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Staying safe in the air
May 7, 2015   
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An ultramodern facility for testing aircraft engines is under construction at the Rzeszów University of Technology in southeastern Poland in a project that aims to take flight safety to the next level.

Once completed and operational, the facility will enable Polish aviation engineers to avoid high costs related to testing critical aircraft engine parts abroad.

Out of the many components of any aircraft, some are crucial to flight safety because any damage to them could lead to disaster. Such “critical” parts include turbine discs, turbine blades and lubrication systems. These and other parts will be tested for quality and durability at the new facility at the Rzeszów University of Technology. Comprising four special test stands, this will the first and so far only laboratory to enable such tests in Poland, making it possible to cut costs by 80 percent compared with tests conducted abroad.

Airframes and propulsion systems produced by the aviation industry in Europe are subject to certification by the European Aviation Safety Agency (EASA) headquartered in Cologne, Germany. Certificates issued by the agency permit the use of engines, propulsion systems and whole aircraft, including airplanes and helicopters. The agency has to accept and approve any change producers make to engines and airframes, and the strictest regulations apply to critical parts.

EASA procedures require that a round of calculations and experiments be performed before a new engine module or component can be installed in an aircraft. All prototype components must undergo expensive tests on an engine test stand in an environment close to real-life conditions. In order to reduce the cost of the procedure, individual components can be tested on separate test stands such as those under construction at the Rzeszów University of Technology’s Research and Development Laboratory for Aerospace Materials.

The engine test lab is being developed by a team of researchers led by Prof. Jan Sieniawski as part of the Demostrator+ project financed through the European Union’s Innovative Economy Operational Programme. Access to the facility will mainly be granted to companies from the so-called Aviation Valley cluster in southeastern Poland that work with the aerospace industry and train pilots.

Working on the three-year project, the Rzeszów University of Technology has formed a consortium with aerospace company WSK PZL-Rzeszów, which will contribute around zl.5.5 million. The National Research and Development Center (NCBR) has shelled out a further zl.18.5 million for the project.

Four kinds of test stands will be used to test different engine components and technology, including graphite seals on the first stand, turbine discs on the second, turbine blades on the third, and environmentally friendly materials and anti-corrosion coatings on the fourth.

Tadeusz Gancarczyk, D.Sc., project manager at WSK PZL-Rzeszów, explains that graphite seals are used in plane engines near rotating parts, most of which need to be constantly cooled and lubricated with oil. Seals are necessary to prevent lubricants from leaking between turbine modules and between shafts and turbine housings. The high temperatures in a working turbine necessitate that the seals are made from materials based on graphite. Graphite seals can be tested for durability outside engines, but only on test stands that offer conditions close to those inside a working turbine, Gancarczyk says.

The laboratory the consortium is building is the only facility in Poland to have been certified under the National Aerospace and Defense Contractors Accreditation Program (NADCAP). Engineers and researchers from the laboratory say that as far as safety is concerned, tests of rotating parts are particularly important. WSK PZL-Rzeszów’s Gancarczyk explains that any damage to compressor and turbine discs can cause a plane to crash. “A [damaged] disc shoots out of the engine and cuts right through anything that stands in its way, just like a missile,” Gancarczyk says. These parts are thoroughly inspected when produced and approved for use. Any change to technical parameters and materials requires tests to prove the right choice was made.

One of the test stands in Rzeszów will be used to assess new engine component processing methods as well as production of entire engines and new structural concepts. In the tests, compressor and turbine discs are rotated at high speed until they are damaged, allowing the researchers to precisely identify the conditions in which that happens.

Aviation engines are expensive to test, which is why producers try to avoid making frequent changes. Still, once in several years most engine buyers come up with new and stricter requirements and then, the technology has to be either adjusted or completely reinvented. More efficient technology requires new materials and needs to conform with regularly updated air safety regulations. With a test stand of its own, WSK PZL-Rzeszów will now be able to afford to roll out innovative technology more frequently and at a lower cost, making sure the aircraft parts it produces are more reliable, translating into enhanced flight safety.

WSK PZL-Rzeszów produces modules for small and medium-sized gas turbines and turboshaft engines for U.S. company Pratt & Whitney. It also makes turboshaft engines and transmission gear for Poland’s Sokół helicopter and Bryza airplane.

WSK PZL-Rzeszów also manufactures more than 350,000 turbine blades every year. In a working turbine, such blades need cooling, which necessitates an array of internal cooling channels. In order to ensure the channels are in place, turbine blades are cast on special ceramic cores and the quality and future use of each blade depends on the appropriate positioning of the cores, as that determines the shape of the cooling channels in the final product.

A special stand has been planned at the new lab to test different core positions. Engineers will be able to decide how and where the ceramic cores should be fixed to obtain an optimal thickness of blade walls and ensure an appropriate flow of the cooling gas inside the blades to prevent damage in extreme conditions.

Moreover, the new test stands will be used to study hard anodizing, which is a method used to prevent the corrosion of aircraft parts, especially engine and transmission components, made from light alloys of aluminum and magnesium. Such alloys make it possible to reduce the weight of aircraft.

“Airplanes operate in different conditions,” says Gancarczyk. “While the climate in Poland is easy on transmission gear housings made of aluminum or magnesium alloys, the humid climate of Indonesia and the Philippines, for example, necessitates effective protection against corrosion. Most coating techniques of this kind involve toxic components such as chromium, cadmium and bismuth. The European Union’s Registration, Evaluation, Authorization and Restriction of Chemicals (REACH) directive, which will take effect several years from now, will ban the use of these components in technology, which is why we have started to search for new and environmentally friendly materials whose properties meet the requirements of the aviation industry.”

The Demonstrator+ project will end next year. WSK PZL-Rzeszów will have priority access to the new laboratory, but the facility will also be open to other companies from Poland and abroad. Tests have so far been booked by ANGA, a Polish mechanical seal producer based in Kozy near the southern city of Bielsko-Biała and by German aviation engine producer MTU Aero Engines AG. Companies wanting to conduct tests at the new lab also include Britain’s McBraida of the Rolls Royce group, whose Polish subsidiary is headquartered in Tajęcin near Rzeszów’sJasionka international airport.

Karolina Olszewska
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