In the mid-30s, military theorists in different countries began to view tanks operating in conjunction with motorized infantry as the main strike weapon in a future war. At the same time, it seemed quite logical to create new anti-tank weapons. Well protected from anti-aircraft fire and equipped with special anti-tank weapons, armored attack aircraft could become an effective means of fighting tanks on the battlefield and in eliminating tank wedge breakouts.
As you know, the first attack aircraft with armor protection elements appeared at the end of the First World War. Initially, assault aviation was intended mainly for attacking infantry and cavalry units on the march, destroying enemy transport convoys and artillery positions. The design of specialized attack aircraft continued in the 20-30s, although the slow and weakly armed airplanes of course could not claim the role of an effective anti-tank weapon.
In the Soviet Union, the design of the B-1 armored attack aircraft based on the R-1 single-engine reconnaissance aircraft began in 1926. The P-1 was a copy of the British de Havilland DH.9.
The aircraft has been serially built in the USSR since 1923. Double R-1 with 400 hp M-5 engine. with. had a flight weight of 2200 kg and a maximum speed of 194 km / h. However, the attempt to create the first armored attack aircraft failed. The real capabilities of the Soviet aviation industry then clearly did not meet the specified tactical and technical requirements. In fairness, it should be said that in other countries, aircraft designers have failed to create an attack aircraft protected by armor with acceptable flight characteristics. After a series of unsuccessful attempts, the attention of foreign designers abroad was mainly focused on the creation of dive bombers. In addition, twin-engine heavy fighters were supposed to be used as attack aircraft.
On the contrary, in the USSR, the idea of creating an armored attack aircraft was not abandoned, and in the 20-30s a number of projects of single-engine and twin-engine vehicles appeared. But all of these aircraft had common drawbacks. Since the armor protection was not integrated into the power circuit of the structure, it turned out to be a "dead" weight and overweight the attack aircraft. Forward and downward visibility was generally unsatisfactory, and the engines were not powerful enough to achieve high speed. Small arms of rifle caliber did not pose a threat to tanks and armored vehicles, and the bomb load was minimal.
Therefore, in the 1930s, the Red Army Air Force used specialized modifications of the R-5 reconnaissance biplane as attack aircraft: R-5Sh, R-5SSS and P-Z, as well as I-5 and I-15 fighters. As combat experience showed, these vehicles had common drawbacks: lack of armor protection for the crew, engine, fuel tanks and weak offensive weapons. In addition, the aircraft built on the basis of the R-5 reconnaissance aircraft had a clearly insufficient flight speed and relatively large geometric dimensions, which increased their vulnerability to anti-aircraft guns and enemy fighters. Losses of unarmored attack aircraft could be minimized in the case of an assault strike against a ground target from one approach, at maximum speed from extremely low altitudes (5–25 m) or from a jump to an altitude of 150–200 m. It is clear that when using such tactics, aiming was difficult and there was no talk of attacking individual tanks or armored vehicles.
In the mid-1930s, on the basis of operating experience and a comparative assessment of the tactical and technical data of existing aircraft in service with assault brigades, the idea of a "military aircraft" appeared, which would ensure the solution of basic combat missions. It was assumed that on the basis of the basic design, combat aircraft would be created that could be used as an attack aircraft, a close-range bomber and a reconnaissance spotter. At the same time, the maximum speed was supposed to be 380-400 km / h, the range was 1200 km. Crew of 2-3 people. Normal bomb load up to 500 kg, overload - up to 1000 kg. However, it was unrealistic to create a single combat aircraft that could equally successfully solve all combat missions, and common sense prevailed. The emphasis in combat missions performed by the universal "military aircraft" was shifted from reconnaissance to bombing.
Later, this program was implemented under the code "Ivanov". Almost all Soviet aviation design bureaus took part in the creation of a massive single-engine strike combat aircraft intended for action in the near-front zone of the enemy. The military recommended building a short-range bomber with an air-cooled engine, as having greater survivability in battle, compared to a water-cooled engine. Among the possible options were offered motors: M-25, M-85 and M-62.
In 1939, the BB-1 (Su-2) aircraft was adopted as a short-range bomber. It could be used as an attack aircraft and a scout. Double Su-2 with 1330 hp M-82 engine. with. showed on tests a maximum speed of 486 km / h.
