The designation of the Il-22 was later used once more, for a special air command post based on the turboprop transport aircraft Il-18D.
The first Soviet jet bomber, the Il-22 was a innovative, under-powered, design that was abandoned in favor of the simpler IL-28. The aircraft served as an experimental without reaching production status. The Il-22 had a rather fat fuselage of circular cross-section, and an unswept wing with four jet engines underneath. The beginning of the design of this machine was preceded by enormous work on the study of captured materials, a large number of scientific studies, and the choice of aerodynamic dimensions and layouts.
In the prewar years, and throughout the war period, the concerns of the country's leaders, the air force and the aviation industry were aimed at achieving and maintaining a sufficient quantitative level of the aircraft in the ranks. Economic and production difficulties in the country did not allow to pay increased attention, so necessary for the successful implementation and completion of new research, experimental and design developments, limiting them during the war period to creating modifications of existing equipment to maintain its combat effectiveness.
This was one of the reasons that, by the end of the war, not a single jet-powered military aircraft was in the largest quantitatively air force of the USSR, while the German military industry since 1944 began production of jet aircraft, which by the end of the war were already mass-produced. Jet aircraft, however, still in small quantities, were already in service with the British and American Air Force.
This situation violated the parity, which was far from the Soviet's favor, which caused serious concern of the military and political leadership of the country. In the spring of 1944, the State Defense Committee adopted decrees on the creation in the USSR of aircraft jet engines and aircraft with such engines. The starting point for the start of this work was to be captured German engines and aircraft, the study of which allowed them to gain the necessary experience and quickly master the technology of their production. The result of these endeavors was the first Soviet jet fighters, on which domestic RD-10 and RD-20 turbojet engines were already installed. The encouraging results obtained at this stage of the development of jet technology allowed us to consider the possibility of building multi-engine jet engines.
In 1946, A.N. Tupolev, P.O. Sukhoi and S.V. Ilyushin was invited to launch design and research work in the field of creating front-line jet bombers. The Council of Ministers ordered the Ilyushin design bureau on 12 February 1946 to begin work on a bomber that would use four of the new TR-1 jet engines. Design team S.V. Ilyushin was proposed to design and build an IL-22 aircraft with four TR-1 engines designed by A.M. A cradle with a bomb load of 2000 kg, a flight range of 1250 km and a speed of 750 km / h with a take-off mass of 24 tons and a period of presentation for flight tests in July 1947.
Experiences with the first generation of jet fighters had revealed unsuspected problems involved with high-speed flight and Ilyushin devoted a lot of effort to mitigate them. The long, thin unswept wing was conventional in appearance, but it was shaped to improve lateral stability at high angles of attack and to prevent the onset of tip stall.
Another problem discovered by the jet fighters was unexpectedly dropping a wing at high speeds and high altitudes. This was traced to manufacturing defects in the wings that made no difference at low speeds and altitudes, but meant that each wing had a slightly different airfoil and hence, a different amount of lift. To counter this Sergey Ilyushin and his team developed a new manufacturing technique that reversed the traditional practice where the internal supporting members were affixed to the assembly jig and the aircraft's skin panels were then attached.
This new method meant that the skin panels were placed in the jigs where the correct curvature and shape could be guaranteed and the internal structure was then fastened to them. This required that manufacturing joints be used along the chord lines of the wings and tail surfaces, which split the spars and ribs in half. Similarly the fuselage built the same way, although it was split vertically along the centerline. This new technique did impose a small weight penalty, but had the unexpected advantage of greatly accelerating the assembly process as the internal equipment could be installed before the halves were joined together. This allowed several teams to work on a single sub-assembly before they were mated.
Most of the other multi-engined jet aircraft in existence when the Il-22 was being designed either had the engines in a nacelle (singly or in pairs) directly attached to the underside of wing or were buried in the wing itself. Clustering them in a nacelle offered several advantages over individual nacelles as it reduced overall drag and minimized interference drag, but had the major operational disadvantage that an uncontained fire in one engine could disable its neighbors as well and the early jet engines were not paragons of reliability so this was a significant risk. Ilyushin chose to put the TR-1 engines ahead and below the wing leading edge on short horizontal pylons. This gave them the beneficial effect of acting as anti-flutter weights and proved to be more efficient aerodynamically than underwing nacelles. This also facilitated engine changes and maintenance by making them more accessible to the ground crews.
