Beginning of work on a second generation supersonic aircraft [SPS-2] at the Tupolev OKB can be attributed approximately to 1971-1973. Based on the experience of development Tu-144, Concorde, and also the projects of American SST, in 1973 the OKB prepared a preliminary design for an SPS-2, which received the designation Tu-244. The main problem was obtaining the competitive status with respect to the being in operation themselves and in the development main subsonic passenger aircraft.
The competitive ability of this aircraft (in comparison with the usual subsonic liner) had to be ensured by economic effectiveness, ecological acceptability and conveniences for the passengers. In this case economic effectiveness (smaller specific expenditures) was specified on the larger productivity of SPS-2, than in the subsonic machines (due to the speed), which it had to ensure the transportation of the growing passenger flows with a smaller quantity of aircraft, in comparison with the park of subsonic aircraft. The difference in the cost of the necessary quantity of each passenger aircraft and in the expenditures for their operation had to compensate for the air carrier an increase in the expenditures for fuel, connected with the use less economical SPS-2.
The ecological acceptability of the SPS-2 in many respects determined the success or failure of the project. The solution of this problem was connected with the determination of the level of the environmental impact SPS-2 on the environment (sonic boom, noise in the locality, the emission of harmful substances, including the influence of ejections on the ozone layer). All these problems to one degree or another stood also with the creation SPS-1, but at the moment of their initial design (the first half of the 1960s), they were not regarded as fundamental. Basic task stood in the creation and the introduction in the operation of actually flying SPS.
Work on SPS-2 had been conducted at the OKB already for 25 years. In these years several different Tu-244 projects were prepared, being differed from each other in terms of an aerodynamic layout, concrete constructive solutions by the airframe, the power plant and by technical flight data. A basic difference in the prepared projects SPS -2 from SPS -1 became the higher level of the aerodynamic characteristics of aircraft, the large efficiency of power plants, and also the growth of their mass-and-size parameters, during the guarantee of transportation of the large number of passengers to the long range of flight. Work on SPS-2 in OKB over long years was led directly A.A.Tupolev. Later the chief designer on the theme SPS -2 was A.L.Pukov, while the technical director of the work on Tu-244 was M.I.Kazakov.
One of the first designs of OKB of the Tu-244 aircraft was a project of 1973 with four engines with the takeoff thrust on 37,500 kG with a specific fuel consumption cruising in the supersonic regime of 1.23 kg/kgf X hour. In this project the takeoff mass of aircraft reached 360 tons, the payload of 30 tons (in the diverse variants of the layouts of passenger cabins it could be placed from 264 to 321 passengers). Wing area reached 1100m2. At cruising speed of 2340 km/h the aircraft with the normal payload had a flying range 8000 km. According to its diagram this project was further development of the Tu-144.
Basic efforts with the development of aerodynamic layout were directed toward an increase in the assigned flying range. For this purpose the relative midship sections of the fuselage and pods decreased on the aircraft, the wing increased in area and lengthening the fuselage. The design used the mechanization of the leading wing edge of in the form slanted nose sections (deviation it was provided for in the subsonic regimes). It also arranged separate pods with the axisymmetrical air ducts after the line of maximum wing thicknesses, and optimized the shape of surface of wing taking into account interference with the pods and so forth as a result it was possible with the testings of model in wind tunnel to obtain cruising to Mach=8,75-9,0 to Mach=2,2 and in the subsonic regime Mach=14,8.
At the end 1976 a resolution of the VPK of the USSR for the SPS-2, which determined order of development and basic data Tu-244. According to this resolution, during the first stage was designing SPS-2 comparatively small sizes with a takeoff mass of 245-275 tons, the wing area of 570-750m2 and with the engines with the takeoff thrust 22500-27500 kG. Subsequently the passage to SPS-2 of larger dimensions was planned. By 1985 the OKB prepared the technical proposal on Tu-244 with four variable cycle engines with a takeoff thrust of 24000 kG. The project provided for the creation of a Tu-244 with parameters greater than the dimensions of the Tu-144[D]: a takeoff mass of 260 tons, a wing area of 607m2, and 150-170 passengers. The calculated flying range was 7000-10000 km, and the supersonic cruising lift-drag ratio was determined to be 8.65. The special feature of project became the application of variable cycle engines in combination with the shortened intakes in comparison with Tu-144 air ducts. Application of variable cycle engines made it possible to optimize the work of power plant to a greatest degree in different flight conditions and made it possibile to carry out highly economical subsonic flight above the zones with the high density of population.
