NASA has tested and developed technologies to reduce noise from aircraft. After a number of test flights with a renewed landing gear, the sound of the airframe decreased by 70 percent. These special test flights were done at NASA’s Armstrong Flight Research Center in California.
In order to achieve the noise reduction, NASA tested various designs on various airframe components of a Gulfstream III research aircraft. These were for example fairings on the landing gear, cavities and special wing flaps (ACTE).
In the new fairings there are small holes through which air can flow. As a result, part of the air can also be passed around the landing gear. The hoods are designed with detailed computer simulations, making it possible to minimize noise without increasing aerodynamic resistance.
The focus was also on cavities. The cavities in a landing gear often cause noise, because of the cavity between the landing gear and the body of the aircraft. In the NASA design, sound-absorbing foam was placed on the back wall. A net has also been used that has been stretched over the cavity. In this way the airflow changes and the noise is reduced.
A third adjustment has been made to reduce the noise of the wing flaps. A flexible valve has been used that has no gap between the valve and the body of the aircraft.
Reducing aircraft noise is particularly important for local residents. For them the noise can be very disturbing. It also promotes the expansion and growth of air transport, which has economic interests for the industry.