Aviation of World War II
The successful operations of the Il-2 on the fronts of the Great Patriotic War gave a powerful impetus to the further expansion of development work on aircraft of this class. Design Bureau P.0.Sukhoi achieved great success in this matter, where such excellent armored attack aircraft as the Su-6 and Su-8 were created. However, their mass production was never established, since the M-71 engines, for which these aircraft were designed, were not mass-produced.
New attack aircraft were also designed at the Design Bureau of S.V. Ilyushin. The work went in two directions. The first was to enhance the bombing properties of the aircraft and enhance its armor protection. Such a heavy attack aircraft was built (IL-8), but its tests were delayed, and it was not mass-produced. The second direction implied a sharp improvement in flight data with the same artillery and small arms and armor protection as the IL-2. The IL-10, which was built in 1944, became such an attack aircraft. Compared to the IL-2, this aircraft had smaller dimensions, significantly better aerodynamics, and a more powerful AM-42 liquid-cooled engine.
The problem of “the best materiel for assault operations” became especially acute after the battle on the Kursk Bulge, when the experience of combat, in addition to serious shortcomings in the management and organization of combat operations of the Air Force, as well as the training of flight personnel, revealed a clear discrepancy between the flight and combat qualities of Il -2 to the requirements for combat use in conditions characterized by the highest dynamics and massive use by the enemy of military air defense and fighter aviation weapons.
In the reporting documents of a number of formations on the experience of the combat use of the Il-2 in the Kursk salient, it was noted that in some parts of the loss in the Il-2 from anti-aircraft fire reached 60 - 65% of all combat losses. The number one enemy for ground attack aircraft was the firepower of the enemy’s military air defense and, above all, small-caliber anti-aircraft artillery (MZA, 20-37 mm) and heavy-caliber anti-aircraft machine guns (12-13 mm), the fire of which was most effective at the main heights of the combat use of attack aircraft. Since the MZA guns had a high speed of horizontal and vertical aiming and, in addition, the adjustment of the fire by anti-aircraft crews was carried out along the route, and not according to the bursts of shells, the attack aircraft could provide the most effective counteraction to their fire by sharp and simultaneous changes in course, altitude and speed.
The best type of anti-aircraft maneuver when attacking a target, as shown by the experience of the war, was the battle formation "circle of aircraft". The "circle" made it difficult to set the course, speed and range on the sights, and also deprived the enemy of the opportunity to make the correct corrections to the data for firing. And the smaller the radius of the "circle" in the projection, the greater were the errors of the anti-aircraft gunners. In addition, a smaller number of anti-aircraft crews could participate in countering, that is, the probability of hitting an aircraft decreased.
The attack aircraft could achieve the least opposition from anti-aircraft gunners by building a “circle” not in a horizontal plane, but in an inclined one, approaching, in the limiting case, the vertical. However, in order to build an optimal, from the point of view of minimizing the probability of hitting an aircraft (the angle of inclination is approximately 50 - 40 °, the dive angle is 40 - 45 °), the Il-2 "circle" did not have the necessary vertical maneuverability.
In addition, effective suppression of small targets in a rapidly changing ground situation and a strong saturation of the battlefield with various military equipment was possible only if an energetic attack maneuver was developed in a very limited space. It was required immediately after the detection and recognition of the target to take an advantageous starting position, attack the enemy, and during repeated visits be in the "circle", maintaining visual contact with the target.
At the same time, air battles over the Kursk Bulge clearly showed that the integrity of the battle formation of attack aircraft in a group and continuous fire interaction between crews are the most important means of reducing losses from enemy aircraft. For many commanders and pilots, it became clear that it was almost impossible to avoid fighter attacks only due to one speed - the Messerschmitts and Focke-Wulfs surpassed the Il-2 in speed at all main altitudes of combat use and were able to quickly perform the necessary maneuver to occupy an advantageous starting position and effectively carry out the attack. In addition, the Luftwaffe pilots very skillfully used the tactics of strikes "from around the corner" (mainly on the extreme attack aircraft in the group), attacking unexpectedly and at high speed from the direction of the sun or from clouds. The calculation was based on surprise, high accuracy and the power of fire. No reservation saved the attack aircraft from fatal defeats. Pilots and gunners were injured or killed (shooters 2.3 times more often than pilots), the wooden planes and fuselages of the Il-2 turned into wood chips, the cables and rods of the control system were interrupted, etc. - the attack aircraft fell, went for an emergency landing or failed as a result of damage.
