The Ilyushin Il-2 (Cyrillic: Илью́шин Ил-2) was a ground-attack aircraft (Cyrillic: Штурмови́к, Šturmovík) in the Second World War, produced by the Soviet Union in very large numbers. With 36,183 examples of the Il-2 produced during the war, and in combination with its successor, the Ilyushin Il-10, a total of 42,330 were built, making it the single most produced military aircraft design in all of aviation history, as well as one of the most produced piloted aircraft in history along with the American postwar civilian Cessna 172 and the Soviet Union's own Polikarpov Po-2 Kukuruznik biplane, itself sometimes seen side-by-side with the big armored Ilyushin monoplane on the front lines.
To Il-2 pilots, the aircraft was simply the diminutive "Ilyusha". To the soldiers on the ground, it was the "Hunchback", the "Flying Tank" or the "Flying Infantryman". Its postwar NATO reporting name was "Bark". The Il-2 aircraft played a crucial role on the Eastern Front. Joseph Stalin paid the Il-2 a great tribute in his own inimitable manner: when a particular production factory fell behind on its deliveries, Stalin sent an angrily-worded cable to the factory manager, stating "They are as essential to the Red Army as air and bread. "I demand more machines. This is my final warning!"
The idea for a Soviet armored ground-attack aircraft dates to the early 1930s, when Dmitry Pavlovich Grigorovich designed TSh-1 and TSh-2 armored biplanes. However, Soviet engines at the time lacked the power needed to provide the heavy aircraft with good performance. Il-2 was designed by Sergey Ilyushin and his team at the Central Design Bureau in 1938. TsKB-55 was a two-seat aircraft with an armoured shell weighing 700 kg (1,540 lb), protecting crew, engine, radiators, and the fuel tank. Standing loaded, the Ilyushin weighed more than 4,700 kg (10,300 lb), making the armoured shell about 15% of the aircraft's gross weight. Uniquely for a World War II attack aircraft, and similarly to the forward fuselage design of the World War I-era Imperial German Junkers J.I armored, all-metal biplane, the Il-2's armor was designed as a load-bearing part of the Ilyushin's monocoque structure, thus saving considerable weight. The prototype TsKB-55, which first flew on 2 October 1939, won the government competition against Sukhoi Su-6 and received VVS designation BSh-2. The prototypes - TsKB-55 and TskB-57 - were built at Moscow plant #39, at that time the Ilyushin design bureau's base.The BSh-2 was overweight and underpowered, with the original Mikulin AM-35 1,022 kW (1,370 hp) engine designed to give its greatest power outputs at high altitude. Because of this it was redesigned as the TsKB-57, a lighter single-seat design, with the more powerful 1,254 kW (1,680 hp) Mikulin AM-38 engine, a development of the AM-35 optimised for low level operation. The TsKB-57 first flew on 12 October 1940. The production aircraft passed State Acceptance Trials in March 1941, and was redesignated Il-2 in April. Deliveries to operational units commenced in May 1941.
The 23 mm armament of Il-2 was subject to a competition. One of the first 1940 photographs of the Il-2 show it equipped with two MP-6 guns developed by Jacob Taubin (Яков Таубин) at OKB-16. The MP-6 gun weighed 70 kg and developed an initial muzzle velocity of 900 m/s. It operated on the short recoil principle and had a rate of fire of about 600 rpm. (The development of the MP-6 gun can be traced back to 1937. The initial version was tested in the spring of 1940 on a Bf 110 bought from Germany, because there was no suitable Soviet aircraft on which to mount it. In the summer of 1940 it was tested on the Pashinin I-21.) Factory trials of the MP-6 gun on the Il-2 were conducted in August 1940. In the early Il-2 prototypes, these guns were fed by 81-round clips. In flight, these clips sometimes became dislodged because of their large surface, which caused them to experience significant aerodynamic pressure. Competitive tests were conducted in the spring of 1941 between the MP-6 gun modified to belt-fed and the newly developed, gas-operated Volkov-Yartsev VYa-23, which had otherwise rather similar characteristics. The VYa-23 was declared winner at this trial. Subsequently, in May 1941, development of the MP-6 gun was terminated and Taubin was arrested and summarily executed in October that year.
The Il-2 is a single-engine, propeller-driven, low-wing monoplane of mixed construction with a crew of two (one in early versions), specially designed for assault operations. Its most notable feature was the inclusion of armor in an airframe load-bearing scheme. Armor plates replaced the frame and paneling throughout the nacelle and middle part of the fuselage, and an armored hull made of riveted homogeneous armor steel AB-1 (AB-2) secured the aircraft’s engine, cockpit, water and oil radiators, and fuel tanks.
The Il-2 was eventually produced in vast quantities, becoming the single most widely produced military aircraft in aviation history, but only 249 had been built by the time Nazi Germany invaded the Soviet Union on 22 June 1941.
