Aviation of Word War II
Heavy Attack Aircraft
In order to quickly launch the new attack aircraft into mass production, its layout scheme, wing area and design solutions for many components and assemblies remained the same as on the Il-2 AM-38F, but in many of its geometric parameters (fuselage length, empennage area, rudders etc.) and design, the new machine was a completely new aircraft.
Compared to the Il-2 AM-38F, the Il-8, as well as the Il-2M AM-42 mentioned above, was somewhat larger.
The external aerodynamics of the Il-8 attack aircraft, in comparison with the Il-2, was improved: the oil cooler was placed next to the water cooler in the air channel, which was made according to the Il-2 aircraft type, the engine suction pipe on the new attack aircraft was located on the left side fuselage.
In order to increase longitudinal stability and improve controllability, the wing of the aircraft was shifted back. The take-off position of the flaps was introduced.
The armor of the IL-8 has been strengthened. The engine with units, water and oil cooler were covered with armor 4 and 6 mm thick.
The cockpit had armor thickness of 4, 6, 7 and 8 mm. From the side of the rear hemisphere, the pilot was protected by an armor plate 8 mm thick, and in front - by 62 mm transparent bulletproof glass. Armor plates 6 and 8 mm thick were installed on top of the cockpit canopy.
Navigator-shooter, unlike the IL-2, was fully booked. From the sides it was protected by armor plates with a thickness of 5 and 6 mm, and from the side of the rear hemisphere - by a 12 mm armor plate with an area of 1.07 m². The total weight of the metal armor on the attack aircraft (without attachment points) was 1110 kg.
A hatch was made from the bottom of the fuselage to enter the cockpit of the navigator-gunner. The wing spars of the new attack aircraft were metal, the skin was duralumin.
The tail part on the first copy of the new attack aircraft was made of wood, and on the second - metal.
Small arms and cannon armament of the first copy of the Il-8 consisted of two VYa cannons with 150 rounds of ammunition per barrel and two ShKAS machine guns with 1500 rounds of ammunition.
On the second copy of the IL-8, a metal wing was installed with two ShKAS machine guns and two NS-37 cannons.
The new attack aircraft differed for the better from the usual IL-2 AM-38F also in the correct placement of guns on the plane. The latter were installed on the Il-8-m closer to the axis of the aircraft at the place where the ShKAS machine guns were placed on the Il-2.
Machine guns, on the contrary, were placed where guns were usually installed. The guns themselves were entirely located in the wing of the attack aircraft.
In the center section of the Il-8 AM-42 wing there were 4 bomb bays, the dimensions of which allowed the placement of 600 kg of normal bomb load inside the aircraft. At the same time, small air bombs were placed in these compartments on the doors of the bomb bays as in a bunker.
After the bombs were dropped, the hatches were closed with springs. Two external holders made it possible to hang bombs weighing from 50 to 500 kg.
The bomb load of the new attack aircraft in the reloading version on the internal and external holders reached 1000 kg. That is, it was the same as that of the Pe-2, the main front-line bomber of the Air Force of that time, but with significantly better armor protection.
The normal bomb load of the Il-8 aircraft in the version with NS-37 guns was limited to 400 kg, in overload - 1000 kg (two FAB-500 bombs).
The defensive armament of the aircraft consisted of a UBK machine gun (three magazines of 50 rounds each) on the VU-8 turrets with increased firing angles (up - 48 °, down from the sides - 13 °, to the right - 60 °, to the left - 65 °).
In addition, on the second copy of the Il-8, to protect the lower rear hemisphere in the tail section of the vehicle, a DAG-10 defensive cluster installation was installed with ten AG-2 aviation grenades, the release of which was carried out both from the pilot's cockpit and from the gunner's cockpit .
The AG-2 aviation grenade was developed back in 1937-38. A.F. Turakhin and was a small-sized aerial bomb exploding in the air.
The AG-2 grenade, falling out of the cluster holder, touched the scarf of the well with the protrusion of the parachute box cover, threw out the brake parachute and three seconds later, lagging behind the aircraft, exploded in front of the attacking enemy aircraft. As conceived by the designer, a black cloud of smoke suddenly appearing in front of the enemy aircraft and a dense curtain of fragments should have forced him to abandon the attack.
The first flight of an experienced attack aircraft Il-8 AM-42 (No. 1) took place on May 10, 1943 under the control of test pilot V.K. Kokkinaki. After that, factory flight tests began.
As a matter of fact, it was not so much the aircraft that was tested and brought up as its still far from perfect propeller group. The 24th plant, despite the ongoing extensive development work, for a long time could not achieve reliable operation of the motor.
