NASA researchers have developed and tested new technologies aimed at reducing the noise generated by aircrafts.
NASA officials tested newly designed landing gear that achieved a greater than 70 percent reduction airframe noise—noise produced by non-propulsive parts of an aircraft during landing—during a series of Acoustic Research Measurement (ARM) flights at NASA’s Armstrong Flight Research Center in California.
“The number one public complaint the Federal Aviation Administration receives is about aircraft noise,” Mehdi Khorrami, an aerospace scientist at NASA’s Langley Research Center in Virginia, and principal investigator for Acoustic Research Measurement, said in a statement. “NASA’s goal here was to reduce aircraft noise substantially in order to improve the quality of life for communities near airports. We are very confident that with the tested technologies we can substantially reduce total aircraft noise, and that could really make a lot of flights much quieter.”
To achieve the ultimate noise reduction, NASA researchers tested several different experimental designs on different airframe components of a Gulfstream III research aircraft, including porous landing gear fairings, cavity treatments and an Adaptive Compliant Trailing Edge (ACTE) wing flap.
The new fairings include several small holes that allow some of the air to flow through, while also deflecting some of the airflow around the landing gear.
The researchers were able to design the new fairings using highly detailed computer simulations that enabled a design that maximizes noise reduction without increasing aerodynamic drag.
Landing gear cavities—the regions where the landing gear deploys from the main body of an aircraft—usually leave a large cavity where airflow is pulled in and creates noise.
The researchers designed the cavities by placing a series of chevrons near the front of the cavity with a sound-absorbing foam at the trailing wall. Combined with a net that stretched across the opening of the main landing gear cavity, the new design altered the airflow and reduced the noise resulting from the interactions between the air, the cavity walls and its edges.
Tackling noise caused by the wing flaps, the scientists used an experimental, flexible flap that had been previously flown as part of the ACTE project. This design eliminated the gaps between the flap and the main body of the wing.
“This airframe noise reduction produced by NASA technology is definitely momentous, and the best part is that it directly benefits the public,” ARM Project Manager Kevin Weinert said in a statement. “While there are obvious potential economic gains for the industry, this benefits the people who live near major airports, and have to deal with the noise of aircraft coming in to land. This could greatly reduce the noise impact on these communities.”
