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Su-2 Ivanov (Sukhoi) ANT-51, BB-1, SZ, NW

By the mid-1930s, on the basis of the design and operation of front-line aircraft (light bombers, reconnaissance aircraft, ground attack aircraft), a new type of front-line aircraft of a universal type was created, or as it was then used to say "combined type", which could successfully solve tasks entrusted to these types of front-line machines, as well as perform the functions of a two-seater fighter.

In the second half of the 1930s, a whole series of such machines was developed in almost all leading aviation countries of the world. In the USSR, the creation of such an aircraft became the goal of the Ivanov program, which provided for the design of several design bureaus of experienced single-engine reconnaissance light bombers capable of performing an attack aircraft in the event of additional weapon reinforcement and booking.

One of the first to start the creation of a multi-purpose front-line aircraft was the AN Tupolev Design Bureau. From September 1935 in the brigade of P.O. Sukhoi, experimental development began on a new aircraft, which received the designation ANT-51 or "NW" in the design bureau - "Stalin's task". The initial project was a high-speed reconnaissance aircraft under the M-34FRN engine (1025 hp), the car was supposed to reach a maximum speed of 455 km / h at an altitude of 4000 m. According to the project, aerodynamic and centering calculations were carried out, four experimental wing sections for testing were commissioned. in production. The following year, mainly carried out experimental and layout work on the machine.

At the beginning of 1936 a competition on the program "Ivanov" was announced. The competition was held between TsAGI (Chief Designer A.N.Tupolev), TsKB (Chief Designer N.N.Polikarpov), KhAI (Chief Designer I.Neman), by the collectives of D.P. Grigorovich and S.A. Kocherigin. Moreover, the task stipulated that the Tupolev aircraft would be all-metal, the machines developed under the guidance of Polikarpov, Grigorovich and Kocherigin would be of mixed design, and the Neman would be all-wood.

In the second half of 1936, tasked by the Central Administration of Aviation Industry (CAAI), the designer teams of N.N. Polikarpov, I.G. Neman, S.V. Ilyushin, S.A. Kogerilin, D.P. Grigorovich and P.O. Sukhoi conducted preliminary design studies of attack/recon aircraft with the AM-34FRN piston engine.

A CAAI commission reviewed the designs and arrived at the conclusion that the aircraft " in terms of their geometry, weight and flight performance do not differ very much from one another," and recommended to build three versions of the aeroplane with duralumin, US-technology-based, and wooden and mixed frames. Each version was assigned a chief designer: P.O. Sukhoi (plant No 156, Moscow), I.G. Neman (plant No 135, Kharkov) and N.N. Polikarpov (plant No 21, Gorky).

The commission's recommendations were approved by the country's leadership, and on 27th December 1936 there was published a resolution of Labour and Defence Council (LDC) on Development of High-Speed Long-Range Attack-Reconnaissance Aircraft, later referred to in correspondence under the code name of "Ivanov".

Originally, the design bureau continued to design the ANT-51 for new requirements with an M-34FRN type liquid cooling engine, but in early 1937 the project was redesigned for the M-62 air-cooled engine (800/850 hp), accepted as more reliable combat operation. ANT-51 was carried out according to the scheme of the all-metal single-engine low plan with retractable landing gear. The layout of its fuselage provided for the placement of the main target load under the floor of the pilot’s cabin, and not behind its cabin, as was customary in earlier projects of domestic aircraft of similar purpose. Due to this, it was possible to perform a fairly dense layout of the machine. The pilot and the navigator-gunner housed in a relatively small common cockpit, ending with a shielded machine gun installation under the ShKAS, the trunk of which is in flight, out of range of enemy fighters, retracted to a special fairing. Another ShKAS provided the defense of the lower rear hemisphere, from both machine guns fired the navigator-shooter. The fire could be fought at the same time: from the upper ShKAS - sighting and from the bottom - remotely unceasingly with the help of a pedal.

The offensive armament of the ANT-51 depended on its use. Its design provided for the installation of the four ShKAS wing machine guns. In the bomb bay and on external hangers in the center section, up to 200-400 kg of bombs of up to 100 kg could be suspended. In the variant of the photo surveyor, the ANT-51 could perform day and night reconnaissance with the help of interchangeable photographic equipment and radio communication equipment. The design of the airframe was characterized by high production adaptability: in power units, extruded profiles of aluminum alloys were widely used instead of the previously used steel welded units.

