777-200LR Flight Test Journal: Archives

20 September 2005

Future looks quiet

Boeing Commercial Airplanes: Belur Shivashankara, Eric Nesbitt, Bill Herkes, Stefan Uellenberg and Ron Olsen

Charlotte Whitfield and Mehdi Khorrami, NASA

Steve Petersen, General Electric

Hwa Kwan and Jeff Moe, Goodrich Corp.

Rob Stoker, Boeing Phantom Works

As we mentioned last time, the longer-term technology research we've been undertaking this past summer won't find its way onto a production airplane for 3-5 years. Initially on the 787 and the 747 Advanced.

The future technology we tested in Glasgow, Montana, part of the noise reduction program called Quiet Technology Demonstrator (QTD) 2, brings together partners General Electric (GE), Goodrich and NASA. We've been testing new technology focused on several of the more prominent sources of airplane noise on and around the engines and landing gear.

Our partners each have specific areas of research and development. Goodrich is working on the nacelle inlet, or casing that wraps around the front end of a jet engine, and the landing gear toboggan fairing. The engine nacelle inlet is key to controlling and constraining the inlet noise generated by the propulsion system.

GE researches engines, of course, and noise-reduction affects of newly designed chevrons, the zigzag pattern at the back of engines and nacelles.

The NASA quiet aircraft technology project has two main goals: cut community noise in half by 2007, relative to 1997 baseline, and in half again after that. Their program's airframe system noise reduction component deals with landing gear and the interaction of the propulsion system with the airframe in terms of noise. So they're involved with Boeing in the chevron development program.

With the nacelle inlet, Goodrich fabricated a one-piece inner-barrel liner, which incorporates all of the acoustic treatment forward of GE's fan. When you think about it, fabricating something out of one piece should give you savings in both weight and cost, in addition to better acoustic performance. Also as part of the inlet, Goodrich fabricated a nacelle lip liner, which is the acoustic panel that replaces a traditionally hard-wall leading edge of the nacelle. These two technologies make almost the entire nacelle inlet inner surface sound-absorbent. This substantially reduces engine noise inside the cabin and outside the airplane.

In collaboration and under contract with NASA, Goodrich also fabricated a toboggan-shaped faring, or windshield, that fits in between the wheels and reduces noise from air rushing over the landing gear axles and brake system.

The QTD-2 is showing us how Boeing and GE's new chevron designs are reducing engine noise inside the rear of the cabin and on the ground. The serrated design produces a better mix of the engine's exhaust gas and air that passes through and around the nacelle. A better mix reduces the exhaust noise that hits the rear of the fuselage, meaning quieter take-offs for passengers and the surrounding community.

QTD-2 was a perfect mechanism to work together and accelerate the noise-reduction technology development, even though commercial application is still years away. A flight test brings exposure and added emphasis to getting things done more quickly than would otherwise be possible. A lot of what is going on here is the development of new tools and prediction methods that enable us to design and pick apart what's happening in the total picture of the airplane.

The new tools will enable us to design new engine and airplane configurations. That, in turn, means we will be able to lay out a map of future airplanes and future engine designs that can make airplane community noise a non-issue. That's part of our vision. We see this technology making a difference on the 787, 747 Advanced, next-generation single-aisle, and all new generations of aircraft from here forward.