Reconnaissance at sea was always a major issue. In the olden days, various auxiliary ships such as sloops, brigs, frigates, and the like were used for that purpose. As a result, various attempts were made to increase the view range of the ships. As technological progress unfolded, kites and tethered balloons were used in an attempt to raise the viewpoint as high as possible.
Needless to say, as soon as the aircraft was created, it was immediately put to use for reconnaissance purposes.
The first take-off from a ship, though still a stationary one, was carried out by Eugene В. Ely. On November 14, 1910, the pilot took off in the Glenn Curtiss' Curtiss D from a platform erected over the bow of cruiser USS Birmingham (CL-2). Performing a landing was more difficult, however. It was only on January 18, 1911, that a full-cycle flight (landing with a subsequent take-off) was completed. For that purpose, a 36-meter platform was built on the stern of armored cruiser USS Pennsylvania (ACR-4). For braking purposes, cables tied to sandbags to which an aircraft clung with a special hook were used.
Along with the land-based wheeled aircraft, seaplanes started to emerge. A smooth, flat surface on calm water inspired the desire to use it as an airfield, with no construction works required.
The first seaplane was Henri Fabre's aircraft, which completed its first flight on March 28, 1910, while the first seaplane brought on board a ship (USS Pennsylvania) was also designed by Curtiss. The event took place on February 17, 1911.
Another event important for the development of naval aviation was the successful trial of the Chambers's catapult used for Curtiss' aircraft take-off from the deck of a specially-equipped barge on November 12, 1912.
Further development of naval aviation led to the creation of carrier aviation based on aircraft carriers and seaplanes, in turn based on common ships or special seaplane tenders. In order to work from these ships, special platforms, hangars, cranes, and catapults were built.
The first experiments with the placement of seaplanes on ships in the Russian Empire started in 1912 aboard cruiser Kagul. In particular, the first seaplane tender was steamboat Dnepr, aboard which three Curtiss D seaplanes were stationed. This was followed by the active use of Grigorovich's M-5 and M-9 flying boats.
The progressive development of naval aviation in Russia was interrupted by the revolution, and the Soviet government had to solve the problem of equipping fleet ships with reconnaissance aircraft anew. This process began in 1925 with the placement of seaplanes on ships that underwent repairs. The aircraft equipment went under the name of Combat Unit No.6.
Battleship Parizhskaya Kommuna was one of the first to receive the seaplane Junkers Ju.20. Cruisers of the Black Sea fleet received an instance of the good old AVRO 504K set on floats, named MT-1 («the first for maritime training»). It was obvious, though, that these were all half-measures, as the aircraft were outdated and didn't fit the designated role.
Therefore, a decision was made to develop a system consisting of the ship's catapult and an aircraft. The attempts to make a proprietary catapult and an aircraft didn't bring any quick results, so both of them had to be ordered abroad, in Germany, specifically, where the necessary agreements were reached. The project was taken up by the infamous Ernst Heinkel. The catapult had to be 19 meters long, weigh 18 tons, and be able to rotate a full 360 degrees. The estimated weight of the aircraft was 2,000 kg.
The Germans very quickly designed an aircraft, designated HD.55, based of the mail aircraft HD.15. The aircraft was much appreciated, and in the autumn of 1929, the order for it was increased from 6 to 20 aircraft. The first mass-produced seaplane was supplied to the USSR in January of 1930, and the last one, in August. The aircraft received the designation KR-1 (“korabelnyi razvedchik, or «the first reconnaissance ship»).
The K-3 catapult was constructed, tested, dismantled, and delivered by rail to Sevastopol where it was assembled on the third gun turret of battleship Parizhskaya Kommuna. The first successful launch took place on October 8 of 1930, but it took about a year to adjust it properly.
The German experience allowed the Soviet specialists to quickly master new equipment and rely on their own resources in the future. On July 11, 1933, the Council of Labor and Defense adopted the naval shipbuilding program for 1933-1938. Special attention was given to the construction of new light cruisers that were to be equipped with catapult reconnaissance aircraft. There were plans for the development of a new aircraft, the KOR-1, as well as new catapults. The development of catapults was a recent endeavour, so for the sake of reliability, the order was partially placed to domestic plants (Kirov plant in Leningrad and Plant No.198 in Nikolayev), and partially to the very same Ernst Heinkel.
