OKB Sukhoi BB-1 (Su-2) "Ivanov" Short-Range Bomber with M-87 engine.
A single-engine, mixed-construction monoplane light bomber with retractable landing gear and tail wheel.
This project was developed as an entry in the 1936 competition for the best high-speed long-range ground-attack reconnaissance plane, to be known as the "Ivanov." The design and construction were completed in a record time of 6 months. The first flight of the SZ-1 (SZ: "Stalin's Mission"), with an M-62 engine, was made on August 25, 1937.
The prototype selected for mass production was the SZ-3, equipped with an M-87 engine. In March of 1939, even before government tests were completed, the "Ivanov" airplane (with the M-87A engine) was accepted by the Red Army Air Force. It entered mass production under the designation BB-1 (short-range bomber one).
Unlike the prototypes, the production model had a mixed construction. The fuselage was a wooden monocoque with plywood paneling, and the wings and stabilizer were metal. This choice was made because, due to the many all-metal aircraft in the USSR at the time, metal was in short supply.
The first production aircraft were fitted with air-cooled radial 14-cylinder OKB Tumansky M-87 engines, rated at 950 hp.
The aircraft's armament included a battery of 4 fixed ShKAS 7.62mm machine guns with 850 rounds each, mounted in pairs on each wing. To protect the aircraft's rear, the navigator had a rotating MB-5 turret with another 7.62mm machine gun with 900 rounds of ammunition.
The prototypes had a ventral MB-2 turret with a ShKAS machine gun, but this was removed as it seemed unlikely that any enemy fighter attacks would come from below when the plane was flying at a low altitude. However, it was soon shown that this was a poor decision, as such attacks were frequent in actual combat.
The plane's usual bomb load, when flying at its maximum range, was 400 kilograms. Overweight capacity was up to 600 kilograms. The maximum bomb load was 1200 kilograms. Bombs of up to 100 kilograms could be placed both in the internal bomb bay and suspended under the outer wings. KD-1 or KD-2 bomb racks were used to carry and drop these bombs. Rockets were not carried.