The direct support aircraft required not so much a high horizontal flight speed and strong armor, but high maneuverability (in the horizontal and vertical planes) and controllability over the entire range of operating altitudes (that is, from the ground to 1000 - 1500 m) and speeds from minimum (stall speed) to maximum. At conferences and in reports, the flight and command staff of combat units and formations expressed their desire to improve the flight performance of the Il-2 aircraft or replace it with a more advanced aircraft that best meets modern war requirements.
The effectiveness of the fire of the VYa-23 and ShVAK guns when operating on German armored vehicles turned out to be completely insufficient. The fact is that by this time the enemy had almost no light tanks left on the Eastern Front. They were driven out by medium and heavy tanks, against which ShVAK or VYa-23 were practically powerless.
The bomb load of the IL-2, limited at that time to 300 kg, was recognized as insufficient. In combat units, during takeoff and landing on uneven field airfields, when the aircraft was fully loaded, the fuselage often collapsed. In addition, during the transition from the single-seat version of the IL-2 to the double-seat, the centering shifted back and, when fully loaded, the stability and controllability of the machine, which had been “limping” in this regard from birth, became completely unsatisfactory. For the same purpose, the number of rocket guns on the Il-2 was halved, from eight to four. At the same time, the combat capabilities of the main strike aircraft of the Red Army Air Force were seriously reduced.
By the fall of 1943, the military was already clearly aware of the perniciousness of further delays in resolving the issue of “putting a strike aircraft of the battlefield with increased combat effectiveness into supplying the Air Force with spacecraft”. There has been a clear trend towards a drop in the Air Force's interest in heavy multi-purpose aircraft (bomber attack aircraft, reconnaissance aircraft and artillery fire spotter) and its growth in light maneuverable attack aircraft designed exclusively for solving combat missions of direct support for troops in the offensive and defense. The necessary conditions had already been created for such specialization - air superiority in the main operational areas was mainly won by the Soviet Air Force, the issue of the number of aircraft as a whole had already been decided, there was confidence in the imminent establishment of a stable production of a very strong front-line bomber Tu-2, and as a dive bomber the military was quite satisfied with the "pawn" proven in battles. To ensure a qualitative leap in the strike capabilities of the Air Force by the beginning of the summer campaign of 1944, it only remained to give Soviet aviation a modern attack aircraft.
The design of a two-seat attack aircraft was not as straightforward as it seems at first glance. At the initial stage of development, a single-seat version of the attack aircraft was also considered.
On October 29, Ilyushin turned to A.I. Shakhurin with a letter in which he wrote: “... Having familiarized myself at plant No. 18 (in Kuibyshev) with the outcome of the construction of two Il-1 aircraft (Odd aircraft numbers were occupied by fighters and subsequently by the Il- 1 was assigned the index 10). in the single and double versions, I was convinced that the construction of two aircraft is unbearable, so I ask you to remove the IL-1 in the single version from the factory. The deadline for the completion of the Il-1 aircraft in the two-seat version to the plant number 18 should be left the same, i.e. December 10, 1943"
It must be said that the reason for the rejection of a single-seat machine was not only and not so much the difficulties of production. In September, state tests of a similar concept fighter-attack aircraft Il-2I with an AM-38F engine ended unsuccessfully. The act of approving the test results noted: “... Il-2I aircraft can only be used to combat certain types of enemy bomber and transport aircraft with relatively low speeds (He-111, Fw-200, Ju-87, Ju-52 ) at altitudes below 4000 m, however, Fw-200 aircraft can evade IL-2I attacks by climbing due to better rate of climb. The Il-2I can attack the faster Ju-88 and Do-215 bombers only by chance, since the latter, due to their greater speed, always have the opportunity to get away from the Il-2I .... To actively fight enemy fighters, the Il-2I aircraft does not maybe..."
From this it followed that the Il-2I clearly did not take place as a fighter for bombers and transport aircraft, and lost all the main advantages of a “clean” attack aircraft.
Since by this time the Germans practically did not use modern bombers with powerful defensive weapons on the Eastern Front, focusing on the use of FW 190G fighter-bombers and FW 190F attack fighters, for which the “shops” and "Yakovlevs", then the interest of the military in the armored fighter actually disappeared. Air Force Commander Marshal A.A. Novikov imposed a resolution on the act: "... to consider that the further construction of the Il-2I in the version of the fighter and the installation of the AM-42 engine (GKO Decree No. 3336 of 05/17/43) on the fighter version of the Il-2 is inappropriate." This verdict practically closed further work on a single-seat ground attack fighter.
