NASA Making Progress … Quietly

Airplane in the sky.

In an effort to simultaneously limit a source of pollution and general public annoyance, NASA has undertaken research focused on making passenger airplanes quieter. Much of that noise comes from the engine, but manufacturers have done a pretty good job of eliminating a great deal of that noise by using larger, quieter fans and cutting V-shaped notches in the outer shell of the engine housing.

So, NASA has turned its attention to the airframe, i.e., the body, wings, landing gear, and flaps. Most of this noise reduction comes from improving airflow, which led engineers to:

  • Remove the flaps at the back of the wings and replace them with a section of flexible metal and plastic. This change eliminates the noise created when the flaps are extended, leaving gaps and hard edges in the wing.
  • Place V-shaped blocks in front of the landing gear openings to help streamline airflow. A net was also stretched across the openings, and sound absorbing foam was added to generate further noise reduction.
  • Porous wheel supports were also implemented, allowing air to flow through a series of small holes on the front edge. That helps reduce the aerodynamic impact when the landing gear is down for take-off or landing, which is when most of the noise is heard on the ground.

These modifications were made on two Gulfstream aircraft that were flown over a 250’ spiral array of microphones arranged over a dried-up lake bed at Edwards Air Force Base. The planes flew 1,000 feet above the microphones for three hours. Researchers documented up to a 70 percent reduction in noise. Ideally, these modifications can be scaled up to help limit the noise made by much larger passenger aircraft.

 

Image Credit: Thomas Soellner/Shutterstock.com

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