Production early in the war was slow because after the German invasion the aircraft factories near Moscow and other major cities in western Russia had to be moved east of the Ural Mountains. Ilyushin and his engineers had time to reconsider production methods, and two months after the move Il-2s were again being produced. The tempo was not to Premier Stalin's liking, however, and he issued the following telegram to Shenkman and Tretyakov:
You have let down our country and our Red Army. You have the nerve not to manufacture IL-2s until now. Our Red Army now needs IL-2 aircraft like the air it breathes, like the bread it eats. Shenkman produces one IL-2 a day and Tretyakov builds one or two MiG-3s daily. It is a mockery of our country and the Red Army. I ask you not to try the government's patience, and demand that you manufacture more ILs. This is my final warning.As a result, "the production of Shturmoviks rapidly gained speed. Stalin's notion of the Il-2 being 'like bread' to the Red Army took hold in Ilyushin's aircraft plants and the army soon had their Shturmoviks available in quantity.
The first use in action of the Il-2 was with the 4th ShAP (Ground Attack Regiment) over the Berezina River days after the invasion began. The aircraft was so new that the pilots had no training in flight characteristics or tactics, and the ground crew no training in servicing or re-arming. The training received only enabled the pilots to take-off and land, none of the pilots had fired the armament, let alone learned tactics. There were 249 Il-2s available on 22 June 1941. In the first three days, 4th ShAP had lost 10 Il-2s to enemy action, a further 19 were lost to other causes, and 20 pilots were killed. By 10 July, 4th ShAP was down to 10 aircraft from a strength of 65.
Tactics improved as Soviet aircrews became used to the Il-2's strengths. Instead of a low horizontal straight approach at 50 metres altitude, the target was usually kept to the pilot's left and a turn and shallow dive of 30 degrees was utilized, using an echeloned assault by four to twelve aircraft at a time. Although the Il-2's RS-82 and RS-132 rockets could destroy armored vehicles with a single hit, they were so inaccurate that experienced Il-2 pilots mainly utilized the cannon. Another potent weapon of the Il-2s was the PTAB shaped charge bomblets (protivotankovaya aviabomba, "anti-tank aviation bomb"). They were designated PTAB-2.5-1.5, as they had the size of a 2.5 kg (5.5 lb) bomb, but weighed only 1.5 kg (3.3 lb) due to the empty space in the shaped charge. Up to 192 were carried in four external dispensers (cluster bombs) or up to 220 in the inner wing panels' internal ventral weapon bays. The HEAT charge could easily penetrate the relatively thin upper armor of all heavy German tanks. PTABs were first used on a large scale in the Battle of Kursk.
Thereafter, the Il-2 was widely deployed on the Eastern Front. The aircraft could fly in low light conditions and carried weaponry capable of defeating the thick armor of the Panther and Tiger I tanks.
The true capabilities of the Il-2 are difficult to determine from existing documentary evidence. W. Liss in Aircraft profile 88: Ilyushin Il-2 mentions an engagement during the Battle of Kursk on 7 July 1943, in which 70 tanks from the German 9th Panzer Division were claimed to be destroyed by Ilyushin Il-2s in just 20 minutes. In another report of the action on the same day, a Soviet staff publication states that:
Ground forces highly valued the work of aviation on the battlefield. In a number of instances enemy attacks were thwarted thanks to our air operations. Thus on 7 July enemy tank attacks were disrupted in the Kashara region (13th Army). Here our assault aircraft delivered three powerful attacks in groups of 20-30, which resulted in the destruction and disabling of 34 tanks. The enemy was forced to halt further attacks and to withdraw the remnants of his force north of Kashara.In the Battle of Kursk, General V. Ryazanov became a master in the use of attack aircraft en masse, developing and improving the tactics of Il-2 operations in co-ordination with infantry, artillery and armoured troops. Ryazanov was later awarded the Gold Star of Hero of Soviet Union twice, and the 1st Attack Aircraft Corps under his command became the first unit to be awarded the honorific title of Guards. The Sturmovik nevertheless suffered heavy losses: the Luftwaffe command claimed 6,900 Il-2s in 1943 and 7,300 in 1944. Although these figures were exaggerated by a factor of between 2 to 2.2, the actual losses were substantial. In 1943, one loss corresponded to 26 Sturmovik sorties. About half of those lost were shot down by fighters, the rest falling to anti-aircraft fire.
—Glantz and Orenstein 1999, p. 260.
The main problem with the Il-2 was the inaccuracy of its attacks. Towards the end of war the Soviets were able to concentrate massive numbers of Sturmoviks to support their main offensives. However, particularly against dug-in and armored targets, the effect was often more psychological than actual physical destruction of targets. In the 9 June offensive in the Karelian Isthmus in Finland, the Finnish AA forces were far too few in numbers to counter the armadas of Pe-2 and Il-2, but they quickly found that the Il-2 attacks generally missed their marks widely, particularly with bombs. While some attacks against large unprotected targets such as horse and truck convoys and railyards had devastating results, attacks against dug-in point targets were usually ineffective. The frequent duels between dug-in 20 and 40mm AA guns and Il-2 attackers never resulted in the complete destruction of the gun, while many Il-2s were brought down in these attacks.
