Aviation of World War II
Spotter and Reconnaissance Aircraft
The need for a high-altitude maneuverable reconnaissance aircraft, capable of being over objects for a considerable time, inaccessible to anti-aircraft artillery and enemy fighters, began to be acutely felt in the very first months of World War II, when it became clear that the effectiveness of the combat use of the FV-189 reconnaissance aircraft is very high. At the initial stage of the war, modified Su-2 aircraft were used in this capacity, and from the middle of 1943, Il-2 attack aircraft. It was clear that these machines were of little use for adjusting artillery fire; a specialized aircraft was required. In July 1943, the Air Force Research Institute of the Red Army developed a TTT for a military reconnaissance artillery fire spotter for an experimental aircraft construction plan for 1943-44.
By November 1943, in the Design Bureau P.O. Sukhoi completed the development of a project for a three-seat spotter with two M-62 engines, made according to the scheme of the German reconnaissance aircraft FW-189. The spotter aircraft was included in the draft plan for the construction of experimental NKAP aircraft for 1944-45, but in the process of agreeing and approving the plan, this topic was “reduced”. The launch of a series of specialized artillery spotters in extreme wartime conditions turned out to be an unaffordable luxury for the country's aviation industry.
The first copy of the RK machine was not very successful. Counting on inaccessibility, the designers did not secure their brainchild enough: the armored back of the pilot's seat, 8 mm thick, withstood the fire of conventional machine guns, but could not protect against being hit by armor-piercing bullets of 12.7 mm caliber when firing from short distances. The defensive armament, consisting of five 7.92 mm machine guns, was also too weak.
The aircraft was again included in the work plan and on July 10, 1946, the USSR Council of Ministers approved a resolution on the construction of an experimental reconnaissance aircraft, which obliged P.O. Sukhoi to design and build this aircraft with two ASh-83 engines in two copies with the transfer of the first copy to the State Tests on September 15, 1947.
The construction of the Su-12 aircraft was completed in August 1947.
A design feature of the aircraft was a gondola for the crew, which was attached to the center section. It housed the pilot, to the right of him - the navigator, behind them - the gunner-radio operator, and in the tail section - the gunner serving the rear rifle installation. Each crew member was protected by an armored back made of plates with a thickness of 7 to 12 mm. In the rear cockpit, in addition, bulletproof glass 90 mm thick was installed. Anti-fragmentation armor of the cabin floor - 5 mm thick; side armor - 2 mm steel sheets. The lower hemisphere of the nose lamp is made of special glass 15 mm thick. To quickly leave the aircraft, hatches and front doors had emergency release devices. The keels were a continuation of the tail booms and were made integral with them. The ends of the beams were connected by horizontal plumage.
Photographic equipment was installed on the aircraft, providing planned and prospective photography from high and low altitudes, as well as photographic reconnaissance at night.
In addition to the tasks of adjusting artillery fire, the Su-12 (RK) could perform the tasks of a short-range bomber, 400 kg of bombs of various calibers were suspended in its fuselage beams in the reloading version.
On August 26, 1947, the factory test pilot N.D. Fixson made the first flight on the Su-12. Factory flight tests were completed on 30 October 1947. Along with a large ceiling and an acceptable maximum speed, the possibility of using the machine at extremely low speeds was of particular importance. Such modes were fully provided by the power plant of two ASh-82M (M-93) engines with a power of 2100 hp each. But already during the factory flight tests, which began in August 1947, these engines were replaced by ASh-82FN with four-blade propellers AV-9VF-21K, which could be installed in the vane position. This made it possible to fly a machine with one running engine at altitudes up to 6500 m. Good results were also achieved in such important characteristics for a reconnaissance aircraft as flight range and loitering time. The technical flight range was 1140 km, and its duration was 4 hours 18 minutes against 3 hours specified by the technical requirements. However, as a result of the replacement of engines, the requirements for the maximum speed and ceiling of the aircraft, set by a government decree, were not met.
On December 20, 1947, the Su-12 aircraft (without armament) was officially handed over for state tests, which fully confirmed the data of factory flight tests. In conclusion, based on the results of the tests, a number of defects and shortcomings were noted, which must be eliminated in mass production. Separately, it was stipulated that before launching into the series, it was necessary to conduct repeated state tests of the aircraft with weapons. In the period from July to September 1949, repeated state tests of the Su-12 were carried out, according to the results of which the aircraft was finally recommended for adoption.
In October 1949, a package of documents was again presented to the government for consideration. The submitted material was returned with reference to the discrepancy between the obtained characteristics and the parameters set by the government decree of March 11, 1947. The aircraft was not mass-produced.
TTT - Taktiko tekhnicheskiye trebovaniya - Tactical technical requirements
NKAP - Narodnyy komissariat aviatsionnoy promyshlennosti - People's Commissariat of Aviation Industry
RK - Razvedchik korrektirovshchik - Scout Spotter