During the factory tests of the Il-8, five (!) AM-42 engines had to be replaced on the machine before it was possible to ensure their stable operation in flight. In this regard, the tests of the new attack aircraft dragged on until November 26, 1943.
In view of the fact that significant design changes were made to the AM-42 compared to the engine that was originally submitted for state testing, the State Commission considered it necessary to first conduct preliminary long-term tests of those structural components of the engine that were redesigned anew (for example, suction system, piston group, etc.), and lengthy in-house tests of the motor itself for reliability with new parts, and only after that the motor is allowed to state tests already according to the normal program.
Hundred-hour in-house tests of the AM-42 were successfully completed only on December 23, 1943. In this regard, the first experimental Il-8 attack aircraft with the AM-42 engine was handed over for state tests only in February 1944.
It should be noted that the AM-42 passed state tests only in April-May 1944, according to the results of which it was recommended for mass production.
The state test report indicated that the AM-42 motor had a compression ratio of 5.5, a parallel axle gearbox with a gear ratio of i = 0.6. Supercharger driving, centrifugal, non-switching off with a gear ratio of 11.5.
In takeoff mode, the engine developed a power of 2000 liters. s, at a speed of 2500 rpm, pressure behind the supercharger 1720 mm. rt. Art. and suction mixture pressure 1565 mm. rt. Art. At the same time, the average specific fuel consumption was 330-345 g/l. With. hour.
The time of continuous operation of the engine in takeoff mode was limited to 5 minutes, and the total operating time of the engine in this mode was no more than 5% of the total life of the engine.
In the nominal mode at the estimated altitude (1600 m), the engine developed a power of 1770 liters. s, and on the ground -1750 l. With. In this case, the air pressure behind the supercharger was 1450 mm. rt. Art., and the pressure of the mixture at the suction - 1335 mm. rt. Art. The specific fuel consumption in this mode did not exceed 305-315 g/l. With. hour.
Tests have shown that the maximum allowed speed of the motor in the dive mode was 2550 rpm (no more than 30 s), and the minimum speed at which the motor still ran steadily was 500 rpm.
The throttle response of the motor was no worse than 2-3 s. The weight of the empty motor is 1030 kg with dimensions of 2295x1185x875mm. The time until the first overhaul was determined at 100 hours.
To improve oil purification, two NFM-25 filters were installed in the oil injection line.
Unfortunately, a number of shortcomings of the AM-42 engine, identified during the tests, were not eliminated until the launch of the latter, in June 1944, into serial production at the plant No. 24.
Nevertheless, the heavy attack aircraft Il-8 with AM-42 (the first prototype), despite engine defects (smoking, shaking, clogging of carburetor air valves, rapid wear of piston rings, etc.) successfully flew off from 29 February to March 30, 44th State tests.
Lead test pilot - A.K. Dolgov, Leading Engineer - P.T. Abroshchenko. The aircraft was recommended for mass production as a heavy attack bomber and reconnaissance spotter.
In terms of its aerobatic properties, the attack aircraft turned out to be generally simple and fairly easy to control. The main flight performance data of the Il-8 were noticeably superior to the Il-2, although they no longer fully met modern requirements.
With a normal takeoff weight of 7260 kg (against 6160 kg for the Il-2 AM-38f), the new attack aircraft had a maximum speed of 472 km / h at an altitude of 2500 m (for the Il-2 - 416 km / h at an altitude of 1400 m). The flight range of the Il-8 was almost twice that of the Il-2 and amounted to 1180 km.
However, its maneuverability in the vertical and horizontal planes was worse than that of the IL-2, and was clearly insufficient for the condition of hostilities in the final period of the war.
Il-8 did not go into the series. It was decided by improving aerodynamics to increase its basic flight data.
In accordance with this decision, the engine cooling and lubrication system was completely reconfigured on the second prototype Il-8 AM-42 aircraft, new wings, tail and landing gear were installed, ailerons, elevators and rudders were improved, changes were made to the aircraft equipment, a three-bladed propeller was replaced by a four-bladed one.
The total weight of the armor on the aircraft has increased to 1120 kg. The distribution of armor thickness was made taking into account the experience of the combat use of the Il-2 attack aircraft.
The motor and units were covered from below and from the sides with armor 4, 6 and 8 mm thick. The most affected areas of the attack aircraft armored hull (bottom side) had an armor thickness of 8 mm.
The upper part of the armored hull, which had a double curvature surface, was made of duralumin sheets with a thickness of 1.5 to 4.0 mm. ... The fact is that the upper front part of the Il-2 armored hull, as shown by the experience of its combat use, was practically not affected in air battles.