The heavy armor of the Il-2 also meant that it would typically carry only comparatively light bomb-loads, which together with the poor accuracy of its attacks made it a far less deadly attack aircraft than the contemporary Allied fighter-bombers such as the Republic P-47 Thunderbolt and Hawker Typhoon. The rocket projectiles especially were not effective, even the larger RS-132 (of which four were carried) having a warhead with only 0.9 kg (2.0 lb) of explosives, which compared poorly with the P-47's typical load of ten 5 inch (13 cm) HVARs with each having a 21 kg (46 lb) warhead, or the 8 to 12 "60 lb" (27 kg) warheads of the Hawker Typhoon's RP-3 rockets. Likewise the Shturmovik's bombs were usually only 50 kg (rarely 100 kg), too small to compensate for the typically wide variation from target point. To compensate for the poor accuracy of the Il-2's bombsight, in 1943 the Soviet Command decided to use shaped-charge armor-piercing projectiles against enemy armored vehicles, and the PTAB-2.5-1.5 SCAP aircraft bomb was put into production. These small-calibre bombs were loaded directly into the bomb bays and were dropped onto enemy vehicles from altitudes up to 100 meters (328 ft). As each Il-2 could carry up to 192 bombs, a fire carpet 70 meters (229 ft.) long and 15 meters (49 ft) wide covered the enemy tanks, giving a high "kill" probability. Pilots of 291st ShAP were the first to use the PTAB-2.5-1.5 bombs. During one sortie on 5 June 1943, six attack aircraft led by Lt. Col. A. Vitrook destroyed 15 enemy tanks in one attack, and during five days of the enemy advance the 291st Division claimed to have destroyed or damaged 422 enemy tanks.
Thanks to the heavy armor protection, the Il-2 could take a great deal of punishment and proved difficult for both ground and aircraft fire to shoot down. One Il-2 in particular was reported to have returned safely to base despite receiving more than 600 direct hits and having all its control surfaces completely shredded as well as numerous holes in its main armor and other structural damage. Some enemy pilots favored aiming down into the cockpit and wing roots in diving attacks on the slow, low-flying Il-2 formations. Several Luftwaffe aces claimed to attack while climbing from behind, out of view of the rear gunner, aiming for the Il-2's non-retractable oil cooler. This has been disputed by some Il-2 pilots in postwar interviews, since Il-2s typically flew very close to the ground (cruise altitudes below 50 m (160 ft) were common) and the radiator protruded a mere 10 cm (4 in) from the aircraft.
A major threat to the Il-2 was German ground fire. In postwar interviews, Il-2 pilots reported 20 mm (0.79 in) and 37 mm (1.46 in) artillery as the primary threat. While the fabled 88 mm (3.46 in) calibre gun was formidable, low-flying Il-2s presented too fast-moving a target for the 88's relatively low rate of fire, and while occasional hits were scored Soviet pilots apparently did not treat the 88 with the same respect as high-altitude Western heavy bomber crews. Similarly the attempts in Finland during summer '44 to augment the small numbers of 20/40mm AA in the field army by heavier 76mm guns drawn from homeland defence proved also relatively ineffective and few Il-2s were downed despite attempting different tactics with time-fused fragmentation, contact-fused, and shrapnel ammunition: the heavy guns simply lacked the reaction times to take advantage of the brief firing opportunities presented by the low-altitude Il-2 attacks. Single-barrel 20mm guns were also found somewhat inadequate due to limited firepower: one or two shells were often not enough to destroy the Il-2, and unless the Il-2 was attacking the gun itself, thus presenting effectively a stationary target, scoring more hits during a firing opportunity was rare. However, a single hit from a 37mm AA gun was usually enough to bring down an Il-2. Soviet anti-aircraft artillery also frequently mistook it for German aircraft, often with lethal consequences.
The armored tub, ranging from 5–12 mm (0.2-0.5 in) in thickness and enveloping the engine and the cockpit, could deflect all small arms fire and glancing blows from larger-caliber ammunition. There are reports of the armored windscreen surviving direct hits from 20 mm (0.79 in) rounds. Unfortunately, the rear gunners did not have the benefit of all-around armor protection, especially from the rear and to the sides and suffered about four times more casualties than the pilots. Added casualties resulted from the Soviet policy of not returning home with unused ammunition which typically resulted in repeated passes on the target. Soviet troops often requested additional passes even after the aircraft were out of ammunition to exploit the intimidating effect Il-2s had on German ground troops, who gave it the nickname Schlächter (Slaughterer), perhaps a play on the term Schlachtflugzeug ("ground attack aircraft"). Nicknames such as "The Flying Tank" and "Der Schwarze Tod" (the "Black Death") were coined by soldiers. Luftwaffe pilots called it Eiserner Gustav (Iron Gustav) or the Zementbomber (Concrete bomber). The Finnish nickname maatalouskone ("agricultural machine" or "tractor") derived from a word play with maataistelukone (ground attack aircraft, literally "ground combat aircraft" where kone, literally "machine", in turn is shortened from lentokone, aircraft, literally "flying machine")