NASA officials have tested a newly designed landing gear, which achieved a staggering 70% reduction in airframe noise.

Firstly the reduction is noise produced by non propulsive parts of an aircraft, which was measured during a series of Acoustic Research Measurement flights. (ARM) The tests where conducted at NASA’s Armstrong Flight research center in California.

Due to the number one public complaint to the Federal Aviation Administration is regarding aircraft noise. Mehdi Khorrami, an aerospace scientist at NASA’s Langley Research Center in Virginia, 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.”

First of all NASA researchers tested several different experimental designs on different components of a Gulfstream III research aircraft.

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NASA’s Gulfstream III Aerodynamics Research Test Bed.
Photography Courtesy of NASA.

NASA’s Solution to the problem?

These include porous landing gear fairings, cavity treatments and an Adaptive Compliant Trailing Edge (ACTE) wing flap. The new fairings have several small holes to allow air to flow through and to distribute some of the airflow around the landing gear. Researchers design the new fairings using highly detailed computer simulations the design maximizes noise reduction without extra aerodynamic drag.

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Landing gear cavities Boeing 767. – A large area exposed when landing gear is extended which pulls in air and creates more noise. Photography courtesy of Airways Magazine.

So to tackle the problem researchers designed the cavities by placing a series of chevrons towards the front of the cavity with sound-absorbing foam on the trailing wall. Furthermore a net stretched across the opening of the main landing gear cavity. In conclusion the design altered the airflow and reduced the noise between the air, the cavity walls and its edges. Furthermore to counter noise caused by flaps, scientists used an experimental flexible flap flown as part of the ACTE project. In conclusion the design eliminated the gaps between the flap and the main body of the wing.

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