The cockpit was armored from the sides and bottom with sheets 4.5 and 6 mm thick. The pilot's canopy was made of 64 mm transparent armor with metal edging.
The side covers of the canopy were made of metal armor (6 mm thick) and plexiglass. On the side of the lantern there were sliding windows. An armor plate 8 mm thick was installed above the pilot's head.
In comparison with the first prototype, from the side of the rear hemisphere, the pilot and navigator-gunner were covered, protected by more effective armored walls, formed by two adjacent armor plates 8 mm thick each, with a gap between them.
This armor scheme effectively protected the gunner and pilot from being hit by 20-mm air cannon projectiles. From below and from the sides, the shooter was covered with armor of 4 and 6 mm.
It should be noted that in the future, when the IL-8 was put into serial production, the protection of the shooter from the side of the rear hemisphere was supposed to be strengthened by installing two armor plates 4 mm thick (internal armor plate) and 12 mm (external armor plate), spaced from each other by small distance.
Field tests have shown that the armor resistance of the system of armor plates with a constant distance between them increases significantly if the spacing of plate thicknesses is increased.
In this case, the turn of the axis of the projectile during the passage of the latter through the outer armor plate (thickness 12 mm), which plays the role of a kind of screen, increased significantly, and this led to a sharp decrease in the armor-piercing properties of the projectile.
The air for cooling the radiators of the modified Il-8 AM-42 attack aircraft now came through two tunnels: to the right and to the left of the engine.
The entrance to the tunnel was formed by a cutout in the toe of the center section and a recess in the side of the engine hood.
The temperature of water and oil was regulated by opening armored dampers at the exit of the tunnel. Armored shutters (armor thickness 5 and 6 mm) were controlled from the cockpit. From below, the tunnels were covered with 6 mm armor, and from the sides with 4 mm armored hull. From the side of the rear spar, the tunnels were covered with 6 mm armor.
Such a layout solution made it possible to make the contours of the armored hull smoother than that of the first experimental Il-8, and the more aerodynamically advantageous scheme for blowing radiators reduced their size and resistance.
The aircraft was equipped with more advanced cannons designed by A. Nudelman and A. Suranov NS-23 caliber 23 mm with 300 rounds of ammunition, which by May 4, 1944 had passed the entire complex of ground, and by May 7, 1944 - and flight state tests on the Yak-9 fighter.
The NS-23 guns were developed in OKB-16 for a new 23-mm cartridge with a reduced charge and, compared to the VYa-23, had almost half the weight (37.5-38.2 kg) and 1, 6 times less recoil when shooting.
This circumstance made it possible to design a simpler and lighter wing gun mount on an attack aircraft, which greatly simplified the operation of new guns.
So, two gunsmiths could, in about 10 minutes, dismantle both guns, put the shells in cartridge boxes, mount and load the guns. Similar work on the Il-2 attack aircraft with VYa guns required at least 30 minutes.
The main advantage when installing NS-23 cannons on a new attack aircraft was to increase the accuracy of firing from them, since the dispersion of projectiles during automatic firing from them from an aircraft was approximately 2-3 times less than that of VYa cannons.
Two ShKAS wing-mounted machine guns, just like on serial IL-2, had a total ammunition capacity of 1500 rounds.
The defensive armament was strengthened: instead of the UBK, a new 20-mm air gun designed by M.E. Berezin UB-20 was installed in the gunner’s cockpit on the VU-9 mobile unit, which, in comparison with the ShVAK gun, had less weight (25 kg versus 42 kg) and dimensions.
Note that in August 1944, the installation of the Berezin UB-20 gun on the VUB-3 turret was successfully tested on one of the serial IL-2 AM-38F. However, they did not begin to introduce the installation into the series due to the still low reliability of the gun itself.
To protect the rear lower hemisphere, a DAG-10 cassette with ten AG-2 aviation grenades was installed in the tail section of the experimental Il-8 No.2.
Bomb weapons have also become more powerful. The normal bomb load of a heavy attack aircraft, unlike the serial IL-2, was increased to 1000 kg.
The normal bomb load was placed in four center-section bomb bays.
The attack aircraft could take on board 346 PTAB-2.5-1.5 anti-tank bombs. This is 46 and 150 bombs more than Il-8 No. 1 and IL-2 AM-38F. The external bomb holders of the attack aircraft provided the suspension for two FAB-500s.