From a modern point of view, the refusal to develop a single-seat IL-1 or a single-seat Su-6 does not seem entirely justified. In the conditions of the air supremacy of the Soviet Air Force that emerged at the end of 1943 and the presence of a sufficiently powerful fighter aircraft, it was already possible to somewhat revise the concept of a promising attack aircraft. The fact is that the percentage of meetings of Il-2 attack aircraft with Luftwaffe fighters in the performance of combat missions in the period 1944-1945. on average, it was no more than 10 - 15% of the total number of sorties of groups (according to statistics of the 2nd, 5th, 8th, 16th and 17th air armies). At the same time, the relatively large losses of shooters in air battles became unjustified in relation to the effectiveness of their defensive activities.
So, according to the experience of the assault regiments of the 8th and 17th air armies in the period 1943 to 1945, the average consumption of ammunition for a UBT machine gun in one Il-2 combat sortie was 14.7% or 22 rounds, which corresponds to the duration of firing only 1.32 s. The probability of a shooter being hit by German fighter fire in one attack was approximately 2–2.5 times higher than the ability to shoot down an attack aircraft protected by him under the same conditions, and 3–4.5 times greater than the probability of destroying a German fighter by return fire from an air gunner. That is, in the presence of sufficient escort by fighters, the air gunner almost did not have to fire. He himself and his machine gun became just an extra load, their presence did not seriously affect the combat survivability of the machine. Perhaps for this reason, experienced attack aircraft pilots were not only quite calm about sorties without a gunner, but even sometimes tried to do without him, rightly relying on active maneuver in battle and interaction with cover fighters.
If a single-seat armored attack aircraft with an AM-42 engine was built, its take-off weight would decrease by about 800 kg compared to a two-seat one, and the aerodynamics of the vehicle would also improve. The resulting winnings could be used in different ways. For example, to increase the flight range to 1200 km, to increase the maximum bomb load to 1000 kg, to significantly improve the maneuverability and takeoff and landing characteristics, as well as the flight speed. By and large, there would be a real opportunity to create an armored attack dive bomber, the need for which was so acutely felt by the Air Force when breaking through enemy defenses.
In the variant of the maneuverable high-speed attack aircraft, as shown by the calculations performed according to the simplified method of I.V. Ostoslavsky, the maximum speed, for example, of IL-1 at the ground would be about 540 km/h, at an estimated altitude of 2600 m - 596 km/h, and at an altitude of 5000 m - about 620 km/h. It follows that the main German fighters of that period would have been able to catch up with a single-seat attack aircraft only if there was a significant excess in height or using afterburner systems. Yes, and air combat would not be easy.
A version of a single-seat dive bomber-attack aircraft would have a safety margin of up to 8 g, the ability to dive at angles up to 60 ° and a maximum bomb load of 1000 kg (800 kg of weight savings would go to ensure a margin of safety, to install brake flaps - about 365 kg, and to an increase in the maximum bomb load would have left another 400 kg).
The wing of the Il-1 compared to the Il-2 was thinner (with a relative thickness of 18% at the root) and was assembled from high-speed airfoils: at the root NACA-0018, then at the connectors NACA-230 and at the ends NACA-4410. The wing was equipped with Schrenk-type take-off and landing flaps and Fraise-type ailerons. The landing gear was retracted in flight into the inter-spar space of the center section with the wheels turning 86 ° during retraction, similar to the Su-6, which made it possible to reduce the midsection and drag of the landing gear fairings. To eliminate losses due to the internal resistance of the fuselage to the oncoming air flow, all holes and slots through which air could flow through were sealed on the IL-1, and additional partitions were installed dividing the aircraft into compartments. As a result, the drag of the IL-1 compared to the IL-2 turned out to be almost two times less.
The combat survivability of the aircraft was ensured by the use of an armored hull included in the power circuit and covering the engine, its units, gas and oil tanks with lines. To protect the air shooter and the pilot from the rear hemisphere, shielded armor plates were installed (armored partition of the shooter, armored wall and pilot's headrest), which consisted of two 8-mm armor plates with an air gap between them. Such plates more effectively protected the gunner and pilot from being hit by 20-mm shells from German air cannons and fragments of anti-aircraft shells. Taking into account the experience of combat use of the Il-2, the upper part of the armored hull, almost never hit by fire from the ground, was made of 4 mm thick duralumin sheets. On the other hand, the side walls of the engine hood were reinforced, especially from the bottom, made of armor sheets 6-8 mm thick. The rest of the bonnet armor plates (hatches and covers) and the armor of the gas tanks were 4 mm thick. The screw hub was covered in front with a 6 mm thick disc.