The aircraft's small arms consisted of 2-4 ShKAS machine guns for forward firing and one designed to protect the rear hemisphere. Up to 500 kg of bombs, 10 RS-82 or eight RS-132 could be suspended under the wing.
In total, more than 800 aircraft were built before production ceased in the first half of 1942. The Su-2 turned out to be quite good in the role of a close-range bomber, in any case, in regiments equipped with these machines, the losses were significantly lower than that of the Pe-2, which formally had the best flight data. But the Su-2 was absolutely unsuitable for the role of an anti-tank attack aircraft. Although the air-cooled engine had good survivability, the pilot was only protected by a 9mm armored back. Rapid-fire rifle-caliber ShKASs well mowed down infantry that had not taken refuge, but could only damage the color of the armor of tanks. The aircraft was not adapted for dive bombing, and when dropping bombs in horizontal flight, the probability of hitting a separate tank was very low. For all its merits, the Su-2 was ineffective and too vulnerable when used as an attack aircraft. For this, it was required to strengthen weapons and increase security. Since the main reserves of the Su-2 design were exhausted, it was decided to build a new aircraft. Draft design of a new attack aircraft, aircraft designer P. O. Sukhoi presented in September 1939. On March 1, 1941, the first prototype of the Su-6 armored attack aircraft took off. But the lack of knowledge of the power plant did not allow the promising aircraft to be accepted into service before the start of the war. The Su-6 entered state tests only in January 1942. In wartime, the reluctance to break the production process and reduce the output of combat aircraft already put on stream, albeit with the worst data, played a fatal role in the fate of the Su-6 attack aircraft. More details here: Su-6 attack aircraft.
Simultaneously with the creation of the "military aircraft", work was underway to modify serial fighters into light attack aircraft. A number of specialists of the Red Army Air Force believed that they were capable of replacing specialized attack aircraft with the correct tactics of use. In the event of an attack by ground targets from a dive or at high speed from level flight at low altitude, the high angular velocity of the aircraft sharply reduces the likelihood of its being hit by ground anti-aircraft air defense weapons, and the booking of such an attack aircraft may be insignificant. Particular attention was paid to inflicting dive strikes, while it was possible to ensure high accuracy of bombing against small targets and, therefore, a higher probability of hitting targets than when bombing from level flight. This made it possible to increase the effectiveness of direct air support for troops in breaking through the enemy's fortified defensive zone.
In addition, a light, high-speed attack aircraft, created on the basis of a fighter, could independently defend itself in air combat. The use of fighters existing in the USSR in the role of light high-speed attack aircraft was also facilitated by the fact that they used air-cooled engines - less vulnerable to combat damage. In addition, the better speed and maneuverability of fighters and smaller geometries compared to attack aircraft based on reconnaissance aircraft made them much more difficult targets.
Apparently, the first Soviet fighter modified into an attack aircraft was the DI-6 two-seat escort fighter. This little-known and forgotten plane had a number of innovations. So, for the first time in the USSR, hydrogen was used for welding structural elements on it. In addition, it was the DI-6 that became the first serial biplane on which a retractable landing gear was used. Small arms consisted of two synchronous ShKAS machine guns and one for firing backwards. The maximum speed is 372 km / h.
In November 1935, work began on the DI-6Sh assault modification with the M-25 engine. The attack aircraft differed from the fighter with an armored back and a pilot's seat cup. For forward firing, two PV-1 machine guns (an aviation version of the Maxim machine gun) were intended, four more PV-1s were installed under the lower wing in special fairings at an angle of 3 ° to the longitudinal axis of the aircraft. These machine guns were designed to fire at ground targets from a gentle dive and in horizontal flight. For defense against attacks of enemy fighters from the rear hemisphere, there was a ShKAS, served by a navigator. Bomb load - 80 kg. The aircraft with a takeoff weight of 2115 kg at an altitude of 4000 m demonstrated a maximum speed of 358 km / h.
Despite the fact that the DI-6Sh had a number of shortcomings and did not fully meet the requirements of the Air Force, it was accepted into service, and was built in a small series from the end of 1936. Part of the DI-6 combat fighters was converted into the assault version. According to archival data, more than 200 fighters were sent to the troops, 61 aircraft in the assault version. The DI-6SH was mainly used as a combat training aircraft for practicing the techniques and skills of bombing and assault strikes. Information about the participation of these machines in the war could not be found.