The technical complexity and increasing cost of the programs for creation of the SPS-2 forced the leading aircraft construction firms in the USA, Great Britain, France, Germany, Italy, Japan and by the USSR (Russia) beginning from the end of the 80's to coordinate their studies on SPS-2. This was first of all in the field of environmental impact, and also in the estimation of the need of humanity in SPS and determination of their rational parameters (it should be noted that a similar collaboration was achieved and it is earlier: beginning from the middle of the 1960's between the USSR and France it was fixed, although in the limited volumes, collaboration on some problems of creation SPS-1). At the beginning of the 1990s for the purpose of the solution of the problems of creation SPS -2 at the international level was designed so-called "group of eight", which included firms Boeing, McDonnell-Douglas, British Aerospace, Aerospatiale, Airbus (DASA), Alenia, an association of Japanese aviation corporations and joint stock company ANTK im.AN.Tupolev.
On the basis previous studies on SPS-2, taking into account the prospect of Russian and world markets for a future SPS, the OKB continued in the 1990s to work at different aspects of project SPS-2 in close contact with the leading Russian branch scientific centers (TsAGI (Central Institute of Aerohydrodynamics im. N Ye Zhukovskiy), TsIAM (Central Scientific Research Institute of Aircraft Engines im. P.I. Baranov), VIAM (All-Union Scientific Research Institute of Aviation Materials)). In the second-half of the 1990s the appearance future Russian SPS-2 Tu-244 was more or lessformed, although in the course of further development of design the first flight Tu-244 was possible with the normal development of works not earlier than in fifty years.
The basic aerodynamic configuration "bobtailed aircraft", power plant of four TRD (turbojet engine) in the separate pods, the takeoff mass of 320-350 tons, cruising speed Of [m]=2,0-2,05. Selected takeoff mass, overall sizes and passenger capacity (250-300 and more than passengers) make it possible to ensure competitive ability with the subsonic aircraft (by such, as Boeing 747 and A 310), which take 300-500 place. Layout Tu-244 is subordinated to the guarantee of a high lift-drag ratio both in the supersonic cruise (to 9 and more) and in the subsonic flight conditions (to 15-16), and also in the takeoff and landing regimes for a noise reduction and creation of the increased comfort for the passengers. The wing of trapezoidal planform with the accretion has the complex deformation of median surface and variable profile on the spread. Control in pitch and bank, and also balancing are ensured by elevons, leading edge is supplied with mechanization of the type of the leading-edge slats.
In comparison with Tu-144 the base part of the wing had considerably smaller sweep angle on the leading edge, with the retention of the large sweepback of the root part, which ensures a compromise between the cruises at the high supersonic speeds and at low speed. The wing construction is close to Tu-144. Provision is made for the wide use of composites in the wing construction, fuselage, tail assembly, pods, which must ensure a decrease in the mass of glider to 25-30%. As on the Tu-144, the vertical tail assembly has two-section control and it is structurally similar to wing. The fuselage consists of a pressurized cabin, nose and rear compartment. For the selected passenger capacity of 250-320 people the optimum was a fuselage with a width of 3.9 m and by the height of 4.1 m. The Tu-244 forewent the slanted forward fuselage. The cockpit windows of crew give the necessary survey in flight, and in the takeoff and landing regimes the required visibility is ensured by the system of optical-electronic survey.
An increase in the mass of aircraft required to change the schematic of the landing gear, in contrast to Tu-144, on Tu-244 the landing gear consists of one front and three main struts, from which external have triaxial carts and are removed into the wing, and average counter has bogie and is removed into the fuselage. The takeoff thrust of each engine is determined at 25000 kG, though there was not yet complete clarity with the type: variable cycle engines are examined, and the usual turbofan engines with the ejector nozzle, which ensures noise-absorption on the takeoff and the landing. Systems and equipment Tu-244 must be developed taking into account experience on Tu-160 and Tu-204.
Attempting to ensure the flexibility of approach to the problem SPS, in the operation on the project in OKB were prepared several possible projects Tu-244, that are characterized by masses, overall sizes, passenger capacity and insignificant differences in the assembly and design plan. In one of the last versions Tu-244, OKB proposed, the discussion deals with the aircraft with a takeoff mass of 300 tons, the wing area of 965m2, four TRDD (turbofan engine) with the takeoff thrust on 25,500 kG and with the passenger capacity of 254 people. Calculated practical supersonic flying range with the normal payload is equal to 7500 km.
Information about the aircraft was represented at the Parisian airshow in June 1993. Suppositional period of entering. at operation - 2025 g. potential market is evaluated into more than 100 aircraft.
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