of plant No. 23, a thorough analysis of various options, technical and economic indicators, it was decided to equip the joint venture with an open three-seat passenger cabin, as much as possible unified in design with the cabin of the "classic" U-2. So there was another new modification of the machine. But the designation of the joint venture behind it, nevertheless, was preserved.

The leadership of the aviation industry instructed to organize the serial production of this joint venture, which began at the end of 1933. In 1934, Plant No. 23 built the first series of 101 vehicles. In the future, the release increased, but never exceeded 10% of the total number of built U-2s of all modifications, reaching a maximum value (210 copies) in 1938.

The first joint ventures appeared in the Civil Air Fleet in 1934. In the GU GVF system, they were also designated as PS-3. The cars had registration numbers SSSR-L78, SSSR-L219, etc. At the end of 1939, there were 552 joint ventures in Aeroflot. One copy was handed over to Dobrolet.

The aircraft was used as a passenger aircraft on local routes, as a light administrative aircraft. In the conditions of a small volume of passenger traffic, the relative cheapness of design and operation, the use of a joint venture in the Civil Air Fleet was profitable and economically justified.

By the beginning of the forties, the joint venture had already ceased to satisfy the increased scale of the activities of the Civil Air Fleet. At the end of 1939, the serial construction of this machine was stopped, having released 831 aircraft.

During the Great Patriotic War, the SP was widely used as a liaison and light transport aircraft in the rear and at the front. On the lower wing, cabs designed by G.I. Bakshaev and A.Ya. Shcherbakov. The joint venture was used as a staff aircraft. It was also used to fly behind enemy lines to the partisans.

The machine was operated almost to the complete wear of the material part. Since the factories did not produce the joint venture during the war years, by the end of 1945 only a few of its copies were flying.

Photo	Description
	U-2SP, designed for S.M. Kirov

Light transport aircraft First flight: 1945 Polikarpov

Starting from 1945, a modification of the Po-2L with an equipped cabin for two passengers was built in small batches, leading its lineage from the sanitary S-2. From Po-2SHS, ailerons and rudders with aerodynamic compensation, a trimmer on the elevator passed to him. The cockpit still remained open, and the dimensions of the fuselage did not change. Until 1947, such machines were produced by factory No.387, then No.463 and No.168, some aircraft repair bases. Moreover, sometimes not new aircraft were built, but alterations were made during the overhaul of already significantly flown Po-2s.

Of particular note is the change in the length of the nose of the aircraft - this technique has been used sporadically throughout the entire period of its improvement. For the first time, the fuselage was extended by 300 mm in the area from the attachment point of the wing braces to the fire barrier in the sanitary C-1. The reason for the decision was too rear centering when placing the patient on a stretcher and the need to place the fuel tank in the fuselage. However, in the latest S-1 series and in the S-2 model of 1940, in order to unify with the base U-2, the fuselage remained the same, and the fuel tank was located in the center section of the upper wing. At the end of the war, the S-2 and Po-2L reappeared with a nose extended by 304 mm. This time they tried to place the fuel tank without fail in the fuselage, which greatly facilitated the operation of the aircraft in the field. However, this change did not become the norm, because they continued to produce aircraft with the usual length of the fuselage.

Tests of this Po-2L began in Kazan and continued in October 1946 at the airfield of the Research Institute of Civil Air Fleet Zakharkovo (Moscow, northern Tushino, opposite the building of the Northern River Station). The pilots Spivakovsky, Petrovich and Vasilchenko did not find any differences in piloting technique compared to other Po-2s and highly appreciated the cockpit covered with a plexiglass canopy. The aircraft was recommended for mass production for the Civil Air Fleet. An unknown number of such Po-2Ls were built, but rare photographs of "maize" with a closed cockpit show that there were very few of them.

In the period 1947-49, the last Po-2 series was built at the aircraft factory No.168 in Rostov-on-Don. Some of them were produced as Po-2L. It was used on the local lines of the Civil Air Fleet for the transportation of passengers, cargo and mail. Since 1948, on factory-produced aircraft, the upper wing offset has been reduced from 800 mm to 600 mm, and a closed cabin has been equipped to accommodate two passengers or a doctor and a patient on a standard stretcher. This cabin compared to other modifications was rated as more comfortable. Inside, it was finished in walnut, the sides were sheathed with drape, soft seats with armrests were installed. In addition, there was lighting, a folding table, even curtains were provided.

Po-2L, converted from training Po-2, had all the above differences, however, the comfort of the passenger cabin was considered lower in level. When installing a sliding pilot's canopy, the front of the passenger cabin was fixed.

Light transport aircraft First flight: 1945 Polikarpov

In 1940, TsAGI research was quite successfully used to create the U-2 hydrovariant. At the No.23 aircraft factory in Leningrad, using the theoretical justification for the No.10 model, they developed and built wooden floats, which were installed on a three-seater U-2SP (SP-hydro). Tests conducted with the participation of the Research Institute of the Civil Air Fleet showed quite satisfactory results for the new seaplane.

Also in 1940, another U-2 was equipped with two wooden floats designed by V.B.Shavrov. The experience and technology of floats made for the AIR-6 aircraft was used. On tests, this seaplane, according to Shavrov, showed good flight and seaworthiness: speed 147 km / h, ceiling 3000 m, takeoff run 15 seconds, run 15 seconds.

In 1942, wooden floats with simplified contours were built for the U-2 by engineer A.Ya.Shcherbakov. The truss scheme of their fastening was distinguished by only four vertical posts and two transverse pipes holding the floats together. The required rigidity of the spatial truss was achieved by introducing five pairs of bracing bands.

In 1945, at the air repair base No.402 in Bykovo near Moscow, the passenger Po-2LP (factory No.327118) with the M-11D engine was equipped with floats. The floats were made according to the drawings of the aircraft factory No.23 (made back in 1940) in the workshops of the air division of the border troops of the NKVD of the USSR. Tests of this Po-2LP, carried out in October 1945, showed that with three passengers on board and with a maximum takeoff weight of 1300 kg, takeoff and landing on floats is quite possible. The aircraft entered the redan at a speed of about 60 km / h according to the instrument, at a speed of 80-85 km / h it easily broke away from the water. In level flight, on bends and turns, the flight performance of a float machine practically did not differ from the behavior of a conventional Po-2. On landing, the seaplane was stable, with no tendency to turn or yaw. It was pointed out that the interchange of land and float landing gear is simple and easily done within four to six hours by several aircraft mechanics.

At the same time, it was proposed to equip the aircraft with a self-starting engine, eliminate the possibility of water getting into the carburetor, and include a light anchor or a cat with a mooring ring in the marine equipment.

In general, the new Po-2 hydraulic variant proved to be quite successful, therefore, in the future it was proposed to launch the production of such floats in order to enable the conversion of light aircraft used in the North and Siberia.

An unspecified number of sets of twin floats were later built to equip Po-2s used in border river basins. In 1946, one double-float Po-2 was so successfully operated in geological exploration in Western Siberia that rave reviews led to an order for an aircraft repair plant in Krasnoyarsk to manufacture 100 sets of such floats. Information about the implementation of these plans has not been found.

Bibliography

• World of Aviation №1 2000 /Vladimir Ivanov, Andrey Korshunov, Vladimir Perov, Oleg Rastrenin/
• Polikarpov U-2: "Heavenly slug" /Mikhail Maslov/