Shortly before the start of the war, all I-15bis fighters and a significant part of the I-153 were transferred to the armament of the assault aviation units. In the assault version, the I-15bis carried up to 150 kg of bombs: 4x32 kg or 4x25 kg or, 2x25 kg and 2x50 kg, or 4-8 RS-82. Small arms 4 PV-1 rifle caliber. The maximum speed of the I-15bis was 379 km / h at an altitude of 3500 m.
The I-153 carried the same bomb load, but its machine-gun armament consisted of four rapid-fire synchronous ShKAS. On the I-153P modification with the M-62 engine, two 20-mm ShVAK cannons were installed. Since the aerodynamics of the I-153 were significantly better due to the retractable landing gear, the speed of the aircraft with the M-62 engine with a capacity of 1000 hp. reached 425 km / h.
The I-15bis and I-153 could effectively act against uncovered infantry, cavalry and transport convoys. At the same time, the planes had low anti-tank capabilities and effectiveness in striking engineer-protected targets (bunkers, bunkers, dugouts). The caliber of the bombs and the weight of the bomb load did not provide a sufficiently high probability of hitting such targets. The most effective means of destruction of armored vehicles were RS-82 rockets, but they had a large dispersion and could penetrate relatively thin armor only with a direct hit. In addition, plywood biplanes were very vulnerable even to the fire of rifle-caliber anti-aircraft machine guns, not to mention the 20-37-mm MZA. To reduce losses from anti-aircraft fire, pilots of "plywood attack aircraft" attacked targets at low altitude and from one approach, dropping bombs or launching NAR in one gulp. Often, the followers did not see the attacked targets at all, acting on the commands of the leaders. Naturally, the effectiveness of such strikes was not high. The fighting revealed the low effectiveness of assault variants of fighters against armored vehicles and long-term defensive structures.
I must say that the command of the Red Army Air Force understood in advance the disadvantages of using unarmored and weakly armed fighters in the role of attack aircraft. All types of combat aircraft used in the late 30s as attack aircraft and designed under the Ivanov program had great vulnerability to shelling from the ground. None of the vital parts of these aircraft - the cockpit, engine, oil and petrol systems - were not protected by armor. That significantly reduced the combat capabilities of the assault aircraft. In other words, our assault aviation needed a "flying tank" and in the late 30s, the design of specialized highly protected battlefield aircraft with powerful weapons continued.
The greatest success in the creation of an armored attack aircraft was accompanied by the Design Bureau, led by S. V. Ilyushin. According to the initial project, which appeared at the beginning of 1938, the aircraft, which received the working designation BSh-2, had armor protection of vital components and assemblies with a thickness of 5 mm. The aircraft crew consisted of a pilot and a gunner defending the rear hemisphere. The estimated maximum speed at the ground is 385–400 km / h. Bomb load weight 250-300 kg.
In the future, the flight data, armor protection and armament of the attack aircraft were adjusted. The main feature of the new vehicle was a streamlined armored hull made of AB-1 aviation armor steel, which was manufactured by stamping. The armored hull, included in the power circuit of the airplane's airframe, protected the crew, engine, gas tanks, oil tank, water and oil coolers. The bomb bay was partially covered by armor. To reduce the total weight of the armor without reducing its protective characteristics, the thickness of the stamped armor plates was made uneven - from 4 to 7 mm. The designers proceeded from an analysis of the angles of meeting of fragments and bullets with an armored hull. The aircraft was equipped with an AM-35 water-cooled engine with a nominal power at the ground - 1130 hp. with. Initially, the offensive armament consisted of four 7.62 mm ShKAS machine guns. The tail defended another ShKAS on the turret. Normal bomb load - 400 kg.
The first flight of BSh-2 took place on October 2, 1939. But after passing the tests, the aircraft did not satisfy the military. His flight data were significantly worse than those envisaged by the assignment. The small arms for the attack aircraft were frankly weak, and the front of the cockpit was not covered with transparent armor. In addition, representatives of the Air Force presented absolutely contradictory requirements to the aircraft, without finally deciding whether they needed an attack aircraft or a close-range bomber.
