Ilyushin Il 4

In 1938 a version of the DB-3 was developed with a totally new, easily-built airframe and equipped with two 765 hp (570 kW) M-85 engines but these were soon replaced with two 960 hp (716 kW) M86 engines. As a result the appearance of the design was completely changed, the nose being slim, streamlined and with a large glazed area, with the nose turret of the DB-3 (DB for Dalni Bombardirovschik or long range bomber) replaced by a swivel gun mounting. State acceptance trials were completed successfully in June 1939 and by the end of that year the type was readied for quantity production. This new version was known as the lIyushin DB-3F, later redesignated Il-4 when delivered in quantity to the bomber regiments of the long-range air arm, the ADD. A small number had the same type of dorsal turret as the DB-3, but this was soon replaced by a more effective design. Additionally, the ventral machine-gun ring was replaced by a more complex semi-retractable mount.

The Il-4 remained in large scale production until 1944, the number built being 5,256. The original M-87A engine was replaced by the more powerful M-88B with a two-speed supercharger in 1942. Most aircraft built in 1942 were completed with wooden wing spars as a result of shortage of light alloys due to the German invasion, but metal components were reintroduced in late production machines when new plants in Siberia became operational.

In addition to its use for long-range bombing raids, the Il-4s of the ADD's various long-range bomber corps were used frequently in attacks on tactical targets immediately behind enemy lines, carrying their maximum bombload. The Il-4 also came to be used widely by the mine/torpedo bomber regiments attached to the Baltic, Black Sea and Northern Fleets. When deployed in a torpedo-carrying role the Il-4 was armed with a 2,072 lbs (940 kg) 45-36-AN (Iow-level) or 45-36-AV (high-Ievel) torpedo. There was also provision for an auxiliary external fuel tank mounted under the rear fuselage. During 1943 the Ilyushin Il-4 also saw duties in the reconnaissance role and some even were converted to glider tugs.

The Il-4 was a robust and successful aircraft, a number surviving into the post-war period for use in a variety of support roles. It had sufficient longevity to earn the NATO codename 'Bob'. Four Il-4s purchased from German war booty stores were used by the Finns against the Soviet forces from 1943 to 1945.

In 1943 design work began on the Il-6, an advanced bomber with pressurised crew accommodation for high-Ievel operations, considerable sweepback on the wing leading edge, and power provided by two 1,500 hp (1119 kW) Charomsky ACh-30B diesel engines, but development was abandoned before the prototype had flown.

TsKB-26 - Original company designation for the DB-3.

TsKB-30 - Original company designation for the DB-3F.

DB-3 - Military designation for the first production type.

DB-3F - Military designation for the production type replacing the blunt nose turret with a long more pointed nose.

Il-4 - In 1940 with more than 2,000 aircraft already produced the designation was changed to Il-4, conforming with the new scheme in which aircraft were named for their designers (in this case Sergei Ilyushin). 

Specifications (Ilyshin Il-4)

Type: Three Seat Long Range Bomber and Torpedo Carrier

Design: Design Bureau of Sergei Ilyushin

Manufacturer: State Industries

Powerplant: Two 1,100 (820 kW) M-88B 14-cylinder two row radial engines with two stage superchargers.

Performance: Maximum speed 267 mph (430 km/h) at 21,980 ft (6700 m); service ceiling 31,825 ft (9700 m); initial rate of climb 886 ft (270 m) per minute.

Range: Clean 2,361 miles (3800 km) on internal fuel. With 2,205 lbs (1000 kg) of bombs range dropped to 1,616 miles (2600 km).

Weight: Empty 12,787 lbs (5800 kg) with a maximum take-off weight of 24,912 lbs (11300 kg).

Dimensions: Span 70 ft 4 1/4 in (21.44 m); length 48 ft 6 3/4 in (14.80 m); height 13 ft 5 1/2 in (4.10 m); wing area 717.98 sq ft
(66.70 sq m).

Armament: (Il-4) One 12.7 mm (0.50 in) BS machine-gun and two 7.62 mm (0.30 in) ShKAS machine-guns, plus an internal bombload of 2,205 lbs (1000 kg) or a maximum bombload (internal and external) of 5,512 lbs (2500 kg). Prior to 1942 all machine-guns would have been of the 7.62 mm (0.30 in) ShKAS type. (final types) All machine-guns would have been the 12.7 mm (0.50 in) BS type.

Variants: TsKB-26, TsKB-30, DB-3, DB-3F. Il-4.

Avionics: None.

History: First flight (TsKB-26) 1935; (production DB-3) 1937; (production DB-3F) 1939; final delivery 1944.

Operators: Soviet Union (DA, VMF).