GLASGOW, Mont. – The Boeing Co. and its partners have come to this out-of-the-way corner of northeastern Montana to test ways to make jets as quiet as a Tuesday night in this little town on the prairie.
The technology being tested includes rings of perforated titanium and a cowling made from a nickel-titanium alloy that changes shape at different temperatures. Most of the material being tested will end up on Boeing’s state-of-the-art new 787 jets.
The test equipment itself consists of vast arrays of microphones that record soundwave data that’s dumped into huge computers for processing.
Yet one of the key tasks is making sure that birds don’t perch on any of the 617 microphones Boeing engineers have carefully laid out in a spiral at the end of an abandoned U.S. Air Force air strip.
When that happens, project leader Belur Shivashankara said, they send someone out on a bike to shoo away the birds.
“Science typically happens in remote places,” said Walt Gillette, the Boeing vice president in charge of developing the 787. “You can’t just go to the store and buy three pounds of science.”
The technology being tested in the open Montana skies should make a difference to airline passengers, and to people living in crowded urban areas next to airports, the researchers said.
Airport noise has been a subject of debate in Snohomish County, where studies are underway to determine the feasibility of scheduled air service at the county’s airport, Paine Field.
However, it’s already an unpleasant fact of life in other parts of the world, particularly Japan, where residential areas push up against airports, said Rob Henderson, a spokesman for All Nippon Airways.
“Noise is a very important issue in Japan,” he said. “It’s a very crowded country.”
That’s why ANA is allowing Boeing, Goodrich Corp., General Electric and NASA to conduct three weeks of tests using one of the airline’s brand-new 777-300ER jets.
“This is a great chance for us to get directly involved,” Henderson said.
Instead of installing seats, workers at Boeing’s Everett plant moved in enough computer stations to fill two sections of the ANA jet’s cabin.
On each flight, 20 engineers monitor readings from sets of microphones stuck outside the plane, while the pilots put the plane through simulated take-offs and landings. Others on the ground monitor sounds picked up by microphones on or around the runway.
The network creates an “acoustic camera” that allows the team to point “where on the airplane that noise came from,” Shivashankara said. In previous tests, “we couldn’t tell whether the noise came from the landing gear or the jet exhaust.”
The tests, which will conclude Aug. 25, primarily involve three areas:
* Sound-absorbing materials intended to reduce the noise escaping from the front of the engines;
* Redesigned engine covers – or nacelles – intended to reduce the noise created by air rushing over and through the jet engines;
* And a tobogganlike cover that fits snug between the wheels of the jet’s landing gear, thus blocking wind that otherwise would whistle and shriek as it flowed past the wheels’ struts.
Boeing plans to use the first two technologies on the 787. It won’t use the toboggan on the Dreamliner, Gillette said, but it is trying to design the new jet’s landing gear so that it will be quieter.
Most people associate airplane noise with the roar of jet engines. But in fact, one of the biggest causes of noise is the flow of air over the plane. Landings are particularly noisy, as the wind whistles through and around the extended flaps on the wings and the lowered landing gear.
There are a couple of ways to deal with different jet noises, Gillette said. Engineers can dampen it so it’s less loud, or change the frequency of the noise so that it’s outside the range of what humans can hear.
In some cases, “it’s more efficient to not let it happen,” Gillette said.
Potentially every bolt or seam along the plane could disrupt that air flow and cause noise, said Eric Nesbitt, a Boeing research fellow working on the test program, which Boeing is calling the Quiet Technology Demonstrator 2.
One of the breakthrough developments being tested in Montana does away with some of those. Goodrich, which builds engine nacelles, has come up with a way to cast a one-piece liner for the engine’s air intake.
The black, carbon-fiber surface absorbs sound, and since it has no seams, it doesn’t create any either.
That works fine for the interior of the nacelle, but the lip remained a problem, because ice builds up on that. To solve that problem, Goodrich came up with a perforated titanium lip that absorbs noise, but also can be heated to melt any ice.
The combination, Goodrich believes, should essentially do away with the noise created by the jet engine’s fans – a buzz-saw blast clearly heard in jet cabins.
They’re “very close to being production ready,” Goodrich vice president Colin Cramp said.
GE and Boeing also have collaborated on new chevrons for the trailing edge of the engine cowlings.
When air flows over and through a standard jet engine, one with a smooth back edge, the separate streams collide, creating noise-generating “shock cells.” Newer engines, however, have incorporated the chevrons – serrated edges that better mix the air to eliminate the cells.
GE plans to use the technology on the new GEnx engines it will provide for the 787. The engines also are likely to go on Boeing’s proposed 747 Advanced, as well as Airbus’ A350.
The initial tests have been “very, very encouraging,” said Garreth Richards, a GE jet engine program manager. “We’re going to see the fruition of this technology very quickly.”
It will be a few weeks before the Boeing-led team will have the calculations to determine how well the new technologies work, Nesbitt said. So far, “we’re seeing from our data that it’s noticeably quieter.”
The technology “will be ready for future versions,” said Dan Mooney, Boeing vice president of new product development. “It’ll also be ready for products out beyond the 787.”
Reporter Bryan Corliss: 425-339-3454 or corliss@ heraldnet.com.
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