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‘SILENCER' – low-noise engines making Europe a quieter place

Europe's citizens can look forward to quieter skies as the benefits of a new EU-funded low-noise research project flow into the next-generation engines of both large and small aircraft in the next few years.

Image: © Peter Gutierrez
Image: © Peter Gutierrez

Known as SILENCER, the €110-million, four-year project involves some 50 European companies, universities and research institutes in a concerted effort to reduce jet engine noise while controlling equipment cost, weight and performance. The overall goal is to reduce aircraft noise by as much as 6 decibels by 2008.

A wide range of engine technologies are being tested, from low-noise fans to nozzle jet-noise suppressors, as well as modifications to parts of the aircraft itself such as wings and landing gear in order to reduce their noise ‘signature’.

But achieving this goal presents some difficult technical challenges, explains Eugene Kors, the project's coordinator, who works within the research and development department at French engine maker Snecma. “Jet engines are already much quieter than even a decade ago, so the margin for big leaps in progress is rather narrow, which means we have to look at all performance factors if we're going to 'squeeze out' more silence from the aircraft as a whole,” he says.

Trade-offs are inevitable

Part of the problem, according to Kors, is that nothing comes for free in terms of aircraft performance. “For many solutions, there is a trade-off between noise and fuel efficiency. Or there's a wake penalty,” he says, referring to the pattern of air turbulence, or ‘wake vortex’, that trails behind an aircraft, sometimes for kilometres, that other aircraft must avoid for safety. “So this is a challenge for us, which is why we are looking at an extremely wide range of technologies.”

Technology for retrofitting and re-engining

Airlines generally face two choices for reducing engine noise. One is to re-tool, or retrofit, their existing aircraft engines with so-called ‘hush kits’ and other noise-reducing parts and systems. The other is to re-engine, or completely replace, an old engine with a new one. “An airline's first choice is to retrofit rather than re-engine,” observes Kors.

SILENCER will offer both: new retrofit technologies and newly designed engines. “There are a lot of aircraft engines approaching the 20-year mark of their design, such as those used in Airbus 330s and 340s or Boeing 737s and 747s, so there is a big retro-fit market out there,” he says, adding that SILENCER is also looking ahead to the next-generation engines of the future Airbus 380 and Boeing 787.

Getting the technology to market

Though large aircraft overwhelmingly dominate the aviation sector, SILENCER is not overlooking the industry's niche markets and smaller players. In fact, the latter will likely benefit from the project's research before the mass-market players.

According to Kors, “SILENCER's first applications should be to the smaller and lower-cost end of the equipment market: the business jets and regional aircraft that carry under 100 passengers.” But smaller aircraft mean lower noise levels, so why the priority?

“Business and regional jets are not big sources of noise at large airports,” says Kors, “but at Europe's small and regional airports, where business jets are their sole source of income and traffic, the noise problem can be a major source of complaints. That's why we're looking at their engines too, and planning to bring SILENCER's benefits to them first.”