Aviation of World War II
Work on the creation of a bomber designed to replace the Il-4 in the troops began at the Ilyushin Design Bureau in mid-1942. In general, in terms of tactical and technical characteristics, the new aircraft was close to the Il-4, with the exception of the maximum speed, which was set at 100 km / h higher ...
The IL-6 aircraft was created according to the scheme of a twin-engine low-wing aircraft with a conventional single-fin vertical tail, and its basic dimensions were chosen as those of the DB-4.
The Design Bureau carefully studied the experience of the combat use of the IL-4 and drew the appropriate conclusions. In the new car, the main shortcomings of its predecessor should have been eliminated. Objectively, it was necessary to introduce a co-pilot into the crew, strengthen the booking and defensive armament.
Two 18-cylinder air-cooled radial engines ASh-71 (M-71) with a capacity of 2000 hp were planned to be installed on the plane. The motors were developed in 1941 under the direction of A.D. Shvetsov by splicing two 9-cylinder single stars M-63. The M-71 engine was equipped with a system of direct fuel injection into the cylinders.
The concept of a new bomber was approved by the Air Force, after which the Design Bureau received an order for the construction of one prototype under the designation IL-6. However, it was not without remarks: the military recommended instead of the M-71 engines to supply two 12-cylinder aircraft liquid-cooled diesel engines with in-line ACh-ZOB cylinders with a capacity of 1500 hp each. The diesel was developed under the guidance of A.D. Charomsky, the mass of the engine was 1150 kg. With a turbocharger, the ACh-30B diesel engine developed a power of 1200 hp at an altitude of 6000 m. A less structurally complex and more technologically advanced diesel engine was more economical than the M-71 engine, by 40%. less fire hazardous and did not need the scarce gasoline with an octane rating of 92. Calculations showed that a bomber equipped with diesel engines was capable of carrying twice as much bomb load on the Moscow-Berlin route as an aircraft with internal combustion piston engines.
IL-6 also featured a new wing design with increased sweep along the leading edge and an almost straight trailing edge. The air intake of the radiator was made in the toe of the wing to the right and left of the nacelle, the radiator was installed in the thickness of the wing. The controlled exhaust radiator flap was located on the lower surface of the wing plane.
There were no reinforcing strips installed in the tail section of the Il-4 fuselage on the Il-6. Instead of two small windows in the aft fuselage, one oval-shaped porthole was made. The shape of the niches of the main landing gear has been changed, there are no blisters on the doors. The handrail on the left side of the fuselage has been removed. The shape of the rudder has been changed, a bevel has been made in the upper part, which made it possible to abandon the weight balancer.
The wing span of the Il-6 is 26.07 m, 4.63 m more than that of the Il-4, the length is 17.38 m, 2.6 m more than that of the Il-4. The empty weight of the IL-6 was 11,690 kg, the maximum take-off weight was 18,650 kg.
The IL-6 crew consisted of six people: a navigator, first and second pilots, a radio operator and two air gunners. The pilots were stationed in the cockpit shoulder to shoulder. The total weight of the armor was 400 kg.
Defensive armament included five 20mm ShVAK cannons, all on single mounts. One gun stood in the bow of the navigator, two on the sides, one in the upper turret and one in the lower hatch. The maximum bomb load was 2000 kg. four five hundred aircraft could carry inside the bomb bay. The outer pylons were provided for the suspension of two torpedoes or two 1000-kg bombs.
The prototype of the Il-6 was manufactured by the pilot production of the Irkutsk plant number 39. The aircraft was prepared for testing in the summer of 1943. The first flight was performed on August 7, 1943 by Vladimir Kokkinaki. Tests have shown that the power of the ACh-30B engines is insufficient for such a machine. I had to lighten the plane by removing weapons and body armor. reducing the crew to five. The top of the prototype was painted medium green, the bottom was black.
Factory tests of the prototype dragged on for eight months, many defects were revealed during the tests. The main problems were caused by the unreliable operation of ACh-30B diesel engines. In addition, the pilots noted poor airplane controllability, especially on landing. In April - May 1944, the aircraft was tested at the LII at the Kratovo airfield. LII specialists recommended to shift the center of gravity, change the shape and increase the area of the ailerons to improve controllability.
In the summer of 1944, the prototype was re-equipped with ACh-30BF diesels, which developed 1900 hp at an altitude of 6000 m. The reliability of the ACh-30BF diesel engine was increased by installing a two-stage ignition system, at the first stage, aviation gasoline was used, at the second stage, kerosene. The installation of more powerful engines made it possible to return weapons and armor to the aircraft.
With new engines, the Il-6 prototype during factory tests in the summer of 1944 showed a maximum speed of 464 km/h. The flight range at a cruising speed of 340 km / h with a bomb load of 1000 kg was 5450 km. The service ceiling was 6200 m. The high specific wing loading made it difficult to land, and because of the high landing speed for the IL-6, airfields with long runways were required.
The plane with new diesel engines was again sent for testing at the LII. Here, experts noted the very low throttle response of the ACh-30BF diesel engine and the complexity of its maintenance in the field. By this time, everything became clear to the extreme protractedness of the Il-6 program - by the end of the war with Germany, the plane did not have time. Il-6 became the last bomber with piston engines, designed in the Design Bureau S.V. Ilyushin.