| DB-4 | |
|---|---|
| Role | Long-range bomber Type of aircraft |
| National origin | Soviet Union |
| Manufacturer | Ilyushin OKB |
| First flight | 15 October 1940 |
| Number built | 2 |
| Developed from | Ilyushin DB-3 |
TheIlyushin DB-4 (DB - Дальний бомбардировщик -Dalniy Bombardirovshchik - long-range bomber) orTsKB-56 (TsKB -Tsentral'noye Konstruktorskoye Byuro - central construction bureau) was aSoviet twin-enginedbomber aircraft of the early 1940s. It was a development of theIlyushin DB-3 and was intended as a replacement for the earlier aircraft, but only two prototypes were built; engine problems and the need to concentrate production on existing types following the German invasion of the Soviet Union in June 1941 meant that no more examples were built.
In the late 1930s, theIlyushinOKB (or design bureau) was tasked with designing a replacement for itsDB-3 twin-engined, long-range bomber. Ilyushin carried out design work on the new aircraft, which was given the internal design bureau designation TsKB-56, in parallel with the DB-3F (later designated theIl-4). While the DB-3F was a relatively simple upgrade of the DB-3, the TsKB-56, which had the service designation DB-3, was larger and heavier, in order to meet the requirements for greater performance and a heavier bombload. The DB-4 had a high-mounted wing to accommodate a large bomb bay, with a retractabletailwheel undercarriage fitted, while the radial engines of the DB-3 were to be replaced by the newKlimov M-120, an 18-cylinder liquid-cooled engine of unusual design, with three banks of six cylinders arranged in an inverted "Y"-shape, which was to have a takeoff power of 1,800 hp (1,346 kW). It was to have a crew of four consisting of a pilot, navigator, dorsal gunner and radio operator.[1][2] Defensive armament was threeShKAS machine guns, one in the nose, one in a dorsal turret and one firing through a ventral hatch, while the deep bomb bay could carry 1,000 kg (2,200 lb) of bombs.[3]
The proposed M-120 engines proved to be troublesome, and it was decided to replace them with 1,400 hp (1,044 kW)Mikulin AM-37V12 engines to allow testing of the first prototype to be completed. This aircraft, fitted with a single vertical fin, made its maiden flight on 15 October 1940, withtest pilotVladimir Kokkinaki at its controls. The second aircraft, with twin tails, was completed in November 1940 with M-120 engines, but these were replaced with AM-37s before it flew on 20 February 1941.[3]
Flight testing showed that the aircraft had poor low speed stability, while the fuselage, with its large bomb bay was prone to flexing, resulting in larger tail surfaces being fitted and the fuselage being strengthened.[3] The AM-37 engines, while a development of the earlierAM-35 engine, proved to be unreliable, and plans were made to fit alternative engines, including theShvetsov M-71 andM-82radial engines and theCharomskiy ACh-30Diesel engine, although none of these alternatives were fitted.[1][4] TheGerman invasion of the Soviet Union in 1941 lead to an end of production of the DB-4, with the factory allocated for production evacuated from Moscow to the East, and ordered to concentrate on urgently neededIl-2 ground-attack aircraft and the Il-4 bomber.[5] The two prototypes continued in use as testbeds to aid development of improved versions of the Il-4 and the laterIlyushin Il-6 bomber.[1]
Data from The Osprey Encyclopedia of Russian Aircraft 1875–1995[1]
General characteristics
Performance
Armament