Sukhoi S-80 Nears First Flight

?? Serge Pod #25.01.2000 06:03

Serge Pod


Sukhoi S-80 Nears First Flight

By Vovick Karnozov
AWN Moscow-based columnist
The Sukhoi design bureau is finalising preparatory work on the second S-80 airframe at its flight test base in Zhukovsky near Moscow. The exact day of the S-80 maiden flight will be dependant on the progress with installation and checking on-board systems and avionics, while the airframe itself was completed some two months ago.

The S-80 is a twin-engine multipurpose aircraft. Its development began in the mid-1980s as part of the conversion of the Russian military industrial complex to the production of civil products. The S-80 was conceived as a lightweight and highly economic transport able to operate from short unpaved airfields. It was meant to replace the aging fleet of LET L-410, Antonov An-2, An-14 and An-28 and Ilyushin Il-14 on the regional and feeder lines primary in Siberia and Far East.

In the mid-1980s the aircraft was presented as a vehicle to bring high technologies amassed by Sukhoi and its partners in development and production of military aircraft into civil aviation. Also, it was a touchstone for the Sukhoi design bureau, which historically made only combat aircraft, from which to assess the ability of the famed fighter house to develop a civil product.

At first, the S-80 appeared on the drawing boards as an aircraft in Burt Rutan's style, with numerous aerodynamic surfaces that had to provide ultimate flight performance at all costs. However, as the Sukhoi engineers were getting closer to the realities and needs of the airlines, the S-80 went through a long series of design changes which, in most instances, were confined to various measures on simplifying the original design. Sukhoi engineers joke that the gist of the S-80 evolution process was that "the aircraft was losing an aerodynamic surface every year." It was not earlier than 1990-91 when the external design of the plane was frozen (by that time the S-80 had had no odd aerodynamic surfaces to remove).

Specification to the basic version of the plane calls for a twin-engine aircraft with a maximum takeoff weight of 12,500 kg, able to carry 3,500 kg load (or 26 passengers) at a maximum cruise speed of 535 kmh. Takeoff run is set at 550 m, landing run at 280 m. High field performance and low fuel burn at the cruise are provided by a high aspect wing (with a span of 23.2 m) with modern high-lift devices activated at takeoff and landing. Powerplant is two turboprop engines, either Rybinsk Motors TVD-1500 of 1400 shp each or General Electric CT7-9B of 1750 shp. Certification base is FAR25 and its Russian analogue AP-25.

It ought to be mentioned that although the primary role for the S-80 was to serve feeder and regional lines in remote regions to the east of the Urals, Sukhoi also considered that aircraft for certain military applications, such as delivery of spare parts, fuel and personnel to front-line air bases - the role similar to that of the Sherpa in the USAF. Other possible applications for the S-80 were thought to be medical evacuation, fire-fighting and various patrolling in the interest of civil and military users.

The main military version is the Su-80PT carrying the Strizh airborne integrated system (a radar, infrared and optical sensors). It is able to loiter for 6-9 hours and carry a variety of weapons on underwing stations, including containers with 57-mm rockets, R-73 air-to-air, Vikhr and X-29 air-to-surface missiles. The armed version is intended for border guards and sea police, needing more economical-to-operate air vehicles than the Mi-8/Mi-17 series helicopters.

Still, the S-80 has always been more of a civilian product than military, and the very idea to have military versions was just to have a wider client base for the aircraft. That is why the first aircraft were made in the basic civil version, the S-80GP. The GP can be quickly converted from all-passenger version for 26 seats into a freighter able to carry 3.5 tons of cargo.

Series production of the S-80 is being set up at the KnAAPO factory in Komsomolsk-upon-Amur. Located in the Far East near the Russian-Chinese border on the Pacific Rim coast, the factory has been manufacturing combat aircraft since 1936. KnAAPO got interested in production of the S-80 because it would provide a smooth transition from military to civil products.

Indeed, the S-80 is similar in size to the Su-27 family fighters, the main product of KnAAPO since 1982. This resemblance allowed KnAAPO to use many of its manufacturing technologies originally developed for the Su-27, in preparation to the S-80 production. At the early stages of development work on this aircraft, the decision was made to give up using composite materials. Instead, the focus was placed on aluminum alloys, mostly those that were well-tried on fighters but never used on civil aircraft.

