Soviet air activities during the Second World War are often overshadowed by the more glamourous actions in Western Europe, and the Ilyushin Il-4, despite its beauty, is no different. This rather obscure aircraft was a long range workhorse for the USSR.
It started as a simple upgrade for another bomber, but these changes were so great the aircraft was considered a whole separate machine.
Contents
Background
The onset of the Second World War quickly highlighted the necessity for a capable long-range bomber that could support the vast geographic and operational scope of the Soviet military efforts.
As the war expanded, the Soviets needed an aircraft that could reach distant targets deep within enemy territory, particularly as part of their efforts to disrupt German logistics and industrial capacity.
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Fortunately the Soviet Union already had a long-range aircraft, the Ilyushin DB-3. Designed by Sergey Ilyushin and first flying in 1936, the DB-3 was one of the first Soviet bombers specifically built with long-range capabilities in mind.
The design of the DB-3 focused on achieving a balance between range and payload to meet the specific design criteria of being able to carry a 1,000 kg (2,200 lb) bombload with a 3,000 km (1,900 mi) range at 350 km/h (220 mph).
To do this, Ilyushin spent much time making the airframe as light as possible. The DB-3 featured a monocoque fuselage constructed primarily from duralumin and a cantilever wing, which were advanced features for the time.
It was powered initially by two M-85 or M-86 radial engines, later replaced by more powerful M-87 and M-88 engines in subsequent variants. These engines allowed the DB-3 to achieve a maximum speed of around 360 km/h (224 mph) and a range of approximately 3,800 km (2,400 miles), making it an effective tool for long-distance operations.
In fact, the aircraft set a number of world records thanks to its range and payload capabilities. The DB-3 saw extensive service during the Winter War against Finland in 1939-1940 and was also deployed on the Eastern Front after the German invasion of the Soviet Union in 1941. They were even deployed in Asia, where they were used by China during the Second Sino-Japanese War.
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Its missions included bombing strategic targets deep behind enemy lines, maritime patrol, and reconnaissance duties. The bomber was known for its ruggedness and reliability, which were crucial given the harsh operating environments of the northern and eastern fronts.
Room for Improvement
However, as the needs of the Soviet Air Force evolved, particularly with the looming Second World War, there was a demand for a more advanced aircraft that could carry heavier payloads over longer distances and with better defensive capabilities.
Responding to this need, the Ilyushin design bureau developed the DB-3F, an improved version of the original DB-3. The DB-3F featured several significant upgrades over its predecessor. It was equipped with more powerful engines, the Tumansky M-88, enhancing both its speed and range.
Structural reinforcements were added too, and the defensive armament was substantially increased to improve survivability in combat. The fuselage and wings were also modified to accommodate these changes, resulting in better overall performance and operability. The entire nose section was reworked into a beautiful, aerodynamic glazed cabin.
Perhaps most importantly though, changes were made to make the aircraft much easier to produce. The DB-3 was a high-performing aircraft, but this came at the cost of its artisanal production, which involved delicate welds and riveting, all of which had to be thoroughly inspected after.
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With a more simple airframe, the DB-3F could now be built much easier and much faster. It also received larger fuel tanks, increasing its range.
DB-3F to Il-4
These modifications resulted in a markedly different aircraft, both visually and performance-wise. As a result, the DB-3F was re-designated as the Il-4 in 1942. This change marked its official recognition as a new type, though it retained its lineage through design continuity from the DB-3.
The introduction of the Il-4 was a technological step forward for Soviet aviation. It featured improvements over its predecessor, the DB-3, in terms of speed, defensive armament, and operational range, all while being easier and cheaper to produce.
Investing in such technology was crucial for keeping pace with advancements made by adversarial forces, ensuring that the Soviet Air Force remained competitive and capable of defending the USSR and attacking its enemies effectively.
Design of the Ilyushin Il-4
The Il-4 featured a long, slender fuselage and a high, straight wing, which allowed for stable long-range flight. It was of all-metal construction, but after the German invasion of the Soviet Union in 1941, some were outfitted with wooden components to keep production going.
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One of the most distinct features of the bomber was its long, cigar-shaped nose section. This heavily glazed portion of the aircraft was much more aerodynamic than the blunt nose of the DB-3, and also offered much better visibility for the crew.
Power came from two air-cooled radial engines; one mounted on each wing. Specifically, the Il-4 typically utilized the Tumansky M-88, which was among the most reliable and effective available to Soviet aircraft designers at the time.
Tumansky M-88
The Tumansky M-88 was a 14-cylinder, air-cooled radial engine that was widely used in Soviet aircraft. It was developed from the M-87, which in turn was a copy of the French Gnome-Rhône 14K Mistral Major that the Soviets built under license. The M-88 had some improvements over the M-87, with many of its components made stronger. It also pushed the power up from around 1,000 hp to 1,100.
For the Il-4, this engine offered a good balance of power and reliability, essential for the long overland and overwater flights that characterized many of the bomber’s missions.
Each M-88 engine was capable of producing approximately 1,100 horsepower, contributing to the Il-4’s maximum speed of around 410 km/h (255 mph) and allowing it to carry a respectable bomb load.
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There was an attempt at adding more powerful diesel engines to increase the Il-4’s speed, but these were unreliable so this version did not enter service.
Performance
Inside, the Il-4 it had a crew of four, including a pilot, co-pilot/navigator, radio operator, and rear gunner. Capable of reaching a top speed of approximately 410 km/h (255 mph), the Il-4 had an impressive range of up to 3,800 kilometers (2,360 miles), making it suitable for extended missions deep into enemy territory.