The aircraft was equipped with a PDK-43F compass, an RSI-3MG radio transmitter and an RSI-6MU radio receiver (remote control of the receiver), a RPKO-10 radio semi-compass and a SCh-3 radio identifier. To ensure the operation of radio equipment, two antennas were installed on the machine - one for midrange 3, the second for a communications radio station and RPKO
The photo equipment of the attack aircraft consisted of a photo setup for the AFA-IM camera, providing planned shooting and shooting back at angles of 25 ° and 50 °
In a word, it turned out to be a very good attack aircraft bomber that had increased combat effectiveness when operating on Wehrmacht armored vehicles
Estimates show that a pilot with good flight and gunnery training on the Il-8 AM-42 with NS-23 in real combat conditions could well ensure a guaranteed defeat in the first attack, for example, a German tank destroyer of the Jg Pz 38 (t) type " Hetzer "(attack from the side, glide angle 25-30 °, firing distance 300-400 m) - the probability of defeat is 0.94-0.63, while the pilot of the Il-2 with VYa-23 under the same conditions could hit the Hetzer "only with a probability of about 0.24-0.15
The defeat of heavy armored vehicles was possible only with bomb weapons.
Alteration of the second experimental attack aircraft Il-8 AM 42 (in all working documents it was designated as Il-8 No. 1) at the plant No. 240 was completed in the fall of 1944 and on October 13 under the control of test pilot V.K. Kokkinaki took his first test flight.
Problems arose immediately - due to the lack of propeller development, strong shaking occurred in flights.
Factory flight tests again dragged on for a long time Zhdanov.
V.K. Kokkinaki highly appreciated the aerobatic qualities of the IL-8 with this propeller. He noted that the takeoff is simple, the aircraft is stable in climbing. In level flight, the car was well balanced in the longitudinal ratio, it performed turns without yaws, dived steadily, and “turned” well on the target. The withdrawal from the dive and landing were simple, the attack aircraft had no tendency to stall at high leveling.
In December 1944, S. V. Ilyushin wrote to the People's Commissar for the Aviation Industry A.I. Shakhurin with a proposal "... to start serial production at plant No. 30 of a two-seat armored attack aircraft Il-8 with an AM-42 engine."
Ilyushin wrote: "The Il-8 aircraft successfully passed the State tests in March 1944. During this time, a number of improvements were made to the aircraft, which increased the aircraft's maximum speed by 50 km and the bomb load by 200 kg.
In this form, the aircraft passed factory flight tests. Transfer to State trials is delayed due to bad weather.
The IL-8 aircraft has a further development perspective. With the AM-43 engine (two-stage supercharged) it will have a top speed of 640 km/h while maintaining all other data.
The Il-8 aircraft is an outstanding single-engine aircraft in terms of the amount of bomb load, range, armor power and fire protection, which allows it to perform combat operations in a very wide range.
IL-8 is a modification of the IL-2 aircraft with the preservation of all the main overall dimensions. 50% of parts and equipment remain unchanged, and of the 50% of equipment that is subject to alteration, 25% will only undergo refinement. In addition, all conveyor lines are saved.
Thus, the introduction of the Il-8 aircraft into production can be carried out very quickly..."
Due to the lack of conditioned AM-42 engines to ensure the production of the Il-10 attack aircraft already launched in series, this proposal by Ilyushin was rejected by the leadership of the NKAP.
State tests of the Il-8 with AM-42 (the second prototype) began after the end of the war - on May 27, 1945.
With a flight weight of 7610 kg, the attack aircraft showed a maximum speed near the ground - 461 km / h, and at an altitude of 2800 m -509 km / h, a service ceiling of -6900 m, a takeoff run of 520 m, and a maximum flight range of 1140 km.
At the end of the test report, it was noted: "The aircraft has good stability, high payload, powerful armament, easy to operate and has a significant range and speed of flight, which allows us to recommend it for introduction into mass production as an attack aircraft - bomber."
Taking into account the end of the war and the presence in mass production of the Il-10 attack aircraft, to which the Il-8 was inferior in terms of maximum speed, rate of climb, maneuverability, takeoff run and landing run, the launch of the latter in a series was considered inappropriate.
In the development of the Il-8 aircraft, the pilot aircraft construction plan for 1945 provided for the construction of a heavy armored bomber with an AM-43 engine with direct fuel injection into the cylinders, which was a further development of the AM-42 engine.
The motor had a takeoff power of 2300 hp. With. and rated power at an estimated height of 2300 m - 2000 l. With.
It was assumed that with this engine it would be possible to bring the flight data of the Il-8 to the level of the lighter Il-10 attack aircraft.
So far, the authors have not been able to find any data on the construction of the Il-8 heavy attack aircraft with the AM-43 engine in the archives. Apparently, the aircraft was not built due to the underdevelopment of the motor.