"Why would you want to know how loud a helicopter is?" Robin asked.
"Good question," her mother answered. "Some
helicopters will be used to fly in and
out of airports and vertiports. They will fly over cities. We don't want them
to be so
noisy that they bother the people living in the city. The NASA flight test team
will fly
three different landing approaches to learn which approach is the quietest."
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