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Aug. 27, 2001

Jonas Dino

Ames Research Center, Moffett Field, CA

650/604-5612 or 650/604-9000

Bill Uher

Langley Research Center, Hampton, VA




Residents of communities near airports may someday breathe an audible sigh of relief as a result of NASA tests using one of the world's largest wind tunnels to evaluate a variety of 'quiet' aircraft technologies.

Aircraft are at their 'loudest' when landing gear, wing flaps and slats are deployed, creating large amounts of wind turbulence and generating lots of noise. Engineers at NASA Ames Research Center, in California’s Silicon Valley, with support from NASA Langley Research Center, Hampton, Va., will use Ames' 40 x 80-foot (12.2 x 24.4-meter) subsonic wind tunnel to test design modifications that reduce aircraft noise on a 26 percent-scale model of a Boeing 777 aircraft.

"This wind tunnel test is the culmination of eight years of work to make aircraft quieter during the time when the most noise is produced -- take-off and landing. This is the first time that all of these noise-control devices will be tested together. Each device works separately, but this test will determine how well they work together," said engineering lead Kevin James of NASA Ames.

"These technologies, developed by NASA and an industry airframe-noise reduction team, will revolutionize the design of future generations of commercial aircraft. Communities will experience less noise, and their citizens' quality of life will be improved, with the implementation of the advanced technologies to be demonstrated in this critical experiment," said Bill Willshire, noise reduction program manager at Langley. The research to develop quieter aircraft is funded under the Aerospace Vehicle System Technology Noise Reduction Program managed by Langley.

The model -- known as the Subsonic Transport Acoustic Research (STAR) model -- consists of the left half of the aircraft. It will be mounted with the wing vertical in the test section. The model is complete with a wing, landing gear, leading edge slats and flaps that are fully extended to duplicate take-off or landing conditions.

"This model is one of the most detailed wind tunnel models of a commercial aircraft ever tested. The model has all of the control surfaces and parts of the real aircraft. It has a semi-wingspan of 26 feet (7.25 meters) and is built to a tolerance of 0.030 of an inch (0.0762 centimeters)," said James. "The Boeing 777 was picked for the development of these quiet modifications because it is an already a relatively quiet aircraft. We wanted the challenge of making it even quieter," he added.

To determine noise levels, the test will use one large, fixed acoustic-sensor array and one mobile acoustic (or "microphone") array that can cover the entire length of the model. Acoustic arrays enable engineers to measure the noise generated from small portions of the model. With the microphone array, noise generated from the flap edge can be separated from noise generated from the slat. The benefit of the microphone array is very much like that of a microscope, allowing researchers to look at individual noise-generating parts. The model is also heavily loaded with sensors that monitor wind-speed, turbulence and pressure.

"We’ve learned a great deal over the past several years and have significantly improved our sensor array designs. A mobile array was needed because some of the noise produced is very directional. The sensor needs to be in position to ‘see’ the noise in order to accurately detect the noise," said James.

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Note to Broadcasters: A video file related to this news release is scheduled for distribution via satellite on NASA Television on August 27, 2001. Because feed times and the schedule are subject to change, please check the NASA TV video file line-up on the web at
NASA TV is available on GE-2, transponder 9C at 85 degrees west longitude, with vertical polarization; frequency is on 3880.0 megahertz, with audio on 6.8 megahertz. For general questions about the video file, call NASA Headquarters, Washington, DC: Fred Brown at 202/358-0713



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