NASA // July 3, 2018
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Significantly Reduced Urban Impact
BREVARD COUNTY, FLORIDA – A series of NASA flight tests has successfully demonstrated technologies that significantly reduce the noise of aircraft and communities near airports.
The Acoustic Research Measurement (ARM) flights, held in May at NASA's Armstrong Flight Research Center in California, tested technology to address aircraft noise or noise generated by non-propelling parts of the aircraft during landing. The flights have successfully combined several technologies to reduce the aircraft noise level by more than 70 percent.
"The Federal Aviation Administration's biggest public complaint concerns aircraft noise," said Mehdi Khorrami, a NASA researcher at Langley Research Center in Virginia and Principal Investigator for Acoustic Research Measurement. "NASA's goal was to significantly reduce aircraft noise in order to improve the quality of life near airports, and we are very confident that the technologies we tested will significantly reduce the overall aircraft noise, which could make many flights much quieter
NASA tested several experimental designs on various aircraft components of a Gulfstream III research aircraft in Armstrong. These include the chassis and cavity treatments developed and developed in Langley, as well as the Adaptive Compliant Trailing Edge (ACE) flaps, which were previously used to investigate aerodynamic efficiency has been tested by aerial technology. The plane flew at a height of 350 feet over a 185-sensor microphone assembly, which was used at Rogers Dry Lake at Edwards Air Force Base in California.
The element "Noise Reduction Technology" addressed aircraft noise caused by air flow undercarriage on approach. The experimental chassis tested by NASA has porous panels on the front, consisting of many tiny holes that allow part of the air to flow through the panel and at the same time divert some of the airflow around the chassis
Porous Concepts have been studied, but NASA's unique design resulted from highly detailed computer simulations that gave NASA engineers the ideal design for maximum noise reduction without increasing air resistance.
Another area of focus were landing gear cavities, also a known cause of aircraft noise. These are the regions where the landing gear unfolds from the main body of an aircraft and typically leaves a large cavity in which the airflow can be drawn in, producing noise. NASA applied two concepts to these sections, including a series of angles placed near the front of the cavity, with a sound-absorbing foam on the rear wall, and a net extending across the opening of the main landing gear cavity. This changed the air flow and reduced the noise resulting from the interactions between the air, the cavity walls and their edges.
To reduce winglet noise, NASA used an experimental, flexible flap previously flown within the ACTE project, exploring the potential for flexible, seamless flaps to increase aerodynamic efficiency. Unlike conventional wing flaps, which typically have gaps between the flap and the main body of the wing, the ACTE flap built by FlexSys Inc. of Ann Arbor, Michigan, is a seamless design that eliminates these gaps.
Significant reduction in aircraft noise needs to be realized so that air traffic growth can maintain its current trend. Reducing noise by using NASA technology is an important achievement in this effort as it can result in quieter aircraft that benefit communities near airports and promote airport operations.
"This noise reduction caused by NASA technology is definitely important and, best of all, it benefits the public directly," said Kevin Weinert, project manager at ARM. "While there are obvious economic benefits to the industry, this benefits people living near major airports and dealing with the noise of land-based aircraft, which could greatly reduce noise impact on these communities . "
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