Together with other civil products, most notably the Beriev Be-103 light amphibian and a dozen of models of high-speed motor boats and yachts, the S-80 production should give KnAAPO a 50% share of civil production in the total output.

KnAAPO decided to give its financial support to the S-80 project and establish a closer than ever cooperation with Sukhoi on this aircraft. In particular, it was agreed that even first development prototypes would be built not at Sukhoi's own experimental aircraft factory in Moscow (which would be of normal practice), but at KnAAPO.

So far, the factory in the Far East has accomplished two airframes. The first one went to SibNIA academy in Novosibirsk for ground tests. The second airframe was completed as a first operable aircraft. The third airframe, taking shape at the factory, will most likely get an insertion into the standard fuselage.

In a typical Russian style, Sukhoi did not spend much time in consultations with airlines on the S-80 design and configurations at the early stages of the project, leaving these issues for the time the first experimental aircraft would be ready for inspection. First relatively large meeting between the developers, manufacturers and potential users of the S-80 took place in May 1998 at KnAAPO.

By that time the airframe of the second aircraft had taken shape, while Sukhoi and KnAAPO had prepared detailed booklets on the aircraft giving the idea of its operational economics. The new airplane was met with enthusiasm by Siberian and Far East airlines. They appreciated the aircraft design. The twin-boom, high-wing layout provides an easy access to the fuselage, including that to the rear part of the cabin fitted with a large cargo ramp. Cargo can be loaded and unloaded from the rear fuselage directly to or from a standard truck. Another good thing is the wide fuselage allowing an ordinary adult person to stand in full height in the aisle.

However, the airlines did have a number of ideas on aircraft improvement so as to get it better suited to their needs. One of those was a proposal to extend the fuselage so as to increase the seating capacity from 26 to 30 or 34. A bigger aircraft would have lower fuel burn per seat at minimal weight and speed penalty.

Calculations made by Sukhoi engineers showed that the airlines were right. A move to a bigger aircraft is technically reasonable. Delays with availability and refinement of the Rybinsk Motors TVD-1500 engine made Sukhoi accept the General Electric CT7-9 for installation on first prototypes and export versions of the aircraft. But the CT7-9 is somewhat bigger and more powerful than the Russian engine. The excess of power does make an idea of a longer fuselage look reasonable.

Although the potential market for the S-80 was estimated by Sukhoi and KnAAPO at a relatively large figure of 800 units, there have been a series of extensive delays with completion of the first operable aircraft. These were caused by shortage of financial resources of the developer and the manufacturer. Naturally, they have preferred to spend their money on military programs in a pursuit for new export orders for Su-27/Su-30 fighters. Russian banks have not been willing to grant credits at low interest rates for long-term aviation projects. At the same time, activities of foreign investors were low too, partly due to the fact that both Sukhoi and KnAAPO are "military" companies.

While Sukhoi has been turned into a joint stock company with its shares available on the market, KnAAPO has remained a unitary state enterprise. KnAAPO leaders continue to oppose any move to turn their enterprise into a joint stock company, pointing at bad results from similar changes at neighboring factories in the Far East. They have their own vision how to attract foreign investors. There is a plan to separate civil production from the military and offer potential investors to financially participate in setting up production of civil products on risk-sharing principles.

KnAAPO representatives say that despite the negative influence of the Rouble fall in August 1998, political and economical turbulence in Russia, some foreign investors and large industrial companies remain interested in long-term cooperation with the Russian industry. In the case of the S-80 and Be-103 projects, KnAAPO is looking for "regional co-operation" with "Pacific" countries, including the US and Southeast Asia. Investors from certain countries situated near the Russian Far East might be given certain advantages in the projects.

The S-80 is already an international project, involving US suppliers of engines, propellers, avionics and interior. General Electric and its industrial partners have delivered to Sukhoi and KnAAPO two operable CT7 engines, associated equipment and instruments for the first operable aircraft. Also, General Electric is cooperating with Rybinsk Motors on setting up a CT7 assembly line in Rybinsk.

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