The side sheets of the gunner's and pilot's cockpits were 6 and 8 mm thick, respectively, the lower side sheet of the pilot's cockpit was 5 mm thick. From above, the pilot covered himself with an 8-mm plate mounted on a lantern. Cabin floors were made of 6 mm sheet. Tunnels of water and oil coolers from the side of the rear spar were covered with 10-mm armor, and the armored shutters at the exit of the tunnel had a thickness of 5 and 6 mm. The hinged side "lids of the cockpit canopy were made of metal armor 6 mm thick and plexiglass. Transparent armor 64 mm thick was placed in the visor. The gunner's head was not covered with either metal or transparent armor.
Survivability was also increased through the use of sealed fuel tanks and increased strength rods in the elevator control system. Oddly enough, but the system for filling gas tanks with neutral gas was not provided, although the need for it on a combat aircraft by this time was already obvious. There was also no duplication in the elevator control channel.
When designing the aircraft, the designers took into account the experience of combat use and operation of the Il-2. Four guns were installed on the aircraft - at the first stage, 20 mm caliber, later - 23 mm caliber; 8 RS-82 rockets were located on the wing beams: a bomb bay and an external suspension allowed the use of various-caliber bombs with a total weight of 600 kilograms. The weight of the aircraft ready for takeoff exceeded the empty weight (4680 kg) by almost two tons. In the process of modernization, the designers finalized the vehicle mainly along the lines of enhancing firepower. A training version of the UIL-10 machine was also designed. The first test flight was made on April 18, 1944 by test pilot V.K. Kokkinaki. Factory tests took less than a month, and on May 13, 1944, the vehicle was handed over for state tests.
The latter were held literally in record time - in just two weeks. The test results exceeded all expectations: in terms of maximum horizontal speed, the IL-10 surpassed its predecessor by almost 150 km/h. In addition, at low flight altitudes (up to 2000 m), the Il-10 was almost as fast as the single-seat enemy fighters Me-109G2 and FW-109А-4. An interesting fact is that in the process of conducting state tests, test pilots of the Il-10 conducted demonstrative air battles with the best domestic fighter La-5FN. This machine, by the way, in its flight-tactical characteristics surpassed all the fighters that were in service with the Luftwaffe in 1944.
High flight speed, good maneuverability and effective armor protection determined the high combat qualities of the IL-10. If the escort of the Il-2 attack aircraft by fighters was considered mandatory, then the Il-10 often did not need them. Moreover, according to the combat data complex, the IL-10 at low altitudes could conduct an active air battle with enemy fighters.
By May 1, 1945, 630 Il-10 attack aircraft were transferred to the active army, but only a few aviation regiments that had it in service had a chance to take part in hostilities. However, the Il-10 aircraft was massively and effectively used in the war with imperialist Japan. Here it is especially necessary to note its combat use by pilots of naval aviation, who successfully carried out top-mast bombing on the new machine. Il-10 and its post-war modification Il-10M were in service until the early 60s, when they were replaced by jet aircraft.
Il-10U (UIl-10) is a training version of the two-seater Il-10. An instructor's seat with a second control was equipped in the rear cockpit.
Serial UIl-10 (manufacturer No. 106085) produced by plant No. 1 with a flight weight of 5680 kg (empty weight 4571 kg) showed a maximum flight speed near the ground of 502 km / h, at an altitude of 2500 m - 560 km / h. The time to climb 1000 m was 1.5 minutes, and the height of 3000 m was 4.8 minutes. The takeoff run is 485 m, and the run is 520 m. Landing speed is 145 km/h.
The main differences between the UIl-10 and the combat IL-10 were as follows: the gunner's cockpit was converted into an instructor pilot's cockpit, in which a second aircraft control was mounted, an instrument panel was installed with a speed indicator, turn indicator, attitude indicator, altimeter, compass. On the plane, the armored partition between the cockpits of the pilot and gunner was removed. The VYa-23 guns, the VU-8 defensive installation with the UBT machine gun, the AG-2 air grenade holder and 2 RO beams were removed from the armament. The system of the mechanism for closing the bomb bays has been changed.
In the conclusions of the test report, it was indicated that in terms of piloting technique from the first cockpit, the training attack aircraft is no different from the IL-10, and from the second cockpit - from the UIl-2. However, the review (especially on landing) of the IL-10 was worse than that of the IL-10.
Armament: two 7.62 mm ShKAS machine guns, up to 4 RS-82 or RS-132; bomb load - normal version - 400 kg