To increase the combat survivability of the aircraft, protective fuel tanks were used. To facilitate the work of the flight and ground crews, the autopilot, the heating system, the oxygen apparatuses, the light and sound signaling of the landing gear assembly and release, the aircraft intercom system, the electrical inertial engine starting system, etc. were included in the composition of the aircraft systems and equipment.

Having resumed work on the project, in early 1937, P.O. Sukhoi produced a design based on the air-cooled M-62 engine as a more rugged solution for battlefield environment. The new aeroplane's design made extensive use of extruded sections, and pressed and moulded structural members made of aluminium alloys and fabric-based laminates, whereas the use of the template method made it possible to simplify aeroplane engineering procedures and set up a production line. The project received shop designation of "SZ" (stands for "Stalin's Job" in Russian).

The prototype was engineered and built in the record-breaking time of 6 months. On 25th August 1937, M.M. Gromov took off in the first prototype aeroplane, SZ-1. The manufacturer's tests continued, on and off, punctuated with engine failures, till the end of 1938. The plane could not be presented for official testing because of the ban on using the M-62 engine.

December 1937 saw a "clone" (SZ-2) completed, the aeroplane making its first flight on 29th January. On instructions from the People's Commissariat of Defence Industry, in January 1938, SZ-2 was handed over for joint testing with the Air Forces, which took place in Yevpatoriya, with the Scientific Research Institute of Air Forces represented by Yu.A. Makarov and K.A. Kalilets. The tests were completed on 26th March, the aircraft having been found up to standard and recommended for series production.

Due to a variety of reasons, the Ivanov of I.G. Neman failed to be completed, and the aeroplane of N.N. Polikarpov did not take off the ground until late 1938. This meant that the Ivanov of P.O. Sukhoi was the winner of the unannounced competition. The governmental testing completed, SZ-2 arrived at plant No 156 to have its engine replaced, its service life having run its course. Fitted with a new engine, the aeroplane did not make more than a few flights as on 3rd August it was wrecked following the M-62 engine break-up.

A third SZ-3 aeroplane with an M-87 engine took off on 17th November 1938 with test pilot A.P. Chernavsky. After manufacturer's testing and follow-up, the SZ-3 was made available for official tests, which were completed in early April 1939. In terms of its flight performance, the aeroplane met all the requirements of the Air Forces, its superior design and flying qualities held in high regard. In March 1939, with governmental testing still in progress, the people's commissars of defence and aircraft industries petitioned the USSR CPC's Defence Committee (DC) to put the Ivanov aeroplane with M-87A engine into service in the Worker and Peasant Red Army and set up series production. A decision as to which plant to choose for production took a very long time to make, and it was not until July 1939, after PCAI had approved the 1939-40 aircraft prototype engineering plan, that the plant in the Kharkov started to gear up for full-scale production of the aeroplane designated BB-1 (for "short-range bomber one" in Russian). At the same time, P.O. Sukhoi was appointed Chief Designer of plant No 135.

Unlike its prototypes, the production aeroplane had an airframe featuring mixed materials (fuselage, a wooden monocoque with plywood sheathing; and a wing and tail group made of metal). This was due to the fact that the USSR did not yet have enough metal to build all-metal aircraft.

In 1940, the BB-1 (since December 1940 known as Su-2), having undergone a number of modifications, changed its production configuration, receiving M-88 and M-88B engines; the last production aeroplanes, about 60 in total, were fitted with the M-82 engine. Moreover, in 1940 the production facilities for the aeroplane were expanded with plant No 31 in Taganrog and No 207 in the town of Dolgoprudny. A total of 910 Su-2 aeroplanes had been produced by the spring of 1942.

In the period of 1939-41, concurrently with full-scale production, the design bureau of P.O. Sukhoi worked on different versions of the aeroplane. It produced a number of alternative designs of the aircraft to boost its battlefield performance, including improvements to its aerodynamics, retrofitting it with new engines (M-63TK, M-81, M-89, M-90), and other initiatives.

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Page last modified: 20-10-2018 18:43:51 ZULU