The TU-98 (TU-24) was a medium-range supersonic bomber. It is a prototype supersonic a/c built in the Design Bureau and one of the first heavy supersonic a/c in the USSR. First flight - 7 September, 1956. There were projects for modernization of "98" a/c - "98A" (TU-24), "98B", but they were stopped at testing phase of one of flight exemplars which data contributed much to further supersonic Tupolev's aircraft.
Starting in late 1949, the OKB AN Tupolev together with TsAGI conducted a series of theoretical and applied works aimed at substantiating the selection of the main parameters of prospetive heavy aircraft, designed to achieve high transonic and supersonic flight speeds. Initially, the work was concentrated in the direction of a profound modification of the OKB's successful project "88" (Tu-16), in terms of increasing the power of the power plant and increasing the sweep of the wing and tail to 45 degrees or more without significant changes in the configuration of the fuselage, equipment, weapons and quantity crew of the initial project.
These projects of a search nature include projects considered in the Design Bureau at the turn of the 40's and 50's and the internal designation of the aircraft "97" and the plane "103". The first project envisaged the creation of a transonic bomber on the basis of the Tu-16 by replacing engines of the AM-3 type with a maximum take-off thrust of 8,750 kgf for VD-5 engines with a take-off maximum thrust of 13,000 kgf and the introduction of an aerodynamically clean wing (without gondola landing gear extensions) on the line of quarters of chords equal to 45 degrees.
A later draft of the "103" provided for the transfer of the Tu-16 power plant to four VD-7 engines (the maximum expected thrust of the earth was 11,000 kgf) or four AM-13 engines with a similar thrust. The engines were to be installed in pairs one above the other as on the Tu-16 in the center wing at the sides of the fuselage, the general scheme of the wing was preserved (including the chassis of the chassis), but its sweep increased to 45 degrees. Initial estimates for the project "103", conducted in the Department of Technical Design Projects under the guidance of SM Eger, spoke of the possibility of creating a long-range bomber in the class of the Tu-16 with supersonic flight speed. During these preliminary works, the OKB and TsAGI gradually accumulated the necessary knowledge to create projects for heavy supersonic combat aircraft, some of which found practical implementation in the experimental and serial aircraft of the Tupolev Design Bureau.
Beginning from 1952-1953 in the Tupolev Design Bureau, active design works were launched at once for three types of supersonic aircraft covering the whole gamut: from front-line bomber to intercontinental carrier aircraft. The first in this series was the aircraft "98" ( Tu-98).
Work on the topic began in the design bureau in the first half of 1952 and at the initial stage basically closed up in search of the most optimal aerodynamic and constructive wing scheme for the future supersonic aircraft. In the team of OKB projects the theme received a cipher - "5201 airplane". The work relied on the TsAGI research of 1948-1952 on wings with a sweep angle of 55. During the preliminary studies on the topic, in addition to this wing for the aircraft variants with a wing in 35° and 45° were considered, while searching for the most rational engine placement, air intakes, as well as the choice of engine type.The possibility of using the AM-3 and TRD-I TRDs (the original designation AL-7), less powerful than AM-3 but three times lighter, was considered.
The design of the front-line supersonic bomber OKB began in late 1952. The official basis for the commencement of work was the release of the Resolution of the Council of Ministers of the USSR #5330-2089 of December 29, 1952, according to which the MAP. and the OKB A. Tupolev ordered to work out the issue of creating a front-line bomber with a speed of at least 1200 km / h. Specific proposals of the OKB had to be submitted to the Council of Ministers of the USSR by March 29, 1953. Survey works on the subject in cooperation with TsAGI OKB began in mid-January 1953, this stage of preliminary searches continued until mid-1954. In the team of projects under the leadership of BM Kondorskiy, the Department of Technical Projects, in close interaction with TsAGI, the shape of the future supersonic aircraft gradually evolved. Several variants of initial aerodynamic layouts with different wing shapes in the plan were considered.
After preliminary studies, for the "98" project, a midplan scheme was chosen, with an aerodynamically clean thin swept wing and a swept tail unit. In an effort to ensure a high aerodynamic quality of the wing on the cruise supersonic modes, the developers refused the location of the main chassis legs in the wing and completely placed them in the fuselage compartments. The requirement to achieve supersonic speeds forced to abandon all kinds of additional superstructures on the fuselage: completely abandoned the fuselage gun turrets, leaving only a stern installation, the size of the transparencies of the crew cabins were minimized as much as possible.
Important innovations in the layout of the aircraft was the placement of powerful turbojet engines with afterburners in the tail section of the fuselage, the supply of air through long air ducts, the introduction of air intakes with fixed central bodies in the form of small semi-cones at the entrance and the application of the boundary layer drain system, made in the form of a gap between the air intakes and the fuselage.
To reduce the wave resistance in the transonic zone, the aerodynamic configuration of the "98" aircraft provided for a small reduction of the fuselage at its junction with the wing, which corresponded to the rule of squares then entering the practice of world aircraft construction (intuitively, at the level of the engineering subconscious, this rule was used in the layouts of various elements of OKB aircraft since the 1940s with the Tu-2, giving the greatest effect on the Tu-16).
