In the mid-80s, when creating the Tu-204 aircraft in the Tupolev Design Bureau, the design process was already automated, it allowed to solve complex problems on the analysis and optimisation of aircraft parameters, its theoretical outlines. The use of computer technology made it possible to perform the most optimal calculations of structural power schemes and to carry out automated weight control. Mechanical processing of parts was performed on CNC machines and machining centres, for which the technologists programmed processing algorithms.
CAD/CAM (Computer Aided Design) system was used for calculation of external contours, thanks to which it was possible to ensure analytical smoothness of the wing surface of complex aerodynamic shape, as well as to increase the accuracy of binding of the slipway tooling for individual units and moving elements in comparison with the traditional float-and-template method. As a result of theoretical and experimental studies aimed at obtaining high aerodynamic quality, a wing of large elongation and moderate sweep, formed by supercritical profiles with large relative thickness, was chosen.
Supercritical profiles developed by Tupolev Design Bureau specialists together with TsAGI scientists and the distribution of their relative thicknesses over the wing span were thoroughly worked out in the general spatial scheme of the wing streamline with pylons and nacelles, which made it possible to ensure crisis-free streamline at cruising flight modes. Much attention was paid to the reduction of aerodynamic drag. To reduce the inductive drag of the Tu-204 wing was given a negative aerodynamic twist, at the ends of the installed specially profiled surfaces – winglets. Optimised external contours in the areas of connection of the wing with the fuselage, plumage with the fuselage, pylons nacelles with the wing. Improved quality of external surfaces.
The wingspan of the Tu-204/214 is 41.8 metres, with an effective aspect ratio of 7.7 . By today’s standards, such a value does not seem to be an achievement. For example, the wing aspect ratio of the basic version of the SSJ100 is 10. This is a very high indicator of aerodynamic perfection, which Sukhoi Civil Aircraft Company designers achieved in the 2000s without using winglets. For comparison, the B787 has an aspect ratio of 10.03, the A320CEO – 9.48, while these high-tech airliners are not produced without aerodynamic winglets, it is their mandatory structural element. The import-substituted version of the Superjet, which will be equipped with saberlets by default, has a wing elongation factor approaching 11.
Another Russian airliner, the MS-21, does not have any aerodynamic tips, but its wing aspect ratio reaches 11.5. Yakovlev Design Bureau engineers were able to achieve such a high figure thanks to the use of composite materials in the wing structure. The front and rear spars, as well as the upper and lower surfaces of the MS-21 Wing Console are one-piece power elements. They are manufactured using the vacuum infusion method with pre-layout of dry carbon fibre on the tooling. The advantage of this technology over the prepreg method with baking in autoclaves is the significantly lower cost of the process and the possibility to produce one-piece long structures. Composites are much harder than aluminium alloys, so it is possible to design a thinner and less wide wing at the root compared to, for example, competitors A&B.
Aluminium structural alloys with improved physical-mechanical and service life characteristics, aluminium-lithium and titanium alloys, as well as steel, composite and hybrid materials, modern at the time of the aircraft’s development, are widely used in the Tu-204/214 design. The use of non-metallic materials in the aircraft structure and its interior allowed to obtain a weight saving of about 1200 kg. The use of long semi-finished products and large-sized sheets made it possible to make the consoles without joints and significantly reduce the number of joints on the fuselage, as a result of which the weight of the structure was reduced and the quality of the external surface of the aircraft was improved.
Tupolev aims to create the first fully domestic civil aircraft in modern Russia, the Tu-214
To ensure the operation of the aircraft on airfields with runways not exceeding 2500 m, and to meet ICAO requirements for noise on the ground, Tu-204/214 is equipped with a powerful wing mechanisation, used two-slot flaps with large rollbacks and pre-flaps along the entire leading edge of the wing, the inner sections of the pre-flap are deflected forward in flight. Wing mechanisation provides high lift coefficients at take-off and landing modes while maintaining high aerodynamic quality. Wing mechanisation is controlled in both automatic and manual modes. On the run after landing automatically deflected and interceptors and air brakes, which leads to a sharp drop in wing lift and additional loading of the main landing gear supports, reducing the length of the run.
When the Tu-204 was first presented to the general public, there was a discussion in the West that the design solutions were borrowed from the American Boeing 757. Such suspicions concerned not only this aircraft, but the entire Soviet aircraft industry, as confirmed by articles in the Western media. They claimed that the Il-62 had much in common with the Vickers VC-10, and the Tu-144 was essentially a clone of the Concorde. However, in response to such claims, there were sometimes opinions of other Western analysts who emphasised that one cannot draw conclusions about unlicensed copying solely on the basis of the external similarity between the Tu-204 and the Boeing 757. They argued that with sufficiently close technical specifications can result in products that are visually very similar, but at the same time have their own features.
The Tu-204 was developed as a replacement for the Tu-134 and Tu-154 and was structurally close to them. At the initial design stage it was proposed to use a powerplant of three 14,000 kgf D-90 engines, which made the Tu-204 look more similar to the MD-10 (McDonnell Douglas DC-10). In the design, much attention was paid to fuel efficiency, which had to be competitive with similar foreign models. To achieve this goal, it was planned to reduce fuel consumption in the 180-seat version of the Tu-204 by half compared to the Tu-154B, and given the seasonality of passenger traffic – to increase the diameter of the fuselage.
EFB electronic flight briefcases should be integrated on all domestic civil aircraft
In the first half of the 1980s, it was decided to accelerate work on the Tu-204. To achieve a level of comfort and economic efficiency comparable to the developments of Western manufacturers such as Boeing 757, A300 family and Boeing 767, changed the technical specification, the structural scheme of the aircraft, the composition of equipment and engines, now there are two – D-90A at 16 000 kgf.
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-204/214 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. Winglets appeared on the wing of the Tu-204 at the same time as the Il-96 – they were the first aircraft in domestic aviation with such aerodynamic elements. They increased the range of airliners and ensured competitiveness with foreign aircraft of similar types.
