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Aviation History
1996
1996 - 2521.PDF
Slow slow, quick quick, slow The Sukhoi Su-37 made a spectacular impact. ALEXANDER VELOVICH/MOSCOW SPECTACULAR EVIDENCE that the Russian aircraft industry is still alive came to the 1996 Farnborough air show with the international debut of Sukhoi's thrust- vectoring Su-37 Flanker. The aircraft is a fur ther development of the Su-2 7/3 5 fighter series and, although it is characterised by its designers as an experimental development prototype, it is much more of a basis for a combat fighter than was the US/German X-31 research aircraft which was used to entertain the public with exotic manoeuvres attheParisairshowinl995. The Su-3 7 has an integral flight-control sys tem, with a sidestick implementing thrust vec toring through control algorithms. Other in novations include wide field-of-view head-up display and liquid-crystal multi-function dis plays on the instrument panel. Sukhoi acknowl edges that French electronic equipment has been installed in the fighter, but refuses to reveal die name of the manufacturer (probably Sextant Avionique), hidden under the acronym "FPI". Sukhoi began experiments with thrust vec toring in the late 1980s, when Lyulka developed a two-dimensional nozzle for its AL-31 engine, which was tested on one of Sukhoi's Su-2 7 de velopment prototypes. Although valuable expe rience was gained, it was decided that axi- symmetric configuration of die jet nozzle would be more promising. Lyulka concentrated on die development of an engine modification, designated the AL-3 7F. Another flying testbed, with one of the engines equipped with an axisymmetric nozzle, was test ed in the early 1990s. In 1995, two thrust-vec toring engines were installed on a modified version of the Su-27M, with the constructor's number 711. While the modified Flanker re- FARNBOROUGH REVIEW Fasterfuture Dornier's aircraft range faces changes. ANDRZEJ JEZIORSKI/MUNICH THE 30-SEAT DORMER 328 turbo prop, which was first flown in December 1991, has always been a problem for its manufacturer, Oberpfaffenhofen-based Dornier Luftfahrt. While its performance, compared with that of its rivals, is impressive, the 328's 335kt (620km/h) maximum cruise speed falls lOkt short of initial targets, and the aircraft is about 1,000kg heavier than first hoped. In a sluggish market, burdened by high costs, Dornier has lost money on every 328 sold, and a long-await ed 50-seat version has never materialised. In June, die former Daimler-Benz Aerospace subsidiary's ownership changed, and so did the outlook for the 328. Dornier Luftfahrt's new owner, Fairchild Dornier — 80% of which belongs to Fairchild Aircraft of San Antonio, Texas—has revived die stretch and is now look ing at re-engineing the 328 with turbofans (FlightInternational, 11-17 September)—a first in aviation history. According to Fairchild Dornier marketing director Josef Simmerl, the company started interviewing potential 328-stretch customers in late 1995, and was confronted with strong inter est in jet aircraft. Dornier then embarked on a concept study of its 50-seater, with a simultane ous side study on a turbofan variant. The results could now lead to a family which includes the current turboprop 30-seater, alongside 30- and 50-seat turbofans. "Lhave to say we like the idea of a fan over a turboprop at 50 seats," says Fairchild Dornier president James Robinson. As for the 30-seat turbofan, called die 3 2 8-3 00, Robinson believes that the speed with which Dornier could corner this niche gives the company an edge. The air craft could be flown a year after launch, with the 50-seat Dornier 328-700 following, another year behind,'with certification taking a further year for each. This means, however, another three-year wait for an operational stretched 328, and the continued absence of a 50-seat variant, which has already cost Dornier dearly. It was a con tributing factor to; the recent decision by Horizon to drop the 328: the airline already operates a dozen 328s, and at first wanted as many as 60. "The 50-seater [jet] is a critical element of the long-term planning, but there are already two competitors in this market," says Robinson, • ceived the designation Su-3 5, it was decided to give the 711a new model number, the Su-37. The nozzfe of the A1-37F engine has thrust vectoring only in pitch, but Lyulka general designer Victor Chepkin says that the bureau "...has a full [two-axis]-vectoring nozzle in its pocket", akhough it is unlikely to be used on die Su-37 because its tail boom and twin-engined configuration makes it difficult to vector thrust in yaw. The vectoring mechanism is driven by hydraulic actuators, with a back-up system to return the nozzles to neutral position by com pressed air. There are no restrictions on engine thrust, so full afterburner can be engaged while the nozzles are fully deflected. Differential thrust-vectoring is used for bank control at extremely low speed, and that, too, was demon strated. A similar nozzle design is believed to be implemented on the fifth-generation Lyulka Al-41 powering the Mikoyan 1.44 advanced fighter demonstrator, which is expected to be flown soon. Besides thrust vectoring, the AL-3 7F has had its thrust increased to 2 8kN (6,3 501b), from the 2 5 kN of the AL- 31F. This has been achieved by raising airflow through the fan to 12 Okg/s from the current 112kg/s on the AL-31. The dry mass of the new thrust-vectoring engine is 1,600kg, only 70kg heavier dian the series pro duction model. Another factor of improvement is the increase in turbine-inlet temperature, from l,450°Cto 1,530°C. This is made possible by changing the design of the circular combus tion chamber. The most spectacular thrust-vectoring manoeuvre demonstrated at Farnborough was a backward flip-flop, during which the aircraft was pitched up instandy, fell on its back and was recovered into level flight, continuing half a loop from the inverted position at almost zero airspeed, with an extremely tight turning radius compared with the length of the aircraft. The Su-37 programme suffers from inade quate financing. The aircraft is also being used to test some of the electronic equipment and design solutions which may be incorporated on board die Sukhoi Su-34 bomber. • FLIGHT INTERNATIONAL 18 - 24 September 1996 41
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