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Analysis & Opinion

Superjet to be tested for strength

15:02 13/02/2007

MOSCOW. (RIA Novosti political commentator Viktor Litovkin)

Late in January, an An-124 Ruslan transport aircraft landed in Zhukovsky airfield near Moscow, or, to be precise, in the Gromov Flight Research Institute's field.

There was nothing remarkable about the fact as such transports often touch down here. But one thing made the event stand out.

The plane carried the body and wings of a new Russian regional passenger jet (RRJ), or Sukhoi SuperJet-100 - a joint project of Sukhoi, Boeing and Ilyushin - flown over from Komsomolsk-on-Amur. From the aerodrome the fuselage and wings were taken to the Central Aerohydrodynamics Institute (TsAGI), assembled and placed in the hall for static testing. This is a unique facility which can handle planes weighing up to 500 tons. For reference, the RRJ tips the scales at 70 tons in complete configuration, naturally with the engines.

In the next few months, the airliner, described as a preprototype and made in Novosibirsk and Komsomolsk-on-Amur using a technology approved by the Sukhoi Civilian Aircraft design bureau, is to undergo a series of tough tests for static and dynamic strength, heat resistance, air resilience, etc. It will also be put through its paces in aerodynamic and gasodynamic chambers and much else, as provided for by its program. The tests are scheduled to wind up in August.

"Before taking to the air the plane must get about nine clearances to obtain a passport to the skies," said Dr. Vladimir Kargopoltsev, director of the Institute.

One of them - "drainage" - was described by Dr. Vladimir Vermel, head of the Institute's advanced planning.

"You want to know what 'drainage' is? It means many holes drilled in the model's body and connected by pipes to pneumo-switches to gauge air pressure along the model surface during the flight. All these findings are fed into a computer, and we get answers to several questions: one is how the engines work in tandem, and if they are placed right. The second is where to install smoke exhausts and air conditioning intakes ... All of this is important for passenger comfort and safety. We want the SuperJet to be a breakthrough product for our aviation industry. And we'll do our best to make it one. So far the tests have shown our designs are correct and meet all the requirements."

This Sukhoi passenger plane is not a first-comer to the Institute. Its wind tunnel indexed T-128, the largest in the Eastern Hemisphere, has tested several half-life-size models of the SuperJet. There is also a cockpit simulator for its future test pilots to run through a variety of flying modes. Even when the pilot cannot send the plane into an uncontrolled spin - either the wheel would be locked, or a sound signal given to indicate human interference went over the permitted level. The pilot would also be warned he was doing something wrong. This is another of its safety features.

The laboratory for static and dynamic testing has set up several rigs to test the RRJ's wing strength, landing gear and much else. A composite wing option is being considered, the Institute director said, which may enhance the plane's efficiency. Designers think the aircraft's flying life could be raised to 70,000 hours, compared with the standard 30,000 to 40,000 hours. This is a serious challenge calling for overall strength and vibration tests.

The present wing, Kargopoltsev went on, would be test-destroyed. Scientists and designers need to know what load limits the construction can bear, and where to stop in taxing the aircraft, as well as what to do to avoid such loads weighing down on the plane at critical moments. "We believe it is crucial not to just plan theoretical resources for growth, but to translate them into actual physical progress," he said. "For example, we have developed algorithms that improve take-off and landing safety six-fold. We just preclude the wing-tip touching the ground at these modes, which are most dangerous."

"Although the body would not be destroyed completely, this is a very costly experiment on a life-size model," Kargopoltsev explained. "Instead, special safety belts will be tightened around the fuselage before the passenger cabin is pressurized so that maximum loads would not tear it apart and the laboratory walls with it."

"Not so long ago we did the same job on a new A380 Airbus body," the director said. "The plane is indeed unique both in size and in manufacturing technology. But we found that its designers overlooked some little details in the wing design. These are trifles, but noticed in time they will help the EADS to improve the construction."

TsAGI's services are used not only by European aircraft manufacturers, but also by the U.S. company Boeing (which tested its Boeing-767 here), Indian HAL, which tested a model of its LCA light fighter jet, Brazilian Embraer-170 and Embraer-190. Currently the Institute is testing a Chinese aircraft whose name and details are kept secret. The tunnel has been used on four models of the T-50 fifth-generation Russian jet fighter, or PAK FA, which means the advanced system for front-line aviation, and other projects not reported in the press. "All this is evidence," Kargopoltsev said, "that the crisis in the Russian aircraft industry, so hyped up recently, is an exaggeration. Otherwise our services would not be in such a demand."

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