In the first half of the 1980s, it was decided to accelerate work on the Tu-204. The plane is designed to achieve comfort and economic efficiency comparable to the Boeing 757, Airbus A300 family, and Boeing 767.
By installing winglets it was possible to obtain a wing with an aspect ratio of 7.7, which was a good value for the 80s. We can compare, for example, with Il-62M, which has a wing elongation of 6.4, or Tu-154M – 7.83, Yak-42D – 7.6, Boeing 757 – 7.8 and Boeing 747 – 7.
On the Tu-204 and 214 winglets are installed vertically and are necessary to improve the fuel efficiency of the airliner, providing it with an increase in aerodynamic quality by 2.2%, as well as saving 500-600 kg of fuel when flying at maximum range. When the Tupolev Design Bureau created the Tu-204 aircraft in the mid-1980s, the design process was already automated, allowing it to tackle complicated problems involving the analysis and optimization of aircraft specifications, as well as theoretical outlines. Both the models are powered by two – PD-90A engines developing 16 000 Kilogram-force.
The external contours were calculated using a Computer Aided Design system, which allowed for analytical smoothness of the wing surface of complex aerodynamic shape, as well as increasing the accuracy of binding of the slipway tooling for individual units and moving elements when compared to the traditional float-and template method. Following theoretical and practical research to achieve good aerodynamic quality, a wing with considerable elongation and moderate sweep, built by supercritical profiles with large relative thickness, was selected.
Supercritical profiles developed by Tupolev Design Bureau specialists in collaboration with TsAGI scientists, as well as the distribution of their relative thicknesses over the wing span, were thoroughly worked out in the overall spatial scheme of the wing streamline with pylons and nacelles, allowing for crisis-free cruising flight modes. Much emphasis was placed on reducing aerodynamic drag. To reduce inductive drag, the Tu-204 wing was given a negative aerodynamic twist at the ends of specially shaped surfaces called winglets. External contours have been optimized in the locations where the wing connects to the fuselage, the plumage connects to the fuselage, and the pylons and nacelles connect to the wings. Improved external surface quality.
The Tu-204 and 214 have a wingspan of 41.8 meters and an effective aspect ratio of 7.7. By today’s standards, such a value does not appear to be an accomplishment. For example, the basic SSJ100 has a wing aspect ratio of 10. This is an excellent symbol of aerodynamic perfection, which Sukhoi Civil Aircraft Company designers achieved in the 2000s without adding winglets. For instance, the Boeing 787 has an aspect ratio of 10.03, and the A320NEO has 9.48; however, these high-tech airliners are designed with aerodynamic winglets; which are a required structural part. The import-substituted Superjet, which will be outfitted with saberlets by default, has wing elongation factors approaching 11.
The MC-21 has no aerodynamic tips, but its wing aspect ratio is 11.5. Engineers at Yakovlev Design Bureau achieved such a high value by using composite materials in the wing structure. The front and rear spars, as well as the upper and lower surfaces of the MC-21 Wing Console, are all one-piece power elements. They are made using the vacuum infusion process, with a pre-layout of dry carbon fiber on the tool. This approach has a benefit over the prepreg method with autoclave baking in that it is substantially less expensive and allows for the production of one-piece lengthy structures. Composites are much harder than aluminum alloys, allowing for a thinner and less wide wing at the root than competitors A&B.
The Tu-204 and 214 designs make extensive use of aluminum structural alloys with better physical-mechanical and service life properties, aluminum-lithium and titanium alloys, as well as steel, composite, and hybrid materials that were modern at the time of the aircraft’s construction. The use of non-metallic materials in the aircraft’s structure and interior allowed for weight savings of approximately 1200 kilograms. The use of long semi-finished products and large-sized sheets allowed the consoles to be made without joints, significantly reducing the number of joints on the fuselage, lowering the structure’s weight, and improving the quality of the aircraft’s external surface.
Tu-204 and 214 are equipped with powerful wing mechanization, use two-slot flaps with large rollbacks and pre-flaps along the entire leading edge of the wing, and the inner sections of the pre-flap are deflected forward in flight to ensure aircraft operation on airfields with runways not exceeding 2500 m, as well as to meet ICAO requirements for ground noise. Wing mechanization achieves high lift coefficients during takeoff and landing while retaining good aerodynamic quality. Wing mechanization is controlled both automatically and manually. On the run after landing, interceptors and air brakes are automatically deflected, resulting in a sudden drop in wing lift and increased loading of the main landing gear supports, decreasing the length of the run.
When the Tu-204 was first introduced to the public, there was speculation in the West that the design solutions were derived from the American Boeing 757. Such doubts surrounded not only this aircraft but the entire Soviet aircraft industry, as evidenced by publications in Western media. They claimed that the Il-62 shared many similarities with the Vickers VC-10, while the Tu-144 was practically a Concorde clone. However, in reaction to such charges, several Western researchers have stated that one cannot make inferences regarding unlawful copying purely based on the exterior similarities between the Tu-204 and the Boeing 757. They maintained that with sufficiently near technological standards, items might be superficially identical while still having distinct functionality.
The Tu-204 was developed to replace the Tu-134 and Tu-154, and it was structurally similar to them. Initially, it was suggested to use three 14,000 kgf D-90 engines to power the Tu-204, giving it a more similar appearance to the MD-10. Fuel efficiency was a major consideration in the design, as it needed to compete with equivalent international models. To achieve this purpose, it was planned to lower fuel consumption in the 180-seat version of the Tu-204 by half when compared to the Tu-154B, as well as to expand fuselage diameter due to the seasonality of passenger traffic.
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