In March 1955, the Design Bureau presented the customer with a draft design and a model of the aircraft. The constructed aircraft "98" had a number of constructive and technological features, which for the middle of the 1950s represented a certain interest. The bulk of engineering solutions was aimed at accomplishing the main task - obtaining supersonic flight speeds. The aircraft "98" was a classic monoplane with a medium-swept wing and a swept tail unit. Two engines AL-7F with a static non-spiral traction of 6,500 kgf and with a static thrust at the afterburner of 9,500 kg were located in the tail part of the fuselage. To ensure that unperturbed airflow enters the engines, elongated air ducts, starting with unregulated air intakes, installed in the front of the fuselage behind the cockpit in front of the wing.
For the first time in the practice of the OKB, the "98" used a stern remote cannon, the control of which was to be carried out by the navigator-operator from the cockpit. Especially for the aircraft "98" under the leadership of A.V. Nadashkevich (Deputy A.N. Tupolev for armament) and Chief Designer I.T. Toropov, who headed the specialized design bureau for aircraft armament systems, a fodder remote installation for two gun type AM-23. Installation of the DK-18 in the fairing was mounted under the keel of the aircraft, the ammunition set on the aircraft was 300 rounds (150 per barrel). The aiming was carried out using the PRS-1 radar sight "Argon", the antenna unit of which was placed on the top of the keel in its rear extremity.
The design stage for the 98 aircraft was completed by July 1955, by this time the aircraft was built up in pilot plant at #156 by 70%. From February 1955 to February 1956, the experimental aircraft stood in anticipation of the AL-7F engines. The aircraft was tested by the crew as a part of test pilot VF Kovalev and test navigator KI Malhasyan (leading test engineer Gribakin). September 7, 1956 was the first flight. The progress of work on the aircraft "98" was controlled at the highest level. Delays with debugging and testing found the appropriate response from the leadership. On January 25, 1957, the Resolution of the Council of Ministers of the USSR - 71-44 came out, followed by the Order of the MAP - 30 of 27.02.57, which had the following content: "On the unsatisfactory state of work on the creation and finishing of front-line bombers Yak-26 and Tu-98".
Test flights on the "98th" continued until 1959. Despite the great efforts of the OKB, the heroism of the test pilots, it was not possible to bring the plane to the level of the air force transfer to the state tests. Initially, the tests were bogged down in the mass of problems, improvements and failures inherent in the "98" aircraft, one of the first heavy supersonic machines that, with its first heavy flights, paved the way for future Tupolev supersonic vehicles brought to the level of serial production (the Tu-22 family).
A direct development of the "98" aircraft was the long-range intercepting fighter-interceptor missile carrier Tu-128 (the "128" aircraft), which had the official official designation Tu-28. In the course of the factory tests, the Air Force commander Marshal E. Ya. Savitsky became interested in the "98" aircraft. Having become acquainted with him more closely, he came to A.N. Tupolev with the proposal to create air defense aircraft, the aircraft is constructively close to the "98th" car, but with a completely different purpose. Air Defense urgently needed a long-range fighter-interceptor armed with heavy air-to-air missiles and equipped with a powerful airborne radar system for detecting air targets and aiming airborne missiles on them.
The Tu-98 made its first flight in 1955. Information about the new Soviet supersonic frontal bomber leaked to the West for the first time in 1956, apparently during the visit to the USSR at Kubinka Air Force base outside Moscow of General Twining in the summer of 1956, although the 98 was not presented to him (he saw the Tu-91, Il-54 and Il- 40). From 1956 to 1960, Western sources, confused by continued testing of Backfin-type aircraft, reported that the aircraft was in service as the Yak-42.
In 1957, the aircraft flew over the Tushino airfield, accompanied by experimental E-4 and E-5 fighters, while preparing for the traditional air parade [which that year did not take place]. The aircraft received the NATO designation "Backfin". Soon, Western analytical services attribute the new Soviet aircraft to the Yakovlev design bureau and the Yak-42 designation appeared on the pages of Western publications (apparently, along with information on the Tupolev supersonic aircraft). In 1958, an elaborate analysis in a German magazine claimed that fifteen "Yak-42 Backfins" were being built each month. In reality, there was no production. Pieces of information on Yakovlev's works came to the West. The plane was often misidentified as Il-140, and the "98th" appeared in the West as an airplane of Yakovlev OKB almost until the second half of the 1960s. In reality, the Yakovlev Yak-42 (codenamed Clobber) was a Soviet medium-range commercial transport Aeroplane that entered service in 1978 based on the Yak-40. The Yak-42 is powered by three ZMDB Progress D-36 turbofans providing a top speed of 810 km/h.
The Soviet military decided that instead of buying a direct replacement to the Il-28, they would use fighter-bombers and strike aircraft. The Tupolev bureau revised the Tu-98 into the Tu-102, with a longer, slimmer fuselage and with the main landing gear moved to trailing edge fairings on the wings. The Tu-102 first flew in 1958 and entered service as the Tu-28P "Fiddler," a long-range interceptor. Some features of the Tu-98 even were passed on to the Tu-22 "Blinder."
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