The bomber was typically equipped with up to 2,700 kg (5,512 lb) of bombs, which could be carried internally and externally if needed. The aircraft could also carry torpedos and sea mines, which the Soviets used to good effect. For ground attack missions, rockets could be attached to underwing racks.
One of the most noteworthy features was its ability to carry an auxiliary fuel tank in the bomb bay, significantly extending its operational range. This adaptation was particularly important given the vast distances of the Eastern Front and the strategic need to reach remote targets deep within German-held territory. By using the bomb bay for additional fuel storage, the Il-4 could sacrifice some of its bomb load for greater range.
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It isn’t clear, but the Il-4 may have sometimes flown with skis in winter operations. This was a crucial adaptation for operating in the harsh Soviet winters, allowing the aircraft to take off and land in snow-covered fields and airstrips. This was a common practice for Soviet aircraft, and predecessors to the Il-4 had been fitted with skis.
Defensive Weapons
The Ilyushin Il-4 was equipped with a robust defensive armament system designed to protect it during its long-range bombing missions deep into enemy territory. The role of the Il-4, carrying out bombings and reconnaissance over vast distances, necessitated effective defenses against enemy fighter attacks.
The defensive armament of the Il-4 consisted of multiple machine gun positions strategically placed around the aircraft to cover various angles of attack. Located on the top of the fuselage, the dorsal turret was one of the key defensive features of the Il-4. It was originally armed with a 7.62 mm machine gun, but this was later upgraded to a larger 12.7 mm Berezin UB machine gun.
This weapon provided a high rate of fire and good stopping power against enemy fighters approaching from above and behind. Situated on top of the fuselage, the turret could rotate 360 degrees, enabling the gunner to cover a large portion of the upper hemisphere.
Underneath the fuselage, the ventral position was equipped with a 7.62mm ShKAS machine gun. This position was crucial for defending against attacks from below the aircraft. Although less powerful than the dorsal gun, the ShKAS was known for its extremely high rate of fire, making it effective at deterring pursuing fighters.
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Additional defensive armaments included fixed forward-firing machine guns in the nose, used primarily for strafing ground targets, and a rear-facing gun in the tail. The tail gun, typically another 12.7mm Berezin UB machine gun, provided critical defense against attacks from directly behind the aircraft.
The defensive armament of the Il-4 was reasonably effective against the fighter aircraft of the era. The combination of 12.7mm and 7.62mm machine guns offered a balance between firepower and coverage.
However, the aircraft’s overall defense depended heavily on the skill and coordination of its crew members, as well as the tactical situation. While the guns provided significant defensive capability, they could be overwhelmed by multiple attackers or by fighters employing hit-and-run tactics at high speeds.
The effectiveness of the Il-4’s defensive armaments was also influenced by its operational altitude and speed. Operating often at high altitudes to evade enemy interceptors, the Il-4’s machine guns were most effective when enemy fighters were forced into predictable approaches, mitigating some of the aircraft’s vulnerability due to its relatively slow speed compared to contemporary fighters.
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Service
The Ilyushin Il-4 had a distinguished and extensive service history during Second World War, serving as one of the primary long-range bombers in the Soviet Air Force throughout the war – even though it was a rather old design by 1945.
Almost as soon as the war started the Il-4 was in the thick of the action. With its long-range, many were located far behind the lines and survived the initial onslaughts. It was also one of the few aircraft at the time of Operation Barbarossa that could hit targets in Germany. In fact, just two months after Germany’s invasion of the USSR began, Il-4s conducted a bombing raid on Berlin.
Admittedly, the damage was limited, but it was a propaganda victory like the US’ Doolittle raid on Japan. Soon though, Soviet manufacturing capabilities were severely impacted when German forces approached its industrial heartland.
Factories were literally packed up and moved behind the Ural mountains in a herculean effort that is often attributed as being one of the most important factors in preventing a Soviet defeat. The move impacted the Il-4’s production, and some aircraft were even made with wooden components in a bid to try and keep up numbers.
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As a priority aircraft, the manufacture of the Il-4 was quickly fired back up in 1942. Throughout the war it was deployed extensively on the Eastern Front, where it undertook long-range bombing missions against German military and industrial targets.
These missions were helpful in disrupting German supply lines and manufacturing capabilities, directly supporting Soviet ground offensives. The Il-4 proved particularly valuable during the crucial battles of Stalingrad and Kursk, where its ability to strike deep behind enemy lines played a pivotal role. Despite this, most missions were relatively short-ranged, where the Il-4 could instead carry a heftier bomb load.
The Il-4 was versatile enough to be used in other vital roles too, such as a maritime patrol bomber in the Baltic and Black Seas. The Il-4 was also adapted for use as a torpedo bomber, becoming a significant threat to German shipping by attacking transport and warships. Its long range and good payload capacity made it suitable for laying naval mines as well.
However, one of the most useful roles carried out by the Il-4 was reconnaissance. Its long endurance allowed it to loiter above the enemy and report back to units below. Sometimes this was done on essentially a real-time basis.
By the end of the war the Il-4 was very much out of date, having stayed in service far longer than would have been typically expected due to the desperate circumstances. Once the war ended the aircraft was quickly phased out.
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In total around 5,000 Il-4’s were made, which is comparable to the amount of B-26 Mauraders produced by the US. Despite this, there are no complete aircraft that survived. A handful are on display in Europe, but these were assembled from numerous aircraft.
