NASA And Industry Team Tests Aircraft Noise-Reducing Technologies

Experts at NASA's Langley Research Center in Hampton, Va., andindustry team researchers developed advanced noise reduction concepts.They used wind tunnels and computer simulations to initially test theconcepts.

With the initial conceptual testing completed, the team is assessingthe ideas and actual hardware at a test flight facility in Glasgow,Mont. The researchers are using a large, specially equipped 777passenger jet provided by Boeing. The test facility was outfitted withsophisticated microphone arrays and other measurement devices to recordnoise levels.

The Quiet Technology Demonstrator 2 is a three-week test flightprogram to validate the ideas, including two improved chevron designson the engine and a cover that fits on the landing gear. Chevrons arescalloped or serrated edges already used on some newer jet engines. Oneimproved chevron design includes asymmetrical scallops around theengine.

"The new design tailors the chevrons to take into account the airflow and acoustic differences that occur when the engine is installedon the aircraft," said Charlotte Whitfield, NASA's Quiet AircraftTechnology manager of airframe system noise reduction.

Laboratory tests show the advanced chevron shape will reduce noiseas much as four decibels during take-off and when flying at cruisealtitude. Results of the flight tests may lead to changes in aircraftconfigurations, future airplane engine and landing gear designs.

Goodrich Corporation's Aerostructures Division, Chula Vista, Calif.,and Goodrich Corporation's Landing Gear Division, Cleveland, designedand built a toboggan-like shaped cover for the 777's main landing gear.

The cover streamlines the gear and makes it less noisy. NASA andGoodrich tested this concept in a wind tunnel on a 26 percent scalemodel of the 777 landing gear. NASA research indicated when landing,air rushing past conventional landing gear is almost as loud as enginenoise. The covered gear concept could reduce landing noise by anotherthree decibels.

When testing is completed, Boeing will deliver the new technologyequipped 777 to All Nippon Airways (ANA), in Tokyo. The aircraft willjoin the ANA passenger fleet and provide additional noise data based onregular operations. GE Transportation Aircraft Engines, Cincinnati alsoparticipated in the research.

The goal of NASA's Quiet Aircraft Technology project is to reduceperceived aircraft noise by 50 percent in 10 years and by 75 percent in25 years, using 1997 levels as the baseline. The project is part of theVehicle Systems Program in NASA's Aeronautics Research MissionDirectorate. The program's goal is to demonstrate breakthroughaerospace technologies.

For information about the Vehicle Systems Program, including Quiet Aircraft Technology, on the Internet, visit:

http://www.aeronautics.nasa.gov/vspFor information about NASA and agency programs on the Internet, visit:

http://www.nasa.gov/home/index.html