After analyzing the possible options, the AM-38 engine was installed on the attack aircraft (maximum power at the ground is 1625 hp), which is optimal for use at low and medium altitudes. The cockpit was slightly raised in order to improve forward-downward visibility. As a result of the shelling at the range, changes were made to the armored hull - the upper side walls of the cockpit were 8 mm thick, instead of 6 mm, and the side walls covering the main gas tank and oil tank were made 6 mm instead of 5 mm. The canopy of the cockpit was made of transparent armor. To improve the longitudinal stability of the aircraft, the engine was moved forward by 50 mm. The wing sweep along the leading edge has increased by 5 °, and the stabilizer area has increased by 3.1%. In place of the gunner's cockpit, a 12-mm armor plate and an additional gas tank were installed. Due to the unavailability of the 23-mm MP-6 cannons, a pair of 20-mm ShVAK was placed in the wing instead. For zeroing and firing at manpower, two ShKAS machine guns were used. The attack aircraft's armament was enhanced by installing eight guides for firing RS-132 rockets. The bomb load remained the same - 400 kg (overload 600 kg). An aircraft with a takeoff weight of 5125 kg (payload weight 1245 kg) in flight at the ground showed a maximum speed of 422 km / h, and at an altitude of 2300 m - 446 km / h. With an average speed of 357 km / h, the flight range near the ground with a normal combat load and a fuel supply of 470 kg was 600 km.
Despite a number of shortcomings and an unfinished engine, the attack aircraft was launched into mass production on February 15, 1941 under the designation Il-2. Simultaneously with the start of serial assembly, work was carried out to eliminate the shortcomings and improve the aircraft.
State tests of the IL-2 of serial construction, which began on June 5, 1941, showed that the speed at the ground and at an altitude of 2500 m with a flight weight of 5335 kg and a take-off engine power of 1665 hp. with. the production car became higher - 423 km / h and 451 km / h. And the takeoff and landing characteristics have improved. This was due to the modification of the AM-38 engine and an increase in its take-off power.
The flight performance of the IL-2 was significantly reduced with the external suspension of bombs and rockets. For example, the suspension of two FAB-250 bombs when flying near the ground "ate up" 43 km / h, and the suspension of eight RS-82 reduced the speed by 36 km / h. Even before the state tests of the serial attack aircraft on the Il-2, 23-mm VYa guns were successfully tested. Compared with the 20-mm ShVAK projectile, the 23-mm projectile weighing 200 g was twice as heavy and had a significantly higher armor penetration. The VYa guns were more suitable for arming an attack aircraft, but during the entire period of the war, the industry did not manage to establish their production in sufficient quantities, and therefore a significant part of the Il-2 was produced with relatively low-power 20-mm cannons.
Despite the fact that many aircraft designers were engaged in armored attack aircraft, the Il-2 became the only combat aircraft of this purpose brought to mass production by the beginning of the war. Even taking into account the fact that the attack aircraft was not yet well mastered by the flight and technical personnel and had a number of "childhood ailments", from the very beginning it proved itself well in combat. The IL-2 worked most effectively on motorized columns, infantry, and artillery positions. Quite effectively, armored attack aircraft processed the enemy's front edge with timber and earth fortifications.
In the first months of the war, the optimal tactics of action against the accumulations of enemy troops were worked out. Transport convoys and armored vehicles on the Il-2 march were usually attacked from low-level flight (approach altitude 25-35 meters) along the convoy or at an angle of 15-20 degrees to its long side. As a rule, the first blow by RS and guns was applied to the head of the column in order to block its movement. The range of opening fire is 500-600 meters. Before using the main armament, tracer bullets from ShKAS machine guns were zeroed in. Most often, aiming was carried out "along the column" without choosing a specific target.
The effectiveness of IL-2 fire on cars, fuel tankers, armored personnel carriers and artillery tractors was quite high. After bombarding the target with rockets and aircraft cannons, bombs were dropped. Depending on the combat situation, the countermeasures of fighters and anti-aircraft artillery, the number of combat approaches could vary. In a number of cases, attack aircraft managed to inflict very high losses on the enemy and destroy most of the equipment that was in the composition of the columns.