For the first time in the Soviet Union, a progressive technological method of assembling bearing surfaces was carried out, using the outer skin of the structure as the initial technological base. This made it possible to separately assemble two halves of any bearing surfaces or parts of the fuselage, separated in the plane of the chords or, respectively, in the plane of symmetry. The innovation made it possible to sharply increase the productivity of assembly work, and most importantly, to increase the correspondence of the outer contours of the aircraft to their theoretical value, which was especially important for performing safe flights at transonic speeds.
Neither the thin wing nor the engine nacelles offered any place to store the main landing gear so the fuselage was designed as a flattened oval to give them as wide a track as possible. This also provided plenty of room for the 9,300 kg (20,500 lb) of fuel stored in three bags, one each ahead, above and behind the bomb bay. This could carry up to 3,000 kg (6,600 lb) of bombs. The fuselage nose was largely glazed and came to a point, much like the noses of the Boeing B-29 Superfortress, Heinkel He 111 and Arado Ar 234, to reduce drag. The Il-22 had a crew of five, two pilots in the nose, the bombardier-navigator in front of them in the tip of the nose, the dorsal gunner/radio operator immediately behind the pilots and the rear turret gunner behind the tail.
A 23-millimetre (0.91 in) Nudelman-Suranov NS-23 autocannon with 150 rounds was fixed on the lower starboard side of the nose; it was fired by the pilot who had a primitive ring sight to use for aiming. The dorsal turret mounted two 20-millimetre (0.79 in) Berezin B-20E guns with 400 rounds per gun and was capable of almost 360° of traverse; special microswitches prevented the gunner from firing into the bomber's tail. The turret was remotely controlled by the radio operator and was powered by electric motors for both traverse and elevation. The gunner and his gunsight, used a small observation blister at the rear of the main crew compartment to lay the guns on their target. The sight automatically compensated for parallax between the gunner and the turret as well as the required amount of target lead and the shell's ballistics.
The remote-control system offered several advantages including a smaller turret that had less drag, the guns could be fixed more rigidly to their mounts, the sight was not exposed to vibrations from firing and could track targets more smoothly and the gunner's comfort did not have to be sacrificed to optimize the performance of the turret. The major disadvantage, of course, was that the remote control system was exceedingly complicated for the period and prone to breaking down. The rear gunner was placed at the very tail of the Il-22 to optimize his field of fire in an electro-hydraulically powered Il-KU3 turret that mounted another NS-23 cannon. The turret could traverse a total of 140°, elevate 35° and depress 30°.
Creating IL-22, designers relied on the most powerful TR-1A gas turbine engine in the Soviet Union, created under the leadership of Arkhip Lyulka. Although its thrust exceeded one and a half times the similar parameter of German turbojet engines, it was also insufficient for a front-line bomber. In June 1946, the design of the Il-22 bomber was completed, and that same summer its factory flight tests began, but with less powerful TR-1 engines. The first flight of the new IL-22 jet bomber, performed on July 24, 1947, was the logical conclusion of the previous hard work of a large team of scientific and technical specialists, which made it possible to create the first Soviet aircraft of this type in an extremely short time. Crew commander V.K.Kokkinaki expressed his opinion on the behavior of the car in the air. “It’s easy to fly and extremely obedient to steering. Aerodynamic properties of the aircraft are excellent. The piloting is affected by insufficient engine power, which is quite fixable in the future.”
But the pilot’s conviction was premature. In the first flight on July 24, which lasted 15 minutes, the aircraft caused a lot of trouble to its creators. When landing, both tires first collapsed, and on the run the cameras of both wheels of the main landing gear burst. The plane descended from the concrete strip to the ground, the landing gear could not withstand the loads and broke.
Throughout the entire flight test period, which lasted until the beginning of 1948, the aircraft flew with a deliberately limited take-off weight, since the take-off thrust of 1,600 kgf declared by the creators of the TR-1 engines actually turned out to be significantly lower and amounted to only 1,300 kgf. Nevertheless, a large amount of various research was carried out on the plane, and the experience gained and numerous technical innovations were successfully used to create further machines.
Insufficient thrust and increased fuel consumption of the TR-1 engines did not allow obtaining the calculated values of speed and flight range. The lack of prospects for their improvement led in February 1948 to the decision to refuse to transfer the machine to state tests. Some authors in their works call this aircraft the first full-fledged combat bomber. This is not true. The presence in its design of errors that are inevitable in the design of fundamentally new machines, such as the difficulty of loading bombs into the compartment from the surface level of the airfield due to the too low clearance of the fuselage, made this aircraft experimental, and its creation was a great contribution to the further development of jet bomber USSR Aviation. Suffice it to say that almost simultaneously, with the creation of IL-22, the OKB was tasked with developing another bomber, the IL-24, with two more powerful jet engines.
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