The Beriev Be-4 or KOR-2 was a flying boat that was used by the Soviet Union during World War II.
The Beriev-4 had a single Shvetsov M-62 engine that was capable of propelling it at speeds of up to 356 kilometres per hour. The armament of the Beriev consisted of two 7.62mm machine guns and up to 400 kilograms of payload. To occupy all the positions on the aircraft, the Be-4 required a crew of at least three men. The operational range of the Be-4 was around 1,150 kilometres with an operational ceiling of around 8,100 metres.
The total weight of the Be-4 was about 2,228 kilograms while the total length was around 10.5 metres. The wingspan was 12 metres. In reality, the Be-4 was quite small for a flying boat, though it was designed this way. Another key design feature of the Beriev was its inverted gull wing design, though this was required by the exceedingly large mid-mounted engine. Parts of the Beriev were taken from the previous KOR-1 such as the tailsection.
The Beriev Be-4 was initially developed in 1941 to replace earlier developments with production beginning quickly following promising test results. Though, production and further tests had to be prolonged because the factory producing the Be-4 had to be dismantled and moved back into the Soviet Union. The first produced models were then used to equip the new aircraft was the Soviet Black Sea Fleet in 1942. Production finally began again in 1943. Like most other flying boats, it was used as a reconnaissance and submarine patrol aircraft. It was also used upon several cruisers. The type was used until 1945 with good success. In total, around forty-seven models had been produced during World War II.