The KOR-1 was to combine the functions of a scout, a spotter, and a dive bomber. The assignment for the aircraft was prepared in the first half of 1934, and on November 22, 1934, Yakov Alksnis, head of the Red Army's Air Force, approved the aircraft single-float biplane design. The development was led by the Central Engineering Bureau for Marine Aircraft headed by the engineer, Beriev. The project was influenced by the trend for «two-environment» aircraft which could be easily transformed into the overland version, and vice versa.
The first flight took place on September 4, 1936. The plane behaved well in the air, while its seaworthiness left much to be desired. However, the state trials revealed a significant number of defects which hadn't been noticed early on. As a result, the rectification works lasted until mid-1938 and the aircraft was put into service after that. All-in-all, 12 aircraft were built, 1 of them lost to an accident. None of them was used as a scout during the war.
Despite being put into service, the KOR-1 did not satisfy the customer either by its tactical or operational characteristics. Therefore, a decision was taken to instantly start designing an aircraft that would replace the KOR-1. The assignment presupposed the creation of a light reconnaissance bomber that was to carry offensive and defensive small arms and have the ability to perform rescue functions. The latter implied a good seaworthiness, so it's no surprise that the aircraft became a flying boat as a result. The assignment was offered to several engineering bureaus at once, in particular, to Shavrov, Nikitin, Beriev, and Chetverikov.
This call for proposals was won by Beriev's engineering bureau. The project draft was ready on August 7, 1939, and the first prototype was completed in the autumn of 1940. The state trials were conducted in the period from February 2 to February 18 of the following year and were declared a success. The start of the war complicated the production process and the initial order included only 20 aircraft. Altogether, 51 aircraft were built, with the highest production period between 1944 and 1945—38 aircraft in all. In the initial stage of the war, the aircraft equipment aboard ships was considered burdensome and the aircraft were written off «to the shore». The KOR-2 took part in combat operations primarily as basic scouts and patrol aircraft, and were armed with depth charges to attack submarines. Such attacks were numerous but with no evidence of success. Restoration of the aircraft combat unit on ships dates back to as late as 1944, but even then, the KOR-2 gained no merit as a reconnaissance aircraft. But that had nothing to do with the aircraft: these were the conditions in which the Soviet fleet existed during the Great Patriotic War.
Nikitin's and Shavrov's «paper aircraft»
Based on the suggestions for the KOR-2, we were able to create 2 aircraft.
The first one is Nikitin's KOR-2 M-62 project, based on his previous work—the NV-4 seaplane with the M-11 engine. On the outside, the aircraft resembles the American Loening OA-1 and the Grumman J2F, both featuring a special trait: the space between the float and the hull was used to accommodate the observer.
The Shavrov's KOR-2 M-105 project features a very interesting design, primarily due to the unusual placement of the engine in the hull of the flying boat with the intermediate shaft connecting the engine with the airpropeller installed upon the boat's hull. It was proposed to make the under-wing floats completely retractable to the lower surface of the wing. This arrangement in combination with a powerful engine (1,100 hp, which is quite a lot for a reconnaissance aircraft) promised strong flying capabilities.
History often develops in spirals, and this time it went full circle: following the prototyping of the KOR-3, in 1945, Beriev's engineering bureau presented a project for a reconnaissance aircraft designated KL-145, probably in response to the return of catapult aircraft on ships. Externally, it strongly resembles the KOR-2, styled for the end of the 40's and equipped with a ASh-21 engine powered by only 615 hp. Clearly, even the advanced design couldn't help to achieve high performance.
Beriev's KOR-3 projects
At the time the KOR-2 was put into service, the fleet felt the need for an aircraft with better characteristics. Beriev proposed two projects: one for the float version and one for the flying boat.
The aircraft designed according to the two-float scheme had a two-keel vertical tail and an M-64R engine with a capacity of 1,200 hp. But, as was often the case, the engine was never produced. Therefore, the project was quickly remade to accommodate the М-87А engine with its 950 hp. For this project, it was again considered necessary to have the «changing-for-the-wheels» option.
Wishing to significantly improve the aircraft’s flight performance, Beriev used the VK-107 engine with a capacity of 1,500 hp, which is quite a lot for this aircraft type. Apparently, designers at Beriev's EB appreciated Shavrov's idea, and they also planned to place the engine in the boat, which significantly reduced the drag of the propeller-driven group. The highlight of the project was the contra-rotating propellers, which solved the problem of the propeller's reactive torque due to its heavier construction. The rest of the aircraft was a natural result of the KOR-2 evolution.