Ilyushin Il-54 'Blowlamp' - Design
At that time, pproaching the speed of sound, not to mention overcoming it, was a very difficult task. In the course of research, it was found that to obtain a supersonic flight speed, it was necessary to use a 55° sweep wing along the line of the chords quarters, which is distinguished by a small profile thickness. Such a configuration of the plane made it possible to obtain high speed with sufficient controllability, but the aerodynamic characteristics at cruising speed were poor. This made it difficult to take off and land, and in addition, it required increasing the fuel supply to obtain the required flight range.
The design bureau together with the Central Aerohydrodynamic Institute developed and studied several options for the appearance of the prospective bomber and chose the most profitable one, characterized by the optimal ratio of dimensions, weight and flight characteristics. Based on this proposal, two layout schemes for the aircraft were soon developed. The first of them was approved at the end of March 1953 and became the basis for further work, which continued over the next several months.
The first version of the IL-54 project proposed the construction of an all-metal midplane with a thin swept wing. The power plant was supposed to consist of two turbojet engines placed in the root of the wing. The horizontal plumage was placed on top of the keel. Upon further study of such a scheme, it was found that the engine nacelles located in the immediate vicinity of the fuselage create unacceptable drag interference. In addition, the placement of the main landing gear supports in the wing made special demands on its power set.
According to the results of preliminary studies, the first layout scheme was abandoned. Further development of the IL-54 project was carried out on the basis of the second proposal of the Design Bureau and TsAGI. Now it has been proposed to use a high wing with nacelles mounted on pylons. This could provide significant technical and operational benefits. Also in the new project, it was necessary to use a bicycle chassis that was non-standard for domestic aviation, since the aircraft had the minimum available volumes to accommodate its racks.
In connection with the requirements, the new aircraft would have been markedly different from previous developments of the Design Bureau S.V.Ilyushin. The bomber received a spindle-shaped fuselage of large elongation, characterized by small cross-sectional dimensions. Most of the fuselage had an elliptical vertically oriented section. The fuselage layout was formed using the experience of previous projects.
The nose of the fuselage was given under the navigator’s cockpit with glazing, forming a pointed nasal fairing. Directly behind the navigator were the cockpit with a drop-shaped transparency and the front landing gear. Behind them located the instrument compartment. The central volume of the fuselage contained a bomb bay and large fuel tanks. The tail was given over to the second niche of the chassis, part of the instruments and the aft cockpit of the radio operator gunner.
According to the results of preliminary studies, the Il-54 bomber received a 55° sweep wing along the line of the chords quarters. The wing had medium lengthening and narrowing. At the heart of the wing there was a caisson made on the basis of a large number of stringers. A technological connector ran along the chord line along the entire wingspan. A significant part of the trailing edge was devoted to the installation of flaps. Near the endings were ailerons. The wing received large streamlined wingtips, necessary to accommodate part of the chassis units. To obtain the required roll stability, it was necessary to use a negative angle of the transverse V.
To improve aerodynamics, it was decided to use engine nacelles suspended under the wing on trapezoid pylons. Streamlined nacelles with frontal air intakes and a tail section under the nozzle were placed at a small distance from the fuselage and were below the wing. Engine loads were transferred to the caisson through the pylons. The leading edge of the pylon smoothly passed into the aerodynamic ridge on the upper surface of the wing. Thanks to the highly located wing, the air intakes of the gondolas remained at a high altitude above the runway, which reduced the likelihood of foreign objects entering. The high wing made it possible to get rid of some of the aerodynamic problems that existed in previous projects. One of the results of this was the use of the tail of a traditional design. A keel with a large sweep of the leading edge was installed in the rear of the fuselage. Below it, on the fuselage, was a swept stabilizer with a significant angle of transverse V. All plumage planes were equipped with their own rudders.
The power plant of the Il-54 bomber consisted of two AL-7 turbojet engines with a full thrust of 6,500 kgf. In the future, the use of "forced" AL-7F motors was not ruled out, which, when using the afterburner, could develop a thrust of 10,000 kgf. The engines had autonomous systems for supplying fuel from the fuselage tanks. Gondolas were equipped with automated fire extinguishing means.
The thin wing and dense layout of the fuselage did not allow the use of a chassis of a traditional design. Instead, it was necessary to apply the so-called "bicycle" layout. Under the cockpit and behind the cargo compartment there were niches for two racks equipped with a pair of large diameter wheels. The front strut received controls for taxiing on the ground. The bicycle design is always heavier, but the designers were forced to use it because of the inability to put the usual chassis into a thin, highly located wing, which is necessary to achieve supersonic sound with relatively weak 1st generation engines installed. Even at the stage of theoretical study, it was found that the rear support can only be located at a considerable distance from the center of gravity, because of which the front load is too heavy. This problem was solved with the help of a special rear strut, on the take-off it decreased its length. As a result of this, the angle of attack almost doubled, the lifting force increased, and the load on the front strut was reduced.
The IL-54 received a set of various electronic equipment. Behind the cockpit was the instrument compartment, in which, among other things, there was an observation and sighting radar station. The radar antenna was placed on the bottom of the fuselage, behind the front landing gear niche. Aiming defensive weapons was facilitated by a radar sight. The crew had internal communications. In the aft cabin was a radio station for communication with the ground.
The crew consisted of three people, located in their own cabins. The navigator in charge of using the weapon was in the bow cabin; the pilot was placed behind him. The radio operator gunner worked in the tail cabin. All cabins were airtight and had oxygen supply facilities. On the sides and floor of the cabins there was a developed reservation. Access to the bow cabin was provided by a hatch in the starboard side of the fuselage. The shooter had his own hatch in the bottom. All three crew members had ejection seats. The pilot was thrown up, the navigator and gunner down. It was also envisaged the use of upper evacuation hatches for independent leaving the car.
The normal bomb load of the aircraft was 3 tons, the maximum - 5 tons. Like previous vehicles, the new Il-54 could take on board several small-caliber bombs or one of the maximum possible mass. The bombing was carried out at the command of the navigator, who was looking for targets using an optical or radar sight.
For defense, it was proposed to use three automatic guns NR-23 with a caliber of 23 mm. One of them was on the left side of the bow of the fuselage and served as a course weapon. This gun was controlled by a pilot who had his own sight. Two other guns were mounted on the Il-K8 fodder. According to the instructions of the radio operator arrow, this installation, which had electric drives, could fire at targets within a horizontal sector 105° wide with vertical guidance angles from -30 ° to + 40 °. Gun guidance was carried out by a radio operator gunner using a control station equipped with an optical and radar sight.
Specialized modifications of the bomber were worked out, which had one or another difference. So, the torpedo bomber Il-54T was supposed to get a larger cargo bay, the length of which was increased by 2 m. In addition, this project provided for the processing of the nose fairing in order to improve visibility from the position of the navigator. The cargo compartment of the reconnaissance Il-54R, in turn, was given for the installation of cameras. In the project of the IL-54U training aircraft, it was proposed to abandon the navigator and place a pilot instructor in his place, for which duplicated control should be used. In the strike configuration, the Il-54 was supposed to have a length of slightly less than 29 m, a wingspan of 17.65 m and a height of 7.9 m. The area of the swept wing was 84.6 sq.m. The empty mass was 24 tons. The normal take-off mass was set at 40.66 tons, and the maximum take-off weight was a ton more. According to calculations, at the ground the aircraft could reach speeds of about 1150 km / h, at an altitude of 1250 km / h. Cruising speed was lower - 910 km / h. The flight range with a normal load and its collection in the middle of the flight is 3000 km. Ceiling - 14 km.
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