A completely different picture was obtained when attacking individual tanks on the ground. Only pilots with sufficiently high qualifications could achieve hitting several shells in a single tank from a low level flight or a gentle dive. According to experienced pilots, the most effective shooting from an Il-2 aircraft at tanks, in terms of firing accuracy, orientation on the ground, maneuvering, time spent on a combat course, was firing from a glide at an angle of 25-30 ° at a height of entry into gliding 500-700 m, and input speed 240-220 km / h (output height - 200-150 m). Since the speed of the IL-2 at this gliding angle did not increase significantly - only by 9-11 m / s, this allowed maneuvering to adjust the aiming point. The total attack time in this case was 6-9 seconds, which allowed the pilot to make 2-3 short sighting bursts. The range of the beginning of aiming at the tank was 600-800 m, and the minimum distance of opening fire was 300-400 m. In this case, 2-4 shells fell into the tank.
The hopes that the Il-2 would be able to effectively deal with enemy tanks did not come true. As a rule, fire from 20-23 mm guns did not inflict significant damage on tanks. It soon became clear that the armor-piercing 20-mm projectile of the ShVAK cannon is capable of penetrating German armor up to 15 mm thick (Pz. II Ausf F, Pz. 38 (t) Ausf C tanks, Sd Kfz 250 armored personnel carriers) at meeting angles close to normal, with a distance of no more than 250-300 m. At meeting angles of 30-40 °, characteristic of an attack from a low-level flight or from a gentle dive, the shells, as a rule, ricocheted.
The 23-mm VYa shells had the best armor penetration. Aircraft with such guns began to arrive in August 1941. An armor-piercing incendiary 23-mm projectile weighing 200 g at a distance of up to 200 m along the normal pierced 25-mm armor. IL-2 with VYa-23 cannons could hit the armor of light tanks, when attacking the latter from behind or from the side at gliding angles up to 30 °. Thus, 20-mm and 23-mm air cannons could effectively fight only with armored personnel carriers, armored vehicles and light tanks. In addition, not every penetration of armor with a small-caliber projectile, which had a small armor effect, led to the destruction or incapacitation of the tank. For this reason, the proposal of S. V. Ilyushin did not meet with understanding to equip the attack aircraft 14, 5-mm machine guns, created on the basis of the VYa cannon. The greatest armor penetration was possessed by the 14.5-mm cartridge with the BS-41 bullet, which used a tungsten carbide core. At a distance of 300 m, the BS-41 confidently pierced 35 mm armor. However, tungsten carbide, used for the manufacture of APCR shells, was a scarce material throughout the war. Experts reasonably noted that the consumption of 14.5-mm aviation ammunition would be ten times higher than when firing from anti-tank rifles, and the effectiveness is not much higher than when using 23-mm shells.
By and large, attempts to equip the attack aircraft with 37-mm cannons turned out to be a dead-end direction. In the second half of 1942, a small series of the IL-2 variant was produced, armed with ShFK-37 cannons. The 37-mm ShFK-37 aircraft cannon was developed under the leadership of B. G. Shpitalny. The ammunition load included armor-piercing incendiary-tracer (BZT-37) and fragmentation-incendiary-tracer (OZT-37) shells.
The designers hoped that the attack aircraft with 37-mm cannons would be able to fight against medium and heavy enemy tanks. On tests, the BZT-37 armor-piercing incendiary projectile ensured penetration of 30 mm of German tank armor at an angle of 45 °, at a distance of no more than 500 m. The projectile pierced armor with a thickness of 15 mm and less at meeting angles of no more than 60 °. The frontal 50 mm armor of medium German tanks was penetrated by a 37-mm projectile from distances of no more than 200 m at an encounter angle of 5 °. Theoretically, the IL-2 with 37-mm cannons could hit the PzKpfw III, PzKpfw IV, Pz. 38 (t) tanks and self-propelled guns based on their base when firing at the side. On tests, it turned out that more than 50% of hits of 37-mm armor-piercing shells on a medium tank and 70% of hits on a light tank put them out of action. In case of hitting the chassis of tanks, rollers, wheels and other parts received significant damage, which deprived the tank of mobility.
