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Flying the Quieter, Cleaner Skies
When Fay Collier talks about tadpoles, he's not really talking about tadpoles.

Sure, the smears of color he points to on his slide resemble a creature you might find in a pond, but they represent something far bigger.

As the project manager for the Environmentally Responsible Aviation (ERA) Project, Collier heads a team that, as one of its challenges, is looking for ways to reduce aircraft noise around airports. Those "tadpoles" are a visual representation of that noise. A long, fat tadpole on the far left of the slide represents current noise level standards. A short, narrow tadpole on the far right represents where Collier and his team would eventually like noise levels to be.

Fay Collier, NIA lecture.

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Fay Collier, project manager for the Environmentally Responsible Aviation (ERA) Project, talked about the progress the ERA Project is making Nov. 27 as part of the National Institute of Aerospace's 10th anniversary lecture series. Credit: NASA/Joe Atkinson

What's noteworthy is that the short tadpole is a mere 2 percent the size of the long one. From an auditory standpoint, that would be something like the difference between a bomb and a firecracker. Getting airplane noise down to firecracker levels is still a long-term goal. In the nearer term, Collier thinks that he and his team can hit 8 percent of the current standard — still an aggressive goal.

But it's an important goal for them to reach, because, Collier says, "noise is the number one constraint to growing the air transportation system."

Collier talked about the work the ERA Project is doing to make aircraft quieter and more fuel efficient Nov. 27 as part of the National Institute of Aerospace's 10th anniversary lecture series.

Now heading into phase two of a six-year, two-phase plan, the ERA Project, which started in fiscal year 2009, began by investigating technologies that might help reduce the impact of aviation on the environment.

"I had $650 million in ideas that we had to sort through," Collier said, "and we ended up with about $200 million over these three years to execute."

Some of the ideas Collier and his team had to sort through involved drag reduction, weight reduction and specific fuel consumption/noise reduction.

They also looked at ideas that would make airframes quieter, like high-lift systems and improved landing gear, and ways to make propulsion quieter, especially in relation to engine fans.

The airframe and propulsion technologies come together in something called propulsion airframe aeroacoustics. That's where the ERA Project integrates the airframe and propulsion technologies with powered noise simulators — something that's being done at the 14 x 22-Foot Subsonic Tunnel at NASA's Langley Research Center.

"We're right now just starting to do that test program to demonstrate that we can actually make progress toward that aggressive noise goal I talked about," he said.

In addition to looking at advanced technologies, the ERA Project also looked at some advanced vehicle concepts. Lockheed Martin submitted a box-wing design with ultrafan engines. Northrup Grumman proposed a flying-wing concept. And Boeing offered up a blended-wing body.

The blended wing body has been flight tested in the form of the X-48C, which is "pretty daggone quiet" according to Collier.

"This little airplane has over 100 flights at this stage," he said, "so that's really something to be proud of."

And while it may be a while before the blended-wing body shows up in the commercial fleet, Collier and his team believe many of the lessons they've learned in studying it can be passed down to the next generation of traditional tube-and-wing aircraft.

He also believes open rotor and ultra high bypass (UHB) engines are important to the work the ERA Project is doing. They're quieter than traditional engines and burn less fuel.

"If this technology that we're working on comes to fruition and it finds its way into the fleet by 2025 on all [travel class aircraft], we can get to this elusive carbon neutral place that is part of our national goal," Collier said.

It's yet to be seen just how much of that technology will make it into the commercial sector. In the meantime, the ERA Project is preparing to move forward with phase 2 of its plan, which will involve demonstrating eight of the most promising integrated technologies from phase 1.

And hopefully, after the project wraps in 2015, the real tadpoles swimming directly beneath the flight paths of major American airports will be a little less bothered by the noise and pollution from above.

By: Joe Atkinson

The Researcher News
NASA Langley Research Center
Editor & Curator: Denise Lineberry
Executive Editor & Responsible NASA Official: Rob Wyman