However, in practice, the installation of the ShFK-37 on the Il-2 did not justify itself. Due to the large dimensions of the ShFK-37 air cannons and their magazines, the capacity of 40 rounds was placed in bulky fairings with a large cross-section under the wing of the aircraft. Due to the design features, the gun had to be lowered strongly down relative to the construction plane of the wing. This seriously complicated the design of attaching the cannon to the wing (the cannon was mounted on a shock absorber and, after firing, moved with the magazine). The flight data of the IL-2 with the ShFK-37 air cannons, in comparison with the serial attack aircraft armed with 20-23 mm cannons, has significantly deteriorated. The maximum speed and maneuverability of the aircraft have decreased. He became more inert and difficult in piloting technique, especially in turns and turns at low altitude. The pilots noted the increased load on the controls when performing maneuvers.
The accuracy of shooting from the ShFK-37 decreased due to the strong recoil of the guns and the lack of synchronization in their work. Due to the large spacing of the guns relative to the center of mass of the aircraft, the high recoil, as well as due to the insufficient rigidity of the mount of the gun mount, strong shocks, "pecks" and departure from the aiming line occurred, and this, in turn, taking into account the insufficient longitudinal stability of the IL-2, led to a sharp decrease in shooting accuracy. It was impossible to fire from one cannon. The attack aircraft immediately turned its recoil towards the firing cannon, and at the same time there was no talk of aimed fire. In this case, it was only possible to hit the target with the first projectile in the queue. During operation in the troops, the ShFK-37 air cannon gave a large percentage of failures. On average, in every second combat sortie, at least one gun failed, which automatically made it impossible to fire from the second one. The combat value of aircraft with "large-caliber" 37-mm cannons was also reduced by the fact that the weight of the bomb load on these machines was limited to 200 kg.
The first experience of using 37-mm cannons turned out to be negative, but this did not stop the designers, as it seemed very tempting to equip the attack aircraft with powerful cannons capable of penetrating the armor of heavy and medium tanks. In July 1943, tests began on the two-seat Il-2, armed with two 37-mm NS-37 cannons. In total, 96 Il-2 with NS-37 participated in the military tests.
Compared to the ShFK-37, the NS-37 air cannon was much more advanced, reliable and rapid-fire. Thanks to the tape feed, it was possible to reduce the size and weight of the system and place the guns directly at the lower surface of the wing. A relatively small fairing was mounted on top of the gun, consisting of two quick-release flaps. The tape with 37-mm projectiles fit directly into the wing compartment. The weight of one NS-37 with ammunition was a little over 250 kg.
However, as in the case of the ShFK-37, the installation of the NS-37 cannons significantly worsened the flight data and reduced the bomb load. This was due to the large spread of masses in the wingspan, the significant weight of the ammunition cannons and fairings, which worsen the aerodynamics of the aircraft. The longitudinal stability of the NS-37 attack aircraft was significantly worse than that of the IL-2, armed with 20-23 mm cannons, which negatively affected the firing accuracy, which was further aggravated by the strong recoil of the NS-37. As in the case of the ShFK-37, aimed firing from one cannon was completely impossible.
Nevertheless, in the case of normal operation of both guns, they could be successfully used at real firing ranges. In this case, the fire should have been conducted in short bursts of 2-3 shots each, otherwise the plane began to "peck" strongly, the aiming was lost, and the aiming point adjustment in this case was impossible. According to the reports of the pilots and the data from the photo-machine guns, the number of hits on the target to the spent ammunition was approximately 3%, and hits into the tanks were obtained in 43% of sorties. According to the pilots who participated in the military tests, the IL-2 with 37-mm air cannons, when attacking small-sized targets, did not have any particular advantages over an attack aircraft armed with smaller caliber cannons with a normal bomb load and rockets. Thus, it can be stated that the installation of the NS-37, accompanied by a decrease in flight data and a bomb load, did not justify itself. Based on the results of military tests, it was decided to abandon the serial construction of the Il-2 with NS-37 cannons.
In the second half of the war, the protection of tanks increased sharply, and it became absolutely clear that aircraft cannons could not be the main means of fighting medium and heavy tanks. The penetration of tank armor during shelling from the air was hampered not only by the relatively small caliber of aviation shells, but by unfavorable angles of meeting with the armor. When firing from a gentle dive, in most cases it was impossible to penetrate even the relatively thin 20-30 mm upper armor of tanks. In real combat conditions, shells, as a rule, hit the roof of tanks at unfavorable angles, which sharply reduced their penetrating ability, or even led to a ricochet. In addition, the armored action of all-metal projectiles that did not contain explosives was modest, and not every projectile that penetrated the tank's armor disabled it.
